Crystal structures, spectroscopy and EPR of two distortion isomers of Cu(II) perchlorate with 2,2 '-bi-imidazoline
A. Mohamadou, G.A. van Albada, W.L. Driessen, R. de Gelder, J. Reedijk
POLYHEDRON 2004, 23, 11, 1969-1973

Abstract:
The synthesis, crystal structures, as well as the electronic and spectroscopic properties, of two new mononuclear Cu(II) isomeric compounds containing the ligand 2,2'-bi-imidazoline (biz) are reported. Both Cu(II) compounds, the blue [Cu(biz)(2)(ClO4)(2)] (1) and the violet [Cu(biz)(2)](ClO4)(2) (2), have the same stoichiometry and but differ in the location of the perchlorate anions. The basal plane of both compounds is formed by four nitrogen atoms of two dichelating biz ligands. In compound 1, the apical position is occupied by two oxygen atoms of two perchlorate anions, resulting in an elongated octahedral geometry around the Cu ion. In compound 2, the perchlorate anions are not coordinating to the Cu ion, resulting in a square planar geometry around the Cu atom. Both isomers show different and interesting H-bonding properties. The electronic, EPR and IR spectroscopy results are in agreement with the structural geometry. In frozen solution (at 77 K) the EPR spectrum is identical for both compounds, so in that case they have both the same geometry.