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(μ and Thermochromic {[Cu(μ-Hor)(tmen)] · 1.5H2O}n Complexes

Abstract

The syntheses, FT-IR and UV-Vis spectra, thermal analyses and crystal structures of Mn(II) and Cu(II) orotate 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(μ-HOr)(H<inf>2</inf>O)(2-meim)<inf>2</inf>]}<inf>n</inf> (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(μ-HOr)(tmen)] · 1.5H<inf>2</inf>O}<inf>n</inf> (2), the Cu(II) ion is coordinated by a tridentate 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. © 2008 Elsevier Ltd. All rights reserved.