Ab initio study on N,N-dimethylaminoethanol: Conformers and energies

All the possible rotamers of N,N-dimethylaminoethanol (DMAE) were fully optimized at the ab initio level using hybrid density functional B3LYP/aug-cc-pVDZ method. Twelve local minima for DMAE were found and their geometric parameters, dipole moments, intramolecular hydrogen bonds (HB) and relative energies of all conformers were determined. Their relative energies calculated at MP3 and MP4 (SDTQ) levels of theory further confirm that the gauche′-Gauche-gauche′ (g′Gg′) conformer having the intramolecular HB OH⋯N is the most stable. The vertical ionization energies of the conformers calculated with ab initio electron propagator theory in the P3/aug-cc-pVTZ approximation are in agreement with the experimental data from photoelectron spectroscopy. Combined with statistical mechanics principles, conformational distributions at various temperatures are computed and the temperature dependence of photoelectron spectra (PES) is interpreted. The intramolecular HB OH⋯N influences on the molecular electronic structures in the conformer g′Gg′ was exhibited by Natural bond orbital (NBO) analyzes.