FIRST IONIZATION-POTENTIALS AND CONJUGATION IN MOLECULES OF ETHYLENE DERIVATIVES CONTAINING ORGANOELEMENTAL SUBSTITUENTS OF GROUP-IV ELEMENTS

Unlike the E-HOMO energies, the first vertical ionization potentials ( I-1) of monosubstituted ethylenes depend not only on both the inductiv e and resonance effects but also on the polarizability of the substitu ents, which can be characterized by the sigma(alpha) parameters. The s igma(R)(+), sigma(p)(+), and sigma(alpha) parameters for 12 silicon-, germanium-, and tin-containing groups were determined using the equati ons relating the I-1 values and the sigma(1), sigma(R)(+), sigma(p)(+) , and sigma(alpha) parameters of the substituents in the molecules of organic compounds. The conjugation of organoelemental substituents wit h the double bond is stronger than that with benzene ring; the sigma(R )(+) parameters in the ethylene and benzene series are related by a li near dependence.