Ab Initio and Density Functional Theory (DFT) Study on Clonazepam


Quantum chemical calculations have been carried out to investigate the vibrational frequencies of clonazepam. The FTIR spectrum of clonazepam was recorded in the region 4000 to 400 cm–1 in the solid phase. The optimized geometry, wave number and intensity of the vibrational bands of clonazepam were obtained by ab initio Restricted Hartree Fock (RHF) and Density Functional Theory (DFT) methods with complete relaxation in the potential energy surface using the 6-31G (d,p) basis set. A complete vibrational assignment aided by the theoretical harmonic frequency analysis is proposed. The observed and the calculated wavenumbers are found to be in good agreement. The experimental spectra also coincide satisfactorily with those of theoretical spectra. Theoretical spectrograms for the IR spectrum were also constructed in RHF and B3LYP levels. In addition to this the RHF and DFT based NMR calculation procedure was used to assign the 1H NMR chemical shift of clonazepam. Theoretical values are compared with the experimental data.

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B. Sylaja and S. Srinivasan, "Ab Initio and Density Functional Theory (DFT) Study on Clonazepam," Open Journal of Biophysics, Vol. 2 No. 3, 2012, pp. 80-87. doi: 10.4236/ojbiphy.2012.23011.

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The authors declare no conflicts of interest.


[1] J. H. Skerritt and G. A. Johnston, “Enhancement of GABA Binding by Benzodiazepines and Related Anxiolytics,” European Journal of Pharmacology, Vol. 89, No. 3-4, 1983, pp. 193-198.doi:10.1016/0014-2999(83)90494-6
[2] P. F. Lehoullier and M. K. Ticku, “Benzodiazepine and β-Carboline Modulation of GABA-Stimulated 36Cl-Influx in Cultured Spinal Cord Neurons,” European Journal of Pharmacology, Vol. 135, No. 2, 1987, pp. 235-238. doi:10.1016/0014-2999(87)90617-0
[3] M. J. Frisch, et al., “Gaussian 03, B05,” Gaussian Inc., Wallingford, 2003.
[4] G. Gilli, V. Bertolasi and M. Sacerdoti, “7-Nitro-1,3-Dihydro-5-Phenyl-2H-1,4-Benzodiazepin-2-One (Nitrazepam),” Acta Crystallographica Section B, Vol. 33, 1977, pp. 2664-2667. doi:10.1107/S0567740877009157
[5] S. Mohan and K. Settu, “Vibrational Spectra and Analysis of 1,2,3-Benzotriazole,” Indian Journal of Pure and Applied Physics, Vol. 31, No. 11, 1993, pp. 850-854.
[6] G. A. Neville and H. D. Beckstead, “Fourier Transform Raman and Infrared Study of Nitrazepam, Nimetazepam, Clonazepam and Flunitrazepam,” Vibrational Spectroscopy, Vol. 1, No. 3, 1991, pp. 287-297.doi:10.1016/0924-2031(91)85006-9
[7] V. Krishnakumar and S. Seshadri, “Scaled Quantum Chemical Calculations and FT-IR, FT-Raman Spectral Analysis of 2-Methylpiperazine,” Spectrochimica Acta Part A, Vol. 68, No. 3, 2007, pp. 833-838. doi:10.1016/j.saa.2006.12.067
[8] R. Meenakshi, L. Jaganathan, S. Gunasekaran and S. Srinivasan, “Density Functional Theory, Restricted HartreeFock Simulations and Vibrational Spectroscopic studies of Nicorandil,” Molecular Simulation, Vol. 36, No. 6, 2010, pp. 425-433. doi:10.1080/08927020903583822

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