화학공학소재연구정보센터
Inorganic Chemistry, Vol.42, No.13, 4029-4035, 2003
A quasi-tetrahedral Cu-4 cluster and a helical-chain copper(II) complex with single syn-anti carboxylate bridges: Crystal structure and magnetic properties
A tridentate Schiff base carboxylate ligand, derived from the condensation of pyridine 2-carboxaldehyde with anthranilic acid, reacts with copper trifluoroacetate salt to give rise to the helical chain complex [CU(C13H9N2O2)(F3CCO2)](n) (1) and with copper nitrate to give rise to the tetranuclear complex [{Cu-4(C13H9N2O2)(4)(H2O4}(.)3.5NO(3)(.)0.5N(3)] (2) with the addition of azide salt. The structures of these complexes have been solved by X-ray crystallography. The Cu(II) ions are in a distorted square-pyramidal environment in complex 1. They are sequentially bridged by carboxylate groups in the syn-anti conformation, resulting in the formation of an infinite helix like chain along the crystallographic c-axis. The crystal structure of complex 2 consists of tetranuclear [Cu-4(L)(4)(H2O)(4)](4+) (L = C13H9N2O2-) cations and isolated NO3- and N-3(-) anions in the ratio 1:3.5:0.5, respectively, involving bridging carboxylate groups in the syn-anti conformation. For 1 the carboxylato-Cu(II) coordination is apical-basal, while for 2 it is basal-basal. From the magnetic susceptibility measurements the complex 1 is found to exhibit very weak antiferromagnetic interaction whereas a weak ferromagnetic coupling has been established for complex 2. The magnetic behavior can be satisfactorily explained on the basis of the structural data for these and related complexes.