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Inne
Assembling novel heterotrimetallic Cu/Co/Ni and Cu/Co/Cd cores supported by diethanolamine ligand in one-pot reactions of zerovalent copper with metal salts.
Autorzy
Rok wydania
2004
Czasopismo
Numer woluminu
43
Strony
7868-7876
DOI
10.1021/ic048955w
Kolekcja
Język
Angielski
Typ publikacji
Artykuł
The three novel heterotrimetallic complexes [Ni(H2L)2][CoCu(L)2(H2L)(NCS)]2(NCS)2 (1), [Ni(H2L)2][CuCo(L)2(H2L)(NCS)]2Br2·2H2O (2), and [CuCoCd(H2L)2(L)2(NCS)Br2]·CH3OH (3) have been prepared using zerovalent copper; cobalt thiocyanate; nickel thiocyanate (1), nickel bromide (2), or cadmium bromide (3); and methanol solutions of diethanolamine in air. The most prominent feature of the structures of 1 and 2 is the formation of the “pentanuclear” aggregate {[Ni(H2L)2][CoCu(L)2(H2L)(NCS)]2}2+ made up of two neutral [CoCu(L)2(H2L)(NCS)] units and the previously unknown cation [Ni(H2L)2]2+ “glued together” by strong complementary hydrogen bonds. With Cd2+ instead of Ni2+, a different structure is obtained: the [CoCu(L)2(H2L)(NCS)] unit is now linked to the Cd center through coordination of the oxygens of L groups on the Co atom to form the discrete heterotrimetallic molecular species 3. Cryomagnetic measurements of the compounds show that, in all cases, the magnetic behavior is paramagnetic; the polycrystalline EPR spectra contain signals due to monomeric copper species only. At the same time, the EPR spectra of frozen DMF and methanol solutions of 1−3 reveal the presence of triplet-state species that can be generated only by a coupling of the Cu2+ centers within a dimer. The species responsible for the appearance of transitions within the triplet state are thought to be Cu(II) dimeric centers formed by aggregation of two {CuCo(H2L)(L)2} fragments of 1−3 present in solution. The residual monomeric spectra in the g ≈ 2 region are indicative of the existence of an equilibrium in solution between the dimeric and monomeric Cu(II) centers in aggregated and free {CuCo(H2L)(L)2} fragments, respectively, with varying degrees of stability. The fragmentation process of 1−3 in solution was screened by electrospray ionization mass spectrometry.
Słowa kluczowe
Copper, Ions, Ligands, Metals, noncovalent interactions
Adres publiczny
https://doi.org/10.1021/ic048955w
Strona internetowa wydawcy
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