Vibrational assignments, normal coordinates analysis, force constants, and DFT/MP2 computations of
Belal Surour1, Ahmed E Hassan2, Honsi Anwar3
1Department of Chemistry, Faculty of Science (Men's Campus), Al-Azhar University, Nasr City, 11884, Cairo, Egypt; Megachem Company, El-Nozha, Cairo, Egypt.
None:
The vibrational assignments of 5-Chloro-2,4,6-trifluoropyrimidine have been early investigated, however, the proposed fundamentals were not spanned to their appropriate species owing to neglecting the overall symmetry. Nevertheless, the lack of force constants (FCs) determination encourages us to reinvestigate the molecule. Aided by DFT (B3LYP, B3P86, B3PW91, ωBX97) and MP2 = full quantum chemical computations, we have provided a reliable vibrational analysis of all normal modes based on the C2v point group. Different methods of the currently used normal coordinate analysis were also validated. Our results are compared with available infrared and Raman spectral data, including estimated infrared intensities, Raman scattering activities, genuine FCs in internal coordinates, and potential energy distributions (PEDs). Using NCA in a well-defined internal coordinate that enables us to estimate FCs based on G.F. Wilson led to better fundamental interpretations than those obtained from atomic displacements in Cartesian coordinates, VEDA, and MOLVIB programs. The current investigation potentially offers corrected vibrational mode assignments, filling gaps in prior literature and aiding in accurately characterizing fluorinated pyrimidine derivatives.
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