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Specific Interactions of Divalent Metal Ions with Phosphonic Analogues of Dipeptide Inhibitors of Proteases

Gałęzowska J.

Polish Journal of Chemistry

2005

Vol. 79 / nr 3

603-617

Potentiometric and spectroscopic methods were used to evaluate the binding ability of two dipetides with C-terminal phosphonic group. This phopshonate moiety is quite effective in the coordination of metal ions. The two phosphinate analogues, which are very effective enzyme inhibitors, were found to be also powerful ligands for Cu2+ ions involving both amino and phosphinic groups in metal ion coordination.

One-, Two- and Non-Coordinated Cr02- 4 Entity in the Nickel(II) Complexes. Structural and Spectroscopic Investigation

Pietraszko A., Bronowska W., Wojciechowska A., Staszak Z., Cieślak-Golonka M.

Polish Journal of Chemistry

2002

Vol. 76 / nr 2-3

309-324

A systematic investigation of the chromate ion in [Ni(II)-(2,2_-bpy)-CrO4 2_ ] systems has been carried out. The effect of the Ni(II) ion and the organic ligand on the mode of the chromate position in the [Ni(bpy)3]CrO4_7.5H2O(1), [Ni(bpy)2(OCrO3)(H2O)]_5H2O(2) and catena-(ž-CrO4-O,O_)[Ni(bpy)(H2O)2]_2H2O (3) complexes has been shown. [Ni(bpy)3]CrO4_7.5H2O crystals (1) have a monoclinic symmetry with space group C2/c and 8 chemical units, forming a unit cell with a = 13.641(3) A, b = 22.939(5) A, c = 23.351(5) A and _ = 104.69(3) deg, whereas the [Ni(bpy)2(OCrO3)(H2O)]_5H2O crystals (2) have a monoclinic symmetry with space group P21/c and 4 chemical units per unit cell with a = 10.854(2) A, b = 22.665(5) A, c = 10.623(2) A and _ = 108.93(3) deg at room temperature. The chromate ion in 1 is not coordinated to the nickel(II) ion. The geometry around the Cr(VI) atom is pseudotetrahedral. Untypical for the chromate ion monodentate coordination has been found in the complex [Ni(bpy)2(OCrO3)(H2O)]_5H2O. The chromate position has been also elucidated from the digitally resolved IR spectra. The coordination of the chromate ion in 2 and 3 was also observed for the single crystal at 4K, in reflectance and solution electronic spectra through the appearance of a new transition at ca. 15000 cm-1. The full characterization of the chromophores present in the complexes: NiN6, NiN4O2, NiN2O4 and NiO6 have been obtained on the basis of the detailed analysis of the electronic spectra at 4K(Gaussian deconvolution followed by digital filtration).