Two-electron reduction of nitroaromatic compounds by flavin mononucleotide. DFT computational study

Abstract

The mechanism for reduction of nitroaromatic compounds by flavin mononucleotide (FMN) was examined at MPWB1K/tzvp level. The solvent effects were calculated using a PCM(Pauling) and SMD(Pauling) solvation models for ions and neutral molecules, respectively. Calculated thermodynamics of the reduction of nitro group to nitroso group suggests consequtive four-steps’ process (electron–proton–electron–proton transfer) where the first proton comes from solution, while the second one – from FMN. Water molecule releases during fourth step of the process. Electron attachment to nitrocompound and electron lose by reduced FMN facilitate the breaking of N–O bond and proton release, respectively. Calculations show that reduction of nitro group to nitroso group in studied nitrocompounds is a thermodynamically feasible with 56–59 kcal/mol Gibbs free energy release. The most easy electron transfer proceeds for TNT (2,4,6-trinitrotoluene) and NTO (5-nitro-2,4-dihydro-3H-1,2,4-triazol-3-one). While the most energy release occurs during proton transfer in case of ANTA (5-amino-3-nitro-1H-1,2,4-triazole).

Keywords

• nitroaromatics
• reduction
• flavin mononucleotide
• DFT