Solvatochromic behavior of non-activated indolinobenzospiropyran 6-carboxylates in aqueous binary solvent mixtures. Part II1

The solvatochromic behavior of non-activated indolinobenzospiropyran 6-carboxylates SP-1–2 in aqueous binary solvent mixtures was investigated.Marked negative solvatochromism was exhibited by SP-1–2 in the whole region of solvent polarity examined. Excellent linear relationships were observed between λmax and the solvent polarity parameter, ET(BM), for the aqueous binary solvent mixtures. The sensitivity of the binary solvent system toward the transition energies of the MC form was highest in the water–methanol solvents in all SP molecules examined. As of other merocyanine dyes in neat solvents, the MC form of spiropyran 6-carboxylates in the aqueous binary solvents showed a negative solvatochromism. The aqueous solvent was found to affect the solvatochromic behavior of the merocyanine dyes by increasing the sensitivity of the chromophore to the effects of solvation via H-bonding.