Search

The double lactonization of D-glucaric acid can result in two isomeric molecules which are: the D-glucaro-1,4:6,3-dilactone and the D-glucaro-1,5:6,3-dilactone. In the present article we try to understand the differences between these molecules. To this end, all the conformations have been modeled and optimized in order to find the most stable structures. Energies, frontier orbitals (HOMO and LUMO) as well as other electronic and spectral properties have been calculated in vacuum, acidic and aqueous media using the polarizable continuum model (PCM). The calculations were investigated by performing semi-empirical PM6 and density functional theory (DFT) at the B3LYP level of theory. The obtained results do not motivate a possible observation of the two dilactones simultaneously in the same medium, which explains the absence of this coexistence in the scientific works carried out to date.

This study is based on the valuation of a few model molecules. The objective of this research is focused on linear optical (LO) and nonlinear optical (NLO) enhancement of five organometallic molecules based on different metallocenes. These molecules were subjected to several calculations by different long-range functionals CAM–B3LYP, LC–BLYP, LC–wPBE, wB97X, M11, and the following three Minnesota functionals: M06–2X and M08–HX in comparison with the MP2 approach. Hence, the CAM–B3LYP functional gave the closest NLO values to the MP2 method. Second, molecule 3A based on nickelocene recorded the highest static (βtot) value which is 76.46 Χ 10−30 esu and 4803.4 Χ 10−30 esu under the laser wavelength λ = 532 nm. Third, intramolecular charge transfers (ICTs) of the molecules studied are all directed in both directions (donor to acceptor and vice versa). Finally, the specific solvent for molecules 2A and 3A is acetonitrile, and the maximum wavelengths obtained for the isolated or solvated molecule are all located in the near UV; the corresponding interval is between 250 and 395 nm.

International audience; The equilibrium geometries of 1,3,4-thiadiazole derivatives have been determined and analyzed at DFT level employing B3LYP/6-31G(d) basis set. The molecular electrostatic potential surface (MESP) that reveals centers of reactivity of the molecule and substitution effects of the molecular system have been studied using the HSAB principle (Hard Soft Acid and Base).Results such us, fundamental vibrational modes, 1H NMR isotropic chemical shifts, frontier orbital energies (HOMO, LUMO), band gap energy, dipole moments, net charges are reported and discussed in terms of reactivity of 1,3,4-thiadiazole derivatives. The HOMO and LUMO analysis were used to elucidate information regarding charge transfer within the molecule. Isotropic chemical shifts were calculated using the Gauge-Independent Atomic Orbital (GIOAO) method. Finally, a comparison between the experimental data and the calculated results appeared a good agreement and show exceptional reactivity. © 2019 Editura Academiei Romane. All rights reserved.

Series of twenty-four compounds was the field for applying multi-parameter optimization (MPO) methods and qualitative approximations of structural activity relationships in order to determine the role of various physico-chemical and quantum descriptors used in QSAR modeling as independent variables. Anaplastic lymphoma kinase (ALK) inhibitory activity was considered as a component in this study. In order to illustrate the quantitative relationships between the molecular descriptors and the activity of pyrazolone derivatives, we have applied a multiple linear regression (MLR) procedure. By adopting cross-validation with the leave-one-out method, we could estimate the predictability of models. Our results suggest a QSAR model based on the following descriptors: S, V, LogP, POL, Ref, HOMO, LUMO, E, , HBA, PSA and NRB, for the inhibitory activities against ALK. Results show high correlation between experimental and predicted activity values, indicating the validation and the good quality of the QSAR model. Copyright © 2018 American Scientific Publishers All rights reserved.

In this work, we studied by means of density functional theory (DFT) and time-dependent DFT(TD-DFT) using the effect of the mixture composition C4mimBF4/acetonitrile on the charge transfer in Coumarin 153(C153) after photoexcitation. The mixture composition was characterize by their corresponding static dielectric constant e m . The PBE0 and M06-2X functionals combined with linear response (LR) and state specific (SS) solvation schemes were used to obtain various electronic properties of C153 in both ground and excited states. Our results show that the calculated fluorescence Stoke shift, using the state specific solvation scheme correlates well with the corresponding experimental data obtained for C153 dissolved in other solvents have the same static dielectric constant as of the C4mimBF4/acetonitrile mixture. The charge transfer was quantified using descriptors such as charge qCT, distance dCT, and the dipole moment μCT between the ground and the excited state. These descriptors were calculated based on four different partial atomic charge models, namely Mulliken, Natural Populations Analysis, Hirshfeld, and Merz–Kollman. The charge transfer also was quantified using descriptors based on the electrostatic surface potential namely the polarity index. Both PBE0 and M06-2X functionals combined with the Linear Response solvation scheme result in a systematic increase of the qCT, dCT, and μCT with increasing e m , while they decrease for most of the partial atomic charge models when the State Specific solvation scheme is used. This later result points out that this solvation scheme is not suitable for the description of the excited state of C153 in this mixture. Our results show that the extent of change of these descriptors is small and indicates that the effect of the mixture composition on the charge transfer in C153 is weak.

International audience; Molecular geometry, electronic properties, effect of the substitution, and structure physical-chemistry relationship for thiazolidine-2,4-dione derivatives have been studied by density functional theory (DFT) theory. In the present work, the calculated values, namely, net charges, molecular electrostatic potential (MESP) contours/surfaces have also been drawn to explain the electronic activity of thiazolidine-2,4-dione, bond lengths, dipole moments, heats of formation, Quantitative structure- activity relationship (QSAR) properties, Lipinski's and Veber's parameters, Ligand efficiency (LE), Lipophilic Efficiency (LipE), etc., are reported and discussed in this paper. Copyright © 2016 American Scientific Publishers.

The entropy generation optimization of a hemispherical anchor agitated batch reactor has been studied, to optimize the heat transfer in the process of production of a cosmetic cream cooled by a jacket at industrial scale. The main objective of this optimization of the cooling condition was the improvement of the product quality and the reduction the energy consumption of the process. The phenomenon considered is two-dimensional, axisymmetric and permanent. The entropy generation optimization has been carried out successfully by the simulation of the heat transfer throw the reactor wall and the agitated fluid. The results give the optimum speed velocity for agitation and the optimal cooling time and coolant temperature.The entropy generation optimization of a hemispherical anchor agitated batch reactor has been studied, to optimize the heat transfer in the process of production of a cosmetic cream cooled by a jacket at industrial scale. The main objective of this optimization of the cooling condition was the improvement of the product quality and the reduction the energy consumption of the process. The phenomenon considered is two-dimensional, axisymmetric and permanent. The entropy generation optimization has been carried out successfully by the simulation of the heat transfer throw the reactor wall and the agitated fluid. The results give the optimum speed velocity for agitation and the optimal cooling time and coolant temperature.

In the present paper we have a focus in a study of theoretical characterization of three double headed acyclo-C-nucleosides, which are a recent target of experimental studies. The structural and electronic properties of double headed acyclo-C-nucleosides, 1,4-bis (3-mercapto-1H-1,2,4-triazol-5-yl) butane-1,2,3,4-tetrol, 1,4-bis (4-amino-5-mercapto-4H-1,2,4-triazol-3-yl) butane-1,2,3,4-tetrol and 5,5'-(1,2,3,4-tetrahydroxybutane-1,4-diyl) bis (1,3,4-oxadiazole-2(3H)-thione), have been investigated theoretically by performing semi-empirical molecular orbital, ab initio Hartree-Fock (HF) and Density Functional Theory (DFT) calculations. Geometries of the three molecules are optimized at the level of Austin Model 1 (AM1). The electronic properties and relative energies of the molecules have been calculated by HF and DFT in the ground state.

Using UV-visible spectrophotometric data of (1:1), electron donor-acceptor complexes (AD 1 , AD 2 and AD 3 ) have been investigated. The complexes concerned are n-butyl amine (D1) and cyclohexyl amine (D2) and phenyl hydrazine (D3) as electron donors with iron (III) ion as an electron acceptor (A) in methanol at 25°C. The values of formation constant (kAD), molar extinction coefficient (e AD ), and absorption band energy of complexes were estimated. The ionization potential of the

International audience; In the present study, Quantitative structure-activity relationship (QSAR) study have been performed on twenty molecules of 1,2,5-thiadiazole derivatives. The compounds studied are the analogues of aceclidine as potent M1 muscarinic agonists. A multiple linear regression (MLR) procedure was used to design the relationships between molecular descriptors and biological activity of the 1,2,5- thiadiazole derivatives. The predictivity of the model was estimated by cross-validation with the leave-one-outmethod. Our results suggest a QSAR model based on the following descriptors Log P , HE, Pol, MR, MV, and MW, SAG, and Etotal. High correlation between experimental and predicted activity values was observed, indicating the validation and the good quality of the established QSAR models. © 2018 American Scientific Publishers.

This paper study the energy efficiency of the mixing and cooling of a non-Newtonian fluid manufactured on an industrial scale in a stirred tank reactor equipped with jacketed cooling side. The purpose of this study is to optimize the heat transfer to degrease the cooling time and recommend a technologic innovation to realize this purpose without altering the quality of this product. First the different production processes are analyzed. The decrease of the shear stress with time indicates that this fluid is non-Newtonian and has to be characterized. The rheological behavior of this fluid is determined by a series of viscosimetric measurements, at different shear rates (30 to 400 s−1), and at different temperatures in the range (20° C to 80 °C), representing the stress and temperature conditions recorded during production, storage and packaging cycles of this product. Experimental results show that the nature of the fluid is pseudo-plastic with flow behavior index n

Qualitative and Quantitative structure activity relationship (SAR/QSAR) analysis was applied to eighteen Quercetin derivatives using a combination of various physicochemical, steric, electronic, and structural molecular descriptors. A multiple linear regression (MLR) procedure was used to model the relationships between molecular descriptors and the chemotherapeutic activity of the Quercetin derivatives. The stepwise regression method was used to derive the most significant models as a calibration model for predicting the inhibitory activity of this class of molecules. The best QSAR models were further validated by a leave one out technique as well as by the calculation of statistical parameters for the established theoretical models. High agreement between experimental and predicted inhibitory values, obtained in the validation procedure, indicated the good quality of the derived QSAR models. Copyright © 2018 American Scientific Publishers All rights reserved

QSAR studies have been performed on twenty-one molecules of 1,3,4-oxadiazoline-2-thiones. The compounds used are among the most thymidine phosphorylase (TP) inhibitors. A multiple linear regression (MLR) procedure was used to design the relationships between molecular descriptor and TP inhibition of the 1,3,4-oxadiazoline-2-thione derivatives. The predictivity of the model was estimated by cross-validation with the leave-one-out method. Our results suggest a QSAR model based of the following descriptors: logP, HE, Pol, MR, MV, and MW, qO1, SAG, for the TP inhibitory activity. To confirm the predictive power of the models, an external set of molecules was used. High correlation between experimental and predicted activity values was observed, indicating the validation and the good quality of the derived QSAR models.

International audience; Quantitative structure activity relationship (QSAR) methods have been applied in several scientific studies including chemistry, biology and toxicology and drug discovery to predict and classify biological activities of virtual or newly-synthesized compounds. QSAR models can also be used in designing new chemical entities and are now regarded as essential tools in pharmaceutical industries to identify promising hits and generate high quality leads in the early stages of drug discovery. QSAR studies were performed on a series of pyrazine as anti-proliferative agents. A multiple linear regression (MLR) procedure was used to envisage the relationships between molecular descriptors and the activity of pyrazine derivatives. The predictivity of the model was estimated by cross-validation with the leave-one-out method. Our results suggest a QSAR model based of the following descriptors: logP, HE, SAG, Pol, qC3 for the anti-proliferative activity against the HEPG2 (human liver cancer cell) and logP, HE, MR, SAG, Vol, qC2, qC5, qC6, LUMO for the anti-proliferative activity against the SW1116 (human colorectal carcinoma cell). To confirm the predictive power of the models, an external set of molecules was used. High correlation between experimental and predicted activity values was observed, indicating the validation and the good quality of the derived QSAR models. Copyright © 2017 American Scientific Publishers All rights reserved.

The bonding within the series of [trans-Cl(η2-dppe)2RuC≡C(4-C6H4X)]n+ complexes (1-Xn+; n = 1, 0 and X = NO2, C(O)H, C(O)Me, F, H, OMe, NMe2) has been examined by IR, ESR, and UV−vis−near-IR spectroscopy together with computational modeling. A strong substituent effect is evidenced for radical delocalization from the metal to the functional arylacetylide fragment. This effect is also apparent in the large anisotropy change of their ESR signatures. DFT calculations substantiate these experimental observations and permit discussion of the influence of the X substituent on spin delocalization in compounds containing isolobal metal fragments. Evidence is given that the ESR anisotropy alone cannot reliably be used to compare the metallic character of the unpaired electrons in closely related families of pseudo-octahedral cationic Ru(III) functional arylacetylides with rhombic symmetry when the complexes possess different coordination spheres. ESR anisotropy constitutes nevertheless a useful benchmark for this ...

The Trotter factorisation of the Liouville propagator is applied to derive reversible reference system propagator algorithms (RESPA). This strategy is used to treat constant temperature molecular dynamics simulations of liquid methane based on a Nose heat bath. It is shown how the RESPA method can be used to compute thermodynamics, structural and transport properties of liquid methane. The results reported in this paper are also compared to constraint molecular dynamics simulations, quantum methods and experimental data.

Molecular dynamics (MD) simulations have been performed on Luteolin (Lut) dissolved in various solvents (methanol, 1-propanol, 2-propanol, 1-butanol, dimethylsulfoxide, acetone and hexane) with the purpose to characterize the local structure around the hydroxyl (OH)1 and carbonyl (C double bond; length as m-dash O) moieties and to correlate the findings with the experimental vibrational spectroscopy and NMR results. The local structure is analyzed through the calculation of the radial distribution functions (RDF), the nearest neighbor radial and orientation distribution functions as well as the distribution of the dihedral angle involving the Cdouble bond; length as m-dashO and the adjacent (OH)1 atoms. Our results show that the Cdouble bond; length as m-dashO moiety is interacting in a similar way with the protic solvents while the intra molecular hydrogen bond between this moiety and the (OH)1 hydroxyl group is weakened in favor of the intermolecular hydrogen bond between the (OH)1 and the protic and aprotic solvents.

The interactions of luteolin with three alcohols (methanol, 1-propanol, 1-butanol) and dimethylsulfoxide (DMSO) were studied by FT-Raman, Vis-Raman and UV-Raman spectroscopies, coupled to density functional theory calculations. No large shift was observed for the bands in the spectra of luteolin in alcohols or DMSO in the 1700–1550 cm− 1 region. This is possibly related to the presence of a strong intramolecular hydrogen bond involving the 5-OH and the carbonyl of luteolin, as suggested by literature data [V. Exarchou, A. Troganis, I.P. Gerothanassis, M. Tsimidou, D. Boskou, Tetrahedron 2002, 58, 7423–7429] and DFT calculations. Furthermore, DFT calculations suggest that the CO stretching of luteolin is implicated in several vibrational modes, whereas the most upshifted band in the 1700–1550 cm− 1 can be interpreted as arising mainly from a 5-OH bending. The results are discussed in the framework of vibrational spectroscopy studies on flavonoids, of the photophysical properties of luteolin, and of the reported literature of vibrational spectra of luteolin under different conditions, in particular when interacting with biomolecules. Fil: Marrassini, Carla. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Farmacología. Cátedra de Farmacognosia; Argentina Fil: Idrissi, Abdenacer. Université Lille 1; Francia Fil: de Waele, Isabelle. Université Lille 1; Francia Fil: Smail, Khadidja. Université des Sciences et de la Technologie d’Oran Mohamed Boudiaf; Argelia Fil: Tchouar, Noureddine. Oran University of Science and Technology - Mohamed Boudiaf; Argelia Fil: Moreau, Myriam. Université Lille 1; Francia Fil: Mezzetti Alberto. Université Lille 1; Francia

The perturbation of a dithienylethene system by a ruthenium carbon-rich system, and vice versa, was used to reach a unique and sophisticated light- and electro-triggered multifunctional switch featuring multicolor electrochromism, electrocyclization at remarkably low voltage, and photo/electro tuning of electronic communication.