X-ray structures and properties of five-coordinate copper(II) complexes with a quadridentate N4 ligand and with a quinquedentate N5 ligand
作者:H. Elias、E. Hilms、B. Wannowius、H. Paulus
DOI:10.1016/s0020-1693(00)88140-2
日期:1990.12
Complexes Cu(biquinen)(H2O)(BF4)2 (1), Cu(biquinen)(H2O)(ClO4)2 (2) and Cu(biquidien)(ClO4)2 (3) with the N4 Schiff base biquinen (1,2-bis(8-quinolylmethyleneimino)ethane) and with the N5 Schiff base biquidien (1,5-bis(8-quinolylmethyleneimino)-3-aza-pentane) were prepared. 1 crystallizes in the trigonal space group P3(2) with a = 1018.0(3), c = 2032.2(7) pm and Z = 3; 2 in the monoclinic space group Cc with a = 1865.7(9), b = 995.1(5), c = 1715.7(8) pm, beta = 128.59(2)-degrees and Z = 4; 3 in the triclinic space group P1BAR with a = 1419.6(8), b = 1095.8(6), c = 917.7(6) pm, alpha = 74.16(2), beta = 75.55(2), gamma = 88.95(2)-degrees and Z = 2. In all three complexes the copper is five-coordinate with a N4O set of donor atoms in 1 and 2 and a N5 set of donor atoms in 3. The coordination geometry of the chromophors Cu(biquinen)(H2O)2+ in 1 and 2 and Cu(biquidien)2+ in 3 is distorted trigonal bipyramidal, with the water in 1 and 2 being coordinated in an equatorial position. In aqueous solution 1 and 2 give the same Vis absorption spectrum with a broad band at 609 nm, whereas for 3 this weak d-d band is shifted to 578 nm. In water/dioxane (3:1) the imine nitrogens of the Schiff base biquinen have pK(a) values of 9.25 and 6.63, respectively (I = 0.5 M NaClO4; T = 25-degrees-C).