THE SPECTROCHEMICAL PROPERTIES OF NONCUBIC TRANSITION-METAL COMPLEXES IN SOLUTIONS .2. MIXED TETRAGONAL DISTORTED NICKEL(II) PYRIDINE COMPLEXES IN METHANOL

The electronic spectra of tetragonal nickel(II) complexes of the type Ni(Py)4L2 (where Py = pyridine and L = NCS, Cl, Br or I), have been measured in methanol solutions at room temperature. The experimental curves were resolved by Gaussian analysis. The various ligand-field parameters are discussed in terms of their chemical utility and their relation to ligand-field strengths. The ligand-field parameters were examined by two minimization algorithms: the Davidon-Fletcher-Powell method (gradient estimation) and the Powell method (non-gradient). The standard deviations of the parameters were obtained from the former. It was found that the stereochemistry of the complexes in methanol solution differed from that in chloroform solution or in the solid state.