QSAR modeling of antiradical properties of phenolic compounds using DFT calculations

This paper describes a quantitative structure – activity relationship study of the antiradical properties of 31 flavonoids belonging to different groups such as: flavonols, flavonones, dihydroflavonols and biflavonones. Using density functional theory (DFT) calculations, some structural characteristics such as frontier molecular orbitals, molecular descriptors, have been studied. To gain insights into the chemical structure and property of the studied compounds, many types of descriptors are generated by using DFT/B3LYP 6-31G(d,p) and other software.Also, The Principle Component Analysis (PCA), Multiple Linear and Nonlinear Regression (MLR and MNLR), and Artificial Neural Network (ANN) have been investigated to select the descriptors, and to generate the correlation models that relate the structural feature to the biological activity. The statistical results of the MLR, MNLR, and ANN indicate that the determination coefficient R2 were 0.811, 0.646, 0.982, respectively. A good correlation coefficient is obtained, and the antiradical activities of these compounds are well predicted. These models are expected to be useful for screening of polyphenolic antioxidants

Theoretical investigation of new organic materials based on fluorene and thiophene for photovoltaic applications

In this study, five compounds of novel acceptor-donor organic materials containing 9,9-d imethyl-9H-fluoren, (2,5) dimethyloxy-4-(thiophen-2yl) thiophene linked to cyanoacrylic acid via several dyes  based alternating donors are investigated. The geometries, electronic absorption and emission spectra of these six compounds are studied by Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD/DFT) calculations. The HOMO, LUMO, Gap energy, λmax, Voc of these compounds have been calculated and reported in this paper. The objective of this study; is to evidence the relationship between chemical structure of these organic materials and their properties optoelectronic of ways has conceive thereafter the compounds with effective character for solar cells.

A theoretical study of regio and stereoselectivity nitration of thymol and carvacrol using DFT approach

This work is a detailed theoretical study of the nitration aromatic substitution reactions of thymol and carvacrol. In this process, a mixture of nitric and sulfuric acids is used to produce the nitronium agent NO2+. The computational calculations were performed at the Gaussian 09 using the DFT approaches. The first task of the computing study was to determine the optimized geometry of these compounds using the Becke three-parameter hybrid exchange functional and the Lee-Yang-Parr correlation functional (B3LYP) with the 6-311+G (d, p) basis set. Geometry optimization calculations have been carried out to find the global and local minima for reactants and intermediates, respectively, and to locate the saddle points for the transition states. The vibration frequencies have been calculated in order to check the character of the stationary points obtained after the geometry optimization. It is expected only positive frequencies for reactants, intermediates and products, but only one negative imaginary frequency for transition states.The analysis of the nucleophilic fk- Fukui Function and Pk- Parr functions allows characterising the C4 carbon atom as the most nucleophilic center of thymol and carvacrol, in clear agreement with the regioselectivity obtained. Calculation of activation energies, analysis of the potential energy surface and the Gibbs free energy indicates that this reaction takes place through a two-step mechanism

Theoretical study of organic materials based on Thieno[2,3-b]thiophene as layer of bulk heterojunction solar cells

In this study, we report a theoretical investigations on the structural, optoelectronic and photovoltaic properties of a series of conjugated organic molecules containing thieno[2,3-b]thiophene, with different substituents. The DFT calculations were performed by using the quantum chemical methods using B3LYP [1] level with 6-31G(d) [2] basis set for all atoms. All calculations were realized by Gaussian 09 [3] program supported by GaussView 5.0.8 interface. Moreover, the optoelectronic properties (HOMO, LUMO, Egap…) were determined from the fully optimized structures. The absorption properties (λmax, Etr, OS) of these molecules are obtained by TD-B3LYP/6-31G(d) method [4].The studied oligomers can be subdivided in three categories; the first one constitutes by synthetized oligomers [5] but is characterized with the highest energy band values. Thanks to the effect of structural modifications in there chemical structures in the second and the third categories, the energy gap values have known a dramatic decrease. We conclude that these conjugated materials, especially of the third categories, are good candidates for bulk heterojunctions in organic solar cells applications.

Synthesis, structural and crystallographic characterization of new hydrosoluble thymol derivatives with a comparative study of enhanced antioxidant activity

In this study, we synthesized two new Thymol derivatives obtained by reacting Thymol sulfonic acid with respectively two amines: aniline and diethylamine. Spectroscopic analysis by FT-IR, mass spectrometry, (1H, 13C) NMR and XRD elucidated the chemical structure of these two new Thymol derivatives identified as: Diethylammonium 4-hydroxy-5-isopropyl-2-methylbenzenesulfonate (P.1) and Benzenaminium 4-hydroxy-5-isopropyl-2-methylbenzenesulfonate (P.2) obtained respectively with 98% and 52% reaction yields. They match two new Thymol organic salts with specific ionic crystalline form. We investigated a comparative antioxidant activity study based on the DPPH test versus Butyl hydroxy toluene (BHT) as control and Thymol as strating material. The results show that boat synthesized compounds (P.1) and (P.2) are significantly more active with IC50 value 3,44 µg/mL for (P.2) and 6,76 µg/mL for (P.1) versus 21,7 µg/mL for (BHT) and 178.03 µg/mL for Thymol. More interestingly, these two compounds are water soluble and the compound (P.1) was obtained in a good yield reaction (98%)