STRUCTURE DETERMINATION, SPECTROSCOPIC CHARACTERIZATION, AND MAGNETIC-PROPERTIES OF A NOVEL DINUCLEAR COPPER(II) CROWN-ETHER BIPYRIDINE COMPLEX

The synthesis of a novel ligand system (1) composed of two bipyridine units linked by a crown ether moiety is described. Addition of 2 equiv of [Cu(MeCN)4] BF4 to 1 and subsequent oxidation yield a dinuclear mu -hydroxo-bridged copper(II) complex, [(l)Cu2(OH)2BF4] BF4-2H2O (2). Th e structure of this complex has been determined by X-ray crystallograp hic methods. Crystal data: triclinic, space group P1BAR (No. 2), a = 1 0.060(l) angstrom, b = 12.747(2) angstrom, c = 16.787(l) angstrom, alp ha = 92.01(l)-degrees, beta = 103.01(2)-degrees, gamma = 104.01(2)-deg rees. The Cu-O-Cu angles in complex 2 are nonequivalent (94.8 and 98.4 -degrees). One of the coppers is pentacoordinated; the other is hexaco ordinated. Two molecules of 2 are linked by hydroxo ligands, forming a tetranuclear complex in which the CU2(OH)2 units have parallel but sh ifted positions. Magnetic susceptibility and EPR measurements suggest that complex 2 has a triplet ground state, with a triplet-singlet ener gy gap of 16 cm-1.