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Journal of Spectroscopy
Volume 2013, Article ID 538917, 13 pages
http://dx.doi.org/10.1155/2013/538917
Research Article

Structural and Vibrational Study on Monomer and Dimer Forms and Water Clusters of Acetazolamide

1Physics Department, Science Faculty, Istanbul University, Vezneciler, 34134 Istanbul, Turkey
2Electrical-Electronics Eng. Department, Engineering Faculty, Istanbul University, Avcilar, 34320 Istanbul, Turkey
3Physics Department, Science and Letters Faculty, Istanbul Kultur University, Atakoy Campus, Bakirkoy, 34156 Istanbul, Turkey

Received 24 June 2013; Revised 6 September 2013; Accepted 7 October 2013

Academic Editor: Shin ichi Morita

Copyright © 2013 Aysen E. Ozel et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Experimental IR and Raman spectra of solid acetazolamide have been analysed by computing the molecular structures and vibrational spectra of monomer and dimer forms and water clusters of acetazolamide. The possible stable conformers of free acetazolamide molecule in the ground state were obtained by scanning the potential energy surface through the dihedral angles, D1 (1S-2C-6S-9N), D2 (4N-5C-12N-14C), and D3 (5C-12N-14C-16C). The final geometry parameters for the obtained stable conformers were determined by means of geometry optimization, carried out at DFT/B3LYP/6-31G++(d,p) theory level. Afterwards the possible dimer forms of the molecule and acetazolamide-H2O clusters were formed and their energetically preferred conformations were investigated using the same method and the same level of theory. The effect of BSSE on the structure and energy of acetazolamide dimer has been investigated. The assignment of the vibrational modes was performed based on the potential energy distribution of the vibrational modes, calculated by using GAR2PED program. The experimental vibrational wavenumbers of solid acetazolamide are found to be in better agreement with the calculated wavenumbers of dimer form of acetazolamide than those of its monomeric form. NBO analysis has been performed on both monomer and dimer geometries.