Synthesis, characterization and crystal structure of Cu(II) complex with a diimine-dioxime ligand, [Cu-2(LH)(2)](ClO4)(2). Influence of the weak Cu center dot center dot center dot O(perchlorate) interaction on the structure of the Cu2N2O2 metallocycle

The diimine dioxime ligand, 3,3-(1,4-butanediyl-dinitrilo)bis-2-pentanone, 2,2-dioxime (LH2), containing a N-4 donor set was prepared by the Schiff base condensation of 2-hydroxyimino-3-pentanone and 1,4-diaminobutane in two ways: in a protic and in an aprotic solvent. A higher yield of the (LH2) imine was obtained when the synthesis was performed using a protic solvent (C2H5OH) instead of aprotic benzene (78 and 30 %, respectively). The Cu(II) metal complex of diimine dioxime was synthesized in CH3OH from the perchlorate salt of LH2 in a 1:1 mole ratio. The isolated complex was characterized by the elemental analysis, IR spectroscopy and cyclic voltammetry. The structure of [Cu-2(LH)(2)](ClO4)(2) was determined by single-crystal X-ray diffraction analysis. Comparison with structurally related diimine dioxime Cu(II) complexes revealed the influence of a weak Cu center dot center dot center dot O(perchlorate) interaction on the geometry of the metallocycle