title: Experimental and theoretical spectroscopic studies, HOMO-LUMO, NBO analyses and thione-thiol tautomerism of a new hybrid of 1,3,4-oxadiazole-thione with quinazolin-4-one.
abstract: The hybrid 3-(4-chlorophenyl)-2-[(5-thioxo-4,5-dihydro-1,3,4-oxadiazol-2-yl)methylthio]quinazolin-4(3H)-one has been synthesized and characterized using elemental analysis, FTIR and NMR spectroscopy. The thione-thiol tautomeric equilibria has been studied using both DFT/B3LYP and HF methods at different basis sets. The results of calculations showed predominance of the thione form. The molecular structure and vibrational spectra of the stable tautomer are predicted using the same level of theory. The complete assignments of the vibrational modes were performed on the basis of potential energy distribution (PED). The 6-311++G(d,p) gave the best results compared to the experimental data. The chemical shift values of the two tautomers are calculated using GIAO method. The NH proton of the thione tautomer have chemical shift value closer to the experimental data compared to the SH proton of the thiol one. The electronic transitions are predicted using the TD-DFT calculations at B3LYP/6-311++G(d,p) level of theory. The calculated polarizability and first hyperpolarizability showed that the studied compound has better NLO properties than urea. The molecular electrostatic potential (MEP) analysis reveals the sites for electrophilic and nucleophilic attack in the molecule. NBO analysis is carried out to investigate the stabilization energy of various intramolecular charge transfer interactions within the studied molecule.
authors: Chemistry Department, Faculty of Science, Alexandria University, Alexandria 21321, Egypt.
authors: Saied M
authors: SM
authors: Soliman
authors: Chemistry Department, Faculty of Science, Alexandria University, Alexandria 21321, Egypt; Chemistry Department, Faculty of Science, Taibah University, Yanbu Branch, Yanbu, Saudi Arabia.
authors: Mohamed
authors: M
authors: Hagar
authors: Chemistry Department, Faculty of Science, Alexandria University, Alexandria 21321, Egypt.
authors: Farahate
authors: F
authors: Ibid
authors: Chemistry Department, Faculty of Science, Alexandria University, Alexandria 21321, Egypt. Electronic address: eelashry60@hotmail.com.
authors: El Sayed H
authors: ESH
authors: El Ashry
mesh_terms: D004583:Electrons; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D017711:Nonlinear Dynamics; D055620:Optical Phenomena; D010069:Oxadiazoles / Q000138:chemical synthesis / Q000737:chemistry*; D011799:Quinazolines / Q000138:chemical synthesis / Q000737:chemistry*; D052999:Quinazolinones / Q000138:chemical synthesis / Q000737:chemistry*; D055672:Static Electricity; D013237:Stereoisomerism; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013816:Thermodynamics; D013871:Thiones / Q000737:chemistry*; D014732:Vibration
chemical_list: D010069:Oxadiazoles; D011799:Quinazolines; D052999:Quinazolinones; D013438:Sulfhydryl Compounds; D013871:Thiones; C583463:1,3,4-oxadiazole; C061339:4-hydroxyquinazoline
keywords: NBO; NMR; Oxadiazole; Quinazoline; Tautomerism; Thione