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Theoretical study of electric field effects on C-C bond vibrations and optical behavior of acrylonitrile
Muhammad Kashif Majeed1,2, Muhammad Idrees3, M Umar Majeed4
1Eric Jonsson School of Engineering, University of Texas at Dallas, Richardson, TX, 75080, USA. kashifmajeed96@gmail.com.
Context:
External electric fields (EEFs) can significantly influence the structure, stability, and spectroscopic properties of polar conjugated molecules, serving as a controlled model for electrostatic effects in chemically relevant environments. In this study, acrylonitrile was examined to understand how an oriented EEF affects its C2-C3 bond and related optical behavior. The applied field leads to gradual stretching of the C2-C3 bond, a decrease in total energy, an increase in the dipole moment, and a reduction in the dissociation barrier, indicating bond softening and field-induced electronic redistribution. Corresponding changes in the IR spectra show field-dependent shifts and intensity variations in the C2-C3 stretching region, while the UV-visible spectra display a blue shift and enhanced absorption, which are attributed to the modulation of π → π* transitions.
Methods:
The electronic, structural, and spectroscopic properties of Acrylonitrile were systematically investigated using density functional theory (DFT). Geometry optimization and property calculations were conducted at the B3LYP/6-311G(d,p) level under EEFs applied along the molecular axis. The study evaluated field-dependent total energies, dipole moments, frontier orbital energies, and variations in bond lengths, with potential energy scans used to explore changes in the C2-C3 bond dissociation behavior. Infrared and UV-visible spectra were also calculated using the Gaussian 09 software.
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