Experimental (X-ray Diffraction, UV–Vis Spectroscopy) and DFT Studies of 1-Ethyl-3-methylquinoxaline-2-thione

• Published in: Russian Journal of Physical Chemistry A Vol. 94; no. 2; pp. 360 - 369
• Main Authors: Benallal, R., Bougharraf, H., Aamoum, A., Mondieig, D., Negrier, Ph, Essassi, E. M., Kabouchi, B.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01-02-2020; Springer Nature B.V
• Subjects: Biological activity; Biomedical materials; Charge transfer; Chemistry; Chemistry and Materials Science; Dihedral angle; Electron transitions; Ethanol; Lattice parameters; Molecular orbitals; Physical Chemistry; Polarity; Red shift; Spectrum analysis; Structure of Matter and Quantum Chemistry; Unit cell; X-ray diffraction; molecular electrostatic potential; DFT; X-ray; Mulliken charges; 1-ethyl-3-methylquinoxaline-2-thione; HOMO–LUMO
• ISSN: 0036-0244; 1531-863X
• DOI: 10.1134/S0036024420020053

In this paper, we present the experimental and theoretical investigation of 1-ethyl-3-methylquinoxaline-2-thione, molecule exhibiting an important biological activity. We used X-ray diffraction, UV-visible absorption spectroscopy and DFT calculations with 6-31G(
d,p
) basis sets. According to the results, the compound crystallizes in the monoclinic system,
P
2
1
/
c
with eight molecules per unit cell (
Z
= 8,
Z
 ' = 2) and with the lattice parameters (
a
= 7.7882(8) Å,
b
= 15.964(2) Å,
c
= 16.519(2) Å, α = 90°, β = 94.413(11)°, γ = 90°), in which the two fused-rings adopt a planar geometry, and assumes a dihedral angle with the ethyl group, presenting the most stable conformation. UV–Vis absorption spectroscopic properties of 1-ethyl-3-methylquinoxaline-2-thione showed a redshift when the solvent polarity increases from ethanol to DMSO. Detailed analysis of intra and intermolecular interactions as such H-bonding, π–π stacking, electronic transitions, HOMO–LUMO patterns, molecular electrostatic potential maps and Mulliken charges distribution was carried out in order to investigate charge transfer within the molecule for the needs of biomedical applications.