Synthesis, structure, magnetic properties and DFT calculations of novel bis-(5-tetrazolyl)amine copper(II) complexes

Four new multidimensional copper(II) complexes [Cu(BTA)(2,2′-bipy)H2O] (1), [Cu(BTA)(1,10′-phen)] (2), [Cu2(BTA)2(H2O)4] (3) and [Cu(BTA)(en)]n (4) have been synthesized by conventional and hydrothermal reactions of the bis(5-tetrazolyl)amine (H2BTA) with copper(II) salts in the presence of different ancillary ligands. X-ray diffraction studies on these compounds show 1 and 2 are mononuclear entities, in which the BTA ligand acts in a chelate coordination mode and the copper atoms exhibit a coordination environment intermediate between trigonal-bipyramidal and square-pyramidal for 1 and between square-planar and tetrahedral for 2. Complex 3 consists of centrosymmetric dinuclear molecules with the ligand acting in a μ2-1,1′:2 chelate/bridging tridentate coordination mode and 4 is a linear zigzag neutral chain bearing a BTA bridging ligand in a μ2-1,1′:3 chelate/bridging tridentate coordination mode. Complexes 3 and 4 exhibit antiferromagnetic and very weak ferromagnetic interactions, respectively. DFT calculations have been performed in order to explain their respective magnetic behaviors.