جستجوی مقالات مرتبط با کلیدواژه "molecular structure" در نشریات گروه "شیمی"

Quercetin is a potent antioxidant that occurs naturally, but its poor water solubility and stability make it limited suited for therapeutic use. A water-soluble polymer or conjugate with greater stability than natural quercetin is yielded when quercetin is conjugated to an aldehyde-functionalized dextran. The conjugate demonstrated both antioxidant and anticancer properties in vitro. In quantitative structure–property/activity relationship (QSPR/QSAR) research, a topological index is a type of molecular descriptor that simply defines numerical values associated with a substance's molecular structure when modeling various physicochemical properties. In this work, general inverse sum indeg index and neighborhood M-polynomial approaches were used to investigate numerous degree-based and neighborhood degree sum-based topological indices for dextran-quercetin conjugates. Furthermore, a QSPR was conducted to evaluate the effectiveness of the calculated topological indices by contrasting the different topological indices with the physicochemical characteristics of eighteen derivatives of quercetin. The results showed a substantial relationship between the topological indices under investigation and the physicochemical characteristics of the quercetin derivatives.

Herein, five Schiff base molecules derived from para-nitrobenzaldehyde and different aniline derivatives are studied theoretically from the structure and energy perspectives. Density functional theory DFT method with 6-31+g(d,p) basis set is utilized to determine the optimized structure with the lowest energy in terms of the internal coordinates such as bond lengths, bond angles, and torsion angles. The study includes investigating the electronic indicators of the title molecules, such as frontier molecular orbital, electron affinity, ionization potential, and other parameters to predict the sites of reactivity and obtain an insight of the main properties of the molecules. Moreover, the electrostatic potential maps were determined and illustrated for the studied compounds to investigate the reactivity of charges on the surface of the molecules whether being of an electrophilic or nucleophilic nature. The study aims to examine the effect of changing the functional group in para-location of the aniline moieties on the molecular and geometrical properties of the molecules.

We theoretically investigated molecular structure, vibrational analysis, linear and nonlinear optical properties of the piperazine-1,4-diium bis 2,4,6-trinitrophenolate by employing density functional theory at several levels. To understand their linear and nonlinear optical behavior, dipole moment, polarizability, and first order hyperpolarizability β have been calculated and analysed in details. The hyper-Rayleigh scattering first hyperpolarizability, the electric field–induced second harmonic generation, and the depolarization ratios are the targeted quantities. The groups NO2, NH2, C=C, C-N, and phenolic 'O' atom were identified using theoretical vibrational analysis. The calculated of highest occupied molecular orbital, lowest unoccupied molecular orbital, and their energy gap are also presented. Global chemical reactivity descriptors and the three-dimensional molecular electrostatic potential were studied and discussed. Calculations highlight that 1°) predicted geometrical parameters show very good correlations with the corresponding experimental ones. 2°) A good correlation between the calculated and experimental vibration frequencies was also observed. 3°) A direct relationship between the energy gap and β has been obtained. 4°) The variation in β calculated confirmed the nonlinear optical activity of the studied piperazine. This work will help people understand the nonlinear optical properties of piperazine based molecules and provide guidance for the rational design of molecules with excellent optoelectronic properties.

Nickel(II) complex of [NiL2](ClO4)2, where L is an unsymmetrical tridentate ligand of 2-(2-aminoethyl)imino-3-butanone oximehas been synthesized by a template condensation reaction. The complex was characterized on the basis of microanalytical, spectroscopic, and other physicochemical properties. X-ray diffraction study of the complex reveals nickel(II) center in a distorted octahedral environment through two amine nitrogen donors, two imine donors,and two nitrogen atoms of the oxime moieties of the ligand. The antibacterial activity of the complex has been tested against Gram(+) and Gram(-) bacteria. The results of the antibacterial screening indicated that the complex is effective against bacterial growth retardation activity to some extent and its effectiveness is higher forGram(+) bacteria.

The alternative double bonds and conjugation in the polyene compounds are one of the main properties in these compounds. Each carbon-carbon bonds in a polyene compound along the chain has appreciable double-bond character. The p-electrons are therefore not localized but are relatively free to move throughout the entire carbon skeleton as an one-dimensional box. The skeleton be considered as a roughly uniform region of low potential bounded at the ends of the polyene by regions of infinitely high potential. Graph theory provides the useful natural mathematical frameworks for the quantitative codification of classical chemical bonding ideas. One of the useful indices for examination of structure-property relationship is Randić index. Some of properties here considered are associated with the molecular orbital method include and λmax, the difference energy level of the HOMO and LUMO orbitals (ΔE) and the length of the electron moving in carbon skeleton as one-dimensional box in polyene compounds (1-D box model). In this study, the difference of the length of carbon skeleton of polyenes and the length of the electron moving in the carbon skeleton will be discussed. For calculation the λmax of the compounds could use the Fieser-Kuhn rule. The interesting results of concerning among λmax, ΔE, the electron moving in carbon skeleton of simple linear polyenes by the use of 1-D box model and the above indices are presented.

The relationship between the Randic , Wiener, Hosoya , Balaban, Schultz indices, Harary numbers andDistance matrix to enthalpies of formation (Airf), heat capacity, (Cp) , enthalpies of combustion (AH °c ),enthalpy of vaporization (AH °vap) and normal boiling points (bpK)of C2 C10 normal alkanes isrepresented

One of the useful indices in molecular topology is Randić index. The alternative double bonds andconjugation in the polyene compounds are one of the main properties in these compounds. Someof the molecular orbital and structural properties refer to this specialty, such as: molar absorptioncoefficient (εmax) , electrical conductivity and difference energy level of the HOMO and LUMOorbitals, etc. Here, the relationship of the structural topologies such as the Randić indices,adjacency and distance matrixes to molar absorption coefficient (εmax) of the linear conjugatedpolyenes was represented. For calculation the εmax of the compounds could use the Fiser-Kuhnrule. The interesting results of concerning amoung εmax and the above indices are presented.

The molecular geometry of complex of adenine with 8 water molecules was calculated with Hartree-Fock (HF). The standard 6-31G(d) basis set has been employed. The existence of C-H…O Hydrogen bonds between the water molecules and the hydrophobic part of nucleobase is stablished. We optimized structures and computed interaction energies of all complexes of adenine with water molecules step by step, and finally compared them. Moreover, a theoretical investigation of the complex of adenine with 8 water molecules has led to the conclusion that the molecular structure of this molecule cannot be described by conventional chemical formula. The result of an AB initio Hartree-fock study of the structural parameters, atomic charge, dipole moment and thermodynamic change for isolated and poly hydrated adenine complexes are reported. Finally the gauge-invariant atomic orbital (GIAO) method was employed to calculate isotropic atomic shielding of complex using HF theory.