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A new Cu(II) [12]metallocrown-4 pentanuclear complexe based on a Cu(II)-malonomonohydroxamic acid unit.
Autorzy
Rok wydania
2007
Czasopismo
Numer woluminu
31
Strony
1798-1805
DOI
10.1039/B701600J
Kolekcja
Język
Angielski
Typ publikacji
Artykuł
The first example of a Cu(II) [12]-MC-4 hydroxamic metallacrown compound containing a carboxyl group as a supporting donor function is described. The solution equilibria of malonomonohydroxamic acid (MACZ, H2L) with Cu(II) are investigated in aqueous solution using a combination of potentiometry, UV-vis absorption spectrophotometry, EPR spectroscopy and ESI mass spectrometry. Among the four complexes fitting the best speciation model ([CuL], [Cu5L4H−4]2−, [CuL2]2− and [CuL2H−1]3−), a pentameric metallacrown molecule of composition Cu : L = 5 : 4 predominates in solution over the pH 4 to 11 range, and the corresponding complex was isolated in the solid state. The crystallization of the complex [Cu5L4H−4]2− in the presence of [Cu(en)2(H2O)2]2+ cations resulted in the isolation of [Cu(en)2(H2O)2]n[Cu(en)2(H2O)(μ-H2O){Cu5(L4H−4)(H2O)3}2]n·20nH2O (1), whose crystal structure has been determined by X-ray analysis. The structure of 1 consists of centrosymmetric complex cations [Cu(en)2(H2O)2]2+, infinite complex anionic chains [Cu(en)2(H2O)(μ-H2O){Cu5(L4H−4)(H2O)3}2]n2n− and solvate water molecules. Within the complex anionic chains, the decanuclear double-decked bis([12]-MC-4) complex anions {Cu5(L4H−4)(H2O)3}24− are united by the [Cu(en)2(H2O)2]2+ complex cations due to the bridging function of the axial water molecule O(5). The magnetic behaviour of 1, studied in the temperature range 1.8–300 K, suggests the presence of both antiferromagnetic and ferromagnetic contributions to the observed magnetic susceptibility, resulting in a ground state of S = 2 per formula unit.
Adres publiczny
https://doi.org/10.1039/B701600J
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