Investigation of the structures and absorption spectra for some hemicyanine dyes with pyridine nucleus by TD-DFT/PCM approach

A combination of time-dependent density functional theory (TD-DFT) and the polarizable continuum model (PCM) is applied to study the ground-state geometries and the properties of electronic absorption spectra for some hemicyanine dyes with pyridine nucleus. The crystal parameters of 1-methyl-4-(p-dimethylaminostyryl)-pyridinium and π → π∗ type absorption bands of a series of hemicyanine dyes with pyridine nucleus are all reasonably reproduced at the PBE1PBE(PCM)/6-31 G(d) level. Regression analysis is used for studying theoretical results of the absorption maxima in methanol and water. Compared with experimental counterparts, estimated overall uncertainties in the absorption maxima are about ±2%.