title: Synthesis, NMR, FT-IR, X-ray structural characterization, DFT analysis and isomerism aspects of 5-(2,6-dichlorobenzylidene)pyrimidine-2,4,6(1H,3H,5H)-trione.
abstract: The synthesis and spectral characterization of the 5-(2,6-dichlorobenzylidene)pyrimidine-2,4,6(1H,3H,5H)-trione;3 was reported. The solid state molecular structure of 3 was studied using X-ray crystallography. The relative stabilities of the seven possible isomers of 3 were calculated by DFT/B3LYP method using 6-311 G(d,p) basis set. The calculated total energies and thermodynamic parameters were used to predict the relative stabilities of these isomers. The effect of solvent polarity on the relative stability of these isomers was studied at the same level of theory using PCM. It was found that the keto form, (T0), is the most stable isomer both in the gaseous state and solution. In solution, the calculated total energies of all isomers are decreased indicating that all isomers are stabilized by the solvent effect. The vibrational spectra of the most stable isomer, 3(T0) are calculated using the same level of theory and the results are compared with the experimentally measured FTIR spectra. Good correlation was obtained between the experimental and calculated vibrational frequencies (R(2)=0.9992). The electronic spectra of 3(T0) in gas phase as well as in solutions were calculated using the TD-DFT method. All the predicted electronic transitions showed very little spectral shifts and increase in the intensity of absorption due to solvent effect. Also the (1)H- and (13)C-NMR chemical shifts of the stable isomer were calculated and the results were correlated with the experimental data. Good correlations between the experimental and calculated chemical shifts were obtained.
authors.affiliation: Department of Chemistry, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia; Department of Chemistry, Faculty of Science, Alexandria University, P.O. Box 426, Ibrahimia, 21321 Alexandria, Egypt. Electronic address: ambarakat@ksu.edu.sa.
authors.forename: Assem
authors.initials: A
authors.lastname: Barakat
authors.affiliation: Department of Chemistry, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia.
authors.forename: Hany J
authors.initials: HJ
authors.lastname: Al-Najjar
authors.affiliation: Department of Chemistry, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia.
authors.forename: Abdullah Mohammed
authors.initials: AM
authors.lastname: Al-Majid
authors.affiliation: Department of Chemistry, Rabigh College of Science and Art, King Abdulaziz University, P O Box 344, Rabigh 21911, Saudi Arabia; Department of Chemistry, Faculty of Science, Alexandria University, P.O. Box 426, Ibrahimia, 21321 Alexandria, Egypt.
authors.forename: Saied M
authors.initials: SM
authors.lastname: Soliman
authors.affiliation: Department of Chemistry, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia.
authors.forename: Yahia Nasser
authors.initials: YN
authors.lastname: Mabkhot
authors.affiliation: Department of Chemistry, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia.
authors.forename: Mohammed Rafi
authors.initials: MR
authors.lastname: Shaik
authors.affiliation: Department of Pharmaceutical Chemistry, College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh 11451, Saudi Arabia.
authors.forename: Hazem A
authors.initials: HA
authors.lastname: Ghabbour
authors.affiliation: Department of Pharmaceutical Chemistry, College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh 11451, Saudi Arabia; X-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, Penang 11800, Malaysia.
authors.forename: Hoong-Kun
authors.initials: HK
authors.lastname: Fun
mesh_terms: D001597:Benzylidene Compounds / Q000737:chemistry*; D018360:Crystallography, X-Ray; D054879:Halogenation; D007536:Isomerism; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D011744:Pyrimidinones / Q000737:chemistry*; D011789:Quantum Theory; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D001597:Benzylidene Compounds; D011744:Pyrimidinones
keywords: DFT; Isomers; NMR; Pyrimidine; Vibrational spectra