DFT computations,vibrational spectra,monomer, dimer,NBO and NMR analyses of antifungal agent: 3,5-Dibromosalicylic acid |
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Authors: | V Balachandran S Rajeswari S Lalitha |
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Institution: | 1. Department of Physics, A.A. Government Arts College, Musiri 621 201, India;2. P.G. & Research Department of Physics, Periyar EVR College (Autonomous), Tiruchirappalli 620 023, India |
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Abstract: | The experimental and theoretical study on the structures and vibrations of 3,5-dibromosalicylic acid (DBSA) are presented. The FT-IR and FT-Raman of the title compound have been recorded. The molecular structures, vibrational wavenumbers, infrared intensities, Raman activities were calculated. The energies of DBSA are obtained for all the eight conformers from density functional theory with 6-311++G(d,p) basis set calculations. From the computational results, C1 or C5 forms are identified as the most stable conformers of DBSA. The spectroscopic and theoretical results are compared with the corresponding properties for DBSA monomer and dimer of C1 (or C5) conformer. Intermolecular hydrogen bonds are discussed in dimer structure of the molecule. NBO analysis is useful to understand the intramolecular hyperconjugative interaction between lone pair O9 and C7 O8. The calculated HOMO–LUMO energies reveal charge transfer occurs within the molecule. The polarizability, first hyperpolarizability, anisotropy polarizability invariant has been computed using quantum chemical calculations. The isotopic chemical shift computed by 1H and 13C nuclear magnetic resonance (NMR) chemical shifts of the DBSA molecule, calculated using the gauge invariant atomic orbital (GIAO) method, also shows good agreement with experimental observations. |
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