5. Theoretical Comparative Study of the Structure, Dynamics and Electronic Properties of Three Ally Molecules: Allicin, Methyl Propyl Disulfide (MPD) and Allyl Methyl Sulfide (AMS)

Handan Yildirim¹, Abdelkader Kara¹, Talat S. Rahman¹, Emine Deniz Calisir², Sakir Erkoc^{2 (*)}, Mahmut Selvi³, Figen Erkoc³

¹ Department of Physics, Kansas State University, Manhattan, KS 66506, USA

² Department of Physics, Middle East Technical University, 06531 Ankara, Turkey, erkoc@erkoc.physics.metu.edu.tr

³ Department of Biology Education, Gazi University, 06500 Ankara, Turkey

(Received 17 November 2005; accepted 26 January 2006)

Abstract: The structural, dynamic and electronic properties of three ally molecules (allicin, methyl propyl disulfide, allyl methyl sulfide) have been investigated theoretically by performing calculations at three levels of accuracy: semi-empirical molecular orbital (PM3 and AM1), ab-initio (RHF) and density functional theory (DFT). The geometries of the molecules have been optimized, their vibrational spectra and the electronic properties have been calculated in their ground state in gas phase. For each of the three molecules, we found that the optimized geometries resulting from the calculations based on the three levels of accuracy, are very similar. However, we found that an accurate description of the vibrational properties of these molecules necessitates calculations at the ab-initio level. We also found that the electronic structure of the molecules performed at the DFT level to be satisfactory.

Keywords: Allicin, methyl propyl disulfide, allyl methyl sulfide, antioxidant, garlic, semi-empirical  method, ab-initio calculation, density functional method

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