Structural analysis of binuclear copper(II) complexes by DV-X alpha calculations of CuK-edge XANES spectra

The structures of two binuclear copper complexes of N ,N',N ",N "'-tetrakis (2-aminoethyl)-1,4,8,11-tetraazacyclotetradecane (TAEC) in crystal form and in aqueous solution were determined by DV-X alpha analysis of XANES (x-ray absorption near-edge structure) spectra. The results revealed that a Br- i s bridged to bind the two CU2+ ions within [Cu-2(TAEC)Br](ClO4)(3) aqueous solution and crystals, and that in [Cu-2(TAEC)(C1O(4))(2)](C1O(4))(2), the two Cu2+ ions are bridged via O, probably OH-, in aqueous solution, in cont rast with a non-bridged structure found in crystals, These binuclear comple xes tend to have anion-bridged structures, but form an unbridged structure depending on the stability of the crystal field. Copyright O 1999 John Wile y & Sons, Ltd.