Coordination polymers of Mn(II) and Cu(II) orotate with 2-methylimidazole and N,N,N ',N '-tetramethylethylenediamine ligands: Syntheses, spectroscopic and thermal analyses and crystal structures of mer-[Mn(mu-HOr)(H2O)(2-meim)(2)](n) and thermochromic {[Cu(mu-HOr)(tmen)] center dot 1.5H(2)O}(n) complexes

Abstract

The syntheses, FT-IR and UV-Vis spectra, thermal analyses and crystal structures of Mn(II) and Cu(II) ororate coordination polymers with 2-methylimidazole (2-meim) and N,N,N',N'-tetramethylethylenediamine (tmen) ligands are described. The orotate ligand acts as a bridging ligand with two different coordination modes, the {mer-[Mn(mu-HOr)(H2O)(2-meim)(2)]}(n), (1) complex displays an linear chain structure in which each Mn(II) ion exhibits a distorted octahedral coordination by a tridentate orotate, two 2-meim and one aqua ligand. in {[Cu(mu-HOr)(tmen)] center dot 1.5H(2)O}(n) (2), the Cu(II) ion is coordinated by a tridenrate orotate and one bidentate tmen ligand, and exhibits a square pyramidal geometry. These polymer chains are linked by hydrogen-bond interactions forming a three-dimensional network. Complex 2 exhibits an irreversible thermochromic effect. After dehydration, the color of the complex changes from blue to green. (C) 2008 Elsevier Ltd. All rights reserved.