Charge Transfer Transition: Investigation of the Effect of Solvents on Electronic Spectra of N-Alkyl/ N-Alkylphenyl Derivatives of p-Nitroaniline

The UV absorption spectra of N-alkyl and N-alkylphenyl derivatives of p-nitroaniline were recorded in acetone, acetonitrile, DMSO, toluene, chloroform and dichloromethane.The absorption maxima were calculated (TD-DFT) in the same solvents, using Gaussian 09 software package for windows at B3LYP/6-31G (d, p) level.Both calculated and experimental values of λ max increases with increase in solvent polarity indicating that the absorption involves a charge transfer transition.The interactions of a single molecule of polar and non-polar solvents with the substrate were studied by calculations.The results show that polar solvent (acetone) interacts more strongly than non-polar solvent (toluene) due to H bonding and causes a greater reduction in HOMO-LUMO gap and an increase in λ max .