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

A series of phenoxo-bridged homo- and hetero-dinuclear complexes of 4-methyl-2,6-bis(5-methylpyrazol-3-yl)-phenol (H(3)L(1)) have been synthesized and characterized. Variable-temperature magnetic susceptibility measurements carried out for the homo-dinuclear complexes [Cu-2(H(2)L(1))(2)][ClO4](2) 1, [Cu-2(H(2)L(1))(acac)(2)][ClO4] 2, [Cu-2(H(2)L(1))(mu-OH)Cl-2] 3, [Ni-2(H(2)L(1))(2)(H2O)(4)][ClO4](2) 4 and [Fe-2(H(2)L(1))(4)-(mu-OH)(2)]. 4H(2)O 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(H(2)L(1))(2)][ClO4](2) . H2O 5 and [ZnMn(H(2)L(1))(2)Cl-2] 6 have been examined. The H-1 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.