Negative solvatochromism of push–pull biphenyl compounds: a theoretical study

We have investigated the negative solvatochromism observed for 4-(phenyloxido)-N-methylpyridinium in solvents of varying polarity using a hierarchy of solvation models (continuum, discrete, and mixed) combined with a (TD)DFT description. Overall, the significant hypsochromic shift measured in the experiments is reproduced qualitatively and quantitatively through calculations. More in detail, the role played by the solvent in tuning the spectral properties of POMP has been correlated with geometrical and electronic effects, and the π–π aggregation effects of POMP have been shown to be important in solvents of low and medium polarity.