Quantitative prediction of absorption maxima in the electronic spectra of unsaturated compounds: Extrapolation from fragments to molecules in quantum chemical calculations

The possibility of quantitative prediction of maxima in the electronic absorption spectra of unsaturated organic compounds is studied by the Pariser-Parr-Pople method with fitted parameters. The quantum chemical methods are classified according to the type of extrapolation: from elementary particles (physical constants) to molecules, from atoms to molecules, and from fragments to molecules. N. G. Chernyshevskii Saratov State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 6, pp. 1016–1022, November–December, 1996. Translated by I. Izvekova