Probing the Fermi resonance of pyridine surrounded by hydrogen bonding network by density functional theory

The Fermi resonance (FR) occurs between the ring breathing vibrational (nu 1) and the triangular stretching (nu 12) mode of pyridine in aqueous pyridine solution was studied using Raman spectroscopy combined with density functional theory (DFT) calculations. The effect of H -Bond on the FR in the mixture was performed by MD analysis. Combined with the FR parameters, it was found that due to the H -Bond effect the FR coupling changed significantly when the pyridine mole fractions were near 0.7 and 0.5, respectively. The water H -Bond network structure is most favorable for pyridine molecule bonding at a pyridine mole concentration around 0.5, and water preferentially affinity to the pyridine molecule at x = 0.7. In addition, we analyzed the O-H vibrational region at different mole fractions and theoretically calculated Py associated O-H in specific molecular bonds.