Solvatochromic behavior of 1-(p-dimethylaminophenyl)-2-nitroethylene in 24 binary solvent mixtures composed of amides and hydroxylic solvents

The molar transition energy (ET) polarity values of 1-(p-dimethylaminophenyl)-2-nitroethylene were collected in mixed solvent systems comprising a formamide [N,N-dimethylformamide (DMF), N-methylformamide (NMF) and formamide (FA)] and a hydroxylic (water, methanol, ethanol, propan-1-ol, propan-2-ol, butan-1-ol, and 2-methylpropan-2-ol) solvent. Mixed systems containing DMF with the other formamides (NMF and FA) and NMF with FA were also studied. Each solvent system was analyzed in terms of both solute-solvent and solvent-solvent interactions. These latter interactions were responsible for the synergism observed in some mixtures. All data were successfully fitted to a model based on solvent exchange equilibria and the results suggest that both hydrogen bonding and solvophobic interactions contribute to the formation of the solvent complexes responsible for the observed synergistic effects in the PS of the dye.