Abstract
This work presents a theoretical simulation of the infrared spectra of strong hydrogen bond in alpha-phase 2-pyridone dimers, as well as in their deuterium derivatives at room temperature. The theory takes into account an adiabatic anharmonic coupling between the high-frequency N-H(D) stretching and the low-frequency intermolecular N...O stretching modes by considering that the effective angular frequency of the fast mode N-H(D) is assumed to be strongly dependent on the slow mode stretching coordinate N...O, the intrinsic anharmonicity of the low-frequency N...O mode through a Morse potential, Davydov coupling triggered by resonance exchange between the excited states of the fast modes of the two hydrogen bonds involved in the cyclic dimer, multiple Fermi resonances between the N-H(D) stretching and the overtone of the N-H(D) bending vibrations and the direct and indirect damping of the fast stretching modes of the hydrogen bonds and of the bending modes. The IR spectral density is computed within the linear response theory by Fourier transform of the autocorrelation function of the transition dipole moment operator of the N-H(D) bond. The theoretical line shapes of the υN-H(D) band of alpha-phase 2-pyridone dimers are compared to the experimental ones. The effect of deuteration is successfully reproduced.
Highlights
The hydrogen bonding is responsible for the appearance of spectacular changes in IR spectra of associated molecules
The theory takes into account an adiabatic anharmonic coupling between the high-frequency N-H(D) stretching and the low-frequency intermolecular N...O stretching modes by considering that the effective angular frequency of the fast mode N-H(D) is assumed to be strongly dependent on the slow mode stretching coordinate N...O, the intrinsic anharmonicity of the low-frequency N...O mode through a Morse potential, Davydov coupling triggered by resonance exchange between the excited states of the fast modes of the two hydrogen bonds involved in the cyclic dimer, multiple Fermi resonances between the N-H(D) stretching and the overtone of the N-H(D) bending vibrations and the direct and indirect damping of the fast stretching modes of the hydrogen bonds and of the bending modes
In this work we present a theoretical approach for vibrational couplings in moderately strong hydrogenbonded systems and use it for simulating experimental infrared spectra for strong hydrogen-bonded of alpha solid-state phase 2-pyridone crystal dimers
Summary
The hydrogen bonding is responsible for the appearance of spectacular changes in IR spectra of associated molecules. In this work we present a theoretical approach for vibrational couplings in moderately strong hydrogenbonded systems and use it for simulating experimental infrared spectra for strong hydrogen-bonded of alpha solid-state phase 2-pyridone crystal dimers. Wójcik [15] has presented a theoretical model for vibrational couplings in weak and moderately strong hydrogen-bonded systems and use it for modeling experimental infrared spectra for hydrogenbonded crystals and hexagonal ice. The model is based on vibronic-type couplings between high and low frequency modes in hydrogen bridges, Davydov interactions [16] and Fermi resonance [17,18]. The numerical results show that this theoretical approach allows fitting the experimental υN-H infrared line shapes of cyclic alpha-phase 2-pyridone crystal dimer and its deuterium derivative by using a minimum number of parameters. Experimentalist should be able to compare experimental and theoretical data in an easy-to-use way
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
