Facile synthesis of Cu(II) complexes of monocondensed N,N,N donor Schiff base ligands: Crystal structure, spectroscopic and magnetic properties

Four new copper(II) complexes, [(CuL1N3)2](ClO4)2 (1), [(CuL2N3)2](ClO4)2 (2), [CuL3(N3)(ClO4)]n (3) and [CuL4(μ-1,1-N3)(μ-1,3-N3)(ClO4)]n (4) where L1 = N1-pyridin-2-yl-methylene-propane-1,3-diamine, L2 = N1-(1-pyridin-2-yl-ethylidene)propane-1,3-diamine, L3 = N1-(1-pyridin-2-yl-ethylidene)ethane-1,2-diamine and L4 = N1-(1-pyridin-2-yl-ethylidene)propane-1,2-diamine are four tridentate N,N,N donor Schiff base ligands, have been derived and structurally characterized by X-ray crystallography. Compounds 1 and 2 consist of double basal–apical end-on (EO) azide bridged dinuclear CuII complexes with square-pyramidal geometry. In complex 3 the square planar mononuclear [CuL3(N3)] units are linked by weakly coordinated perchlorate ions in the axial positions of CuII to form a one-dimensional chain. Two such chains are connected by hydrogen bonds involving perchlorate ions and azide groups. Compound 4 consists of 1-D chains in which the CuII ions with a square-pyramidal geometry are alternately bridged by single EO and end-to-end (EE) azido ligands, both adopting a basal–apical disposition. Variable temperature (300–2 K) magnetic susceptibility measurements and magnetization measurements at 2 K have been performed. The results reveal that complexes 1 and 2 are antiferromagnetically coupled through azido bridges (J = −12.18 ± 0.09 and −4.43 ± 0.1 cm−1 for 1 and 2, respectively). Complex 3 shows two different magnetic interactions through the two kinds of hydrogen bonds; one is antiferromagnetic (J1 = −9.69 ± 0.03 cm−1) and the other is ferromagnetic (J2 = 1.00 ± 0.01 cm−1). From a magnetic point of view complex 4 is a ferromagnetic dinuclear complex (J = 1.91 ± 0.01 cm−1) coupled through the EO bridge only. The coupling through the EE bridge is practically nil as the N(azido)–CuII (axial) distance (2.643 Å) is too long.

Four new copper(II) complexes of the general formula CuLN3ClO4, where L represents four similar tridentate N,N,N donor Schiff base ligands, have been synthesized in a very convenient way and structurally characterized. Two of the complexes consist of double basal–apical end-on (EO) azide bridged dinuclear CuII complexes and are antiferromagnetically coupled through the azido bridges. The third one is a perchlorate bridged one-dimensional CuII chain; two such chains are connected by hydrogen bonds. It shows two different magnetic interactions through the two kinds of hydrogen bonds; one is antiferromagnetic and the other is ferromagnetic. The fourth compound consists of 1-D chains in which the CuII ions are alternately bridged by single EO and end-to-end (EE) azido ligands. From a magnetic point of view it is a ferromagnetic dinuclear complex coupled through the EO bridge only.Figure optionsDownload as PowerPoint slide