Synthesis, chemical characterization and crystal structure of the (oxalato-O,O ')bis(1,10-phenanthroline)copper(II) pentahydrate

Violet single-crystals of the complex [Cu(ox)(phen)(2)]. 5H(2)O (1), where ox(2-) is oxalate and phen is 1,10-phenanthroline, were obtained by slow ev aporation of a solution previously prepared by dissolving Cu(ox). 1/3H(2)O in a water-acetonitrile solution of phenantroline. Its crystal structure co nsists of neutral mononuclear [Cu(ox)(phen)(2)] units and crystallization w ater molecules which are held together by face-to-face stacking interaction s between the phenantroline aromatic rings and an extensive three-dimension al network of O-w-H . . .O/O-w hydrogen bonds. The copper atom is hexaco-or dinated to two oxygen atoms of a bidentate oxalato ligand and to four nitro gen atoms belonging to two phen ligands in a distorted octahedral cis arran gement. The e.p.r. Q-band spectrum of I shows an axial-type signal with g-t ensor values of g(parallel to) = 2.28 and g(perpendicular to) = 2.06, which is consistent with the axially elongated octahedral geometry of the copper (II) chromophore found in the structural work. The relation g(parallel to) much greater than g(perpendicular to) > 2.0 indicates a d(x(2) - y(2)) grou nd state. Variable temperature susceptibility measurements (5-300 K) reveal s the occurrence of magnetically isolated paramagnetic centers in the cryst al structure. Thermal degradation of the compound I under synthetic air atm osphere starts between 50 and 110 degreesC with an endothermic process attr ibutable to the release of the crystallization water molecules. (C) 2001 El sevier Science B.V. All rights reserved.