Wydział Chemii

Anna Berlicka

Lechosław Latos-Grażyński

2009

Inorganic Chemistry

48

7922-7930

10.1021/ic900973d

Naukowa

Angielski

Artykuł

The paramagnetic six-coordinated iron(II) 3,8,13,18-tetraaryldithiaethyneporphyrin (ES₂P)₂Fe^II complexes of the double-decker type have been synthesized using iron pentacarbonyl as the metal source. The complex contains two porphyrinic macrocycles coordinated to the iron(II) in the sandwich-like fashion as determined by ¹H NMR. The ¹H NMR spectra of (ES₂P)₂Fe^II have been examined in detail in the 180 − 366 K temperature range. Functional group assignments based on the selective deuteration, analysis of T₁ relaxation times and the NOESY experiment have been made at 313 and 210 K. The variable temperature ¹H NMR studies allowed to elucidate the dynamic behavior of (ES₂P)₂Fe^II which involves rotation of dithiaethyneporphyrin rings around the metal ion. To account for the observed conformational rearrangements a cube, a square antiprism or a distorted triangular dodecahedron structure of (ES₂P)₂Fe^II defined by the mutual orientation of two macrocyclic ligands have been considered. The six vertexes of a polyhedron are occupied by two pyrrolic nitrogens and four sulfur atoms, while two remaining vertexes are filled with two ethyne moieties. The dynamic rearrangements of (ES₂P)₂Fe^II involve two enantiomeric couples of four fundamental staggered rotamers. The fast dynamic process engaging rotation of two dithiaethyneporphyrin ligands has been detected at 298 K. At low temperature range two rotamers have been identified as they presented the individual spectroscopic patterns. Considering the multiplicity of resonances the fast rotational oscillation involving one enantiomeric pair has been observed at 210 K, while all other processes are slow. The exchange between diastereomers has been confirmed at 210 K as the EXSY correlations linking diastereomeric resonances have been detected at the NOESY map.

https://doi.org/10.1021/ic900973d

https://www.acs.org/content/acs/en.html