HOMODINUCLEAR LANTHANIDE COMPLEXES - LN(2)L(3) (H2L EQUALS TETRADENTATE SCHIFF-BASES) - MAGNETIC-PROPERTIES (SOLID-STATE) AND SPECTROSCOPICSTUDIES (SOLUTION)

The Ln(2)L(3) complexes have been known for a long time but no structu ral characterization is yet available. A first hypothetical structure supposed that the two lanthanide centres were isolated while a second structure, based on spectroscopic arguments, indicated that the two la nthanide centres are held together by one of the three L2- deprotonate d Schiff bases acting as a bridging ligand via its two phenoxo oxygen atoms. It is the reason why we studied the magnetic properties of Gd2L 3 complexes. Indeed, the temperature dependence of the magnetic suscep tibility of Gd2L3 complexes suggest the presence of an antiferromagnet ic interaction in both complexes. The parameters resulting from the fi tting process give J values varying from -0.140(3) to -0.100(2) cm(-1) . The Gd-2(thd)(6) complex which has been structurally characterized e lsewhere and which comprises gadolinium ions doubly bridged by oxygen atoms gives a J value of -0.082(1) cm(-1). Such results confirm the pr esence of oxygen bridges between the two gadolinium centres in the Gd2 L3 complexes. Solution studies show that both Ln(2)L(3) complexes are dissociated into [LnL(2)](-) and [LnL](+) C species. These mononuclear species have been isolated and characterized. (C) 1998 Elsevier Scien ce S.A.