Effect of substitution of electron-donating and -withdrawing groups on the stability of flavin-diaminepyridine complexes-a density functional theory study

Flavin molecules are currently attracting considerable interest in a wide range of biochemical and molecular electronic researchers. A systematic theoretical study on the effect of substitution of electron-donating and -withdrawing groups at the meta and para position of flavin molecule was carried out. The geometry of isolated flavin molecules and flavin-diaminepyridine (DAP) complexes were optimized at B3PW91/6-311++G(d, p) level of theory. Further, the single point energy and natural bond orbital calculations were carried out with CC-PVTZ basis set. The ionization energy and electron affinity of a flavin molecule with different functional groups are presented. The chemical hardness, chemical potential, electrophilic power and Fukui functions were calculated and used to study the change in molecular stability and hydrogen bonding tendency of the flavin molecule due to the substitution of different functional groups. The stabilization energy due to hydrogen bond and interaction energy of flavin-DAP complexes were presented and the results were analyzed in the light of substitution effect.