Vibrational spectra, ab initio/DFT electronic structure calculations, and normal coordinate analysis of 2-bromo-5-fluorobenzaldehyde

Tom Sundius, C.S. Hiremath

Research output: Contribution to journalArticleScientificpeer-review

Abstract

FT-IR (4000-400 cm(-1)) and FT-Raman (3500-50 cm(-1)) spectral measurements of solid samples of 2-bromo-5-fluorobenzaldehyde (BFB) have been done. Ab initio (RHF/6-311G*) and DFT (B3LY/6-311G* and B3PW91/6-311G*) calculations have been performed giving energies, optimized structures, harmonic vibrational frequencies, depolarization ratios, infrared intensities, Raman activities and atomic displacements. Furthermore force field calculations have been performed by normal coordinate analysis. Force field calculations showed that several normal modes are mixed in terms of the internal coordinates. A complete assignment of the observed spectra, based on spectral correlations, electronic structure and normal coordinate analysis, has been proposed. Optimization leads to C-S symmetry with O-trans and O-cis isomers, with respect to aldehydic oxygen and bromine, with O-trans-isomer as the low energy stable form. The energy difference between the two isomers is 2.95084 kcal/mol. The results of the calculations have been used to simulate IR and Raman spectra for BFB that showed excellent agreement with the observed spectra. The SQM method, which implies multiple scaling of the ab initio and DFT force fields has been shown superior to the uniform scaling approach. (C) 2009 Elsevier B.V. All rights reserved.
Original languageEnglish
JournalSpectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy
Volume74
Issue number5
Pages (from-to)1260-1267
Number of pages8
ISSN1386-1425
DOIs
Publication statusPublished - Dec 2009
MoE publication typeA1 Journal article-refereed

Fields of Science

  • 114 Physical sciences

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