Highly correlated ab initio molecular orbital methodologies have been used in the study of substituent effects on the singlet-triplet gaps of a series of nitrenium ions and their corresponding isoelectronic carbenes. Calculations in solution were carried out with the isodensity polarizable continuum models, IPCM. The results show a net stabilization of the singlet species as a result of electronic density donation of the substituents to a vacant p orbital located in the central atom. It is shown that this "π-donor-π-acceptor" dependence of the singlet-triplet gap is more significant in the case of the nitrenium ions, due to the presence of a positive charge. In addition, it was found that the singlet-triplet gaps decrease with the polarity of the solvent, most likely due to stabilizing electrostatic interactions between the solvent and the charge distribution of the singlet.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry