POLAROGRAPHIC INVESTIGATIONS ON SOLVATOCHROMIC AND THERMOCHROMIC NICKEL(II) COMPLEXES IN NONAQUEOUS SOLUTIONS

Abstract Reduction and oxidation potentials have been measured at different temperatures for solvatochromic and thermochromic mixed Ni(II) complexes with tetramethylethylenediamine and benzoylacetonate in dichloroethane (DCE), nitroethane (NE), N,N-dimethylformamide (DMF) and dimethylsulfoxide (DMSO). In DCE and NE square planar complexes are present, whereas octahedral coordination is found in DMF and DMSO. The results show that the entropy related temperature coefficients of the half wave potentials of the ligands depend strongly upon the coordination to the Ni-central atom, whereas the temperature coefficients of the Ni-potentials are invariant towards changes of the solvent. Isokinetic behaviour is found for all the ligand half wave potentials. The question is raised as to how the isokinetic temperatures are related to Raman active vibration frequencies.

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