Structures and Electronic Spectra of Aquadiiminebis(succinimidato)copper(II) Complexes with Square Pyramidal [CuN4O] Chromophores (Diimine=1,10-Phenanthroline and 2,2′-Bipyridine)

Copper(II) complexes [Cu(succim)(2)(phen)H2O]center dot H2O (1) (succim= succinimidate, phen = 1,10-phenanthroline) and [Cu(succim)(2)(bpy)H2O] (2) (bpy = 2,2'-bipyridine) were prepared and the crystal structures were determined by X-ray crystallography. The coordination geometries are found to be five-coordinated square-based pyramidal [CuN4O] for each complex. Crystal data for complex 1 are monoclinic with space group P2(l/n); a = 9.602(4), b = 12.003(4), c = 17.618(4) angstrom; beta = 100.38(3)degrees; V = 1997(1) angstrom(3); Z = 4. Crystal data for complex 2 are monoclinic with space group P2(l/n); a = 9.616(2), b = 11.616(3), c = 15.871(2) angstrom; beta = 90.61(2)degrees; V = 1772.8(6) angstrom(3); Z = 4. The axial Cu-0(water) bond distances cf the present complexes (2.548(5) angstrom for 1 and 2.673(4) angstrom for 2) are appreciable longer than those of other square pyramidal trans-[CuN4O] complexes. The diffuse reflectance spectra showing a broad peak at about 17000 cm(-1) analyzed by means of Gaussian curve fitting and angular overlap model (AOM) calculations with respect to d(xy), d(yz), and d(zx) orbitals distributing in the [CuN4] basal plane. According to the analyses, transferability of AOM parameters is valid for succim. The ligand field of bpy can be described by the same parameters as py (py = pyridine). However, it is necessary to set a larger pi-bonding AOM parameter for phen than that of py to reproduce the experimental results. The reason for this is out-of-plane lone pairs and pi-conjugation of phen. The assignment of the one-electron orbital sequences is presumed to be d(x2-y2) > d(z2) > dz(2) > d(xy) > d(yz) > d(2x) based on the AOM calculations for each complex.