Protonated salicylaldehyde: Electronic properties

Abstract: The excitation spectrum of protonated salicylaldehyde has been recorded in the 20,800–22,400cm−1 region (480–450nm). The first excited state of protonated salicylaldehyde is a ππ∗ state, largely red shifted as compared to the ππ∗ transition of its neutral analogue. Like protonated benzaldehyde and in contrast to some other protonated aromatic molecules such as benzene or tryptophan in which the excited state dynamics is so fast that no vibrational structure can be observed, the vibrational bands are well resolved and assigned. This molecule has many low energy isomers and the simulations of the electronic spectrum via ab initio excited state optimizations and Franck–Condon calculations are precise enough to assign the observed electronic spectrum to one of the isomers. [Copyright &y& Elsevier]