Succinate bridged dimeric Cu(II) system containing sandwiched non-coordinating succinate dianion: Crystal structure, spectroscopic and thermal studies of [(phen)(2)Cu(mu-L)Cu(phen)(2)]L center dot 12.5H(2)O (H2L = succinic acid; phen=1,10-phenanthrol

摘要

A mixed ligand and dimeric Cu-II complex [(phen)(2)Cu(mu-L)Cu(phen)(2)]L center dot 12.5H(2)O (H2L = succinic acid) containing bridging succinate moiety and also non-coordinated succinate dianion was prepared from polymeric Cu(II) succinate by nucleophilic reaction with o-phenanthroline (phen) followed by depolymerization. The dimeric product was characterized by crystallographic, spectroscopic and thermoanalytical studies. The complex crystallizes in triclinic crystal system and is composed of succinate bridged [(phen)(2)Cu(mu-L)Cu(phen)(2)](2+) complex cations, non-coordinated succinate anions and hydrogen bonded water molecules. Within the dimeric cationic unit, each of the Cu atoms is octahedrally coordinated by four N atoms of both phen ligands and both O atoms of a carboxylate moiety of the bridging succinate group in chelating form. Through intermolecular pi-pi stacking interactions, the complex cations form positively charged 2-D layers, between which the non-coordinating succinate anions and water molecules are sandwiched. Both the electronic and EPR studies indicate that the dimeric complex undergoes partial dissociation in solution state to exist in two structural forms. The kinetic and thermodynamic parameters involved in three stage thermal decompositions of the dimeric complex could also be evaluated using Coats-Redfern method. (c) 2005 Elsevier B.V. All rights reserved.