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دسترسی آزاد مقاله
1 - Electronic Structure, Biological Activity, Natural Bonding Orbital (NBO) and Non-Linear Optical Properties (NLO) of Poly-Functions Thiazolo [3,2-a]Pyridine Derivatives. DFT Approach
Shimaa Hussien hussien moustafaThe optimized structures of studied compounds 23-28 are non planner with the two phenyl at C3 and C9 are out of the molecular plane of thiazolo[3,2-a]pyridine as indicated from a dihedral angles of 710 and 1160 respectively, using DFT-B3LYP method with 6-311G(d,p) as ba چکیده کاملThe optimized structures of studied compounds 23-28 are non planner with the two phenyl at C3 and C9 are out of the molecular plane of thiazolo[3,2-a]pyridine as indicated from a dihedral angles of 710 and 1160 respectively, using DFT-B3LYP method with 6-311G(d,p) as basis set. The natural bonding orbital (NBO) analysis of the parent molecule 23 have been analyzed in terms of the hybridization of each bond, natural charges, bonding and antibonding orbital's, and second order perturbation energy (E(2)). The calculated EHOMO and ELUMO energies of the studied compounds can be used to explain the extent of charge transfer in the molecule and to calculate the global properties; the chemical hardness (η), global softness (S), electrophilicity (ω), and electronegativity (χ). The effect of substituent's of different strengths on the geometry, energetic and nonlinear optical properties are analyzed and discussed. The NLO parameters: static dipole moment (µ), polarizability (α), anisotropy polarizability (Δα), and first order hyperpolarizability (βtot), of the studied compounds have been calculated at the same level of theory and compared with the proto type Para-Nitro-Aniline (PNA). The results of (βtot) promising electrical properties. The 3D plots of the molecular electrostatic potential (MEP) for some selected compounds were investigated and describing the electrophilic and nucleophilic sites. The biological activity of the studied compounds was tested against gram positive, gram negative and Fungi. A correlation between energetic, global properties and biological activity were investigated and discussed. پرونده مقاله -
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2 - Theoretical Analysis on the Conformational Features of the HCO—Gly—L—Leu—NH2 Protected Dipeptide Motif: Ab initio and DFT Exploratory
B. Chahkandi M. Chahkandi S. M. Sadati Amin M. GiahiFor better understanding of conformational stability of the dipeptide model HCO—Gly—L—Leu—NH2,ab initio and DFT computations at HF/6-31G(4 6-311++G(d,p) and B3LYP/6-31G(d) levels oftheory were carried out. Geometry optimization of the dipeptide w چکیده کاملFor better understanding of conformational stability of the dipeptide model HCO—Gly—L—Leu—NH2,ab initio and DFT computations at HF/6-31G(4 6-311++G(d,p) and B3LYP/6-31G(d) levels oftheory were carried out. Geometry optimization of the dipeptide within the leucine (Leu) side chainangles (x2 ,x2) resulted in three stable conformations as followings: anti-anti, the most stable one,(Xi = 180°, x2 = 180°), Gauche (+)-trans (xi= 60°, x2 = 210°) and 270°-Gauche (-)(x4 = 270°, x2 =3001. The thermodynamic properties E, H, G, and S by changing dihedral angles '111 (DO and (Di(D11) of glycine (Gly), ‘1J2 (D6), and (62 (D4) of Leu and keeping the SC dihedral angles of the anti--anti conformer were obtained by frequency calculations at the same levels. The calculations indicatethat the BB has the highest stability bearing 'P I (DO = 180°, (1:11 (D11 ) = 180°, T2 (D6) = 150°, and 02(D4) = 210°. پرونده مقاله -
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3 - AB Initio Calculations of NMR Spectra for H20114C9N4 As A New Nanosemiconductor Molecule
E. Pournamdari M. MonajjemiBCN compounds have been researched theoretically and experimentally widely. In this paper, weintroduce the theoretical prediction of ternary B-C-N compounds. NMR spectroscopy was employedextensively to study these ternary nanostructures. We discuss the utilization of ch چکیده کاملBCN compounds have been researched theoretically and experimentally widely. In this paper, weintroduce the theoretical prediction of ternary B-C-N compounds. NMR spectroscopy was employedextensively to study these ternary nanostructures. We discuss the utilization of chemical shiftinformation as well as ab initio calculations of nuclear shielding for H20134C9N4 structuredetermination. We calculated B NMR and N NMR spectra with computational aspects of the NMRspectra using the gauge-invariant atomic orbital (GIAO) and continuous set of gauge transformations(CSGT) methods at different DFT computational methods (BILYP and LSDA), with a 6-31 G basisset at the GAUSSIAN 98 program package which are discussed. The purpose of this study is to carryout a more detailed analysis of the H20134C9N4 as a new nanosemiconductor system. پرونده مقاله -
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4 - Quantum-chemical modeling of the stacking mechanism for the 1H-4H proton transfer in pyridine derivatives. A DFT study
Jumber Kereselidze Marine Kvaraia George MikuchadzeThe stacking mechanism of the 1H-4H proton transfer in 4-pyridone, 4-pyridinthione and p-aminopyridineare constructed. For quantitative description of this process by means of the quamtumchemicalmethod density functional theory (DFT) the activation energy (<E#), reac چکیده کاملThe stacking mechanism of the 1H-4H proton transfer in 4-pyridone, 4-pyridinthione and p-aminopyridineare constructed. For quantitative description of this process by means of the quamtumchemicalmethod density functional theory (DFT) the activation energy (<E#), reaction energy (<E)and tautomeric equilibrium constant (KT) has been calculated. The results of calculations have shown,that the values of the energetical and kinetical characteristics, from the point of view of chemicalreactions, in reasonable limits varies, that allows one to make the conclusion in favour of competenceof the offered stacking mechanism for the 1H-4H proton transfer in pyridine derivatives. It is a newone-stage synchronous and unique mechanism for the 1H-4H proton transfer. پرونده مقاله -
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5 - A QSAR Study of 2-carboxamide-1,4-di-N-oxide quinoxaline Derivatives
Mohamad Reza Talei Bavil Olyai Hadi Behzadi Payman Roonasi Khaton TaghipourA set of density functional theory (DFT) calculations were performed on 2-carboxamide-1,4- di-N-oxide quinoxaline (2CdNOQ) derivatives. The optimized structure of these compounds in three forms was obtained. Some electronic parameters including dipole moment (μ),io چکیده کاملA set of density functional theory (DFT) calculations were performed on 2-carboxamide-1,4- di-N-oxide quinoxaline (2CdNOQ) derivatives. The optimized structure of these compounds in three forms was obtained. Some electronic parameters including dipole moment (μ),ionization potential (I), electron af finity (A), LUMO energy (εLUMO), HOMO energy (εHOMO),electronegativity (χ), hardness (η), electrophilicity (ω), and differences between HOMO andLUMO energies (εLUMO–εHOMO), for the most stable conformer, were calculated. Quantitativestructure–activity relationship (QSAR) models of the biological activity (IC50) of these compounds were established using the calculated quantum mechanical descriptors. Also, the first, second, total, and mean N-O bond dissociation enthalpies were also obtained theoretically and were correlated to reported experimental inhibition. پرونده مقاله -
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6 - [n]Sila-acenes (n=2-4): The Influence of Ring Size on the Properties
Hossein Ghiasi Reza GhiasiThe structures and properties of [n]sila-acenes (n=2-4) were investigated by density functional theory method. The results of calculations were obtained at B3LYP/6-311G (d,p) level on model species. Energetic criteria suggest that 2-1b (n=2), 3-1b (n=3), and 4-1b (n=4) چکیده کاملThe structures and properties of [n]sila-acenes (n=2-4) were investigated by density functional theory method. The results of calculations were obtained at B3LYP/6-311G (d,p) level on model species. Energetic criteria suggest that 2-1b (n=2), 3-1b (n=3), and 4-1b (n=4) isomers enjoy stabilization. By frontier orbital analysis, these systems are among the most stable of the family. Also, calculations indicate the most stable isomers have the most first hyperpolarizability values. The aromaticity of all molecules has been studied by nucleusindependent chemical shift. پرونده مقاله -
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7 - New Pt(II) Complexes with Heterocyclic Ligands Derived from Benzimidazole: Synthesis, Characterization, DFT Calculations and Catalytic Activities
Parisa Sadeghzadeh Mehdi Pordel Safar Ali Beyramabadi Abolghasem DavoodniaIn this work, the synthesis, spectral characterization, DFT calculations, and catalytic activity of thenew Pt(II) complexes with the ligand derived from benzimidazole derivatives have been described.The new heterocyclic ligands were obtained from the reaction of o-amino چکیده کاملIn this work, the synthesis, spectral characterization, DFT calculations, and catalytic activity of thenew Pt(II) complexes with the ligand derived from benzimidazole derivatives have been described.The new heterocyclic ligands were obtained from the reaction of o-amino-ketones with hydrazinehydrate in high yieldandPt(II) complexes prepared from the coordination of the new ligands toPt(II) cation. The new compounds have been characterized by spectral and microanalytical data.The DFT calculations at the B3LYP/6-311+G(d,p) level were also applied to gain further insightinto the geometry of Pt(II) complexes. The catalytic activity of Pt(II) complexes in Biginellireactionwas also examined as heterogeneous catalysts. The results showed that the 3,4-dihydropyrimidin-2(1H)-ones have been synthesized, in excellent yields, under solvent-free conditions, by reaction oftert-butyl acetoacetate, alcohol, arylaldehydes, and urea in the presence of Pt(II) complexes as anefficient and heterogeneous and catalyst. پرونده مقاله -
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8 - Fluorouracil functionalized Pt-doped carbon nanotube as drug delivery nanocarrier for anticarcinogenic drug: a B3LYP-D3 study
Zahra Khalili Masoud Darvish Ganji Maryam MehdizadehThe interaction between drugs and nanostructured materials such as nanotubes is proving to be of fundamental interest for drug delivery and nanobiosensing. In the present work, the interaction of Fluorouracil, as an anticarcinogenic drug, with pristine CNT and Pt-doped چکیده کاملThe interaction between drugs and nanostructured materials such as nanotubes is proving to be of fundamental interest for drug delivery and nanobiosensing. In the present work, the interaction of Fluorouracil, as an anticarcinogenic drug, with pristine CNT and Pt-doped CNT was investigated at the B3LYP-D3/TZVP level. Full optimization procedure has been carried out for all interacting systems to better understand the trends in binding nature of drug molecule interacting with the selected nanocarrier. We have evaluated the various stable configurations at both gas phase and aqueous solution for the considered complexes based on their interaction nature. Calculated adsorption energies indicated that Fluorouracil can form stable binding with Pt-CNT in aqueous media with adsorption energy of −1.12 eV which was found to be a chemisorption process. Charge analysis revealed that, upon binding of Fluorouracil to the nanocarrier, the overall charge on the host and guest systems changes and significant charges have been transferred from Fluorouracil to the substrates. Quantum molecular descriptors calculations also demonstrate the significant changes in the electronic properties of the nanostructures due to the Fluorouracil attachment. Interaction between Fluorouracil and pristine CNT however has been found to be typical for the physisorption with adsorption energy of about −0.405 eV. Our findings offer fundamental insights into the functionalization of the Pt-doped CNT and envisage the applicability of these nanostructured materials as a novel drug delivery vehicle for the transportation of anticarcinogenic drug within thetarget cells. پرونده مقاله
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