Diego M. Gil

Quantum chemical studies on molecular structure, spectroscopic (IR, Raman, UV–Vis), NBO and Homo–Lumo analysis of 1-benzyl-3-(2-furoyl) thiourea

Vibrational and electronic spectra for 1-benzyl-3-(2-furoyl) thiourea were calculated by using density functional method (B3LYP) with different basis sets. The complete assignment of all vibrational modes was performed on basis of the calculated frequencies and comparing with the reported IR and Raman spectra for that thiourea derivative. UV-visible absorption spectra of the compound dissolved in methanol were recorded and analyzed using time dependent density functional theory (TD-DFT). The calculated values for the geometrical parameters of the title compound are consistent with the ones reported from XRD studies. The stability of the molecule, related to hyper-conjugative interactions, and electron delocalization were evaluated using natural bond orbital (NBO) analysis. Intra-molecular interactions were studied by AIM approach. The HOMO and LUMO analysis are used to determine the charge transfer within the molecule. Molecular electrostatic potential map was performed by the DFT method.

Structural, vibrational and electronic characterization of 1-benzyl-3-furoyl-1-phenylthiourea: an experimental and theoretical study

1-Benzyl-3-furoyl-1-phenylthiourea is a thiourea derivative synthesized and characterized by means of vibrational spectroscopy (IR and Raman) multinuclear NMR (1H and 13C) and elemental analysis. The geometrical parameters of this compound obtained from XRD studies were compared with the calculated values [B3LYP/6-311++G(d,p)] showing a good agreement. As determined by XRD analysis performed previously, the title compound exhibits the U-shape conformation with the CO and CS double bonds in anticlinal geometry. This conformational feature is mainly dictated by the substitution degree on the thiourea core and the ability to form an intramolecular N–H⋯OC hydrogen bond. The UV-visible absorption spectra of the compound in methanol solution were recorded and analyzed using time dependent density functional theory (TD-DFT). Molecular stability was investigated by applying the natural bond (NBO) analysis. Intermolecular interactions were evaluated by means of the AIM approach. The calculated HOMO and LUMO energies show that the charge transfer occurs in the molecule. The molecular electrostatic potential map was calculated by the DFT method. Non-linear optical (NLO) behavior of the title compound was investigated by determining the electric dipole moment, polarizability α, and hyperpolarizability β using B3LYP/6-311++G(d,p) approximation.

Ab-initio and DFT calculations on molecular structure, NBO, HOMO–LUMO study and a new vibrational analysis of 4-(Dimethylamino) Benzaldehyde

The experimental and theoretical study on the molecular structure and a new vibrational analysis of 4-(Dimethylamino) Benzaldehyde (DMABA) is presented. The IR and Raman spectra were recorded in solid state. Optimized geometry, vibrational frequencies and various thermodynamic parameters of the title compound were calculated using DFT methods and are in agreement with the experimental values. A detailed interpretation of the IR and Raman spectra of the title compound were reported. The stability of the molecule arising from hyper-conjugative interactions and charge delocalization has been analyzed using NBO analysis and AIM approach. The HOMO and LUMO analysis were used to determine the charge transfer within the molecule and some molecular properties such as ionization potential, electron affinity, electronegativity, chemical potential, hardness, softness and global electrophilicity index. The TD-DFT approach was applied to assign the electronic transitions observed in the UV-visible spectrum measured experimentally. Molecular electrostatic potential map was performed by the DFT method. According to DSC measurements, the substance presents a melting point of 72.34°C and decomposes at temperatures higher than 193°C.

SYNTHESIS OF Pb2Fe2O5 BY THERMAL DECOMPOSITION OF Pb2[Fe(CN)6].4H2O

Inthe present work the synthesis, thermal analysis and structural characterization of Pb2[Fe(CN)6].4H2O are described in orderto obtain mixed oxides with technological properties. The starting materials and the decomposition products were characterized by IR spectroscopy, powder X-ray diffraction (XRDP) and scanning electron microscopy (SEM). The crystal structure of Pb2[Fe(CN)6].4H2O has been refined by Rietveld analysis using X- ray powder diffraction data. It Crystallizes in the monoclinic system with space group P21/m and the cell unit parameters are a = 10.9755(2)A, b = 7.6285(1)A, c = 8.5696(1) A y s = 98.8375(9)°. Pb2Fe2O5 has been obtained by a simple method, the thermal decomposition of Pb2[Fe(CN)6].4H2O at 700 °C in air. Pb2Fe2O5 crystallizes in the tetragonal system with cell unit parameters a = b = 7.80 A, c = 15.82 A. PbO is also obtained.

Layered crystal structure, conformational and vibrational properties of 2,2,2-trichloroethoxysulfonamide: an experimental and theoretical study.

The molecular structure of 2,2,2-trichloroethoxysulfonamide, CCl3CH2OSO2NH2, has been determined in the solid state by X-ray diffraction data and in the gas phase by ab initio (MP2) and DFT calculations. The substance crystallizes in the monoclinic P21/c space group with a = 9.969(3)Å, b = 22.914(6)Å, c = 7.349(2)Å, β = 91.06(3)°, and Z = 8 molecules per unit cell. There are two independent, but closely related molecular conformers in the crystal asymmetric unit. They only differ in the angular orientation of the sulfonamide (SO2NH2) group. The conformers are arranged in the lattice as center-symmetric NH · · · O(sulf)-bonded dimers. Neighboring dimers are linked through further NH · · · O(sulf) bonds giving rise to a crystal layered structure. The solid state infrared and Raman spectra have been recorded and the observed bands assigned to the molecular vibration modes. Also, the thermal behavior of the substance was investigated by TG-DT analysis. The stability of the molecule arising from hyper-conjugative interactions and charge delocalization has been analyzed using natural bond (NBO) analysis.

DFT calculations of structure and vibrational properties of 2,2,2-trichloroethylacetate, CH3CO2CH2CCl3

The molecular structure and conformational properties of 2,2,2-trichloroethylacetate, CH(3)CO(2)CH(2)CCl(3), were determined by ab initio (MP2) and DFT quantum chemical calculations at different levels of theory. The theoretical study was complemented with experimental measurements such as IR and Raman spectroscopy. The experimental and calculations confirm the presence of two conformers, one with anti, gauche conformation (C1 symmetry) and another with anti, anti form (Cs symmetry). The conformational preference was studied using the total energy scheme, NBO and AIM analysis. The infrared spectra of CH(3)CO(2)CH(2)CCl(3) are reported in the liquid and solid phases and the Raman spectrum in liquid phase. Using calculated frequencies as a guide, evidence for both C1 and Cs conformers is obtained in the IR and Raman spectra.

Synthesis, crystal structure, conformational and vibrational properties of 6-acetyl-2,2-dimethyl-chromane

The 6-acetyl-2,2-dimethyl-chromane compound was synthesized and characterized by IR, Raman, UV-Visible and (1)H NMR spectroscopies. Its solid state structure was determined by X-ray diffraction methods. The substance crystallizes in the triclinic P-1 space group with a=5.9622(5) Å, b=10.342(1) Å, c=10.464(1) Å, α=63.81(1)°, β=81.923(9)°, γ=82.645(9)°, and Z=2 molecules per unit cell. Due to extended π-bonding delocalization a substantial skeletal fragment of the molecule is planar. The vibrational modes were calculated at B3LYP/6-31G(d,p) level and all of them assigned in the IR and Raman spectra. The DFT calculated (1)H NMR spectrum (chemical shifts) were in good agreement with the experimental data. The electronic (UV-Visible) spectrum was calculated using TD-DFT method in gas phase and it was correlated with the experimental data. The assignment and analysis of the frontier HOMO and LUMO orbitals indicate that the absorption bands are mainly originated from π→π(*) transitions. According to DSC measurements the substance presents a melting point of 93°C and decomposes at temperatures higher than 196°C.

Synthesis, structural and spectroscopic studies of 1-(2-FUROYL)-3-phenylthiourea: a theoretical and experimental approach

ABSTRACT The thiourea derivative 1-(2-Furoyl)-3-phenylthiourea (FPT) was synthesized and characterized by using spectroscopic (IR, Raman, UV–VIS, 1H and 13C NMR) and structural methods (powder X-ray diffraction data). The experimental measurements were complemented with quantum chemical calculations. FPT crystallizes in the monoclinic crystal system, space group P21/c, with cell parameters a = 4.7679(5) Å, b = 20.9704(2) Å, c = 12.5109(5) Å and β = 109.811(10)°, V = 1176.87(3) Å3. In the crystal structure, the thiourea group makes dihedral angle of 43.8(5)° with the furoyl group, whereas the benzene ring is inclined by 24.3(4)°. The anti-syn geometry of the thiourea unit is stabilized by intramolecular N–H  …  O hydrogen bond between the H atom of the syn thioamide and the carbonyl O atom. In the crystal structure, molecules of FPT are packed through N–H···S, C–H···O and C–H···C hydrogen bonds, and a π–π interaction with offset arrangement. Hirshfeld surface analysis was performed in order to evaluate and quantify intermolecular interactions. The Hirshfeld surface analysis indicated that the H···H interactions comprise the majority of interactions. Shape index and curvedness clearly indicate π–π interactions in the compound FPT. GRAPHICAL ABSTRACT

Vibrational studies (FTIR and Raman), conformational analysis, NBO, HOMO-LUMO and reactivity descriptors of S-methyl thiobutanoate, CH3CH2CH2C(O)SCH3.

In the present article, the molecular structure of S-methyl thiobutanoate, CH3CH2CH2C(O)SCH3 was determined by ab initio (MP2) and DFT calculations using different basis sets. The infrared and Raman spectra for the liquid phase were also recorded and the bands observed were assigned to the vibrational normal modes. The experimental and calculations confirm the presence of two most stable conformers, one with pseudo anti-syn conformation and another with gauche-syn conformation. The study was completed using natural bond orbital (NBO) and AIM analysis. The molecular properties like dipole moment, molecular electrostatic potential surface (MEP) and HOMO-LUMO molecular orbitals were calculated to get a better insight of the properties of the title molecule. Global and local reactivity descriptors were computed in order to predict reactivity and reactive sites on the molecule for nucleophilic, electrophilic and radical attacks.

Exploring weak intermolecular interactions in thiocyanate-bonded Zn(II) and Cd(II) complexes with methylimidazole: crystal structures, Hirshfeld surface analysis and luminescence properties

Four new thiocyanate-Zn(II) and -Cd(II) complexes with 1-methylimidazole (1-MeIm) and 2-methylimidazole (2-MeIm), namely, Zn(1-MeIm)2(SCN)2 (1), Zn(2-MeIm)2(SCN)2 (2), Cd(1-MeIm)4(SCN)2 (3) and polymeric [Cd(2-MeIm)2(SCN)2]n (4), have been synthesized and characterized by IR, Raman and UV-Vis spectroscopy. The thermal behavior for all complexes was evaluated by thermo-gravimetric analysis and differential thermal analysis. The crystal structures of complexes 1–4 were solved by single-crystal X-ray diffraction methods. A study of intermolecular interactions in the solid state compounds revealed that molecules are linked by weak N–H⋯S and C–H⋯S hydrogen bonds and also by C–H⋯π interaction in the case of structures 2–4, which are responsible for the formation and stability of the molecular assemblies. Hirshfeld surfaces and 2D-fingerprint plots allowed us to visualize the intermolecular contacts and their relative contributions to the total surface for each compound. A comparative analysis against similar halogen-bonded complexes was carried out to investigate the tendency of inter-molecular interactions to form contacts in crystals by using the enrichment ratio descriptor. The emission spectra of the free imidazole derivatives and their Zn(II) and Cd(II) complexes were recorded in acetonitrile solutions. The emissions observed in the spectra of complexes were ascribed to the intra-ligand transitions and ligand-to-metal charge transfer and we have observed an interesting correlation between the fluorescence intensities and C–H⋯π interactions.