Influence of Hydrogen Bonding and Polarity on the Spectral Properties of 4-Aminophthalimide Clusters Formed with Triethylamine and Dimethyl Sulfoxide in Solution

The time-dependent density functional theory (TDDFT) method has been carried out to study the influences of hydrogen bonding and solvent polarity on the spectral properties of 4-aminophthalimide (4AP) clusters formed with hydrogen-accepting solvents triethylamine (TEA) and dimethyl sulfoxide (DMSO). The ground- and S₁-state geometry structure optimizations, hydrogen bond energies, absorption and emission spectra for both the 4AP monomer and its two triply hydrogen-bonded clusters 4AP + (TEA)₃ and 4AP + (DMSO)₃ have been calculated using DFT and TDDFT methods respectively with the hybrid exchange correlation functional PBE1PBE and split-valence basis set 6-311++G(d,p). It has been demonstrated that the two hydrogen bonds I and II formed with the amine group of 4AP are significantly strengthened while the hydrogen bond III formed with the imide group is slightly weakened due to the intramolecular charge transfer from the amine group to the two carbonyl groups of the 4AP molecule upon photoexcitation. In addition, the hydrogen bonds formed by 4AP with DMSO are stronger than those formed with TEA, which together with its strong polarity, should be the main reasons for the more redshifts of both the absorption and the fluorescence spectra of 4AP in solvent DMSO than those in TEA.