Experimental and theoretical investigation on conformational and spectroscopic properties of dimethyl dithiodiglycolate, [CH3OC(O)CH2S]2

Dimethyl dithiodiglycolate (DTG), [CH3OC(O)CH2S]2, was synthetized by complete oxidation of methyl thioglycolate (MTG) with I2, and characterized by gas chromatography coupled with electron-impact mass spectrometry. Fifteen stable conformers were found with the B3LYP/6-31 + G* approximation, with calculated populations at ambient temperature higher than 1%. The IR and Raman spectra of liquid DTG were interpreted for the first time, in terms of equilibrium between four conformers. The UV–visible spectra of DTG in solutions of ethanol, isopropanol and acetonitrile present a low-intensity band around 230 nm, interpreted mainly as arising from n → π* transitions localized at the C[dbnd]O groups, according to the prediction of TD-DFT calculations.Fil: Juncal, Luciana Celeste. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Química Inorgánica ; ArgentinaFil: Bava, Yanina Belén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Química Inorgánica ; ArgentinaFil: Tamone, Luciana Mariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Química Inorgánica ; ArgentinaFil: Seng, Samantha. Université de Lille 1 Sciences et Technologies; FranciaFil: Tobón, Yeny A.. Université de Lille 1 Sciences et Technologies; FranciaFil: Sobanska, Sophie. Université de Lille 1 Sciences et Technologies; FranciaFil: Picone, Andrea Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Química Inorgánica ; ArgentinaFil: Romano, Rosana Mariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Química Inorgánica ; Argentin

Insight into the conformational space of n-benzyl-n-(furan-2-ylmethyl)acetamide by NMR spectroscopy and DFT calculations

In this study, the conformational behavior of N-benzyl-N-(furan-2-ylmethyl) acetamide in chloroform was addressed by using a combined experimental/theoretical strategy using NMR spectroscopy and quantum chemical calculations. The 1H and 13C one‑dimensional NMR spectra, as well as the two-dimensional HSQC-DEPT and HMBC-DEPT NMR spectra, evinced the presence of a hindered cis(E)-trans(Z) rotational equilibrium in solution. DFT calculations were performed at different theoretical levels using the polarizable continuum model (PCM) and predicted nine (four Z and five E structures) stable conformations. The interconversion dynamics among the different confirmations were established in terms of four different rotational equilibria in CDCl3. The chemical shifts in the 1H and 13C NMR spectra of the compound are similar to the values calculated for the two most abundant conformational equilibria at room temperature, one caused by two Z rotamers and the other by two E rotamers. The compound was also characterized for the first time by FTIR, Raman spectroscopy, and GC/MS spectrometry. Additionally, several acylation methodologies for synthesizing the title compound from N-benzyl-1-(furan-2-yl)methanamine were tested which resulted in high yields (> 90%) under very convenient conditions (10 min, at room temperature).Centro de Investigación y Desarrollo en Ciencias Aplicada

Crystal structure, spectroscopic characterization and Hirshfeld surface analysis of aquadichlorido{N- [(pyridin-2-yl)methylidene]aniline}copper(II) monohydrate

The reaction of N-phenyl-1-(pyridin-2-yl)methanimine with copper chloride dihydrate produced the title neutral complex, [CuCl2(C12H10N2)(H2O)]·H2O. The CuII ion is five-coordinated in a distorted square-pyramidal geometry, in which the two N atoms of the bidentate Schiff base, as well as one chloro and a water mol­ecule, form the irregular base of the pyramidal structure. Meanwhile, the apical chloride ligand inter­acts through a strong hydrogen bond with a water mol­ecule of crystallization. In the crystal, mol­ecules are arranged in pairs, forming a stacking of symmetrical cyclic dimers that inter­act in turn through strong hydrogen bonds between the chloride ligands and both the coordinated and the crystallization water mol­ecules. The mol­ecular and electronic structures of the complex were also studied in detail using EPR (continuous and pulsed), FT–IR and Raman spectroscopy, as well as magnetization measurements. Likewise, Hirshfeld surface analysis was used to investigate the inter­molecular inter­actions in the crystal packing.Centro de Química InorgánicaInstituto de Física La Plat

Estudio de la fotoreactividad de partículas individuales de interés atmosférico por medio de técnicas de levitación acopladas a espectroscopia micro-Raman

International audienc

Micro Raman spectroscopy and Raman imaging for the study of (photo)reactivity and heterogeneity of single levitated droplets

International audienceIn atmospheric chemistry, each aerosol particle acts as a small mobile reactor where several heterogeneous chemical reactions lead to the modification of its size, chemical composition and structure; as well as the consumption and release of chemical agents from its gaseous environment. Despite its relevance, information on the chemical and photochemical processes that occur in atmospheric aerosols is still scarce, mainly due to the instrumental difficulties involved in studying such processes on a surface scale. In this regard, Micro-Raman spectroscopy coupled to a levitation technique, through an environmental levitation cell, is especially useful for studying - at micrometric scale - the in-situ modifications of aerosol when exposed to reactive or damp environments without the influence of a contacting surface (Krieger, et al. 2012). This work deals with two main objectives. On one hand, the monitoring of physical- and photo-chemical processes occurring in levitated single particles; and in the other hand, the coupling and instrumental developments carried out to perform Raman imaging studies of single levitated particles. We will show the coupling between the confocal Raman microscope and the adapted photochemical environmental levitation cell, as well as the heterogeneous distribution of (photo)chemical products on levitated particles (less than 10 µm of size) evidenced by reconstruction of the Raman spectral image.This work was supported by funds from the “Laboratoire d’Excellence” (LABEX) -CaPPA- (ANR-11-LABX-0005-01) and CPER research project CLIMIBIO.Andreae, M. O., and Crutzen, P. J. (1997). Science 276, 1052-1058. Krieger, U. K., Marcolli, C., and Reid, J. P. (2012). Chem. Soc. Rev. 41, 6631-6662

Experimental and theoretical IR study of methyl thioglycolate, CH3OC(O)CH2SH, in different phases: Evidence of a dimer formation

The IR spectrum of methyl thioglycolate (MTG) was studied in three different phases, and interpreted with the aid of DFT calculations. The gas phase IR spectrum was explainable by the presence of the most stable conformer (syn-gauche-(-)gauche) only, while the IR spectrum of the liquid reveals strong intermolecular interactions, coincident with the formation of a dimeric form. The matrix-isolated spectra allow the identification of the second conformer (syn-gauche-gauche), in addition to the most stable form. The MTG dimer was also isolated by increasing the proportion of MTG in the matrix. The theoretical most stable structure of the dimer, which calculated IR spectrum agrees very well with the experimental one, is stabilized by a double interaction of the lone pair of the O atom of each of the C[dbnd]O groups with the antibonding orbitals σ* (S[sbnd]H).Fil: Bava, Yanina Belén. 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"; ArgentinaFil: Tamone, Luciana Mariel. 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"; ArgentinaFil: Juncal, Luciana Celeste. 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"; ArgentinaFil: Seng, Samantha. Universite Lille; FranciaFil: Tobón, Yeny A.. Universite Lille; FranciaFil: Sobanska, Sophie. Universite Lille; FranciaFil: Picone, Andrea Lorena. 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"; ArgentinaFil: Romano, Rosana Mariel. 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"; Argentin

Gas-phase and matrix-isolation photochemistry of methyl thioglycolate, CH₃OC(O)CH₂SH : Influence of the presence of molecular oxygen in the photochemical mechanisms

The photochemistry of methyl thioglycolate (MTG), CH3OC(O)CH2SH, in gas phase and in matrix isolation conditions was studied by means of FTIR spectroscopy, and the influence of the presence of molecular oxygen on the photochemical mechanisms was investigated. The UV–vis broad-band photolysis of MTG in gas phase originates CH3OC(O)CH3 and S8, while in matrix conditions the photoproducts are CH3OH, H2CS, and CO, interacting inside the matrix cage. The photolysis of MTG in the presence of O2 conducts to the formation of SO2, independent of the experimental conditions, being CH3OH, HC(O)OH, and CO the other photoproducts for the gas-phase photolysis, and H2CO, CH4, and CO2 for the experiments performed in Ar matrix conditions.Centro de Química Inorgánic

Experimental and theoretical IR study of methyl thioglycolate, CH₃OC(O)CH₂SH, in different phases : Evidence of a dimer formation

The IR spectrum of methyl thioglycolate (MTG) was studied in three different phases, and interpreted with the aid of DFT calculations. The gas phase IR spectrum was explainable by the presence of the most stable conformer (syn-gauche-(-)gauche) only, while the IR spectrum of the liquid reveals strong intermolecular interactions, coincident with the formation of a dimeric form. The matrix-isolated spectra allow the identification of the second conformer (syn-gauche-gauche), in addition to the most stable form. The MTG dimer was also isolated by increasing the proportion of MTG in the matrix. The theoretical most stable structure of the dimer, which calculated IR spectrum agrees very well with the experimental one, is stabilized by a double interaction of the lone pair of the O atom of each of the C=O groups with the antibonding orbitals σ* (SeH).Centro de Química Inorgánic

Experimental and theoretical investigation on conformational and spectroscopic properties of dimethyl dithiodiglycolate, [CH₃OC(O)CH₂S]₂

Dimethyl dithiodiglycolate (DTG), [CH3OC(O)CH2S]2, was synthetized by complete oxidation of methyl thioglycolate (MTG) with I2, and characterized by gas chromatography coupled with electron-impact mass spectrometry. Fifteen stable conformers were found with the B3LYP/6-31 + G* approximation, with calculated populations at ambient temperature higher than 1%. The IR and Raman spectra of liquid DTG were interpreted for the first time, in terms of equilibrium between four conformers. The UV–visible spectra of DTG in solutions of ethanol, isopropanol and acetonitrile present a low-intensity band around 230 nm, interpreted mainly as arising from n → π* transitions localized at the C[dbnd]O groups, according to the prediction of TD-DFT calculations.Centro de Química Inorgánic