NBO analysis and vibrational spectra of 2,6-bis(p-methyl benzylidene cyclohexanone) using density functional theory

Spectrochim Acta A Mol Biomol Spectrosc. 2009 Jun 16. [Epub ahead of print]

NBO analysis and vibrational spectra of 2,6-bis(p-methyl benzylidene cyclohexanone) using density functional theory.

Padmaja L, Amalanathan M, Ravikumar C, Hubert Joe I.

Centre for Molecular and Biophysics Research, Department of Physics, Mar Ivanios College, Thiruvananthapuram 695015, Kerala, India.

Vibrational analysis of the 2,6-bis(p-methyl benzylidene cyclohexanone) [PMBC] compound was carried out by using NIR FT-Raman and FT-IR spectroscopic techniques. The equilibrium geometry, various bonding features and harmonic vibrational frequencies of PMBC have been investigated with the help of B3LYP/6-31G(d) density functional theory method. The optimized geometry clearly demonstrates cyclohexanone ring chair conformation is changed into half-chair conformation. The shortening of C-H bond length and blue shifting of the CH stretching wavenumber suggest the existence of improper weak C-Hcdots, three dots, centeredO hydrogen bonding, which is confirmed by the natural bond orbital analysis. The Mulliken population analysis on atomic charges and the HOMO-LUMO energy are also calculated.

PMID: 19640777 [PubMed - as supplied by publisher]