Electronic structure, electric moments and vibrational analysis of 3-(2-methoxyphenoxy) propane-1,2-diol by ab initio and density functional theory (original) (raw)

2011, Journal of Atomic and Molecular Sciences

The molecular properties and harmonic wavenumbers of 3-(2-methoxyphenoxy) propane-1,2-diol have been calculated using ab initio and density functional theory. The polarizability and first static hyperpolarizability of the title molecule have been calculated at different basis sets. In general a good agreement between experimental and calculated normal modes has been observed. The frontier orbital and molecular electrostatic potential surface study has also been employed to understand the active sites of 3-(2methoxyphenoxy) propane-1,2-diol. PACS: 31.15.A, 31.15.es, 31.15.ap ½½ Key words: Density functional theory, frontier orbital energy gap, first static hyperpolarizability ½¾ ½¿ 1 Introduction ½ With the standard quantum chemical models (i.e., without the inclusion of parity violation), ½ there is no difference whatsoever in energetics, vibrational frequencies, polarizabilities, NMR ½ spectra, or any other non-chiral property for a given pair, i.e., (R) and (S) forms of enan-½ tiomers [1-4]. Differences in the properties of enantiomers arise either only within chiral en-½ vironments or interactions with other chiral compounds. The present investigation therefore ½ deals with the quantum chemical study of molecular structural, energetic and vibrational data ¾¼ of one of the pair i.e., (R) enantiomer of 3-(2-methoxyphenoxy) propane-1,2-diol [MPPD], in ¾½ gas phase, due to its biological and pharmaceutical importance. The drug MPPD, also known ¾¾ as guaifenesin, is an expectorant, used extensively in anti-tussive and is capable of increasing ¾¿ the excretion of phlegm from the respiratory tract. Bredikhin and others have carried out ¾ * Corresponding author. Email address: ÓÒ ÖÔÖ × ½ Ñ ÐºÓÑ (O. Prasad) http://www.global-sci.org/jams 212 c 2011 Global-Science Press L. Sinha, A. Kumar, V. Narayan, et al. / J. At. Mol. Sci. 2 (2011) 212-224 213 extensive studies on the structure, solid state properties and issues related to the effective ¾ resolution procedure for MPPD [5-7]. ¾ The vibrational spectroscopic analysis is known to provide immensely invaluable molecu-¾ lar structure elucidation in synergy with quantum chemical calculations. In order to obtain a ¾ complete description of molecular dynamics, vibrational wavenumber calculations along with ¾ the normal mode analysis have been carried out at the DFT level employing the basis set ¿¼ 6-311+G(2d,2p). The optimized geometry of molecule under investigation and its molecu-¿½ lar properties such as equilibrium energy, frontier orbital energy gap, molecular electrostatic ¿¾ potential energy map, dipole moment, polarizability, first static hyperpolarizability have also ¿¿ been used to understand the properties and active sites of the drug. ¿ 2 Experimental ¿ 2.1 Structure and Spectra ¿