Experimental, characteristic evidence and surface photovoltage properties of a series of Cu/Mn complexes with bipyrazolyl-pyridine and different spanning dicarboxylate

By introduction of different spanning flexible dicarboxylate as auxiliary ligands, novel complexes with N-heterocyclic ligand, [Cu(H2L)(ox)]·2H2O (1), [Cu2(HL)2(Hglu)]·2CH3OH·H2O (2), and [Mn(H2L)(ad)]·H2ad (3) (H2L = 2,6-di-(5-methyl-1H-pyrazol-3-yl)pyridine, ox = oxalic acid, glu = glutaric acid, ad = adipic acid) are synthesized with hydrothermal method. Structural analysis reveals that the coordination modes of metal center in these complexes are various, in complexes 1 and 2, Cu(II) atom is five-coordinated to form a distorted square pyramid geometry. While in complex 3, Mn(II) atom is six-coordination mode, forming a distorted octahedron. In complexes 1–3, the N-heterocyclic ligand is coordinated with one or two metal centers. While in complexes 2 and 3, two metal centers are connected by bridging coordination fashions of flexible dicarboxylate and N-heterocyclic ligands, which are different from those in complex 1. In addition, the surface electron behaviors of complexes 1 and 3 have also been studied. The results show that the surface photovoltage (SPV) response signals increase when the positive electric field enhances in the range of 300–800 nm. This result reveals that these complexes have the potential characterization of being able to trap photogenerated electron or hole, enhancing the separation extent and restrain the recombination of the photogenerated electron and hole.