Ab initio and electron spectroscopy study of carbonyl derivatives

The bands present in the low ionisation energy region (Ei[less-than-or-eq] 12 eV) of the He I photoelectron spectra, and the low energy resonances of the electron transmission spectra of some substituted carbonyls XC(O)R (X = Et2N, alkyl, EtS and EtO; R = Me and CH2SR) have been assigned to the corresponding molecular orbitals by comparison with the assignments reported for simple related molecules. Fully optimized 3-21G ab initio calculations reproduce the assignment of the spectra and available geometric parameters and therefore have been used to determine the electronic charge distribution among the various atoms and groups in the studied compounds. A combined analysis of the theoretical and experimental data provides a detailed understanding of the electronic interaction among the X, CO and R groups in the molecules studied.