Exploring C H•••O hydrogen bonds in dihydrocoumarin from combined vibrational spectrocopy and DFT calculations

Abstract

The complete vibrational spectra assignment of dihydrocoumarin is performed through a combined vibrational spectroscopy and DFT calculations approach. To provide effective information, vibrational analysis was also performed for α-pyrone and coumarin related systems. The presence of extra components in the νCdouble bondO band profile can only be understood by both Fermi resonance and monomer/dimer equilibrium phenomena, the latter established by C–H···O hydrogen bond with ΔH° value of −8.4 ± 0.9 kJ mol−1. The analysis of the νC–H region indicates that both the methylene and aromatic C–H groups have a significant contribution to the formation of C–H···O bonded dimers in liquid dihydrocoumarin.

Mariela Nolasco, Patrícia Vaz, Pedro Vaz, Paulo Ribeiro-Claro.


Full Article

On the effects of Gaussian program version and SCRF defining parameters: isopropylamine as a case study.

Abstract

The present study reports a performance evaluation of the new Gaussian program version G09 relatively to the previous one in what concerns the SCRF formalism. The potential improvements achieved by changing program version and other SCRF defining parameters (like radii and SCRF models) were evaluated, by comparing the predicted values of several molecular properties with the corresponding experimental values reported in the literature. The relevance of the dispersion effects in the prediction of those molecular properties was inferred by considering the G09 newly implemented B97D DFT. On the whole, the results showed that the precision achieved in the molecular properties prediction is strongly dependent on the choice of the computation defining parameters. Moreover, direct comparisons between results obtained using either G03 or G09 require precaution.

A M Amado, S Fiuza, LAEB de Carvalho, Paulo J. A. Ribeiro-Claro.


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Solid-state vibrational spectroscopic investigation of cocrystals and salt of indomethacin.

Abstract

Knowledge and control of the solid forms of active pharmaceutical ingredients are important aspects of drug development in the pharmaceutical industry. In this paper, the process of the molecular self-assembly of saccharin cocrystals and the 2-amino-5-methylpyridine salt of indomethacin, in terms of the hydrogen bonding patterns, has been studied in the solid-state using vibrational spectroscopy (Raman and infrared). Interaction patterns in the respective crystalline states were obtained from the single crystal data. The effects of cocrystal and salt formation on the frequencies of the vibrational modes of motion were explained by vibrational spectroscopy and supported by quantum chemical calculations at the density functional theory level, leading to unambiguous assignment of the vibrational spectra of the starting materials and their respective products. Both Raman and infrared spectroscopies were useful, reliable tools for characterizing and distinguishing the indomethacin cocrystals and salt.

Hassan Refat H. Ali, Amjad Alhalaweh, N. F. C. Mendes, Paulo Ribeiro-Claro and Sitaram P. Velaga.


Full Article

Structural Studies and Cytotoxicity of Trimethyl(ferrocenylmethyl) ammonium Iodide Encapsulated in β-Cyclodextrin

Abstract

nclusion complexes that comprise β-cyclodextrin (β-CD) and trimethyl(ferrocenylmethyl)ammonium iodide (1) have been prepared by codissolution of the host and guest in ethanol/water, accompanied by either conventional heating at 40 °C for 26 h (to give 2) or microwave-assisted heating for 30 min (to give 3). Solids were isolated and characterized by elemental and thermogravimetric analyses, powder X-ray diffraction (XRD), and IR, Raman, and 13C{1H} CP/MAS NMR spectroscopy. Powder XRD indicated the presence of microcrystalline inclusion compounds with supramolecular structures that comprise β-CD head-to-head dimers arranged into infinite channels. A small crop of single crystals of the inclusion compound 2 were obtained and analyzed by XRD. Despite diffraction being very poor above a resolution of around 1 Å, the data could be indexed to the space group P1 (in agreement with powder XRD) and a reasonable structural model could be achieved when the asymmetric unit was composed of two directly located β-CD hosts, 1.4 iron atoms, and a small fraction of iodide anions. By using these data as a starting point, DFT calculations were carried out and led to a model of the crystal structure that comprised 2:1 (host/guest) and 2:2 adducts. The cytotoxic and antiproliferative activities of 1 and 2 were tested against the breast adenocarcinoma MDA-MB-231 and osteosarcoma MG-63 cell lines. Results indicate that both 1 and 2 are cytotoxic against the MDA-MB-231 line but exhibit negligible activity on the MG-63 line.

Sofia M. Bruno, José A. Fernandes, Joana Marques, Sara C. Neto, Paulo Ribeiro-Claro, Martyn Pillinger, Filipe A. Almeida Paz, Maria Paula M. Marques, Susana S. Braga, Isabel S. Gonçalves.


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1,3,5-Tris(bromomethyl)benzene.

Abstract

The asymmetric unit of the title compound, C9H9Br3, is composed of a single molecule. Two bromo substituents are located on one side of the plane of the aromatic ring and the third is on the opposite side, with the molecular unit exhibiting an approximate noncrystallographic Cs point group. The crystal structure is rich in Br…Br, CH2…Br and CH…π weak intermolecular contacts which mediate the crystal packing of individual molecules. These interactions promote a red-shift of a handful of vibrational modes (associated with the pendant –CH2Br groups) compared with values from theoretical density functional theory (DFT) calculations.

Fernandes, J. A.; Vilela, S. M. F.; Ribeiro-Claro, P. J. A.; Paz, F. A. A.


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©Copyright 2024 - Computational Spectroscopy Lab - Department of Chemistry - University of Aveiro - 3810-193 Aveiro
©Copyright 2024 - Computational Spectroscopy Lab - Department of Chemistry - University of Aveiro - 3810-193 Aveiro

©Copyright 2024 - Computational Spectroscopy Lab - Department of Chemistry - University of Aveiro - 3810-193 Aveiro