Quantum chemical approach for chemiluminescence characteristics of di-substituted luminol derivatives in polar solvents

The presence of electron donating substituents altered the electronic properties of the luminol and this phenomenon was evaluated in relation to the chemiluminescence potential of the studied disubstituted luminol derivatives using three different theoretical calculation methods: Restricted Hartree Fork (RHF), Density Functional Theory (DFT) with hybrid function of Becke three-parameters Lee, Yang and Parr (B3LYP), i.e. (DFT-B3LYP), and Møller-Plesset Perturbation Theory (MP2). Different behavior was observed for the studied molecular structures in different phases (gas, water, and dimethylformamide) to emphasize the influence of molecular environment on the chemiluminescence property, regardless of the theoretical methods employed. Time-dependent DFT with correction terms enabled accurate prediction of frontier orbital energies such that calculated energy gaps could reasonably correlate with the lowest excitation energies. Besides, the electron donating moiety induced better chemiluminescence property depending on the donating power, position as well as the number of such substituents. Dimethylamino-substituted luminol showed better quantum chemical parameters and spectra pattern to have much-enhanced chemiluminescence properties possibly. Specifically, its positional isomer named 6,8-bis(dimethylamino)-5-amino-2,3-dihydro-1,4-phthalazinedione showed a greater potential of being a better chemiluminescence reagent in various analytical assays.