L. Serrano-Andrés, M. Fülscher
Dec 4, 1996
Citations
1
Influential Citations
28
Citations
Journal
Journal of the American Chemical Society
Abstract
The Complete Active Space (CAS) SCF method and multiconfigurational second-order perturbation theory (CASPT2) have been used in a theoretical analysis of the electronic spectra of glycine and N-acetylglycine. The calculations comprise a large number of singlet valence and Rydberg excited states. The electronic spectrum of glycine is dominated by excitations located at the carboxylic acid group. Two valence π → π* states (named NV1‘ and NV2‘) have been computed at 8.10 and 10.20 eV with intensities 0.194 and 0.125, respectively. We found in glycine two weak valence n → π* states 5.65 and 6.51 eV above the ground state. One involves excitations from the lone pair orbital on the carboxylic oxygen. The second can be characterized as an intramolecular charge transfer state from the amine terminal group to the peptide unit. A n → σ* excited state comprising excitations from the in-plane lone pair of the nitrogen is suggested to be responsible for a weak band around 8.6 eV. The spectrum of N-acetylglycine is sho...