N-hydroxy-monomethoxy-4-aminoazobenzenes:a computational stydy

摘要

Structures and electronic properties of the N-hydroxy metabolites (N-OH-OMe-AAB) of the monomethoxy-4-aminoazobenzene dyes(OMe-AAB) have been calculated using density functional theory with a basis set that includes polarization functions on all the atoms.Positional isomers with the methoxy group ortho tohydroxyamino group (N-OH-3(5)-OMe-AAB) are found to be lower in energy than isomers with the methoxy group mtea to the hydroxyamino group(N-OH-2(6)-OMe-AAB).The geometrical parameters of the phenyl rings for the corresponding isomers of OMe-AAB and N-OH-OMe-AAB are very similar.The length of the C-NHOH bond,however, is significantly longer than the length of the C-NH_2 bond.The energies of the frontier orbitals are more negative for each of the positional isomers of N-OH-OMe-AAB than for the corresponding isomer of OMe-AAB.In particular,the energy of the lowest unoccupied molecular orbital decreases a few kcal/mol for each isomer,suggesting that these N-hydroxy metabolites are slightly more electrophilic.