New ferromagnetic dinuclear triply-bridged copper(II) compounds containing carboxylato bridges: Synthesis, X-ray structure and magnetic properties

The new triply-bridged dinuclear copper(II) complexes, [Cu-2(mu-O2CH)(mu-OH)(2)(dpyam)(2)](ClO4).H2O (1), [Cu-2(mu-O2CCH3)(mu-OH)(mu-OH2)(dpyam)(2)](S2O8) (2), [Cu-2(mu-O2CCH3)(mu-OH)(mu-OH2)(bpy)(2)](NO3)(2) (3), [Cu-2(mu-O2CCH3)(mu-OH)(mu-OH2)(phen)(2)](BF4)(2).0.5H(2)O (4), [Cu-2(mu-O2CCH2CH3)(mu-OH)(mu-OH2)(phen)(2)](NO3)(2) (5) and [Cu-2(mu-O2CCH3)(mu-OH)(mu-Cl)(bpy)(2)]Cl.8.5H(2)O (6) (dpyam = di-2-pyridylamine, bpy = 2,2'-bipyridine, phen = 1,10-phenanthroline), have been synthesized and characterized crystallographically and also their spectroscopic and magnetic properties have been studied. A structural classification of this type of dimers, based on the data obtained from X-ray diffraction analysis in the present work and those reported in the literature has been performed. In these complexes, the local geometry around the copper centre is generally a distorted square pyramid and distorted trigonal bipyramid with different degrees of distortion. The global geometry of the dinuclear complexes can be described in terms of the relative arrangement of the two five-coordinate environments, giving rise to different classes (A-F) of complexes. The most logical explanations have been provided for each class describing different magnetic interactions. Practically, there is a clear correlation between structural data and J values of the class B complexes. Extended Huckel calculations were performed for the present complexes 1-6, as well as for some other class B complexes, showing the different molecular orbitals involved in their corresponding frontier orbitals, together with their energy. The results are found to be useful for the proper interpretation and correlation of the magnetic data and the dinuclear structure of the present complexes. (C) 2007 Elsevier Ltd. All rights reserved.