Theoretical Prediction of the Adiabatic Electron Affinity of Hydantoin based drugs and their derivatives

Abstract The addition of electron to a neutral system can either release or consume energy, which is known as the electron affinity (EA) of the system. EA quantifies the attractive forces between the incoming electron and the nucleus, with greater attraction leading to higher energy release. In this research, the adiabatic electron affinity (AEA) of some hydantoin derivatives, including some important drugs such as phenytoin, allantoin, iprodine, ethotoin and mephenytoin were theoretically predicted by using the B3PW91 method with 6-311 + G(2df,2p) basis set at the B3LYP/6–31 + G(d,p) geometries. The accuracy of the different DFT methods was statistically proven based on the standard AEAs, as determined by the average AEA of the three composite high-level ab-initio methods (G4, G3B3 and CBS-QB3). The results reveal that both the AEA of hydantoin derivatives are predicted to increase or decrease based on the nature of the substituted groups and its position at the hydantoin ring. The natural spin density and the natural atomic charges of the neutral and anionic radicals were computed by using the natural bond orbital (NBO) analysis at the B3LYP/6–31 + G(d,p) level of theory. For the majority of the investigated hydantoins, the NBO shows that the maximum spin density is mainly located on the carbonyl carbon atom (C4). The geometries of the formed anions are distorted compared to their neutral molecules. Adequate linear relationships between the predicted AEA and the energy gaps of the neutral molecules with the correlation coefficient (R2) of 0.9781.