XRD and EXAFS studies of azomethynic copper metallochelates as models of blue copper proteins

Abstract

The structure of two biomimetic copper complexes bis[4-benzylaldimino-3-methyl-1-phenyl-5-thio (seleno)pyrazolato]copper(II)—36 32N6X2Cu (where X=S, Se) have been studied and X-ray patterns of these compounds have been prepared using the Rietveld refinement technique. Both complexes crystallized in a monoclinic lattice, space group-C2/c(15). The unit-cell parameters are a=28.917(3) Å; b=7.000(2) Å; c=17.550(4) Å; β=106.869(1) (1) for C36H32CuN6S2 and a=29.126(6) Å; b=7.042(4) Å; c=17.228(2) Å; β=105.587(2) for C36H32CuN6Se2. Analysis of the copper and selenium K-edge X-ray absorption spectra (EXAFS) of these complexes show that a copper atom is in pseudo-tetrahedric ligand environment N2X2 with typical Cu–N bonds (R=2.00–2.01 Å) and significantly different Cu–S and Cu–Se bonds (R=2.27 Å and R=2.41 Å, respectively) because of different sulfur and selenium ion radii. © 2004 International Centre for Diffraction Data.