Mono- and polynuclear copper(II) complexes based on 2,4,6-tris(2-pyridyl)-1,3,5-triazine and its hydrolyzed form

Three complexes with five-coordinate Cu(II), [Cu(tptz)Cl2]·2H2O (1), [Cu(bpca)Cl]n (2) and [Cu(tptz)(dppz)](PF6)2 (3) (tptz = 2,4,6-tris(2-pyridyl)-1,3,5-triazine, bpca = bis(2-pyridylcarbonyl)amidate anion, and dppz = dipyrido[3,2-a:2′,3′-c]phenazine) have been synthesized and characterized. Complex 2 was prepared from an aqueous solution of complex 1 via copper(II)-assisted hydrolysis of the tptz ligand. The solid state structures of complexes 1 and 2 have been determined by single-crystal X-ray crystallography. Complex 1 contains discrete neutral [Cu(tptz)Cl2] moieties, whereas complex 2 exhibits a polymeric chain arrangement built up of [Cu(bpca)Cl] units linked through the chloro ligands. In both complexes, the CuN3Cl2 coordination polyhedra around the copper(II) centers are best described as nearly square-pyramidal, as ascertained by trigonality index τ value of 0.12 for 1 and 0.02 for 2. The interaction between complex 3 (as its nitrate salt) and calf thymus DNA (CT-DNA) has been investigated by electronic absorption, competitive fluorescence titration, circular dichroism, and flow linear dichroism. The results support the strong binding affinity of the complex to CT-DNA via an intercalative mode.