Syntheses, crystal structures and magnetic studies of new copper(II) complexes of (E)-N′-(phenyl(pyridin-2-yl)methylene)isonicotinohydrazide containing azide and SCN anions

Three new complexes of copper(II) with pseudohalide anions and (E)-N'-(phenyl(pyridin-2-yl)methylene)isonicotinohydrazide (HL), namely azide bridged dinuclear [Cu(L)(mu-N-3)](2) (1), two-dimensional coordination polymer [Cu-2(L)(2)(NCS)(2)](n) (2a) and monomeric [Cu(L-H)(NCS)(2)] (2b), were synthesized. The complexes were characterized by elemental analyses and spectroscopic methods. The structures were unequivocally confirmed by X-ray diffraction, and further studied by means of EPR and magnetic susceptibility measurements. In all three complexes, the isonicotinohydrazide ligand coordinates to the copper center in the enolic form (-C=N-N=). In complex 1, the two bridging azide ligands connect the two metal centers in an end-on (EO) fashion, with the metal centers having an asymmetric square pyramidal geometry. Complex 2b is based on a square pyramid with the neutral isonicotinohydrazide ligand coordinating in a tridentate mode. By contrast, the Schiff base (L)(-) coordinates in a tetradentate ligand fashion in 2a as the oxygen atom of the amide unit in the enol form asymmetrically bridges two Cu centers and a third Cu center is coordinated through the pyridyl-N atom. The EPR spectrum of complex 2a, consisting of two poorly resolved resonance lines, points to the presence of a dynamical Jahn-Teller effect, typical for Cu2+ ions in octahedral environments. (C) 2013 Elsevier Ltd. All rights reserved.