Structural, spectroscopic and docking properties of resorcinol, its -OD isotopomer and dianion derivative: a comparative study

Structural and vibrational properties of resorcinol, its -OD isotopomer and dianion salt were compared with the help of quantum-chemical and spectroscopic techniques. The relative stability computed at the MP4/6-311++G(d,p) level predicted that the syn-syn rotameric form of the resorcinol molecule is about 0.7 kcal/mol higher in energy than the more stable anti-syn and anti-anti forms. Vibrational frequencies calculated for the optimized α-resorcinol and its -OD isotopomer unit cells showed that out-of-plane bending vibrations tend to shift to higher wavenumbers for the solid phase compared to the non-condensed phase indicating strong intermolecular packing forces. OH/OD isotopic shifts were identified for stretching and binding modes, which supported by DFT findings. Infrared, Raman and proton NMR data confirmed a notable change in the overall electronic properties of resorcinol upon the abstraction of the hydroxyl protons. In addition, resorcinol, in its three rotameric configurations, exhibited a stable complexation with keratin-7. While the highly electronegative nature of oxygen atoms contributed effectively to the binding affinity of resorcinol towards keratin-7, careful docking analysis showed that the steric factor play the major role in the keratolytic activity of resorcinol.