(IMIDAZOLE)(3,3'-TRIMETHYLENEDINITRILO BIS (2-BUTANONE OXIMATE)) COPPER(II) PERCHLORATE - SYNTHESIS AND CRYSTAL-STRUCTURE OF A 5-COORDINATECOPPER-PROTEIN MODEL COMPLEX

The synthesis and crystal structure of the novel pentacoordinated comp lex [Cu(DOHPN)(IMIDAZOLE)I(ClO4), (DOHPN = (3,3'-trimethylenedinitrilo bis 2-butanone oxime) are reported. The X-ray crystal structure (spac e group P2(1)/n, a = 11.349(2) Angstrom, b = 14.241(3) Angstrom, c = 1 2.635(3) Angstrom; alpha = 90 degrees, beta = 100.21 (3)degrees, gamma = 90 degrees) shows that the copper(II) ion occupies a distorted squa re-pyramidal geometry with the imidazole ligand occupying the axial po sition. The copper(II)-(N)imidazole distance is 2.125(3) Angstrom and the copper(II)-tetraaza plane distance is 0.385/Angstrom. The tetraaza ligand DOHPN adopts a ''butterfly-like'' geometry with a dihedral ang le of 149.69 degrees. The title complex is the first structurally char acterized compound of the series [Cu(DOHPN)(axial ligand)](n+) where t he axial ligand is a neutral N-heterocycle with known biological relev ance. A comparison of the structural parameters with those observed wh en the axial ligand is H2O or NCS- (N-bonded) gives the following seri es with increasing metal-ligand interaction: H2O > IMIDAZOLE > NCS- (N -bonded).