Research Article Open Access

An Initio Theoretical Study for the Electronic Spectra of β-Thioxoketones

Rita S. Elias1, Bahjat A. Saeed2 and Dhiyaa K. Muslem3
  • 1 Department of Pharmaceutical Chemistry, College of Pharmacy, University of Basrah, Iraq
  • 2 Department of Chemistry, College of Education, University of Basrah, Iraq
  • 3 Open Educational College, Baghdad, Iraq

Abstract

Problem statement: β-thioxoketones exist as equilibrium mixtures of the tautomeric enol and enethiol forms which interconvert very rapidly by intramolecular chelate proton transfer. Accordingly their electronic spectra in the u.v.-visible region exhibit absorption bands arising from transitions within the electronic systems involved in these tautomers. Approach: The structures of several β-thioxoketones were geometrically optimized using B3LYP/cc-pVTZ, B3LYP/6-311++G (2d,p), PM2/6-311++G(2d,p) and B3LYPl6-311G(d,p) and their electronic spectra were theoretically calculated. TD-DFT, EOM-CCSD, CIS and semi empirical ZINDO methods were used to calculate the electronic spectra. Results: The spectrum of the enolic form of thiomalonaldehyde is characterized by three absorption bands at 460, 305 and 223 nm due to H→L, H-1→L and both H→L+1 and H→L+2 transitions. The first band is attributed to n→π* transition within the C = S group while the others are due to transitions with the O-C = C-C = S conjugated system. Both TD-DFT and ZINDO methods were able to predict the electronic spectra of the molecules studied that are in very good agreement with the observed spectra. The observed spectra were agreed to large degree with calculated spectra of the enolic tautomer of the studied compounds. Conclusion: The observed spectra were agreed to large degree with calculated spectra of the enolic tautomer of the studied compounds.

American Journal of Applied Sciences
Volume 9 No. 1, 2012, 152-157

DOI: https://doi.org/10.3844/ajassp.2012.152.157

Submitted On: 14 October 2011 Published On: 24 November 2011

How to Cite: Elias, R. S., Saeed, B. A. & Muslem, D. K. (2012). An Initio Theoretical Study for the Electronic Spectra of β-Thioxoketones. American Journal of Applied Sciences, 9(1), 152-157. https://doi.org/10.3844/ajassp.2012.152.157

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Keywords

  • Electronic spectra
  • electron density difference
  • electrostatic potential difference
  • theoretical program package
  • qualitatively similar
  • intramolecular chelate