Electronic Spectra and Structures of Organic π-Systems. VI. Electronic States of Diazomethane, Ketene, Diazocyclo-pentadiene and Benzenediazonium Ion

The electronic states of diazomethane, ketene, diazocyclopentadiene and benzenediazonium ion were studied by the semi-empirical ASMO LCAO SCF CI method. Both π- and \barπ-systems were taken into consideration. Two types of approximations, Mulliken’s formula and a new semitheoretical formula, were used in the evaluation of the core resonance integrals. The latter gives satisfactory results though it contains no arbitrary adjustable parameters. The longest wavelength singlet-singlet transition of diazomethane, ketene or diazocyclopentadiene is 1π–1\barπ, and that of benzenediazonium ion 1π–1π.