Synthesis, characterization, and anion selectivity of copper(II) complexes with a tetradentate Schiff base ligand

A new mononuclear Cu(II) complex, [CuL(ClO4)2] (1) has been derived from symmetrical tetradentate di-Schiff base, N ,N ′-bis-(1-pyridin-2-yl-ethylidene)-propane-1,3-diamine (L) and characterized by X-ray crystallography.The copper atom assumes a tetragonally distorted octahedral geometry with two perchlorate oxygens coordinated very weakly in the axial positions.Reactions of 1 with sodium azide, ammonium thiocyanate or sodium nitrite solution yielded compounds [CuL(N3)]ClO4 (2), [CuL(SCN)]ClO4 (3) or [CuL(NO2)]ClO4 (4), respectively, all of which have been characterized by X-ray analysis.The geometries of the penta-coordinated copper(II) in complexes 2–4 are intermediate between square pyramid and trigonal bipyramid (tbp) having the Addition parameters (τ ) 0.47, 0.45 and 0.58, respectively.In complex 4, the nitrite ion is coordinated as a chelating ligand and essentially both the O atoms of the nitrite occupy one axial site.Complex 1 shows distinct preference for the anion in the orderView the MathML sourceSCN->N3->NO2- in forming the complexes 2–4 when treated with a View the MathML sourceSCN-/N3-/NO2- mixture. Electrochemical electron transfer study reveals CuIICuI reduction in acetonitrile solution.