A theoretical analysis of how geometrical distortions on Cu(mu-Cl)(2)Cu dimers influence their electronic and magnetic properties

A structural classification of dimers, containing the Cu(mu -Cl)(2)Cu core, based on data obtained from X-ray diffraction analysis reported in the lit erature has been performed. In these complexes, the local geometry around t he copper metal center is generally a square pyramid, with a different degr ee of distortion towards a trigonal bipyramid. The global geometry of the d inuclear complex can be described in terms of the relative arrangement of t he two square pyramids, giving rise to three types of geometries, termed: c oplanar bases, parallel bases and perpendicular bases. Ideal models represe nting these geometries were defined and EH calculations were performed in e ach case, showing the different molecular orbitals involved in their corres ponding frontier orbitals, together with their energy. EH calculations were also carried out for dimers embodying different type of structural distort ions from the ideal models. The results obtained from those EH calculations have proven to be extremely useful for the proper interpretation and corre lation of the magnetic data and dimer structure for those Cu(mu -Cl)(2)Cu c omplexes reported in the literature. (C) 2000 Elsevier Science B.V. All rig hts reserved.