Integrated computational approach to vibrationally resolved electronic spectra: anisole as a test case

A new general and effective procedure to compute Franck-Condon spectra from first principles is exploited to elucidate the subtle features of the vibrationally resolved optical spectra of anisole. Methods based on the d. functional theory and its time-dependent extension for electronic excited states [B3LYP/6-311+G(d,p) and TD-B3LYP/6-311+G(d,p)] have been applied to geometry optimizations and harmonic frequency calcns. Perturbative anharmonic frequencies have been calcd. for the ground state, and the Duschinsky matrix elements have been used to evaluate the corresponding anharmonic corrections for the first excited electronic state. The relative energetics of both electronic states has been refined by single point calcns. at the coupled clusters (CC) level with the aug-cc-pVDZ basis set. Theor. spectra have been evaluated using a new optimized implementation for the effective computation of Franck-Condon factors. The remarkable agreement between theor. and exptl. spectra allowed for revision of some assignments of fundamental vibrations in the S1 state of anisole.