Homo- and hetero-dinuclear metal complexes of bridging ligands containing phenol and azole moieties. Structure, spectroscopy, electrochemistry and magnetochemistry

Abstract

A series of phenoxo-bridged homo- and hetero-dinuclear complexes of 4-methyl-2,6-bis(5-methylpyrazol-3-yl)-phenol (H3L1) have been synthesized and characterized. Variable-temperature magnetic susceptibility measurements carried out for the homo-dinuclear complexes [Cu2(H2L1)2][ClO4]21, [Cu2(H2L1)(acac)2][ClO4]2, [Cu2(H2L1)(µ-OH)Cl2]3, [Ni2(H2L1)2(H2O)4][ClO4]24 and [Fe2(H2L1)4(µ-OH)2]·4H2O 7 have shown that in all the cases the dinuclear metal centres are antiferromagnetically coupled with the following values of the exchange coupling constant J: –242 (1), –55 (2), –170 (3), –24 (4) and –11 cm–1(7). The ESR spectra of the heterodinuclear complexes [ZnCu(H2L1)2][ClO4]2·2H2O 5 and [ZnMn(H2L1)2Cl2]6 have been examined. The 1H NMR spectra of the dicopper(II) complexes 1 and 2 are reasonably sharp and the isotropic shifts of 1 are relatively less compared to those of 2. The crystal structures of 7 and 2·CHCl3 have been determined. That of 7 comprises two edge-shared sterically non-equivalent FeO4N2 distorted octahedra. The structure of 2·CHCl3 consists of two nearly square-planar copper(II) centres supported by a phenoxide bridge. The cryomagnetic behaviour of two phenoxo-bridged dimeric iron(III) complexes derived from a bis(iminomethyl)triphenol and a bis(aminomethyl)triphenol have also been studied.