Solvatochromism of some hemicyanines

► The charge transfer in the probes results in a large solvatochromic shift. ► Bathochromic shift due to the increase in alkyl chain at quaternary nitrogen. ► A polarity switch reverting solvatochromism. ► Quantitative solvent-parameter-absorption spectra/Stokes shift relationships could be established. ► Sensitivity of polarity in dipolar aprotic solvent is more than that in hydroxylic solvents toward transition energy.