PHOTOELECTRON-SPECTRA AND MOLECULAR-PROPE RTIES .148. 1ST VERTICAL IONIZATION ENERGIES OF BETA-TRIMETHYL-SUBSTITUTED ETHERS RO-CH(3-N)[SI(CH3)3]N

The first vertical ionization energies of dialkylethers are lowered up to 3 eV (!) by beta-trimethylsilyl substituents and, therefore, furth er confirm the powerful electron donor effect of -CH3-n[Si(CH3)3]n and -Si[Si(CH3)3]3 groups. The gas-phase photoelectron spectra are assign ed based on geometry-optimized MNDO calculations and the substituent e ffects are discussed in terms of conformationally dependent hyperconju gative second order perturbations.