SYNTHESIS, CRYSTAL-STRUCTURE, AND MAGNETIC-PROPERTIES OF A FERROMAGNETICALLY COUPLED ANGULAR TRINUCLEAR COPPER(II) COMPLEX [CU3(O2CME)4(BPY)3(H2O)](PF6)2
S. Meenakumari et al., SYNTHESIS, CRYSTAL-STRUCTURE, AND MAGNETIC-PROPERTIES OF A FERROMAGNETICALLY COUPLED ANGULAR TRINUCLEAR COPPER(II) COMPLEX [CU3(O2CME)4(BPY)3(H2O)](PF6)2, Inorganic chemistry, 33(10), 1994, pp. 2085-2089
The synthesis, X-ray crystal structure, and magnetic properties of an
angular trinuclear copper(II) complex [Cu3(O2CMC)4(bpy)3(H2O)](PF6)2 (
1), obtained from a reaction of Cu2(O2CMe)4(H2O)2 With 2,2'-bipyridine
(bpy) and NH4PF6 in ethanol, are reported. Complex 1 crystallizes in
triclinic space group P1BAR with a = 11.529(1) angstrom, b = 12.121(2)
angstrom, c = 17.153(2) angstrom, alpha = 82.01(1)-degrees, beta = 79
.42(1)-degrees, gamma = 89.62(1)-degrees, and Z = 2. A total of 6928 d
ata with I > 2.5sigma(I) were refined to R = 0.0441 and R(w) = 0.0557.
The structure consists of a trinuclear core bridged by four acetate l
igands showing different bonding modes. The coordination geometry at e
ach copper is distorted square-pyramidal with a CuN2O2...O chromophore
. The Cu...Cu distances are 3.198(1) angstrom, 4.568(1) angstrom, and
6.277(1) angstrom. There are two monoatomic acetate bridges showing Cu
-O-Cu angles of 93.1(1) and 97.5(1)-degrees. Magnetic studies in the t
emperature range 39-297 K show the presence of a strong ferromagnetica
lly coupled dicopper(II) unit (2J = +158 cm-1) and an essentially isol
ated copper(II) center (2J' = -0.4 cm-1) in 1. The EPR spectra display
an axial spectrum giving g(parallel-to) = 2.28 (A(parallel-to) = 160
X 10(-4) cm-1) and g(perpendicular-to) = 2.06 (A(perpendicular-to) = 1
2 X 10(-4) cm-1) for the normal copper and two intense isotropic signa
ls with g values 2.70 and 1.74 for the strongly coupled copper pair. T
he structural features of 1 compare well with the first generation mod
els for ascorbate oxidase.