Search

The study of two new acylthiourea derivatives (Ar-CO-NH-CS-NH-R) are focused on the bonding interactions supported by X-ray, NMR, UV-Vis, Raman and IR spectroscopy, and NBO, AIM and Hirshfeld surface analysis. The RAHB model is proposed to explain some structural properties. The molecules are stabilized by intra-molecular NH⋯O bonds arranged in the lattice as centre-symmetric dimers held by inter-molecular NH⋯S bonds. The dimers are linked to each other through NH⋯O bonds giving rise to a chain, ribbon-like structure in the network. In vitro bacterial growth inhibition, biofilm formation, biosensor and biofilm metabolic activity were tested considering the broad bioactivity of acylthioureas. Fil: Contreras Aguilar, Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Química Inorgánica "Dr. Pedro J. Aymonino". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Química Inorgánica "Dr. Pedro J. Aymonino"; Argentina Fil: Echeverría, Gustavo Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: Piro, Oscar Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: Ulic, Sonia Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Química Inorgánica "Dr. Pedro J. Aymonino". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Química Inorgánica "Dr. Pedro J. Aymonino"; Argentina. Universidad Nacional de Luján; Argentina Fil: Jios, Jorge Luis. Comision de Investigaciones Cientificas de la Provincia de Buenos Aires. Unidad Plapimu Laseisic.; Argentina Fil: Tuttolomondo, María Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Química del Noroeste. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química del Noroeste; Argentina Fil: Molina, Rocío Daniela Inés. Universidad Nacional de Tucumán. Instituto de Biotecnología Farmacéutica y Alimentaria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Biotecnología Farmacéutica y Alimentaria; Argentina Fil: Arena, Mario Eduardo. Universidad Nacional de Tucumán. Instituto de Biotecnología Farmacéutica y Alimentaria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Biotecnología Farmacéutica y Alimentaria; Argentina

The aim of this study was to evaluate the structural and vibrational properties and biological activity of 2-chloroethyl(methylsulfonyl)methanesulfonate, CH3SO2CH2SO2OCH2CH2Cl (clomesone). The solid-state molecular structure has been isolated and characterized using experimental (X-ray diffraction) and theoretical (DFT method) methodologies. The molecules are packed through C-H⋯O bifurcated interactions and Cl⋯Cl interactions. The experimental investigations are supplemented by quantum chemical calculations and Hirshfeld surface calculations. Furthermore, the infrared and Raman spectra of the solid phase have been obtained, and the observed bands are assigned to the vibrational normal modes. This study is completed using the atoms-in-molecules (AIM) theory and natural bond orbital (NBO) analysis. Finally, we studied the function of clomesone in biofilm formation and investigated a methanesulfonate complex with respect to QS activity., Centro de Química Inorgánica, Instituto de Física La Plata

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. Fil: Gil, Diego Mauricio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Química del Noroeste. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química del Noroeste; Argentina. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química Física; Argentina Fil: Tuttolomondo, María Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Química del Noroeste. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química del Noroeste; Argentina. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química Física; Argentina Fil: Ben Altabef, Aída. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Química del Noroeste. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química del Noroeste; Argentina. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química Física; Argentina

A detailed structural and spectroscopic study of a new thiourea derivative 1-butyl-3-(1-naphthoyl)thiourea (1) is presented with the assistance of theoretical calculations. The X-ray diffraction structure analysis reveals a planar carbonylthiourea group, favoured by intra-molecular NH···O bond. The compound is arranged in the lattice as NH···O and NH···S bonded polymeric ribbons, that extend along the crystal b-axis. Molecular pairs involving N–H···S hydrogen bonds are a dominant contribution to packing stabilisation coming from coulombic component. Hirshfeld surfaces and two-dimensional-fingerprint plots show different intermolecular contacts and its relative contributions to total surface in each compound. The AIM approach shows the nature and strength of the strong and weak intramolecular interactions and the solvent effect, while NBO analysis reveals that the sulphur atom is responsible for the higher hyperconjugative stabilising energy. Fil: Contreras Aguilar, Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Química Inorgánica "Dr. Pedro J. Aymonino". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Química Inorgánica "Dr. Pedro J. Aymonino"; Argentina Fil: Echeverría, Gustavo Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: Piro, Oscar Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: Ulic, Sonia Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Química Inorgánica "Dr. Pedro J. Aymonino". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Química Inorgánica "Dr. Pedro J. Aymonino"; Argentina. Universidad Nacional de Luján; Argentina Fil: Jios, Jorge Luis. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentina. Universidad Nacional de La Plata; Argentina Fil: Tuttolomondo, María Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Química del Noroeste. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química del Noroeste; Argentina Fil: Pérez, H.. Universidad de La Habana; Cuba

Methyl trifluoromethanethiosulfonate, CF3SO2SCH3, was synthesized and characterized by 13C NMR, 19F NMR, and vibrational spectroscopy. This structural study was supported by MP2 and DFT (B3LYP and MPW1PW91) calculations, which revealed a strong dependence of the theoretical structure on the polarization of the basis set. Theoretical data indicate that only one conformer, gauche, is predicted by rotating around the S–S bond. This conformational preference was studied using the total energy scheme and natural bond orbital partition scheme. These results evidence that electron delocalization and especially LP S → σ∗ C(1)-S interactions play an interesting role in the reactivity-structure connection of oxoesters and thioesters. Gas and liquid infrared and liquid Raman spectra were recorded and assigned. The experimental vibrational data along with theoretical force constants (B3LYP) were used to define a scaled quantum mechanical force field, which enabled the reproduction of the measured frequencies with a final root-mean-square deviation of 8.06 cm−1., Centro de Química Inorgánica

The aim of this work is to evaluate the vibrational and structural properties of l-cysteine ethyl ester hydrochloride (CE), and its electronic behavior mainly in relation to the action of the thiol and amine groups at different degrees of solvation. The crystal structure of CE was determined at room temperature by X-ray diffraction methods. Infrared and Raman spectra were collected to compare the behavior of different functional groups in the molecule, both in the solid phase and in aqueous solution. Its UV and circular dichroism spectra were also measured in aqueous solution. The influence of an aqueous environment on the CE spectra was simulated by means of implicit (polarizable continuum model) and explicit (molecular dynamics, solute-solvent clusters) methods. Calculations in explicit and continuous solvent are of interest to explain the behavior of bioavailable sites in this medium. The study was completed by natural bond orbital analysis to determine the presence of hyperconjugative interactions.

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 (single bondSO2NH2) group. The conformers are arranged in the lattice as center-symmetric Nsingle bondH⋯O(sulf)-bonded dimers. Neighboring dimers are linked through further Nsingle bondH⋯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. Fil: Gil, Diego Mauricio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Química del Noroeste. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química del Noroeste; Argentina Fil: Piro, Oscar Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Física; Argentina Fil: Echeverría, Gustavo Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Física; Argentina Fil: Tuttolomondo, María Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucuman. Instituto de Química del Noroeste. Universidad Nacional de Tucuman. Facultad de Bioquímica, Química y Farmacia. Instituto de Química del Noroeste; Argentina Fil: Ben Altabef, Aída. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Química del Noroeste. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química del Noroeste; Argentina

The molecular structure and conformational properties of 2,2,2-trichloroethyl chloroformate, ClC(O)OCH2CCl3 were determined experimentally using gas-phase electron diffraction (GED) and theoretically based on quantum-chemical calculations at the MP2 and DFT levels of theory. Further experimental measurements such as UV-visible, IR and Raman spectroscopy were complemented with the corresponding theoretical studies. All experimental results and calculations confirm the presence of two conformers namely anti?gauche (C1 symmetry) and anti?anti (Cs symmetry). The conformational preference was rationalised by NBO and AIM analyses. Molecular properties such as ionisation potential, electronegativity, chemical potential, chemical hardness and softness were deduced from HOMO?LUMO analyses. The TD-DFT approach was applied to assign the electronic transitions observed in the UV-visible spectrum. A detailed interpretation of the infrared and Raman spectra of the title compound are reported. Using calculated frequencies as a guide, IR and Raman spectra also provide evidence for the presence of both C1 and Cs conformers. Fil: Gil, Diego Mauricio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Química del Noroeste. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química del Noroeste; Argentina Fil: Tuttolomondo, María Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Química del Noroeste. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química del Noroeste; Argentina Fil: Blomeyer, Sebastian. Universitat Bielefeld; Alemania Fil: Reuter, Christian G.. Universitat Bielefeld; Alemania Fil: Mitzel, Norbert W.. Universitat Bielefeld; Alemania Fil: Ben Altabef, Aída. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Química del Noroeste. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química del Noroeste; Argentina

The structural and conformational properties of 2,2,2-trichloroethylacetate, H3CCO2CH2CCl3, have been determined in the gas phase using gas electron diffraction (GED). The experimental measurements were complemented by MP2 and DFT quantum-chemical calculations. Two conformers separated by a shallow rotational barrier have been identified, one of C 1 (syn-gauche) and the other of C s symmetry (syn-anti). All calculations indicate that syn-gauche is preferred in terms of enthalpy, whereas syn-anti seems to be slightly more stable regarding Gibbs free energy. In the gas-phase structure determination, dynamic models based on different potential energy surface scans were used. The one from dispersion-corrected density functional theory, predicting a preference of syn-gauche by 1.7kJmol−1, was found to describe the experimental data best. One- and two-conformer models had to be rejected due to correlations and unrealistically large amplitudes. Experimentally determined structural parameters are in good agreement with both, quantum-chemical calculations as well as GED data for related compounds. Interacting quantum atoms (IQA) analyses revealed that interplay between the carbonyl group and the hydrogen as well as chlorine atoms of the trichloroethyl group accounts for most of the stabilisation of the C 1 conformer. With intramolecular symmetry-adapted perturbation theory (I-SAPT) analyses it was possible to further elucidate the nature of dominant interactions in the two conformers. Herein, preference of syn-gauche can for the most part be attributed to electrostatic and to some extent to induction and dispersion interplays. In contrast this conformer is severely destabilised through steric repulsion. These results were supported by NBO analyses.

Bis (trifluoromethyl) sulfone, CF(3)SO(2)CF(3), was obtained as a byproduct in the synthesis of CF(3)SO(2)SCF(3). The compound was characterized by infrared and Raman spectroscopy as well quantum chemical calculations. Quantum mechanical calculations indicate the possible existence of two conformers symmetrically equivalent with C(2) symmetry. The preference for the staggered form was studied using the total energy scheme and the natural bond orbital (NBO) partition scheme. Additionally, the total potential energy was deconvoluted using a sixfold decomposition in terms of a Fourier-type expansion, showing that the hyperconjugative effect was dominant in stabilizing the staggered conformer. Infrared and Raman spectra of CF(3)SO(2)CF(3) were obtained. Harmonic vibrational wavenumbers and a scaled force field were calculated, leading to a final root mean-square deviation of 7.8 cm(-1) when comparing experimental and calculated wavenumbers.

Trifluoromethyl trifluoromethanethiosulfonate, CF3SO2SCF3 was characterized by 13C NMR, 19F NMR, and vibrational spectroscopy. Infrared spectra of CF3SO2SCF3 were obtained for the gaseous and liquid phases, while the Raman spectrum was recorded for the liquid phase. The experimental data were complemented with quantum chemical calculations. Both experimental and theoretical data indicate that only one conformer, gauche, is possible by rotating around the S–S bond. This conformational preference was studied using the total energy scheme and natural bond orbital partition scheme. These results evidence that electron delocalization and especially LP Y(Y = S, O) → σ* S(6) O(4,5) and LP O(4,5) → σ* S(6) Y interactions play an interesting role in the reactivity of oxoesters and thioesters.

Trichloromethyl trifluoromethanesulphonate, CF 3 SO 2 OCCl 3 , was prepared by quantitative reaction between Ag(CF 3 SO 2 O) and BrCCl 3 . The conformational and structural properties of the gaseous molecule were studied by vibrational spectroscopy (IR (gas, liquid), Raman (liquid) and quantum chemical calculations (DFT and ab initio methods)). Theoretical and experimental vibrational results evidenced the presence of a single conformer with C 1 symmetry. This result is in agreement with the adopted geometry of covalent sulphonates. The conformational preference was studied using the total energy scheme and natural bond orbital partition scheme. Additionally, the total potential-energy has been deconvoluted using six fold decomposition in terms of a Fourier-type expansion.

The molecular structure of trimethylsilyl trifluoromethanesulfonate, CF3SO2OSi(CH3)3, has been determined in the gas phase from electron-diffraction data supplemented by ab initio (MP2) and DFT calculations using 6-31G(d), 6-311++G(d,p) and 6-311G++(3df,3pd) basis sets. Both experimental and theoretical data indicate that only one gauche conformer is possible by rotating about the O–S bond. The anomeric effect is a fundamental stereoelectronic interaction and presents a profound influence on the electronic geometry. We have investigated the origin of the anomeric effect by means of NBO and AIM analysis. A natural bond orbital analysis showed that the lpπ[O bonded to Si)] → σ*[C–S] hyperconjugative interaction favors the gauche conformation. In addition, comparison of the structural and stereoelectronic properties of the title molecule with those of silyl trifluoromethanesulfonate and methyl trifluoromethanesulfonate has been carried out.

The molecular structure of 2-isopropyl-5-methyl-1,4-benzoquinone, C(6)O(2)H(2) (CH(3))(3)CH, has been optimized using methods based on density functional theory (DFT) and Moller-Plesset second-order perturbation theory (MP2). As regards C(6)O(2)H(2) (CH(3))(3)CH, two populated conformations with C(1) (trans) and C(s) (cis) symmetries are obtained, the former being more stable than the latter. The theoretical data indicate that although both anti and cis conformers are possible by rotation about the C-C bond, the preferred conformation is trans. The effects governing the torsion barriers and preferred conformations were analyzed at B3LYP/6-311++G** level. The atoms in molecules (AIM) theory and natural bond orbital (NBO) analysis was applied to the cis and trans conformers in order to detect intramolecular contacts. Furthermore, the infrared spectra for the gas and solid phases and the Raman spectrum for the solid one, were recorded and the observed bands assigned to the vibrational modes.

The molecular structure of trimethylsilyl trifluoroacetate, CF 3 C(O)OSi(CH 3 ) 3 , has been determined in the gas phase from electron-diffraction data supplemented by ab initio (MP2) and DFT calculations using 6-31G(d), 6-311G(d,p), 6-311++G(d,p) and 6-311++G(3df,3pd) basis sets. Experimental data indicate that only one conformer, with C s symmetry [dihedral angle ϕ (CCOSi) = 180°, and all groups staggered], is observed in the gas phase. Theoretical data indicate that both this anti conformer and a gauche conformer, created by rotating about the C(O) O bond, are possible, although the preferred conformation is the staggered anti one. The torsional energies for different values of the CCOSi and COSiC dihedral angles have been calculated using the RHF, MP2 and B3LYP methods with the 6-311++G(d,p) basis set. For rotation around the CC OSi bond, a sixfold decomposition of the rotational barrier has been performed in terms of a Fourier-type expansion, enabling us to analyze the nature of the potential function, showing that the coefficients related to electrostatic interactions and steric effects are the dominant terms. The preference for the anti conformation was studied using the total-energy scheme, comparison of dipole moments, and the natural bond orbital partition scheme. The infrared spectra for the liquid and gas phases and the Raman spectrum for the liquid phase have also been recorded and the observed bands assigned to the vibrational normal modes. The experimental vibrational data, along with calculated theoretical force constants, were used to define a scaled quantum mechanical force field for the target system that enabled us to estimate the measured frequencies with a final root-mean-square deviation of 9.7 cm −1 .

The molecular structure and conformational properties of ethyl trifluoroacetate, CF3CO2CH2CH3, were determined in the gas phase by electron diffraction, and vibrational spectroscopy (IR and Raman). The experimental investigations were supplemented by ab initio (MP2) and DFT quantum chemical calculations at different levels of theory. Experimental and theoretical methods result in two structures with Cs (anti–anti) and C1 (anti–gauche) symmetries, the former being slightly more stable than the latter. The electron-diffraction data are best fitted with a mixture of 56% anti–gauche and 44% anti–anti conformers. The conformational preference was also studied using the total energy scheme, and the natural bond orbital scheme. Also, the infrared spectra of CF3CO2CH2CH3 are reported for the gas, liquid and solid states, as is the Raman spectrum of the liquid. The comparison of experimental averaged IR spectra of Cs and C1 conformers provides evidence for the predicted conformations in the IR spectra. Harmonic vibrational wavenumbers and scaled force fields have been calculated for both conformers. Copyright © 2009 John Wiley & Sons, Ltd.

The molecular structure of methyl trifluoroacetate (CF3C(O)OCH3) has been determined in the gas phase from electron-diffraction data supplemented by ab initio (MP2) and DFT calculations using different basis sets. Experimental data revealed an anti conformation with a dihedral angle θ (CCOC) = 180°. Quantum mechanical calculations indicate the possible existence of two conformers, differing by a rotation about the C(O)O bond. The global minimum represents a Cs-symmetric structure in which the CF3 group has the anti orientation with respect to the CH3 group, but there is another potential minimum, much higher in energy, representing a Cs-symmetric structure with a cis conformation. The preference for the anti conformation was studied using the total energy scheme and the natural bond orbital (NBO) partition scheme. Additionally, the total potential energy has been deconvoluted using a six-fold decomposition in terms of a Fourier-type expansion, showing that the electrostatic and steric contributions are dominant in stabilizing the anti conformer. Infrared spectra of CF3C(O)OCH3 were obtained for the gaseous and liquid phases, while the Raman spectrum was recorded for the liquid phase. Harmonic vibrational frequencies and a scaled force field have been calculated, leading to a final root mean-square deviation of 9 cm−1 when comparing experimental and calculated frequencies. Copyright © 2009 John Wiley & Sons, Ltd.

The molecular structure of 2-fluorostyrene has been optimized at ab initio (MP2 and CCSD) and DFT levels (B3LYP, mPW1PW91) with different basis sets (6-31G∗, 6-311++G∗∗, cc-pVDZ). B3LYP predicts planar structures for both cis and trans conformers, the latter being more stable than the former. mPW1PW91, MP2 and CCSD calculations yield a quasi-planar conformation in agreement with XRD and microwave data. The vinyl–phenyl torsion barrier of 2-fluorostyrene has been calculated at B3LYP, mPW1PW91, MP2 and CCSD levels with 6-31G∗ basis set as well as at MP2/cc-pVDZ level. Results have been compared with experimental data from the vibronic spectrum of the jet-cooled compound through a deconvolution of the total electronic potential energy by a sixfold Fourier-type expansion. As a result, MP2/cc-pVDZ shows the best performance as regards the torsional barrier height for the trans form. The effects governing the torsion barriers and preferred conformations have been analyzed at mPW1PW91/6-31G∗ and MP2/cc-pVDZ levels. To achieve this, two different schemes, i.e. the total electron energy and the natural bond orbital, NBO, partition schemes have been used. The Atoms-in-Molecules (AIM) theory has been applied to the cis and trans conformers in order to detect intramolecular contacts. Furthermore, a twofold aimed analysis of the vibrational spectrum has been performed. First, to obtain a complete assignment nonexistent so far and second, to confirm the being of the predicted cis and trans forms in the liquid and solid states. New records of infrared and Raman spectra, and for the first time, the inelastic neutron scattering (INS) spectrum have been used. Moreover, the mPW1PW91/6-31G∗ harmonic force field has been scaled using a multiple scaling (SQM) force field procedure. To achieve this, the initial scale factors were refined in order to get the best possible fitting between the calculated and experimental frequencies attaining to a final rms deviation of 5 cm−1.

The molecular structure of 2,2,2-trifluoroethyl trifluoroacetate, CF3CO2CH2CF3, has been determined in the gas-phase from electron-diffraction data supplemented by ab initio (MP2) and DFT calculations using basis sets up to 6-311++G(d,p). Both experimental and theoretical data indicate that, although both structures with anti, anti (Cs) and anti, gauche (C1) conformations exist by rotating about the O C(H2) bond, the anti, anti structure is preferred. The difference in free energy was calculated to be 2.1 kJ mol−1 (Cs conformer lower in energy) and as the C1 conformer has a double multiplicity relative to the Cs conformer, the ratio of C1–Cs conformer was predicted to be 0.41: 0.59. This conformational preference was studied using the total energy scheme and the natural bond orbital partition scheme. Additionally, the total potential energy has been deconvoluted using six-fold decomposition in terms of a Fourier-type expansion. Infrared spectra of CF3CO2CH2CF3 have been obtained for the gaseous, liquid and solid phases and the Raman spectrum for the liquid phase. Harmonic vibrational frequencies and a scaled force field have been calculated, leading to a final root-mean-square deviation of 7.3 cm−1.

Ethyl methanesulfonate, CH3SO2OCH2CH3, is well-known as an alkylating agent in mutagenic and carcinogenic processes. Its electronic structure and that of the methanesulfonate anion (CH3SO3-) were determined using optimization methods based on density functional theory and Moller-Plesset second-order perturbation theory. For CH3SO2OCH2CH3, two conformations with symmetries C(s) and C1 are obtained, the former being more stable than the latter. Natural bond orbital (NBO) calculations show the C(s) conformation provides a more favorable geometry of the lone pairs of the oxygen atom linking the ethyl group. The NBO technique also reveals the characteristics of the methanesulfonate anion as a leaving group due to the rearrangement of the excess electronic charge after alkylation. Furthermore, the infrared spectra of CH3SO2OCH2CH3 are reported for the liquid and solid states as well as the Raman spectrum of the liquid. Comparison to experiment of the conformationally averaged IR spectrum of C(s) and C1 provides evidence of the predicted conformations in the solid IR spectrum. These experimental data along with the calculated theoretical force constants are used to define a scaled quantum mechanical force field for the target molecule, which allowed the measured frequencies to be reproduced with a final root-mean-square deviation of 9 cm(-1) and, thus, a reliable assignment of the vibrational spectrum.

The molecular structure and conformational properties of S-ethyl thioacetate, CH3COSCH2CH3, were determined in the gas phase by electron diffraction and vibrational spectroscopy (IR and Raman). The experimental investigations were supplemented by ab initio (MP2) and DFT quantum chemical calculations at different levels of theory. Theoretical methods reveal two structures with Cs (anti, anti) and C1 (anti, gauche) symmetries. The infrared and Raman spectra for different phases were also recorded and the bands observed assigned to the vibrational normal modes. Liquid Raman and infrared spectra in liquid and gaseous state measurements revealed the presence of two conformations anti, anti (Cs symmetry) and anti, gauche (C1 symmetry). The study was completed using natural bond orbital (NBO) analysis. We have also analyzed the internal rotation barrier about the C(O)SCC dihedral angle using a variety of computational approaches and natural bond orbital (NBO) analyses to understand the nature of the potential function and to explain the preferred conformation of the molecule. Fil: Defonsi Lestard, Maria Eliana. Universidad Nacional de Tucumán; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Instituto de Quimica del Noroeste; Argentina Fil: Tuttolomondo, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Instituto de Quimica del Noroeste; Argentina. Universidad Nacional de Tucumán; Argentina Fil: Ben Altabef, Aida. Universidad Nacional de Tucumán; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Instituto de Quimica del Noroeste; Argentina

A new psolaren derivate, (E)-9-(3,4-dimethylpent-2-enyloxy)-7H-furo[3,2-g]chromen-7-one, has been isolated and characterized by experimental and theoretical methodologies. The solid state molecular structure has been determined by X-ray diffraction methods. The substance crystallizes in the monoclinic P21/c space group with a = 4.2389(5), b = 26.090(3), c = 12.482(1) Å, b = 96.990(9), and Z = 4 molecules per unit cell. The crystal structure shows the molecule fused phenyl and hetero-cycle rings to be coplanarwith each other. Ab initio(MP2) and DFT methods have been used to predict the molecular structure in the isolated molecule approximation and the results compared with the experimental data. The MP2/6-311G(d,p) calculations are in good agreement with the X-ray results. The calculatedHOMO?LUMOenergy gap shows that the intra-molecular charge transfer could easily occur, a prediction closely related to the observed bioactivity of this new compound. In addition, the infrared absorption and Raman dispersion spectra were recorded and an assignment of the observed spectral features to molecular vibrations was made. The vibrational study was assisted by quantum chemistry calculations at theMP2and DFT level, which provided theoretical mode frequencies. The study was completed by natural bond orbital (NBO) analysis. Fil: Turbay, S.. Universidad Nacional de Tucuman. Facultad de Agronomia y Zootecnia. Departamento de Cs. Basicas; Argentina Fil: Piro, Oscar Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: Echeverría, Gustavo Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: Navarro, A.. Universidad de Jaén; España Fil: Fernández Liencres, M.P.. Universidad de Jaén; España Fil: Fortuna, Antonio Mario. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Tucuman. Facultad de Agronomia y Zootecnia. Departamento de Cs. Basicas; Argentina Fil: Tuttolomondo, María Eugenia. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química Física; Argentina

The molecular structure and conformational properties of 2,2,2-trichloroethylacetate, CH3CO2CH2CCl3, 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 CH3CO2CH2CCl3 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. Fil: Gil, Diego Mauricio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Química del Noroeste. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química del Noroeste; Argentina Fil: Tuttolomondo, María Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Química del Noroeste. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química del Noroeste; Argentina Fil: Ben Altabef, Aída. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Química del Noroeste. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química del Noroeste; Argentina

The molecular structure of trimethylsilyl trichloroacetate, CCl3 C(O)OSi(CH3 )3 , was determined by ab initio (MP2) and DFT calculations using 6-31G(d), 6-311G(d,p), 6-311++G(d,p) and 6-311++G(3df,3pd) basis sets. The infrared and Raman spectra for the liquid phase were also recorded and the bands observed assigned to the vibrational normal modes. The study was completed using natural bond orbital (NBO) analysis and atoms in molecules (AIM) calculations. The comparison between the calculated molecular geometrical parameters, conformation and vibrational properties and those measured for CX3C(O)OR [X = F, Cl and R = CH3 , Si(CH3 )3 ] was of particular interest in order to check the behavior of the C   O and C  O with respect to the different substitutions. The experimental vibrational data, along with calculated theoretical force constants, were used to define a scaled quantum mechanical force field for the target system that enabled us to estimate the measured wavenumbers with a final root-mean-square deviation of 8.92 cm−1 . Fil: Defonsi Lestard, Maria Eliana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Instituto de Quimica del Noroeste; Argentina. Universidad Nacional de Tucumán; Argentina Fil: Cobos Picot, Rafael Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Instituto de Quimica del Noroeste; Argentina. Universidad Nacional de Tucumán; Argentina Fil: Tuttolomondo, María Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Instituto de Quimica del Noroeste; Argentina. Universidad Nacional de Tucumán; Argentina Fil: Ben Altabef, Aida. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Instituto de Quimica del Noroeste; Argentina. Universidad Nacional de Tucumán; Argentina

The molecular structure and conformational properties of S -ethyl trifluorothioacetate, CF3 COSCH2 CH3, were determined in the gas phase by electron diffraction and vibrational spectroscopy (IR and Raman). The experimental investigations were supplemented by ab initio (Møller Plesset of second order) and density functional theory quantum chemical calculations at different levels of theory. Both experimental and theoretical methods reveal two structures with Cs (anti, anti) and C1 (anti, gauche) symmetries, although there are disagreements about which is more stable. The electron diffraction intensities are best interpreted with a mixture of 51(3)% anti, anti and 49(3)% anti, gauche conformers. This conformational preference was studied using the total energy scheme and the natural bond orbital scheme. In addition, the infrared spectra of CF3 COSCH2 CH3 are reported for the gas, liquid and solid phases as well as the Raman spectrum of the liquid. Using calculated frequencies as a guide, evidence for both Cs and C1 structures is obtained in the IR spectra. Harmonic vibrational frequencies and scaled force fields have been calculated for both conformers. Fil: Defonsi Lestard, Maria Eliana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Química del Noroeste. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química del Noroeste; Argentina. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química Física; Argentina Fil: Tuttolomondo, María Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Química del Noroeste. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química del Noroeste; Argentina. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química Física; Argentina Fil: Wann, Derek A.. University of Edinburgh; Reino Unido Fil: Robertson, Heather E.. University of Edinburgh; Reino Unido Fil: Rankin, David W. H.. University of Edinburgh; Reino Unido Fil: Ben Altabef, Aída. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Química del Noroeste. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química del Noroeste; Argentina. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química Física; Argentina

The molecular structure of methyl methanethiosulfonate, CH 3 SO 2 SCH 3 , has been determined in the gas phase from electron-diffraction data supplemented by ab initio (HF, MP2) and density functional theory (DFT) calculations using 6-31G(d), 6-311++G(d,p), and 6-31 lG(3df,3pd) basis sets. Both experimental and theoretical data indicate that although both anti and gauche conformers are possible by rotating about the S-S bond, the preferred conformation is gauche. The barrier to internal rotation in the CSSC skeleton has been calculated using the RHF/6-31G(d), MP2/6-31G(d), and B3LYP/6-31G(d) methods as well as MP2 with a 6-31G(3df) basis set on sulfur and 6-31G(d) on C, H, and O. A 6-fold decomposition of the rotational barrier has been performed in terms of a Fourier-type expansion, enabling us to analyze the nature of the potential function, showing that the coefficients V 1 and V 2 are the dominant terms; V 1 is associated with nonbonding interactions, and V 2 is associated with hyperconjugative interactions. A natural bond orbital analysis showed that the lone pair → σ* hyperconjugative interactions favor the gauche conformation. Furthermore, the infrared spectra for the liquid and solid phases and the Raman spectrum for the liquid have been recorded, and the observed bands have been assigned to the vibrational normal modes. The experimental vibrational data, along with calculated theoretical force constants, were used to define a scaled quantum mechanical force field for the target system that enabled us to estimate the measured frequencies with a final root-mean-square deviation of 6 cm -1 .