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Abstract: The title compound, 3-ethoxy-4-isopropylaminocyclobut-3-ene-1,2-dione (EIAC) has been synthesized and characterized by NMR, FT-IR, UV–vis spectroscopy and single-crystal X-ray diffraction. The 1H NMR spectra were recorded at 300K and 315K in CDCl3 to determine syn/anti conformers of the compound EIAC. Density functional theory (DFT) calculations, optimized geometrical parameters, vibrational frequencies and chemical shift values of syn/anti conformer in CDCl3 have been performed at B3LYP/6-311G(d) level, and compared with the experimental data. The values provided with the calculations support the experimental data of the compound EIAC. The presence of NO type intermolecular H bond can be perceived from the difference between experimental calculations and results of FT-IR and NMR calculations. In addition, B3LYP/6-311G(d) basis set has been used to calculate the molecular electrostatic potential, frontier molecular orbitals and electronic absorption spectra. HOMO–LUMO electronic transition of 5.12eV is derived from the contribution of the bands n→σ* or π→π*. FT-IR, NMR and X-ray spectral results and additionally DFT calculations exhibit that the compound EIAC exists in keto-enamine tautomeric form. The experimental 1H NMR spectra recorded at 300K and 315K and theoretical 1H NMR data indicate that the compound EIAC is in syn conformer. [Copyright &y& Elsevier]

Abstract: In this work, 3,4-bis(isoproylamino)cyclobut-3-ene-1,2-dione C10H16N2O2 (I), was synthesized and characterized by 13C NMR, 1H NMR, FT-IR, UV-vis spectroscopy and single-crystal X-ray diffraction. DFT method with 6-31G(d,p) basis set has been used to calculate the optimized geometrical parameters, atomic charges, vibrational frequencies and chemical shift values. The calculated vibrational frequencies and chemical shift values are compared with experimental FT-IR and NMR spectra. The results of the calculation shows good agreement between experimental and calculated values of the compound I. The existence of N–H⋯O type intermolecular ve C–H⋯O type intramolecular hydrogen bonds can be deduced from differences between experimental and calculated results of FT-IR and NMR. In addition, the molecular electrostatic potential map and frontier molecular orbitals and electronic absorption spectra were performed at B3LYP/6-31G(d,p) level of theory. HOMO–LUMO electronic transition of 4.90eV are derived from the contribution of the bands π→π* and n →π* The spectral results obtained from FT-IR, NMR and X-ray of I revealed that the compound I is in predominantly enamine tautomeric form, which was supported by DFT calculations. [Copyright &y& Elsevier]

Abstract: 4-(3-(1H-imidazol-1-yl)propyl)-(thiophen-2-ylmethyl)-1H-1,2,4-triazol-5(4H)-one (IPTT), C13H15N5OS, was synthesized and characterized by 13C NMR, 1H NMR, IR and single-crystal X-ray diffraction. The structure of IPTT is stabilized by three intermolecular hydrogen bonds and by intermolecular Cπ interaction. The compound IPTT was modelled by using DFT method. Calculations of vibrational frequencies, gauge including atomic orbital (GIAO), 1H and 13C NMR chemical shifts of IPTT in the ground state, total electronic charge density map and frontier molecular orbitals were performed at B3LYP/6-31 G(d) level of theory were carried out by using DFT method with 6-31 G(d) basis set. The structural parameters obtained by geometry optimization, the theoretical vibrational frequencies and chemical shift values are in good agreement with experimental ones. FT-IR, NMR and X-ray analytical results of IPTT show that the compound exists as keto form, that was supported by DFT calculations. In addition, in vitro studies showed hopeful antitumoral activity of the title IPTT compound. [Copyright &y& Elsevier]

Abstract: The triazol–imidazol compound, 4-(3-(1H-imidazol-1-yl)propyl)-5-p-tolyl-2H-1,2,4-triazol-3(4H)-one (3), (C15H17N5O), was prepared and characterized by 1H NMR, 13C NMR, IR and single-crystal X-ray diffraction. By using the density functional theory (DFT) method with 6-31G(d) basis set, the molecular geometry, vibrational frequencies and gauge including atomic orbital (GIAO) 1H and 13C NMR chemical shift values of the title compound (3) in the ground state were calculated and compared with the experimental data. The calculated results are show that the optimized geometry can well reproduce the crystal structure. X-ray, FT-IR and NMR spectral results of the title compound (3) indicate that the compound exists as keto form. To determine most favorable conformation as theoretically, molecular energy profile of the title compound (3) were obtained as a function of the selected torsion angles T(N1ph name="sbnd" />C7nd T(C8ph name="sbnd" />C10 which is varied from −180° to +180° in every 10 by semi-empirical (PM3) calculations. In addition, DFT calculations of the title compound (3), molecular electrostatic potential and frontier molecular orbitals were performed at B3LYP/6-31G(d) level of theory. [ABSTRACT FROM AUTHOR]

The molecular and crystal structure of the title compound, CHClNO, has been determined by X-ray single crystal diffraction technique. The compound crystallizes in the orthorhombic, space group Pbca with unit cell dimensions a = 7.5537(10) Å, b = 11.5518(13) Å, c = 29.760(4) Å, M = 280.14, V = 2596.8(6) Å, Z = 8, R = 0.065 and wR = 0.191. The title compound exists in the enol-imine tautomeric form with a strong intramolecular O-H···N hydrogen bond. The dihedral angle between the two benzene rings is 37.66(15)°. The asymmetric unit in the crystal structure contains only one neutral molecule. Calculational studies were performed by using AM1, PM3, PM6 semi-empirical and DFT methods. Geometry optimizations of compound have been carried out by using three semi-empirical methods and DFT method and bond lengths, bond and torsion angles of title compound have been determined. Dipole moments (Debye) and the energy parameters of compound (kcal/mol) were calculated by using above mentioned calculation methods. Atomic charge distribution has been obtained from AM1, PM3, PM6 and DFT. In order to determine conformational flexibility on the molecule, molecular energy profile of the title compound was obtained with respect to the selected torsion angle T(N1-C7-C1-C2), which is varied from −180° to +180° in every 10 via PM3 semi-empirical method. Graphical Abstract: A new crystal of ( E)-2-[(2,4-Dichlorophenylimino) methyl]- p-cresol with orthorhombic space group Pbca [unit cell dimensions a = 7.5537(10) Å, b = 11.5518(13) Å, c = 29.760(4) Å, V = 2596.8(6) Å, Z = 8, R = 0.065] has been determined by single crystal X-ray diffraction study and theoretical calculations were performed by using AM1, PM3, PM6 semi-empirical and DFT methods. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]