The electronic spectra of the dithiolato nickel complexes have been calculated with a PPP-CI type program developed for including variable β approximation. This calculation was based on the assumption that the nickel atom have a π-orbital and two π electrons. The calculated longest-wavelengths, λmax′s'of the dithiolato nickel complexes were in good agreement with the observed values. The orbital assignment of the molecular orbitals for bis (ethylene-1, 2-dithiolato) nickel calculated by the PPP-method is in reasonable agreement with them calculated by the INDO-method or the Extended-Huckel-method. The first λmax of the dithiolato nickel complexes was assigned to the HOMO-LUMO transition, as a π-π* transition The bathochromic shift caused by the substitution with the electron-donating group at the 4-position of the phenyl group of bis (1, 2-diary1-1, 2-ethylenedithiolato) nickels might be mainly due to the increase of HOMO energy levels. A linear relationship between experimental longest-wavelengths of the nickel complexes and calculated λmax′s' of the ligand in the nickel complexes was observed.
Some triarylmethane dyes containing a heterocyclic ring were prepared to examine the effect of a heterocyclic ring on the absorption spectra of triphenylmethane dyes. Comparison of Malachite Green and triarylmethane dyes containing a heterocyclic ring shows that replacement of a phenyl group in Malachite Green with a heterocyclic ring as a benzopyran or a pyridine causes a bathochromic shift of λmax. The Resonance Raman technique was applied to the triarylmethane dye containing a pyridine ring, and typical “x-band” and “y-band” of the triphenylmethane dye in the absorption spectra were assigned. The PPP-MO calculation shows that the longest-wavelength of the triarylmethane dye containing a 1, 4-naphthoquinone or anthraquinone is shifted to the near-infrared region. It was found that the quantum yield for decomposition of triarylmethane containing a benzothiopyran ring by irradiation of the UV light was larger than that of triphenylmethane in ethanol, but oppositely in chloroform it was smaller. The steric effect of the methyl substituted triphenylmethane was interpreted by the MM 2 calculations