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

摘要

The structure of two biomimetic copper complexes bis[4-benzylaldimino-3-methyl-1-phenyl-5-thio (seleno)pyrazolato]copper(Ⅱ)-_((36)(32))N_6X_2Cu (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) A; b = 7.000(2) A; c= 17.550(4) A; β=106.869(1) (1) for C_(36)H_(32)CuN_6S_2 and a = 29.126(6) A; b = 7.042(4) A; c= 17.228(2) A; β= 105.587(2) for C_(36)H_(32)CuN_6Se_2. 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 N_2X_2 with typical Cu-N bonds (R=2.00-2.01 A) and significantly different Cu-S and Cu-Se bonds (R = 2.27 A and R -2.41 A, respectively) because of different sulfur and selenium ion radii.