Journal of Saudi Chemical Society (Nov 2023)
Theoretical calculation of the adiabatic electron affinity and vertical electron affinity of some hydantoin drugs
Abstract
Several DFT approaches with 6–311 + G(2df,2p) basis set at the B3LYP/6–31 + G(d,p) geometries were examined to calculate accurate adiabatic electron affinity (AEA) for some hydantoin derivatives. The accuracy of these approaches was statistically examined with respect to the standard reference AEA, which obtained by using G4, G3B3 and CBS-QB3 methods. The results reveal that the least RMSE values were obtained for B3PW91, TPSSTPSS and B3LYP approaches, respectively. The B3PW91 approach in conjunction with the 6–311 + G(2df,2p) basis set at the B3LYP/6–31 + G(d,p) geometries were used to calculate the AEA for some hydantoin drugs, including Phenytoin, Nitrofurantoin, Allantoin, Iprodine, Ethotoin and Mephenytoin, as well as some of phenytoin and nitrofurantoin derivatives. Moreover, the vertical electron affinity (VEA) of all investigated compounds were calculated using the B3LYP/6–31 + G(d,p) level. The substitution effects on the AEA values were studied and discussed. The results reveal that the electron donating groups decrease the AEA and VEA value, whereas, the reverse is true in the case of the electron withdrawing groups. Furthermore, NBO analysis was used to calculate the natural spin density and atomic charges of the neutral and anion species. The results obtained show, in general, that the maximum spin density is located on the carbonyl carbon atom of the hydantoin ring. The changes in the geometrical structures (bond lengths and bond angles) of anions compared to the neutral molecules were also studied and discussed. Correlations between the AEA and VEA with the energy gap with the correlation coefficients (R2) close to unity were shown. Furthermore, the AEA and VEA for some hydantoin derivatives and drugs were also calculated in aqueous solution, and their results are compared with the gas phase results.
