2-(2'-PYRIDYL)QUINOXALINE-(L) AS A BIDENTATE LIGAND - CRYSTAL-STRUCTURE MAGNETIC-PROPERTIES AND QUANTUM-CHEMICAL STUDY OF [CU2CL4L2]

The X-ray crystal structure of the complex [Cu(2)Cl(4)L(2)], where L is 2-(2'-pyridyl)quinoxaline, has been determined. The structure consists of dimeric molecules [Cu(2)Cl(4)L(2)], in which copper ions are bridged by two chloride ligands. The geometry at copper can be described as either a distorted square-pyramidal or a distorted trigonal-bipyramidal. Magnetic susceptibility and EPR data give evidence for exchange coupling with the best fit to the data of the dimeric expression for a pair of exchange-coupled S = 1/2 ions yielding g = 2.134, 2J = - 10 cm(-1) and zJ' = -2 cm(-1). The investigations of the ground-state electronic structure of the complex and its precursor ligand L, along with an orbital interpretation of the magnetic coupling based upon extended Huckel molecular: orbital calculations, are also presented.