Wiadomości Chemiczne

Wiadomości Chemiczne, 1999, 53.

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  1. Some problems of drug design
    Jarosław Polański

  2. Molecular symmetry and stereochemistry
    Marcin Stępień

  3. Microwaves - the application to organic synthesis
    Dariusz Bogdał

  4. The birch reduction of aromatic ethers and ketones
    Mirosław Anioł

  5. The surface reconstruction of (100) face of gold single crystal in electrochemical environment
    Piotr Skołuda

  6. Notatki chaotyczne. XXI. Polski dwugłos o Robercie Bunsenie
    Ignacy Siemion

  7. Zbigniew Malarski
    Lucjan Sobczyk

  8. Dihydrogen complexes of the transition group metals. Part I
    Andrzej F. Borowski

  9. Dihydrogen complexes of the transition group metals. Part II
    Andrzej F. Borowski

  10. Luliberin, its analogs and lutropin
    Apolinary Szewczuk, Ewa Kurowska

  11. Antibiotics as electrophoretic and chromatographic chiral selectors
    Jacek Bojarski

  12. The role of adsorption and catalysis in semiconductors gas sensors.
    I. Sensing mechanism and preparation of resistant sensors

    Ireneusz Kocemba

  13. Pół wieku z chemią wrocławską
    Lucjan Sobczyk,

  14. Dibenzotetraaza[14]annulenes. Part I
    Julita Eilmes, Marcin Ptaszek,

  15. Dibenzotetraaza[14]annulenes. Part II
    Julita Eilmes, Marcin Ptaszek

  16. Metal complexes as potential radiopotentiators
    Janina Jaworska-Kuduk

  17. Problems concerning the value of chromium in biological systems
    Gabriela Gałuszka, Maria Cieślak-Golonka,

  18. The methods of vitamin K3 synthesis
    Jan Kowalski, Jolanta Płoszyńska, Andrzej Sobkowiak,

  19. The protomeric tautomerism and structure of thio-substituted uracils
    Zdzisława Nowakowska, Elżbieta Wyrzykiewicz,

  20. Notatki chaotyczne. XXIII. Mendelejew o wodzie warszawskiej
    Ignacy Siemion,

  21. Śp. Profesor Piotr Nowak (1939-1999)
    Stanisław Olszewski,

  22. 40 years of nickel hydride
    B. Baranowski,

  23. The hydroxyimino derivatives of sugars
    Beata Liberek and Zygfryd Smiatacz,

  24. Electrochemical properties of fullerenes and their derivatives in solutions
    Krzysztof Winkler,

  25. The structure and features of proton exchange membrane fuel cells
    Bogusława Tendaj, Krystyna Marczewska-Boczkowska,

  26. Speciation of manganese in soil and surface water
    Jan Kalembkiewicz; Elżbieta Sitarz-Palczak,

  27. 50 years of "Wiadomości Chemiczne"
    Józef Ziółkowski,

  28. Notatki chaotyczne. XXIV. O języku chemii
    Ignacy Siemion,

  29. Radiochemistry on the verge of its second century
    Jerzy Narbutt,

  30. Heaviest elements: Their properties and synthesis
    Adam Sobiczewski

  31. Chemical properties of transfermium elements
    Aleksander Bilewicz

  32. Nuclear medicine. Radiopharmaceuticals
    Leszek Królicki

  33. Radiochemistry in nuclear medicine. Radiopharmaceuticals
    Krystyna Samochocka

  34. Natural and anthropogenic pollution of the global atmosphere
    Zbigniew Jaworowski

  35. Contribution of the nuclear fields to the chemical isotope effects
    Wojciech Dembiński

  36. Elements of nuclear chemistry in secondary school and university programmes. Is this kind of information necessary?
    Anna Czerwińska, Andrzej Czerwiński

  37. Electronic structure of dipole-bound anions
    Piotr Skurski, Maciej Gutowski

  38. Catalytic hydroboration
    Jerzy Meller, Marek Zaidlewicz

  39. Biochemical activity of fullerenes And related derivatives
    Andrzej Huczko, Hubert Lange, Ewa Całko

  40. Electrochemical properties of fullerene based solid thin layers
    Krzysztof Winkler, Marta E. Płońska

  41. Self-organisation in metal comlexes
    Wanda Radecka-Paryzek

  42. Catalytic oxidation of soot from diesel engines
    Włodzimierz Tylus

  43. Crosslinked liquis crystalline polymers
    Tomasz Ganicz

  44. Chemical engineering at the turn of the centuries
    Antoni Kozioł

  45. Notatki chaotyczne. XXV. O chorobach molekularnych i ich odkrywcach
    Ignacy Z. Siemion

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Jarosław Polański

Zakład Chemii Organicznej, Instytut Chemii Uniwersytetu Śląskiego ul. Szkolna 9, 40-006 Katowice

Although most of the drugs have been discovered serendipitously [3] the rational design of the molecules has been attempted for years. However, only the recent years brought a variety of new techniques providing unquestionably efficient procedures. In particular, the methodology of 2D and 3D quantitative structure activity relationships (QSAR) and combinatorial chemistry should be mentioned.

In this review the basic methodology of the classical Hansch QSAR approach has been briefly discussed [23-52]. In general, classical two-dimensional QSAR fails to distinguish between stereoisomers. This fact inspired the development of the idea of 3D QSAR [53-59]. Just the last year brought the concept that coined the term 4D QSAR covering quantitative description of conformational effects [68].

On the other hand, the comparative molecular field analysis CoMFA [55] (outlined in Fig. 2), which is the most common 3D QSAR scheme, demands perfect alignment of the series of molecules analyzed. Moreover, the results critically depend upon the way of overlaying the molecules. The CoMFA and 4D QSAR analyses base on the statistical techniques of the partial least square (PLS) and cross-validation procedure - Fig. 1 [41-43].

Both from the theoretical and practical points of view more flexible procedures for the alignment of molecules are needed [52, 53]. A comparative technique of self-organizing neural network provides one of alternatives allowing for such more flexible visualization and quantitative analysis of molecular similarity - Figs. 3, 4 [60-65]. The problem of the molecules' alignment can also be solved by the use of the a new 2D QSAR technique, the so-called holographic QSAR (HQSAR) which uses fragmental coding of the molecule - Fig. 5 [70-72].

Combinatorial chemistry is a method that puts together the randomness of screening and the rationality of design [73-84]. The idea of combinatorial synthesis (Fig. 6) consists in the parallel synthesis of the set (combinatorial library) of compounds obtained simultaneously. Depending upon the technique used such libraries can be obtained as complex mixtures of the products of the defined composition or separate compounds. Although it is the diversity of molecular library created by combinatorial procedure that allows for increasing the probability of finding active analogs, combinatorial methods are far from brute randomness [78, 80]. The new methods for the description of the similarity of such libraries have been proposed [79-81]. The newest trend represented by in-vitro nucleic acid selection which is designed to mimic the Nature's evolutionary processes is probably one of the most interesting idea in drug design [82-83]. Just recently this idea has been expanded to the small organic molecules [84].

Wiadomości Chemiczne, 1999, 53, 1.
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Marcin Stępień

Wydział Chemii Uniwersytetu Wrocławskiego, ul. F. Joliot-Curie 14, 50-383 Wrocław

Stereochemistry, often regarded merely as a descriptive discipline, is an inexhaustible source of mathematical problems. Group theory, topology, graph theory, etc. are widely applied to the description of molecular architecture and conformational dynamics, to isomer counting and labelling, interpretation of spectra and more. Both mathematics and stereochemistry benefit from their marriage: new theorems are proved and new molecules synthesised.

This review is concerned with molecular symmetry, an idea which, appropriately generalised, is central to stereochemistry. Depending on what we imagine a molecule to be, whether a rigid body, a set of nuclei, or a graph, the nature of symmetry operations changes. Our attempt is to demonstrate how various symmetry models work, explore their capabilities, and show how they are interrelated by virtue of their common group theoretical framework.

Point groups, derived in the opening section, are by far the most popular symmetry descriptors albeit applicable only to instantaneous configurations of molecules. Point groups, providing little information on the actual structure of a molecule, can be extended into so called framework groups [11] which detail the distribution of atoms over sites of different local symmetry. From the structure of minimal framework groups the frequency of various point symmetries amongst molecules can be inferred. This is illustrated with a number of examples.

The following section introduces the idea of permutational symmetry and its application to non-rigid molecules. The permutation-inversion (PI) group of Longuet-Higgins [38] is defined and exemplified, its semidirect product structure being discussed in some depth. The PI group is then used for the description of selected dynamic processes, such as the rearrangements of bullvalene or 'racemization' of Mislow's ester [51]. Finally, the classification of nuclei used in NMR spectroscopy is expressed in terms of equivalence classes within the PI group.

The final section deals with topological properties of molecules. The principles of graph theoretical approach to molecular symmetry are outlined. Topological stereoisomerism is then defined, and the synthetic philosophy of topological stereochemistry and its achievements are briefly reviewed. We end with a discussion of symmetry properties of topologically non-trivial species, paying particular attention to realizability of automorphisms and chirality of graphs.

Wiadomości Chemiczne, 1999, 53, 17.
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Dariusz Bogdał

Samodzielna Katedra Chemii i Technologii Tworzyw Sztucznych, Politechnika Krakowska, ul. Warszawska 24, 31-1555 Kraków

In the last few years there has been a grawing interest in the use of microwave heating in organic synthesis. The use of such nonconventional reaction conditions reveals several features like: a short reaction time compared to conventional heating, ease of work-up after a reaction, and reduction in the usual thermal degradation and better selectivity. Microwave ovens provide a clean and cheap alternative to conventional oil baths. The popularity of microwave heating for organic synthesis has increased to the extent that it now forms the basis of a number of commercial systems, and has even made its way into undergraduate laboratory courses.

Microwave heating has been proven to be of benefit particularly for the reactions under "dry" media (i.e., in the absence of a solvent, on solid support with or without catalysts) and offers a number of advantages: solvents are often expensive, toxic, difficult to remove in the case of aprotonic solvents with high boiling point. Liquid-liquid extraction can be avoided for the isolation of reaction products. Moreover, the absence of solvent reduces the risk of explosions when reaction takes place in a microwave oven.

In the present article micrawave-assisted organic syntheses are reviewed in the context of their most significant examples.

Wiadomości Chemiczne, 1999, 53, 65.
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Mirosław Anioł

Katedra Chemii, Akademia Rolnicza we Wrocławiu, ul. Norwida 25, 50-375 Wrocław

The reduction of alkali metals in liquid ammonia (the Birch reduction) of aromatic ethers and ketones, especially 2H-chromenes and chromanones, is reviewed. Special attention has been paid to the mechanism of this reaction. The influence of experimental conditions on mechanism and regiochemistry is considered.

The great majority of applications of the Birch reduction is centered on aromatic ethers and it is a powerful synthetic method available to organic chemists. This method describes the formation of enol ethers in excellent yield. However the scope of application is limited because of the loss the alkoxy group.

The reduction of phenyl ketones usually leads to corresponding alcohols and next to hydrocarbons but, in certain cases, it gives products of the benzene ring reduction with partially reduced carbonyl group. Products depend on the position other groups on the benzene ring and their type.

In the case of the reduction of 2H-chromenes, chroman-2-ones and chroman-4-ones the major products are phenols, if the reaction is carried out without an additional source of protons (ethyl or methyl alcohol).

Wiadomości Chemiczne, 1999, 53, 95.
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Piotr Skołuda

Zakład Chemii Fizycznej, Wydział Chemii, Uniwersytet im.A.Mickiewicza, ul.Grunwaldzka 6, 60-780 Poznań

The low-index single crystal surfaces of gold and platinum are known to reconstruct under ultra-high-vacuum conditions [1,2]. It has been demonstrated that many of these reconstruction phenomena can also be observed for the metal surface in contact with an electrolyte [6,17]. The data presented will focus on the surface reconstruction of Au(100) electrode in view of the results of recent electrochemical studies. We shall describe the preparation and the conditions under which Au(100)-(hex) surface is stable in solution. Flame annealed Au(100) surface is reconstructed and it is demonstrated under what condition this initial (thermally induced) reconstruction is preserved during and after the contact with electrolyte [18,19].

The so-called charge-induced reconstruction [27] and its influence on electrochemical adsorption reactions [30] is presented. The kinetics studies of surface structural transition due to charge-induced reconstruction or anion-induced lifting of the reconstruction are discussed in some detail. Finally, the role of the surface charge and the coverage of the adsorbate in the lifting of the reconstruction of Au(100) surface is briefly discussed [39,40 ].

Wiadomości Chemiczne, 1999, 53, 115.
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Ignacy Z. Siemion

Wydział Chemii Uniwersytetu Wrocławskiego, ul. F.Joliot-Curie 14, 50-383 Wrocław

Wiadomości Chemiczne, 1999, 53, 135.
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Lucjan Sobczyk

Wydział Chemii Uniwersytetu Wrocławskiego, ul. F.Joliot-Curie 14, 50-383 Wrocław

An obituary and a short review of scientific activity of Professor Zbigniew Malarski is presented. Particularly important achievements were related to the medium effect on the associating compounds, dynamics of alcohols with large steric hindrance, the structure and spectroscopic behaviour of NHN homoconjugated cations and anions as well as geometrical correlations for OH···N hydragen bonds. Spectacular spectroscopic and geometrical isotope effecs were discovered. Full bibliography is attached.

Wiadomości Chemiczne, 1999, 53, 149.
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Andrzej F. Borowski

Zakład Karbochemii Palskiej Akademii Nauk, ul. Sowińskiego 5, 44-121 Gliwice

In the first part of this review preparative methods and structural studies of s-bonded dihydrogen complexes of the transition group matels have been discribed. The former includes the most common procedures of direct reaction of coordinatively unsaturated complexes with hydrogen gas and protonation of metal hydride species. The M¾(h2 - H2 ) bonding in these complexes is best described as a s(HH) electron density donation to an empty metal d orbital of s symmetry s(HH)®d s (M) augmented by a synergistic back-donation from filled metal d obitals (dp(M) ®(s*(HH)) (Fig. 1).

From among methods of detemining solid state structures, the most accurate are the neutron diffraction studies that have been successfully applied to 11 complexes (Table 1). Progress in broader application of this method is slow due to the need for preparation of large crystals and the shortage in the world of neutron scatering and diffraction facilities.

In solution, the most reliable data are acquired by NMR methods. Large J(HH) coupling constant values of 12 to 34 Hz [68b] and short minimal spin-lattice relaxation time values of ~ 3 ms < T1min < ~ 40 ms are characteristic of complexes containing M¾ (h2 - H2 ) bonds. The dependence of T1min on speed of rotation ensures that T1min values measured for fast spinning H2 ligands are 4 times longer than those observed for slow rotational motion regimes and that the H¾H distance for these two types of motion is linked by the relation: dfast(HH) = 0.793 · dslow(HH) [60]. Taking into account the generally accepted view that dihydrogen complexes may be regarded as intermediates along the pathway to H2 oxidative addition, Morris [18] and Maseras [43] proposed the following classification of hydragen atoms in these complexes: 0.8 - 1.1 Å (dihydrogen complexes), 1.1 - 1.3 Å ("stretched' dihydrogen complexes), 1.3 - 1.4 Å (compressed dihydrides), > 1,6 Å (classical dihydrides).

Wiadomości Chemiczne, 1999, 53, 165.
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Andrzej F. Borowski

Zakład Karbochemii Palskiej Akademii Nauk, ul. Sowińskiego 5, 44-121 Gliwice

The second part of the paper presents the reactivity of dihydrogen complexes beginning with the ability of the coordinated H2 ligand to undergo heterolytic splitting (i.e. their acidic properties). Generally, the low energy of the M¾(h2 - H2 ) bond in dihydrogen complexes results in a facile loss of the H2 ligand and is usually accompanied by substitution, substitution followed by an intramolecular reaction, ligand exchange, or elimination followed by dimerization.

Dihydrogen complexes (most often Ir, Os, Ru) show catalytic activities in isotope H/D exchange reactions in the homogeneous hydrogenation of alkenes, alkynes (Table 4), arenes, ketones, in alkene silylation as well as in hydrogen transfer reactions between solvent (usually an alkohol) and an unsaturated substrate [69]. In the presence of a dihydrogen acceptor (e.g. t-Bu-CH=CH2) dihydrogen complexes are involved in the stoichiometric dehydrogenations of alkanes to alkenes. Only one example of a molecular hydrogen complexes reducing nitrogen or sulfur containing heteroaromatic rings has been reported [81].

Molecular hydrogen complexes may undergo different reactions depending on their role in the catalytic cycle. Under hydrogenation conditions dihydrogen ligand can be easily substituted by unsaturated organic molecules . In this way, H2 molecule stabilizes unsaturated catalysts without bothering the coordination of the substrate (e.g. IRH2(H2)(PMe2Ph)3]+ [70], Scheme 2).

Some dihydrogen complexes are regarded as intermediates for the homolytic activation of dihydrogen (e.g. [M(CO)3(nbd)(H2)] M=CR, Mo [75] and [Rh(HCO)(CO)3(H2)] [89]). In other complexes the H2 molecule acts as a reagent capable of hydrogenating substrate via an intramolecular acid/base reaction (Scheme 4; [78]). Similarly, the heterolytic splitting of H2 ligand in [Ru(OEP)(thf) 2(H2)] by the strong base (KOCH) [9] or in [Ir(bq)H(H2)(PPH3)2]+ by an alkohol [36] promote the H/D isotopic exchange reaction.

The proposed mechanisms for the hydrogenation of alkenes (alkynes) catalysed by dihydrogen complexes are typical for the catalytic cycles of many other homogeneous hydrogenation processes. These include formation of a vacant coordination site (usually by loss of a H2 molecule, but also by dissociation of one of the "arms" of the phosphine ligand [78]) followed by coordination of a substrate, its insertion into a M¾H bond, hydrogenolysis of an alkyl (allyl) moiety followed by product elimination.

Wiadomości Chemiczne, 1999, 53, 191.
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Apolinary Szewczuk, Ewa Kurowska

Laboratorium Biochemii, Instytut Immunologii i Terapii Doświadczalnej Polskiej Akademii Nauk ul. R. Weigla 12, 53-114 Wrocław

The mammalian hormone (or factor) which releases luteinising hormone (LH, lutropin) and follicle stimulating hormone (FSH, follitropin) was isolated from ovine and porcine hypothalami and identified as decapeptide with the following sequence: pGlu1-His2-Trp3-Ser4-Tyr5 -Gly6-Leu7-Arg8-Pro9-Gly10 -NH2 [2, 3].

For synthesis of the luliberin (luteinizing hormone releasing hormone, LH RH) and its analogs solid phase Merriefield technique [14-16, 48] and for purification reverse phase HPLC were usually applied [48-51]. Until now thousands of LH-RH analogs were synthesized and some of them were appllied in gynecology and oncology. Such achievements were possible through replacing proteinic L-amino acids in LH-RH molecule for nonproteinic synthetic D-amino acids [7-11]. The luliberin called also gonadoliberin (Gn-RH) plays an important role as regulator of reproduction. Secretion of lutropin (LH) by anteriol pituitary cells in an pulsative manner is controlled by pulsatile release of LH-RH from hypothalamus [8, 21, 22]. It was well established that the surge of LH at midcycle in woman urines is an authentic predictor of approaching ovulation [83, 109, 110]. In gonades LH stimulates synthesis of sex steroid hormones [83, 111-114]. The well known luliberin analogs were: Buserelin (Suprefact), Zoladex (Goserelin) and Cetrorelix (SB75). They were applied for treatment of prostatic, ovarian and breast cancers, endometriosis and in vitro fertilization [7, 11].

Wiadomości Chemiczne, 1999, 53, 219.
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Jacek Bojarski

Katedra Chemii Organicznej, Collegium Medicum, Uniwersytet Jagielloński, Kraków

In search for new chiral selectors used in electrophoretic and chromatographic enantioseparations D. W. Armstrong et al. introduced in recent years a few macrocyclic antibiotics, such as rifamycins B [2] and SV [4] (Fig. 1), vancomycin [5] (Fig. 2), ristocetin A [9, 48] (Fig. 3), teicoplanin [10] (Fig.4) and thiostrepton [36] (.Fig. 5). It was found that these antibiotics assist in separations of enantiomers of different classes of compounds, among others such as non-steroidal antiinflammatory drugs (profens) and other drugs, amino acids and their derivatives, pyridones, carboxylic acids and herbicides, both as chiral selectors in buffers used in capillary electrophoresis as well as immobilised on silica gel chiral stationary phases in high performance liquid chromatography.

Applications of modified antibiotics [26-28], effects of different factors on enantioselectivity (concentration of the chiral selector, buffer composition, pH, addition of organic modifiers) and comparative enantioseparations of the same enantiomers by different antibiotics and other chiral selectors and stationary phases [21, 24, 42] are also described.

Attempts were made at elucidations of enantiodifferentiating interactions between the molecules of antibiotic selectors and separated enantiomers. Such structural features of antibiotics like functional groups, amide linkages, aromatic rings and "hydrophobic pockets" play important role in these processes. Recently, the application of erythromycin for the separation of enantiomers of dansyl derivatives of racemic amino acids by thin-layer chromatography was reported [51]. The columns with antibiotic chiral stationary phases are now available on the market [40] and speed up applications of this type of selectors in chiral chromatography.

Wiadomości Chemiczne, 1999, 53, 235.
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Ireneusz Kocemba

Instytut Chemii Ogólnej i Ekologicznej Politechniki Łódzkiej, ul. Żwirki 36, 90-924 Łódź

The development of semiconductor gas sensors for the detection of combustion and toxic gases has been in progress for several years. Ceramics gas sensors based on SnO2, TiO2, ZnO have been widely accepted as an important tool for detecting or monitoring gases and vapours like H2, CO , CH4 , H2S , C2H5OH [9-13]. The sensors are manufactured by means of different technologies. The most popular ones are resistant sensors based on SnO2, developed in Japan and currently produced on a large scale. Among these, TGS sensors ( Tagushi Gas Sensors) from Japanese company Figaro are the most popular ones [4]. The principle of the operation of this type of sensors consist in a comparison of electrical resistance of semiconducting oxide in air , and in the presence of the detected gas. The change in resistance is a function of the concentration of the gas. The gas sensing mechanism for a reducing gas such as carbon monoxide involves the reaction of CO with ionosorbed oxygen on the sensor surface leading to a decrease in resistance. The process can be summarised [28,37]

e- + 1/2O2ÛO-

CO + O- = CO2 + e-

Thus, these sets of equations show the catalytic oxidation reaction where the catalyst is a surface of sensor . Catalytic effects play an important role in many areas of gas detection. The work of resistant sensors based on different semiconductors relies on catalytic reaction of the oxygen and detected gas at solid surface. This paper reviews the role of catalysis in the metal-oxide semiconductor device, which measures gas concentrations in terms of the changes in electrical conductivity induced by adsorption or reaction of gases on the solid surface. Although this review is limited to consideration of ceramic sensors , many of the aspects discussed will apply to thin- and thick-films sensors.

Because problem of catalysis in detection gases is very large, the review is divided into four parts : I. Sensing mechanism and preparation, II. The correlation between adsorption and detection, III. The correlation between catalytic activity and detection. In the last part of paper (part IV) I would like to show the role of adsorption and catalysis in other semiconductors gas sensors such as Pd-MISFET, SAW or Zirconia sensors.

In this part of the paper, the mechanisms of detection and the influence of oxide-metal semiconductor preparation on properties of ceramics gas sensors is presented. The results of different works show that the sensing characteristic of a semiconductor gas sensors can be improved by controlling fundamental factors which affects its receptor and transducer functions. The transducer function is related to the microstructure of the sintering specimen. This microstructure is characterised by the grain size (D) and the depth of surface space-charge layer (L) [45] . On the other hand, the receptor function is modified by the introduction of foreign receptors on the surface of sensors. In the particular cases of Pt, Pd and Ag are promotors. These problems are presented in aspects of phenomenon of adsorption and catalysis and the role, which they play in detection of gases.

Wiadomości Chemiczne, 1999, 53, 249.
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Ignacy Z. Siemion

Wydział Chemii Uniwersytetu Wrocławskiego, ul. F.Joliot-Curie 14, 50-383 Wrocław

Wiadomości Chemiczne, 1999, 53, 271.
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Lucjan Sobczyk

Wydział Chemii Uniwersytetu Wrocławskiego, ul. F.Joliot-Curie 14, 50-383 Wrocław

Earliest reminescences from the post 2nd War period, evolution and present state of the chemical education and research in Wrocław are presented.

Wiadomości Chemiczne, 1999, 53, 283.
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Julita Eilmes, Marcin Ptaszek

Zakład Chemii Organicznej, Wydział Chemii, Uniwersytet Jagielloński, ul. Ingardena 3, 30-060 Kraków

The title dibenzotetraaza[14]annulenes (Fig. 1) belong to the class of the synthetic tetraaza macrocyclic ligands of bioinorganic relevance. Their similarity to porphyrins makes them attractive as models of important biological systems like for examle hemoproteins (hemoglobin, myoglobin), cytochromes and metalloenzymes (e.g. oxygenases, peroxidases, catalase) [2. 4].

Dibenzotetraaza[14]annulene and porphyrin ligand both have four coplanar nitrogen donor atoms and substantial bond unsaturation and delocalization in the macrocyclic framework. However, the dibenzotetraaza[14]annulenes are Hückel anti-aromatic (4n), whereas the porphyrins are fully delicakizes aromatic (4n+2). There is also remarkable difference in the conformation of the macrocyclic ligand which is flat in porphyrins and taa system (R1 = R3 = H) and sadlle-shaped in the case of other dibenzotetraaza[14]annulenes (R1 = R3 ¹ H). The conformation of the ligands greatly influences the metal coordination geometries in their metal complexes. Structure of the dibenzotetraaza[14]annulenes is discussed in details in Part II.

The purpose of this article is to provide the readers with the preparative methods of the synthesis of various dibenzotetraaza[14]annulenes. Reactivity of the macrocyclic framework is also reviewed, as a method of further modidication of the ligand structure.

All synthetic methods are divided into two distinct categories, know as non-template and metal-ion template procedures. In the first case, the 2+2 condensation of the substrates takes place leading in one step to dibenzotetraaza[14]annulene ligand. The non-template approach is especially well suited for the synthesis of the H2taa ligands (R1 = R3 = H) and is exemplified by the reaction of n-phenylenediamine with propynal [8, 9], malondialdehyd [11, 12], acroleine and its derivatives [13-15], as well as with vinamidinium salts [16] (Scheme 2-8).

In the template procedures, similar condensation reactions are catalytically improved by metal ions, usually Ni2+ (in some instances also Co2+ or Cu2+), leading to corresponding metal complexes of the dibenzotetraaza[14]annulenes (R1 = R3 ¹ H). Demetallation procedures have to be employed in this case, in order to isolate free ligands [7, 21, 25]. The most often cited template reactions are described in the papers [17-21] and outlined in Schemes 9-13.

The g,g' positions of the dibenzotetraaza[14]annulene ring appeared to be the reactive nucleophilic centres. The reactions with diazonium salts [36, 37], halogenation [38], alkylation [56], acylation by means of mono- and dicarboxylic acids chlorides [39-44, 47] give rise to corresponding mono- and disubstituted products. A wide range of 7,16-substituted derivatives of the dibenzotetraaza[14]annulene complexes have been synthesized by the reaction with glutaryl chloride [25, 48] and further chemical transformations within the g,d-unsatureted lactonic substituents [49, 50]. Oxidation of the macrocyclic Ni(II) complexes leads to dimers [57], reaction with cyanogen allows to synthesize g,g'-cyano and cyanoimine derivatives. A new type of matallorganic dibenzotetraaza[14]annulene complexes was obtained as a result of the reaction of [Co(tmtaa)py)] + with acetylene, nitriles and norbernene [59-61]. Schemes 20-28 outline the reactivity of the dibenzotetraaza[14]annulene ring.

Wiadomości Chemiczne, 1999, 53, 305.
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Julita Eilmes, Marcin Ptaszek

Zakład Chemii Organicznej, Wydział Chemii, Uniwersytet Jagielloński, ul. Ingardena 3, 30-060 Kraków

"Dibenzotetraaza[14]annulenes. Part II" presents an overview of the transition and main groups metal compounds of the title macrocyclic ligands. The results of the crystal structure determination are also summarized.

Synthesis. As it was reported in Part I, the 2 + 2 condensation of o-phenylenediamine with b-dicarbonyl compounds, carried out in the presence of metal ions, leads easily and efficiently to the metal complexes. However, this so called template procedure is limited only to the later transition metals, usually Ni2+, more rarely Cu2+ and Co2+. Consequently, the majority of complexes of other metals, described in the literature, have been synthesized by the insertion of metal into the preformed macrocyclic ligand. The insertion is usually accomplished through the reaction of a free ligand with a salt of the appropriate metal (e.g. [1, 74, 97]) or its labile complex (e.g. [25, 36, 89]), as well as by the reaction with a metallorganic compound (e.g. [51, 109, 110]) (Scheme 1). The use of dilithiated derivatives of dibenzotetraaza[14]annulenes (Scheme2) instead of a neutral ligand proved to be also successful [66, 81].

A number of new metal derivative have been obtained as a result of further reactions of the metal complexes with various reagents. For example, oxidation of a central metal atom [5, 89] and transmetallation [53], as well as metal-carbon [77, 17, 18] and metal-metal [29, 31, 52] bond formation are reported.

Structure. X-Ray crystal structure determination has been done for a number of free ligands and metal complexes of dibenzotetraaza[14]annulenes. Crystallographic data for the main important ligands and complexes may be found in the following papers: H2taa - [128, 132], H2tmtaa - [25], H2omtaa [121, 122], H2dmdptaa - [125], 6,17-dmtaa - [129], [Ni(II)taa] - [124], [Ni(II)tmtaa] - [131], [Cu(tmtaa)] - [130, 133], [Ni(dmtaa)] - ]123]. A review concerning the transition metal complexes has also appeared [126].

It has been found crystallographically that dibenzotetraaza[14]annulene ring in unsubstituted taa system is planar, both in the free ligand H2taa and its square Ni(II) complex [124]. On the other hand, 6,8,15,17-tetrasubstituted macrocycles adopt the saddle-shaped conformation in which o-phenylene rings and diimnate chelate framework are tilted to opposite sides of the plane defined by four nitrogen atoms (Fig. 1).

Non-planar conformation of the macrocyclic framework in the H2tmtaa greatly influences the coordination geometry in their metal complexes. Saddle-shaped deformation together with a relatively small size of the coordination cavity results in the tendency of metal centres to be displaced out of the N4 plane. Consequently, 5-coordination (square pyramidal), found for example in [Fe(III)(tmtaa)Cl] [1], [Cr(III)(tmtaa)Cl] [50] and [Co(III)(tmtaa)] [1, 5], seems to be more favourable than 6-coordination. Moreover, in the 6-coordinated complexes metal ion favour cis cofiguration (trigonal prismatic, e.g. [Zr(tmtaa)Cl2 [66], [Ti(tmtaa)Cl2] [63]) over trans (octohedral, e.g. [Sn(tmtaa)Cl2] [20].

Conformations other than planar and saddle-shaped for dibenzotetraaza[14]annulene framework have been observed in a few cases only: [Ge(omtaa)Te] (inverted saddle-shaped [116], [Ru(tmtaa)(PMePh2)2] [90] and [Ru(omtaa)(PPh3)2] (Fig. 8 [93]), [Pd(tmtaa)] (Fig. 9 [97]) and [Pt(tmtaa)} [104] (step-like structure).

Wiadomości Chemiczne, 1999, 53, 329.
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Janina Jaworska-Kuduk

Wydział Chemii Uniwersytetu Wrocławskiego, ul. F.Joliot-Curie 14, 50-383 Wrocław

This review describes some current approaches in using metal compounds to module the response of tumors and normal tissues to cell killing by ionizing radiation. It is know that many tumors contain necrotic, oxygen-defficient areas which show diminished radiation sensitivity. Normal tissues contain mostly oxic cells; so antihypoxia therapies should be relatively tumor-specific. The biochemical role of oxygen is in fixing, or making permanent, the damage done to the critical DNA targed. Radiation can damage DNA either by direct interaction or indirectly by ionizing created in nearby water molecules. The resulting DNA state depends on a competition between oxygen for damge fixation and reducing species, such as hydrated electron or thiol compounds (¾SH), for chemical restitution ([10] and ref).

Approaches to chemical modification include use of (1) "electron-affinic" sensitizers which act as oxygen mimetics; (2) thiol-binding agents which prolong life and action of OH+ radical that is the most cytotoxic water radiolysis product; and (3) DNA-binding agents which may inhibit repair processes [1].

An ideal radiosensitizer would be nontoxic to aerobic cells. The classic radiosensitizers are the nitroheterocycles as exemplified by nitrofurans and nitroimidazoles. Their nitro groups are "electron-affinic" and hence may interact with damage on DNA induced by radiation in a manner analogous to oxygen [1, 51].

Metal complexes would appear to represent ideal candidates for studies of their potential sensitizing properties, but only few such studies have been carried out. Metal complexes which exhibit greater radiosensitizing properties in hypoxia may be diveded into three classes: (1) cisplatin and related Pt complexes; (2) metal (mainly Pt, Ru, Rh) complexes of nitroaromatic radiosensitizers; (3) complexes of early transition metal series which may act by electron affinity or thiol depletion.

Most radiosensitization studies have been done with clinically used platinum compounds, namely cis-diamminedichloroplatinum(II) (cisplatin), carboplatin and iproplatin. When they are used in conjunction with radiation, they give beneficial results in vitro and in vivo studies, as well as in clinical trials [1, 29, 37, 51]. Some other neutral platinum complexes, possesing cis or trans configuration, were shown to be potentiators of radiation induced cell kill. The means by which the platinum complexes interact with radiation is not clear, but recent studies rule out an electron affinic and thiol depletion mechanisms. One assumes that the radiosensitizing ability of platinum complexes is related to their DNA binding [1, 29, 51]. Platinum compounds are not "true radiosensitizers" because they do not imply oxygen-mimetic or electron accepting mechanisms. Such compounds are proposed to be named modifiers or potentiators.

The metals which bind to DNA were suggested to be used as carriers for electron-affinic compounds. Some moderately promising results were obained in the complexes of platinum group metals with nitroimidazole ligands [1, 37, 51]. The non-platinum group metals have been investigated rather sparsely.

The emerging knowledge of tumor, cellular and molecular biology is providing a better understanding of the clinical results with the hypoxic cell sensitizers and novel approaches to radiation sensitization and protection [10].

Wiadomości Chemiczne, 1999, 53, 349.
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Gabriela Gałuszka, Maria Cieślak-Golonka

Instytut Chemii Nieorganiccznej i Metalurgii Pierwiastków Rzadkich, Politechnika Wrocławska, ul. Smoluchowskiego 23, 50-370 Wrocław

Chromium was discovered in 1797 by Louis Nicolas Vauqelin, a French chemist. The element has valences that range from (-2) to(+6). Under environmental conditions chromium in compounds exists in the trivalent and hexavalent state [1]. Chromium was recognized as an essential trace element in 1959 [28]. The essentiality of Cr(III) was established examining rats fed a Torula yeast diet which proved to be Cr-deficient. Rats developed glucose intolerance which could be reversed only by addition of Cr(III) to the diet. Chromium deficiency in humans results in symptoms comparable to those associated with diabetes and cardio-vascular diseases [16]. The Cr(III) complexes potentiating the insulin action was called GTF (glucose toleranse factor). The yeast GTF has been found to be a low moleclar weight molecule comprised of Cr(III), nicotinic acid, glycine, glutamic acid and cysteine. Among the several possible mechanisms by which GTF migth act, in vivo and in vitro results suggest that the most likely mechanism is a direct enhancement of the insulin activity via facilitating its bonding to cellular receptors [29]. As Cr(III) was recognized as an essential element, dietary intake has been found to range from 13 to 56 mg [40]. However, in contrast to Cr(VI) it is still unanswered question on the level of Cr(III) toxicity [4]. Studies of Cr(III) cellular uptake have determined that much of the intracellular Cr(III) is associated with the nucleus. It has also been shown that Cr(III)-based supplements like Cr(III) picolinate can cause chromosome aberrations in human lymphocytes (Tab. 1). The bioinorganic chemistry of Cr(III) ion is based on investigation of numerous Cr(III) complexes with ligands of biological relevance [1]. With few exceptions, they are six coordinate with the main characteristic of relative kinetic inertness in aqueous solutions.This, for example, rules out the possibility of chromium presence in the enzyme activity centre. Being a hard Lewis acid chromium(III) has an affinity towards oxygen and nitrogen donor ligands. There are several monomeric and dimeric species which may serve as models for GTF (Tab. 2, Fig. 4). As for over 30 years the investigators tried to isolate GTF without success, the view of non-essentiality of this ion received more support [10, 32, 36]. Recently, a candidate for the biologically active form of chromium, low molecular weight subsance (LMWCr) has been isolated by Yamammoto et. al. [69]. LMWCr is an oligopeptide with the molecular weight approximately 1500 which binds 4 chromium ions per molecule [Tab. 3]. The oligopeptide comprises of glycine, cysteine, glutamate and aspartate. Among various model compounds (Fig. 4) the trimer [Cr3O(O2CCH2CH3)6(H2O)3] was found to be active and was proposed for a treatment for adult-onset diabetes [73].

In conclusion, it appears very likely that four decades of intensive research on biological chromium resutlted in finding the answer to the question on the essentiality of this element. The "new GTF", i.e. the active chromium containing species, primarily functions as the activator of insuline receptors whereas the "old GTF" may serve rather as a readily absorbed chromium dietary supplement.

Wiadomości Chemiczne, 1999, 53, 379.
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Jan Kowalski, Jolanta Płoszyńska, Andrzej Sobkowiak

Ketedra Chemii Ogólnej i Elektrochemii, Wydział Chemiczny, Politechnika Rzeszowska, 35-959 Rzeszów

The preparation of 2-methyl-1,4-naphthoquinone (menadione) is a chaleting problem in catalysis research. This reaction is the key step in the synthesis of vitamin K and its derivatives.

The preparation of naphthoquinonea usually requires the direct oxidation of arenes by stoichiometric quantities of chromic acid/sulfuric acid [3-6]. The reaction can be also achieved by the use of Ce(IV) compounds and other transition metal compounds as oxidants [7-11] and with hydrogen peroxide [13, 14]. The other approach is to use Diels-Adler reaction between 1,3-butadiene and p-benzoquinone with the subsequent oxidation of the adduct formed [20, 21]. The indirect electrolysis with ruthenium compounds and dichromate as mediators were also applied in the process [25, 26]. In the previous work [34] we reported that the electrochemical oxidation of 2-methylnaphthalene in glacial acetic acid gives monoacetates, mainly 2-methylnaphthalene-1-acetate, but 2-methylnaphthalene-1,4-diacetate and 2-methyl-1,4-naphthoquinone were also formed This prompted us to investigate the electrochemical behavior of 2-methylnaphthalene-1,4-diacetate [38]. It is shown that the electrochemical oxidation of the compounds in glacial acetic acid yields 2-methyl-1,4-naphthoquinone as a sole product. The process is irreversible and diffusion controled. The material and current yields of the process are 94% and 99%, respectively.

Wiadomości Chemiczne, 1999, 53, 401.
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Zdzisława Nowakowska, Elżbieta Wyrzykiewicz

Zakład Spektrometrii Masowej Związków Organicznych, Wydział Chemii, Uniwersytet im. A. Mickiewicza, ul. Grunwaldzka 6, 60-780 Poznań

The essential biological importance of uracil and its thio-derivatives, as well as the relatively small size of the parent uracil molecule, have motivated a number of experimental and theoretical studies of this species. There are many axamples of biological processes in which the knowledge of the relative stability of different tautomers of one molecule can be very helpful in understanding the molecular mechanism involved.

Tautomerism of pyrimidine bases has been studied extesively in the past decades. Both theoretical [1-3] and experimental [3, 4] efforts have been directed toward the prediction of the molecular structure and properties of possible tautomers. 2-Thiouracil and 4-thiouracil can exist in six tautomeric forms with completed cyclic conjugation (aromatic tautomers). Non-ring conjugated tautomers also exist, but are likly to be little importance [5, 6]. 2-Thiouracil and 4-thiouracil can form four mono O-, S- or N-methyl derivatives, each of which can exist in three tautomeric forms. It has been realized that the relative population of these forms strongly depends on the environment [7]. In particular, the form dominating in the gas phase, or in the nonpolar solvents, may completely disappear in the crystalline state, or in the polar solvents and may be repleced by another tautomeric form. Theoretical calculations based on the quantum mechanical principles may certainly help to resolve the question of the relative stability of various tautomeric forms of thiouracils and to predict the relative gas-phase abundances of those forms. Because of the considerable size of thiouracils by quantum mechanical standard, only semiempirical quasi- ab initio methods have been applied so far.

Crystallographic studies of nucleosides and nucleobases and their derivatives are informative [8, 9] and can be used as a basis for the theoretical evaluation of their electronic structures by a quantum-mechanical approach [10, 11].

Wiadomości Chemiczne, 1999, 53, 415.
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Ignacy Z. Siemion

Wydział Chemii Uniwersytetu Wrocławskiego, ul. F.Joliot-Curie 14, 50-383 Wrocław

Wiadomości Chemiczne, 1999, 53, 425.
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Stanisław Olszewski

Instytut Chemii Fizycznej PAN, ul. Kasprzaka 44/52, 01-224 Warszawa

Wiadomości Chemiczne, 1999, 53, 439.
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B. Baranowski

Instytut Chemii fizycznej P.A.N, 01-224 Warszawa, ul. Kasprzaka 44/52

40 years ago the first two papers were describing the electrochemical preparation of solid nickel hydride [1, 2]. The sequence of events is presented, which led to this discovery [4, 1, 2], starting from a diffusion anomaly [4], caused by a non-uniform distribution of hydrogen in nickel cathodes. The late discovery of nickel hydride, as compared to palladium hydride discovered in 1866, is due to two reasons: a.) the limited penetration depth of nickel hydride [1, 2] Fig. 1 and b.) the high activity of gaseous hydrogen, necessary for a direct synthesis from the elements [21, 23, 25, 29]. This required the construction of a new high pressure equipment (Fig. 3), necessary for high pressures of gaseous hydrogen of the order 104 bar at room temperature [23, 25, 27-30]. These devices enabled not only the measurements of isotherms of formation and destruction of nickel hydride (Fig. 4) [29, 30], but also its kinetics under near equilibrium conditions [41, 21]. The thermodynamics of nickel hydride [23, 33, 34] is characterized, and the magnetic [45-50] and electronic properties are mentioned [51-58]. The new high pressure technique was the ladder for the discovery of superconductivity in palladium hydride [66, 67], as well as the way for preparation of new hydrides [68-72]. Some review articles are mentioned [71-79].

Wiadomości Chemiczne, 1999, 53, 445.
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Beata Liberek and Zygfryd Smiatacz

Wydział Chemii, Uniwersytet Gdański, ul. Sobieskiego 18, 80-952 Gdańsk

The article presents the methods of synthesis, properties and applications of hydroxyimino derivatives of pyranoses and pyranosides. Sugar oximes possessing hydroxyimino group at first, second, third or fourth carbon atom of the pyranoid ring are well know. Here, we focus on the 2-deoxy-2-hydroxyimino derivatives of saccharides, because of the interest they have received. It is due both to the ease in preparation of 2-hydroxyimino sugars and their utility as substrates in synthesis of many important mono- and oligosaccharides structures.

The chemistry of the 2-deoxy-2-hydroxyimino sugars was mostly investigated by R. U. Lemieux and F. W. Lichtentheler.

Lemieux at al. [2,4] worked out a general method of synthesis of 2-hydroxyimino-D-glycopyranosides, which was higly a-stereoselective (nitrosyl chloride method). The addition of nitrosyl chloride to an acetylated glycal led to the formation of a dimeric adduct of O-acetyl-2-deoxy-2-nitrozo-a-D-glycopyranosyl chloride, which reacted with the alcohol to afford a O-acetyl-2-deoxy-2-hydroxyimino-a-D-glycopyranoside. The derivatives of 2-deoxy-2-hydroxyimino glycosides were modified at C-2 to afford 2-acetamido-2-deoxy-a-D-glycopyranosides [10,11] and a-D-glycopyranosides [5-9], respectively.

Jeanloz [13], Van Heeswijk [15], Heyns [16], Paulsen [17], and Mallams [18-22] have employed a nitrosyl chloride pathway to the synthesis of some important biological compounds. Unfortunatelly, usage of more sophisticated donors or acceptors caused the reaction to be less stereoselective.

Lichtenthaler at al. [24-37] elaborated a different methodology of the systhesis of the derivatives of sugars with 2-deoxy-2-hydroxyimino structure. It starts with the conversion of starting saccharide into its 2-hydroxyglycal ester, followed by the three-step sequence hydroxylaminolysis ® benzoylation ®photobromination, which provides 2-deoxy-2-hydroxyimino-a-D-glycopyranosyl bromide, an useful synthetic intermediate in Koenigs-Knorr type glycosylation.

Other methods of synthesis of hydroxyimino sugars consist both in reaction of the corresponding keto-derivative with hydroxylamine [38-45] or reaction of the suitable glycosyl bromide with alkylcobaloxime [49-51].

Nitrosyl chloride pathway was employed to the synthesis of N- and O-glycopyranosides with 2-deoxy-2-hydroxyimino structure of some amines and a-hydroxy-L-amino acid derivatives [54-62]. Obtained N- and O-glycosides were modified in many ways [63-66].

Wiadomości Chemiczne, 1999, 53, 461.
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Krzysztof Winkler

Instytut Chemii, Uniwersytet w Białymstoku Al. Piłsudskiego 11/4, 15-443 Białystok

Fifteen years after the discovery of fullerenes the volume of work in the field of fullerene chemistry continues to expand at an ever-increasing rate. The electrochemical behavior of C60 and other fullerenes received considerable attention. Up to six reversible, one-electron reduction steps have been observed for C60 and C70, while only one, oxidation step at quite positive potential, has been detected. These results are in accordance with the theoretical predictions based on the energy levels distribution in fullerene molecules. The electron transfer processes are coupled with the ion-pair formation reactions. Heterogeneous reduction of C60 and C70 can be classified as an adiabatic process. The electrochemical behavior of higher fullerenes has been also reported. A significant differences in oxidation and reduction potentials have been observed for isomers of higher fullerenes.

Electrochemical properties of fullerene derivatives depend on a degree of inductive effect and the number of adducts bonded to the fullerene cage. The electrochemical properties of five distinct types of derivative have been studied: metallofullerenes, inclusion complexes, transition metal complex adducts and inorganic and organic group adducts.

Metallofullerenes are the derivatives where the fullerene encapsulates a metal atom within the closed carbon cage structure. The change of the electronic structure of the fullerene unit due to the transfer of electrons from metal atoms into the carbon claster results in a completely new electrochemical behavior that is different from that of all other fullerene derivatives and fullerenes themselves. Metallofulerenes are more easily to oxidize. Also, the first reduction process requires less energy than empty fullerene analog. A significant differences in electrochemical properties of isomers have been also observed.

The electrochemistry of inclusion complexes of C60 with cyclodextrin and calixyrene is similar to this observed for uncomplexated fullerenes. The complexation of C60 results in the slight shift of reduction potential toward more negative values. The charge transfer processes are usually coupled with dissociation of the complexes. The solubility of the inclusion complexes in water and other polar solvents is the main advantage of these systems.

For transition metal complexes derivatives of buckminsterfullerene the electrochemical properties are combination of the redox properties of fullerene cage and metal complex units. The reduction processes are attributed to the fullerene localized reduction since the oxidation takes place on the metal centers. It was found that coordination of metal shifts the reduction potential of C60 fragment to more negative potentials. The electron affinity decreases linearly with the substantial addition of each metal fragment. Electron transfer to these metal-C60 complexes causes dissociation of the metal units. The oxidation potentials are strongly affected by the metal nature.

The electrochemistry of organofullerenes is very similar to C60 with a negative shift in the reversible reduction potentials mainly due to the inductive effect of the adducts. Commonly, a three, five or six membered rings outside the fullerene cage are formed by 1,2 addition of organic compounds. For five member ring derivatives the electrochemically induced cyclopropane - fulleroid isomerization has been observed.

Among the C60 containing dimers only C120O exhibits the electrochemical behavior indicating the electronic communication between fullerene units. C120 dimer is unstable and after first reduction step decomposes with the formation of neutral C60 and C60- ion.

This paper reviews the results of the investigation of electrochemical properties of fullerenes and their derivatives.

Wiadomości Chemiczne, 1999, 53, 479.
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Bogusława Tendaj, Krystyna Marczewska-Boczkowska

Katedra Elektrochemii, Wydział Elektryczny, Pollitechnika Lubelska, ul. Nadbystrzycka 38A, 20-618 Lublin

The structure and features of different systems of fuel cell depend on the nature of used electrolyte. The main fuel cells are as follows: alkaline fuel cells (AFCs), phosphoric acid fuel cells (PAFCs), solid oxide fuel cells (SOFCs) and proton exchange membrane fuel cells (PEMFCs) [2, 5]. Fuel cell reactions are listed in Tab. 1. Intense research programs are now realized in order to utilize PEMCs for transportation applications. The structure of PEMCs is shown in Fig. 1. [9].

In PEMCs the anode and cathode reactions occur on the platinum or platinum alloy electrocatalyst surfaces; the electrocatalyst is usually supported by carbon. Electrode surfaces contain 1 mg per cm2 or less [11]. Layers (thickness 180 mm or less) of perfluorinated sulphonic acid ionomers (e.g. NafionÒ) are used as electrolyte membranes [16].

The overpotential of the pure hydrogen supplied PEMC's anode is low. the contamination of hydrogen by CO restricts the performance of the anode, because CO acts as an anode catalyst poison - Fig.5 [1]. Methanol-fed anodes operate at overpotentials as high as 0.3-0.4 V [22]. Oxygen reduction proceeds with rapid fall-off cathode potential. As current density is increasing, formed water disturbs the diffusion of oxygen to the catalyst surfaces [24].

The specific conductivity of the ionomer increases proportionally to the content of absorbed water [26]. The desired water content in membranes of fuel cells is usually supported due to humidification of reactant gases [28]. Reactant gases do not require external humidification, if very thin Nafion membrane (thickness 50 mm) cantain inside highly dispersed platinum. Pt crystallites catalyse the recombination of the crossover H2 with O2. The generated water humidifies the PEMC's membrane adequately [32].

The PEMCs are combined in stacks. They operate in the potential range linearly dependent on current densities of fuel cell electrodes - Fig. 10 [24]. The data [9, 21, 39, 40] collected in Tab. 2 shown that operating voltages of fuel cells in stacks are about 0.7 V. The efficiences of PEMCs, that operate at variables given in Tab. 2, are 40-50% [42].

Wiadomości Chemiczne, 1999, 53, 529.
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Jan Kalembkiewicz; Elżbieta Sitarz-Palczak

Wydział Chemiczny, Politechnika Rzeszowska, ul.Powstańców Warszawy 6, 35-959 Rzeszów

The present paper gives an overview of the literature concerning the speciation of manganese in soil and solutions.

The problem of speciation was approached in two different aspects: as a problem of the separation of a definite chemical form of metal in the material under investigation with the simultaneous protection of separateness conditions of the residual forms and as problem of selecting an analytical method of determination of manganese in the prepared material, generally in solution.

Possibilities of separation and determination of some forms of manganese: Mn(II), Mn(III) and Mn(IV) have been described in the literature in the last years. Different analytical methods have been proposed, spectrometry techniques above all; and among other things, the Atomic Absorption Spectrophotometry (AAS) [12], spectrofluorometry [17], X-ray fluorescence analysis [18] and spectrophotometric analysis [19] were used for detection.

This work also reviews the mineralization method concerning manganese total in soils, rocks and sediments; likewise the prospects of the determination of Mn total content. So far, most investigations have examined the overall concentration of Mn total in soils and sediments, for example by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) [25, 26, 31-33] and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) [29].

The described literature data indicate dynamic and multidivectional development of research work in the field of speciation of manganese in soil and solutions in last years.

Wiadomości Chemiczne, 1999, 53, 549.
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Józef Ziółkowski

Wydział Chemii Uniwersytetu Wrocławskiego, ul. F.Joliot-Curie 14, 50-383 Wrocław

The origin and history of "Wiadomości Chemiczne" ("Chemical News", the journal of Polish Chemical Society) were presented on occasion of its 50th anniversary.

Wiadomości Chemiczne, 1999, 53, 563.
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Notatki chaotyczne. XXI. O JĘZYKU CHEMII

Ignacy Z. Siemion

Wydział Chemii Uniwersytetu Wrocławskiego, ul. F.Joliot-Curie 14, 50-383 Wrocław

Wiadomości Chemiczne, 1999, 53, 579.
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Jerzy Narbutt

Zakład Radiochemii, Instytut Chemii i Techniki Jądrowej ul. Dorodna 16, 03-195 Warszawa

The perspective for radiochemistry one hundred years after its birth has been discussed in connection with the key role of this discipline in the development of science creating the modern world in the first half of the XX century. The recession in nuclear sciences, observed in the last three decades, seems to be coming to the end. Greatly intensified work focused on the treatment and safe disposal of nuclear wastes and on reduction of radioactive pollution of the environment, the rapidly developing nuclear medicine, recent discoveries in nuclear chemistry and physics are a challenge for radiochemists, and opens a broad field for research.

Wiadomości Chemiczne, 1999, 53, 601.
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Adam Sobiczewski

Instytut Problemów Jądrowych im. A. Sołtana. ul. Hoża 69, 00-681 Warszawa

Recent theoretical and experimental studies on nuclei of heaviest elements are shortly described. Much attention is paid to the problem of their stability (decay modes and respective half-live). Role of the shell structure of the nuclei in this stability is stressed. Methods of synthesis, detection and identification of them are also discussed. Prospects of a further extention of the periodic table of elements are considered.

Wiadomości Chemiczne, 1999, 53, 615.
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Aleksander Bilewicz

Zakład Radiochemii, Instytut Chemii i Techniki Jądrowej. ul. Dorodna 16, 03-195 Warszawa.

The chemical properties of transfermium elements are reviewed. The specific aspects of chemical operation with single atoms were briefly discussed. The chemical behaviour of mendelevium, nobelium and lawrencium are similar to that of the heaviest actinides. Only one difference is the stabilization of +2 oxidation state in Md and No compounds. The chemical properties of the first three transactinide elements were compared with the properties of their lighter congeners in groups 4, 5 and 6 of the Periodic Table. The experimental results were compared with theoretical calculations. Special attention was paid to the influence of relativistic effects on the properties of the heaviest elements and their compounds.

Wiadomości Chemiczne, 1999, 53, 631.
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Leszek Królicki

Zakład Medycyny Nuklearnej i Rezonansu Magnetycznego, Wojewódzki Szpital Bródnowski. Kondratowicza 8, 03-242 Warszawa

Nuclear Medicine plays a significant role in modern medicine as a diagnostic and therapeutic method. It is defined as the use of radioactive materials for the diagnosis and treatment of patients. Each examination defines a special function of the investigated organ. This is a crucial difference between radioisotopic and other methods. The progress in nuclear medicine depends on two factors: technical modifications of gamma-cameras and new radiopharmaceuticals. The future of this discipline will depend on the efforts of the teams of physicians, chemists and technologists.

Wiadomości Chemiczne, 1999, 53, 647.
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Krystyna Samochocka

Wydział Chemii Uniwersytetu Warszawskiego, ul. Żwirki i Wigury 101, 02-089 Warszawa

Radionuclides and radiopharmaceuticals play the key role in nuclear medicine, both in diagnostics and therapy. Incorporation of radionuclides into biomolecules, and syntheses of radiolabelled compounds of high biological selectivity are a task for radiochemists working in the multidisciplinary field of radiopharmaceutical chemistry. The most commonly used radionuclide, 99mTc, owes this popularity to its both nearly ideal nuclear properties in respect to medical imaging, and availability from inexpensive radionuclide generators. Also numerous other radionuclides are widely used for medical imaging and therapy. Labelling of biomolecules with radioiodine and various positron emitters is getting increasingly important.

This review describes some chemical and radiochemical problems we meet while synthesizing and using 99mTc-radiopharmaceuticals and radioiodine-labelled biomolecules. Also represented are the recent developments in the design and use of the second generation radiopharmaceuticals based on bifunctional radiochelates. Several principal routes of fast chemical synthesis concerning incorporation of short-lived positron emitters into biomolecules are outlined as well.

The search for chemical structures of high biological selectivity which would be activated by slow neutrons, is related to the method of Neutron Capture Therapy, an interesting option in nuclear medicine.

Wiadomości Chemiczne, 1999, 53, 661.
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Zbigniew Jaworowski

Centralne Laboratorium Ochrony Radiologicznej. ul. Konwaliowa 7, 03-194 Warszawa

Results of determination of natural radionuclides, fission products and heavy metals in contemporary and pre-industrial ice from 14 glaciers in Southern and Northern Hemisphere, and in aerosols collected during three decades from seven altitudes between 0 and 15 km in the troposphere and stratosphere, were used for determinations of fluxes of man-made and natural pollutants into the global atmosphere. For these determinations 137Cs from nuclear explosions and natural 210Pb were used as tracers. Concentrations of natural radionuclides and heavy metals in ice deposited before industrial revolution were higher than in contemporary precipitation preserved as firn in high mountain and polar glaciers. This was due probably to volcanic activity, which was higher before the first part of the 20th century. Man-made contribution to the total atmospheric flux is now 3.5% for 226Ra, 12% for U, 7.4% for Pb, 0.11% for Cd, 62% for V and 5.8% for Hg. The mass of annual global wet precipitation, determined for the first time with radioactive tracers, is 5.7 x 1017 kg. In Poland, the lowest concentration of stable lead in human bones is now in highly industrialized southern districts. Lead level in medieval human bones from these districts reached up to 370 mg/g. Its current average level in inhabitants of southern Poland is 3.5 mg/g, i.e. similar as 1800 years ago.

Wiadomości Chemiczne, 1999, 53, 701.
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Wojciech Dembiński

Instytut Chemii i Techniki Jądrowej 03-195 Warszawa, ul. Dorodna 16

Recent discoveries in the isotope chemistry are presented and discussed. In addition to classic mass (or vibration) isotope shift, the nuclear field shift must be taken into consideration. The direction of nuclear field shift can be opposite to that of mass effect and its absolute value can be higher. The nuclear field shifts influence the values of the separation factors of the even-odd isotope pairs as well as those of even-even isotope pairs (even and odd refer to the number of neutrons in these nuclides). The impact of the new ideas to the understanding of isotope chemistry of the heavier elements is discussed from the historical perspective.

Wiadomości Chemiczne, 1999, 53, 725.
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Anna Czerwińska, Andrzej Czerwiński

Wydział Chemii, Uniwersytet Warszawski. ul. Pasteura 1, 02-093 Warszawa

The evolution of knowledge on radioactivity and radioactive elements has led not only to the development of nuclear science, but it has also created new branches in physics and chemistry. Although Polish scientists contributed a lot into the development of nuclear chemistry and physics, these subjects are at present only facultative at our universities. As a result the low level of knowledge about radioactivity in our society will still decrease. This is not a good forecast for Polish nuclear power programme. The opposite trends can be seen in educational programmes of the European Union countries and the USA. Information about radioactivity and nuclear power engineering is of great importance for authors of schoolbooks on chemistry and physics. The EU countries have considered radioactivity and means of protection against it as one of the fundamental problems of modern sciences. The appropriate knowledge has been accepted as a standard. New school textbooks have been published both for teachers and students on all levels of advancement in the process of teaching.

The centenary of the discovery of radium and polonium by our compatriot Maria Skłodowska-Curie is the unique moment to rise interest in this discipline and to make education authorities aware of its importance. The evolving knowledge of radioactivity and nuclear power engineering should take a significant part in school and university curricula for chemistry and physics classes.

Wiadomości Chemiczne, 1999, 53, 745.
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Piotr Skurski1 , Maciej Gutowski2

1 Wydział Chemii Uniwersytetu Gdańskiego, ul. Sobieskiego 18, 80-952, Gdańsk, Department of Chemistry, University of Utah, Salt Lake City, UT 84112, USA
2 Materials Resources, Pacific Northwest National Laboratory, Richland, WA 99352, USA Wydział Chemii Uniwersytetu Gdańskiego, ul. Sobieskiego 18, 80-952, Gdańsk

Recent photodetachment, photoelectron spectroscopy, and charge transfer collision studies of dipole-bound anions revealed deficiencies in theoretical predictions based on the electrostatic model. The experimental electron binding energies were much larger than theoretical estimations obtained at the Koopmans' theorem or self-consistent field levels. Moreover, photoelectron spectra of dipole-bound anions frequently display vibrational structure whereas a common view was that a dipole-bound anion may be regarded as a neutral molecule with the excess distant electron tethered so weakly to the dipole that the equilibrium geometries of the neutral and the anion are practically the same and therefore no vibrational structure was anticipated on the basis of Franck-Condon factors. In this review we summarize our recent work on electron binding energies in dipole-bound anions as well as on molecular relaxation upon electron attachment. We demonstrate that electron correlation effects contribute significantly to electron binding energies. In particular the dispersion interaction between the excess electron and electrons of the neutral molecule was recognized as a sizable stabilizing contribution. The molecular relaxation upon electron attachment was found to be significant and clearly detectable for hydrogen bonded clusters and small but still noticeable for some valence bonded polar molecules.

Wiadomości Chemiczne, 1999, 53, 759.
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Jerzy Meller, Marek Zaidlewicz

Zakład Chemii Organicznej. Wydział Chemii, Uniwersytet Mikołaja Kopernika, ul. J. Gagarina 7, 87-100 Toruń

Catalytic hydroboration, a rapidly expanding branch of the hydroboration, is reviewed. Catecholborane is the hydroborating agent most often used in catalytic hydroboration. Rhodium, iridium, ruthenium, palladium and other transition metal compounds, including lanthanide iodides, are used as catalysts. The mechanism of catalytic hydroboration is discussed and schemes showing the catalytic action of Wilkinson's catalyst and lanthanide complexes are presented. The reactivity of alkenes in catalytic hydroboration decreases with the increasing substitution of the double bond. Generally, region-selectivities of the catalized and uncatalyzed hydroboration of terminal alkenes and alkynes are similar, the boron atom being placed preferentially at the terminal position. The catalyzed reaaction makes possible higher selectivity by proper choice of the catalyst. However, the catalytic hydroboration of styrene and its derivatives may be directed to form preferentially the Markovnikov type addition products. Stereoselectivities of the catalyzed and uncatalyzed hydroboration of allylic and homoallylic derivatives are often opposite. The catalytic monohydroboration of conjugated dienes and enynes provides the 1,2- and 1,4-addition products depending on the catalyst. Enantioselective catalytic hydroboration of prochiral olefins is described and selected reactions providing products of 1-96 % ee are tabulated. Examples of applications of the catalytic hydroboration to the synthesis of natural products are given.

Wiadomości Chemiczne, 1999, 53, 787.
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Andrzej Huczko, Hubert Lange, Ewa Całko

Wydział Chemii, Uniwersytet Warszawski, 02-093 Warszawa, ul. Pasteura 1

An astonishing scientific interest, embodied in over 15 000 research articles so far, has been encountered since 1985 when fullerenes were discovered. From new superconductors to a rich electrochemistry and reaction chemistry, fullerene nanostructures continue to excite the scientific world, and new findings continue at record pace. This review presents many examples of the biochemical activities of fullerenes and derivatives, e.g. cytotoxic activity, selective DNA cleavage and antiviral activity against HIV.

We also present some results of our testing which show that, despite its chemical and biochemical activity, fullerene matter does not present any health hazard directly related to skin irritation and allergic risks.

Wiadomości Chemiczne, 1999, 53, 811.
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Krzysztof Winkler and Marta E. Płońska

Instytut Chemii, Uniwersytet w Białymstoku

This paper reviews the results of the investigation of electrochemical properties of fullerenes and their derivatives in solid state. These systems can be devided into three groups:

The electrochemical behaviour of crystalline films of fullerenes is very different that of dissolved species. The method of the film preparation strongly influences the redox properties and morphology of the film. Fullerene films are composed of small crystallities. The layers grown upon vapour deposition and electrocrystallisation are more uniform than the solution-coast films.

The redox behaviour of crystalline fullerene films in polar solvents is mainly affected by the size of supporting electrolyte cations. For small cations of alkali and alkaline-earth metals a rapid deterioration in the electrochemical properties of fullerene films is observed during repeated potential cycling. This behaviour of the layer is attributed to the formation of an electrochemically inactive cation intercalated compound or dissolution of the fullerene salt. The manipulation of the time window of experiment and the solvent nature can favour one of the above processes over the other.

In electrolytes with large cations (tetraalkilammonium and metal complexes cations) the reversible intercalation is observed. The reduction of C60 and layer doping with counterions result in changes of the crystallographic structure of the film microcrystals. In opposite to voltammetry of dissolved fullerenes, which exhibit multiple chemically and electrochemically reversible reduction curves, only the first two reductions of the film show chemical reversibility. The extending of the cathodic scan beyond the second reduction of the film results in the film dissolution.

The voltammetric behaviour of LB films and SAMs containing fullerenes and their derivatives are less influenced by the medium. A much smaller structural reorganization upon electrochemical reactions is observed. Redox properties of the fullerene moieties in these structures are similar to these observed in solution. Tightly packed C60 containing self-assembled layers exhibit resistive behaviour due to the resistant to ion incorporation.

Significant progress has been made in the electrochemically induced polymerisation of fullerenes and their derivatives. The oxidation of polythiophene with covalently bound moieties results in the formation of "charm bracelet" type conjugated polymer on the electrode surface. Fullerene unites incorporated into the solid structure retain their electrochemical characteristic. The redox active fullerene based films can also be formed by the electrochemical reduction of either the fullerene epoxide or of a mixture of C60 and O C2 in toluene/acetonitrile solution. The polymerisation is initiated by the active radical dianion C60O2-. The proposed structure for the polymer is ...-C60O-C60O-C60O-.... These films appear to be related to the conducting polymers such as polyaniline, polypyrrole and polythiophene, that are generally obtained by oxidation of corresponding monomers.

The polymeric network can also be formed through a two-component polymerisation that utilises the formation of covalent bonds between transition metal complexes and fullerenes. These films are insoluble in common organic solvents and adhere strongly to the electrode surface. They display very stable redox behaviour due to the presence of fullerene moieties in their structures. A significant decrease in resistivity in the potential region in which it is reduced is also observed. The electrochemical switching between the doped (conducting) and undoped (nonconducting) states involves both electron and ion transport within the film. The overall control of charge percolation through electroactive material is governed by the transport of ions. Laser ablation of some of these electrochemically formed layers results in the formation of C59-2nM (M = Pt and Ir) clusters.

Wiadomości Chemiczne, 1999, 53, 823.
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Wanda Radecka-Paryzek

Wydział Chemii, Uniwersytet im. Adama Mickiewicza, ul. Grunwaldzka 6, Poznań

Inorganic self-organisation involves the spontaneous generation of well-defined supramolecular architectures from metal ions and organic ligands. The basic concept of supramolecular chemistry is a molecular recognition. When the substrate are metal ions, recognition is expressed in the stability and selectivity of metal ion complexation by organic ligands and depends on the geometry of the ligand and on their binding sites that it contains. The combination of the geometric features of the ligand units and of the coordination geometries of the metal ions provides very efficient tool for the synthesis of novel, intriguing and highly sophisticated species such as catenanes, box structures, double and triple helicates with a variety of interesting properties. The article will focus on the examples of inorganic self-organisation involving the templating as a first step for the assembly of supramolecular structures of high complexity.

Wiadomości Chemiczne, 1999, 53, 871.
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Catalytic oxidation of soot from diesel engines

Włodzimierz Tylus

Instytut Technologii Nieorganicznej i Nawozów Mineralnych, Politechnika Wrocławska, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław

Catalytic cleaning of exhaust gas Otto engines is the well known technique, commonly used, particularly in the environment concerned countries. In the half of the eighties, successful implementation of three-way converters (TWC) generated a demand for catalysts for Diesel engines, to meet the increasing requirements of standards for gas emission from moto vehicles.

In those days the problem of reduction of emission of particulates from Diesel engines seemed to be easy for solution by filtration and periodical regeneration of the filters or filter-catalysts. However, the problem turned out to be surprisingly sophisticated. On the other hand, industry offered a new generation Diesel engines which met requirements of the American (1991, 1994) and European (Euro I - 1993) standards. One may have expected that futher development would continue in the some way. Once more the expectations faild. In 1998, the standards accepted by the European Community Countries for 1999/2000 and those expected for 2005/2008 leave no illusions about the need for application of Diesel gas coverters in the future.

The study is a review of the latest development in the field of conversion of Diesel exhaust gas in the context of the currently valid and future legal regulations. However, only catalytic aspects are discussed. The solutions presented comprise combustion of particulates in monolithic flow-through oxidation catalysts and in Diesel particulate filters (DPF) equipped with a catalytic oxidizing coatings, or with injection of easy flammable organic substances before the filter, or with catalytic metal-organic fuel additives. Chemical composition and dynamics of Diesel soot formation are described. Moreover, impact of Diesel particlates on human health is outlined.

Wiadomości Chemiczne, 1999, 53, 887.
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Tomasz Ganicz

Centrum Badań Molekularnych i Makromolekularnych PAN, ul. Sienkiewicza 112, 90-363 Łódź

Liquid crystalline (LC) networks are fast growing group of materials with many possible applications. They can be divided into lightly crosslinked polymers with elastic properties [1, 16-18, 26-31] and highly crosslinked networks with very high molecular order [21, 25, 32-37]. Most of them contain typical, anizotropic, rigid mesogenic units known for other LC materials, but some of them exhibit mesomorphic properties although they do not possess any such units [7, 40-42]. Typical mesogenic groups can be incorporeted into main chains [29-31] or side chains [1, 16-18, 20-23] of polymers or both [26-28].

The density of crosslinking of LC polymers is difficult to measure [21, 23, 44-49], and the effect of crosslinking on LC properties is still not clear [50-53].
Although LC elastomers possess very interesting mechanical properties [7, 12, 15, 18, 25, 55-59] they are still too expensive for any lage-scale applications.

Crosslinking of polymers in liquid crystalline state [58, 63] or applying mechanical stress [3, 12, 15, 59] to already crosslinked LC materials give unique possibility to achieve monodomain orientation of mesogens without any electric or magnetic fields.

The coupling between elastic and mesomorphic behaviour of LC elastomers leads to many useful properties like piezoelectricity [4, 68-72], second harmonic generation [76-78], opalescence [80, 81, 83] and good separation ability [85-87].

Wiadomości Chemiczne, 1999, 53, 905.
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Antoni Kozioł

Instytut Inżynierii Chemicznej i Urządzeń Cieplnych Politechniki Wrocławskiej ul. Norwida 4/6, 50-373 Wrocław

Chemical engineering is a typical applied branch of science, which is engaged in many different processes. Chemical engineering is not only a science discipline but also the art of matter transformation. The example of chemical engineering application is the scaling-up problem presented in Fig. 1. The main aim of the problem is the transition from the laboratory scale, where chemical reactions are considered, to large industrial scale where real processes are carried out. The structure of chemical engineering is shown pictorially in Fig. 2. The main pillars of the structure are physics, mathematics and economics, which are built on the ground of chemistry.

History of chemical engineering science begins at the end of XIX century. There were two different ways of chemical engineering development - the German way and the American way. The two World Wars had the great mutual effect on the development.

Firstly, chemical engineering was mainly empirical science. In the course of time it has become more sophisticated by introduction of the momentum, heat and mass transfer laws. There were many scientists and engineers who built the chemical engineering structure, for example Reynolds, Nusselt, Prandtl, Sherwood, Colburn, Dankwerts and others. Chemical engineering in Poland has been developed by professors: Hobler, Ciborowski, Serwiński, Ziołkowski and others.

The main branches of chemical engineering are: chemical reaction engineering, momentum transfer, heat transfer, mass transfer, simultaneous heat and mass transfer, bioprocess engineering and membrane processes.

There are many international, native and local chemical engineering organizations. The most important is AIChE - American Institution of Chemical Engineers. Many congresses, conferences and symposiums are held by the organizations. The research results are also published in various science and practical journals.

The future of chemical engineering may be seen developing in two directions - the filling of the so called "white blots" and working out new unknown processes.

Wiadomości Chemiczne, 1999, 53, 929.
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Ignacy Z. Siemion

Wydział Chemii Uniwersytetu Wrocławskiego, ul. F.Joliot-Curie 14, 50-383 Wrocław

Wiadomości Chemiczne, 1999, 53, 941.
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