Computational Chemistry

The polaronic effects at the atomic level hold paramount significance for advancing the efficacy of transition metal oxides in applications pertinent to renewable energy. The lattice-distortion localization of photoexcited carriers in the form of polarons plays a pivotal role in the photocatalysis. This investigation focuses on rutile TiO2, an important material extensively explored for solar energy conversion in artificial photosynthesis, specifically targeting the generation of green H2 through photoelectrochemical (PEC) H2O splitting. By employing Hubbard-U corrected and hybrid density functional theory (DFT) methods, we systematically probe the polaronic effects in the catalysis of oxygen evolution reaction (OER) on the (110) surface of rutile TiO2. Theoretical understanding of polarons within the surface, coupled with simulations of OER at distinct titanium (Ti) and oxygen (O) active sites, reveals diverse polaron formation energies within the lattice sites with strong preferen...

<ABS-P> <ABS-P><xps:span class="xps_Image">fx1</xps:span> <ABS-HEAD>Highlights► Tautomers of 2,4-ditellurouracil and 5-fluorotellurouracil were studied using DFT method. ► The keto-enol tautomerism was studied in the gas phase. ► The diketo form is the most stable tautomer. ► Substitution of hydrogen by fluorine causes a decrease in the interconversion barriers. ► The ADME parameters of the most stable diketo and dienol tautomers were predicted. <H1>4 <ABS-HEAD>Abstract <ABS-P>2,4-Ditellurouracil exhibits keto-enol tautomerism via different pathways resulting in seven tautomers. These pathways were studied in the gas phase using density functional theory method. The functionals used were BLYP, B3LYP and BHLYP and the basis sets were 6-311++G(d,p) for all atoms except that LanL2DZ ECP was used for tellurium atom only. The results indicate that the diketo form is more stable as observed for uracil and its sulfur and selenium analogues. The effect of introducing fluorine at position 5 was also investigated and the energy difference between the diketo and dienol forms is reduced. 2,4-Ditellurouracil and its 5-fluoro analogue are expected to exist exclusively as the diketo form due to the high interconversion energy barrier. We extended the investigation to predict ADME parameters of the most stable diketo and dienol tautomers in view of understanding their biological properties. This research enlightens keto-enol tautomerism of 2,4-ditellurouracil and its 5-fluoro derivative with additional insights to biological functions. <KWD>Keywords: keto-enol tautomerism; tellurouracil; DFT; COSMO-RS; ADME

In this work, we make use of a model chemistry within Density Functional Theory (DFT) recently presented, which is called M05-2X, to calculate the molecular structure of the flavonoid Rutin, as well as to predict the infrared (IR) and ultraviolet (UV-Vis) spectra, the dipole moment and polarizability, the free energy of solvation in different solvents as an indication of solubility, the HOMO and LUMO orbitals, and the chemical reactivity parameters that arise from Conceptual DFT. The calculated values are compared with the available experimental data for this molecule as a means of validation of the used model chemistry.

The electronic structures and energies of formation of supramolecular complexes of dipyridylethylene with AgNO 3 were calculated by the semiempirical AM1/d method, at the Hartree-Fock level, and by the density functional theory (B3LYP/6 31G*).

Fiber Fabry-Perot (FFP) filters have been widely used in optical fiber communications, and insertion loss (IL) is one of its important characteristics. Based on theoretically analysis, factors related to IL were discussed. In order to investigate the IL of different structures, simulations are carried out with finite-difference time-domain (FDTD) algorithm. Comparisons are made between the optimized structure and full-size-mirror FFP filter, and fiber-inserted FFP filter as well. Simulation results demonstrated that the finite-size-mirror structure can confine the mode size of the open resonator, hence reduce the IL of FFP filter.

A new aromaticity index is proposed based on the energy of orbital [ 1 + ( 1 2 ) + ( 3 )]. Calculations have been performed on aromatic and heteroaromatic compounds by using DFT method at B3LYP/6-311G+(d,p) level. This new index has been tested on 6 electron compounds and compared with the experimental resonance energy (ERE), the Bird index (I x ), the molar magnetic susceptibility ( M ), the aromatic stabilization energy (ASE), and the isomerization stabilization energy (ISE). In all the cases, a good correlation has been found.

modeling to the general case of in vitro binding affinity Computational chemistry and molecular modeling procedures data between low-molecular-weight ligands and a speallow us to define and compute ad hoc size and shape descriptors cific target receptor, then to obtain meaningful and preon the different prototropic forms assumed by drugs in biotest dictive QSAR models, at least four criteria should be solutions. Together with experimental data measured on a wellsatisfied: (a) adequate quality of biological/pharmacologidentified target receptor, these descriptors are essential eleical data; (b) choice of an informative set of molecules ments for obtaining simple, consistent, comparable, and easily (statistical population of ligands); (c) definition/determiinterpretable theoretical quantitative structure-activity relationnation of the specific different prototropic forms asship (QSAR) models based on the ligand similarity-target recepsumed by the ligands in the biotest solution; and (d) use tor complementarity paradigm. In this context, quantitative size of appropriate molecular/submolecular descriptors and and shape affinity/subtype selectivity relationships have been statistics for the specific problem under study. modeled for a large set of very heterogeneous a 1a -, a 1b -, and a 1d -Receptor binding is a molecular recognition process adrenergic receptor antagonists. The linear QSAR models generthat depends on the properties of both interacting partated have been validated by predicting both binding affinity and ners. If the three-dimensional structure of the receptor selectivity of a test set of noncongeneric antagonists. The satisis unknown, then QSAR modeling will be a quantitafactory results obtained highlight both the simplicity and the vertive search for similarity/diversity of the ligands with satility of the approach presented.

Quantum chemical methods and molecular modeling techniques allow the definition of a large number of molecular and local quantities characterizing the reactivity, the shape and the binding properties of a molecule as well as of molecular fragments and substituents. This study is focused on a systematic comparison of the theoretical molecular descriptors with both empirical (Hammett's and Taft's substituent constants, hydrophobic parameter, Verloop's steric parameters etc.) and experimental (substituent induced chemical shifts, molecular weight and molecular refractivity) descriptors. Fifty selected monosubstituted benzenes, including some charged substituents have been computed in the AM1 framework. Several theoretical descriptors have been extracted from the AM1 electronic wavefunction as well as molecular modeling techniques and they have been analyzed by principal component analysis and the partial least squares method. The results obtained are consistent with previous principal component studies concerning empirical descriptors, and highlight the interdependencies among theoretical and empirical molecular descriptors.

Accurate description of the intrinsic preferences of amino acids is important to consider when developing a biomolecular force field. In this study, we use a modern energy partitioning approach called Interacting Quantum Atoms to inspect the cause of the u and w torsional preferences of three dipeptides (Gly, Val, and Ile). Repeating energy trends at each of the molecular, functional group, and atomic levels are observed across both (1) the three amino acids and (2) the u/w scans in Ramachandran plots. At the molecular level, it is surprisingly electrostatic destabilization that causes the high-energy regions in the Ramachandran plot, not molecular steric hindrance (related to the intra-atomic energy). At the functional group and atomic levels, the importance of key peptide atoms ) and some sidechain hydrogen atoms (H c ) are identified as responsible for the destabilization seen in the energetically disfavored Ramachandran regions. Consistently, the O i-1 atoms are particularly important for the explanation of dipeptide intrinsic behavior, where electrostatic and steric destabilization unusually complement one another. The findings suggest that, at least for these dipeptides, it is the peptide group atoms that dominate the intrinsic behavior, more so than the sidechain atoms. V

The quantum chemical topology method has been used to analyze the energetic profiles in the X -1 CH 3 X ! XCH 3 1 X -S N 2 reactions, with X 5 F, Cl, Br, and I. The evolution of the electron density properties at the BCPs along the reaction coordinate has been analysed. The interacting quantum atoms (IQA) method has been used to evaluate the intraatomic and interatomic energy variations along the reaction path. The different energetic terms have been examined by the relative energy gradient method and the ANANKE program, which enables automatic and unbiased IQA analysis. Four of the six most important IQA energy contributions were needed to reproduce the reaction barrier common to all reactions. The four reactions considered share many common characteristics but when X 5 F a number of particularities occur.

Recently, the quantum topological energy partitioning method called interacting quantum atoms (IQA) has been extended to MPn (n = 2, 3, 4) wave functions. This enables the extraction of chemical insight related to dynamic electron correlation. The large computational expense of the IQA-MPn approach is compensated by the advantages that IQA offers compared to older nontopological energy decomposition schemes. This expense is problematic in the construction of a machine learning training set to create kriging models for topological atoms. However, the algorithm presented here markedly accelerates the calculation of atomically partitioned electron correlation energies. Then again, the algorithm cannot calculate pairwise interatomic energies because it applies analytical integrals over whole space (rather than over atomic volumes). However, these pairwise energies are not needed in the quantum topological force field FFLUX, which only uses the energy of an atom interacting with all remaining atoms of the system that it is part of. Thus, it is now feasible to generate accurate and sizeable training sets at MPn level of theory.

FFLUX is a novel force field based on quantum topological atoms, combining multipolar electrostatics with IQA intraatomic and interatomic energy terms. The program FEREBUS calculates the hyperparameters of models produced by the machine learning method kriging. Calculation of kriging hyperparameters (h and p) requires the optimization of the concentrated loglikelihood Lðh; pÞ. FEREBUS uses Particle Swarm Optimization (PSO) and Differential Evolution (DE) algorithms to find the maximum of Lðh; pÞ. PSO and DE are two heuristic algorithms that each use a set of particles or vectors to explore the space in which Lðh; pÞ is defined, searching for the maximum. The loglikelihood is a computationally expensive function, which needs to be calculated several times during each optimization iteration. The cost scales quickly with the problem dimension and speed becomes critical in model generation. We present the strategy used to parallelize FEREBUS, and the optimization of Lð h; pÞ through PSO and DE. The code is parallelized in two ways. MPI parallelization distributes the particles or vectors among the different processes, whereas the OpenMP implementation takes care of the calculation of Lðh; pÞ, which involves the calculation and inversion of a particular matrix, whose size increases quickly with the dimension of the problem. The run time shows a speed-up of 61 times going from single core to 90 cores with a saving, in one case, of 98% of the single core time. In fact, the parallelization scheme presented reduces computational time from 2871 s for a single core calculation, to 41 s for 90 cores calculation. V

Density functional theory calculations (ωB97X-D/6-311++G(d,p)) are employed to investigate an alternative pathway for Prins-like cyclization. Although strong acids usually catalyze this reaction, 4-amino-1,3-dioxanes are rapidly obtained in high yields without catalyst when benzenamines and acetaldehyde react at low temperatures, in aqueous medium. Considering these conditions, we applied a supermolecule model with explicit water molecules to compute the mechanism for 4-amino-1,3-dioxanes formation from the reactants. The structure of the primary solvation shell was determined by Metropolis Monte Carlo method. In the Prins-cyclization step, we found an unpredicted pathway with non-ionic transition structures or intermediates. Explicit water molecules establish a net of hydrogen bonds allowing prototropism, maintaining the electrical neutrality in the system while two protons transfer occurs. To provide data to further experimental confirmation of this hypothesis, we estimated the kinetic isotope effect for the reaction. We also investigated the use of aliphatic amines, which indicates that the reaction may be of a broader application than first observed experimentally.

The Z-E isomerization of γ-alkylidenebutenolide analogues to natural nostoclides and other natural butenolides was investigated using 1 H nuclear magnetic resonance (NMR) and high performance liquid chromatography (HPLC) data as well as density functional theory (DFT) calculations at the ωB97x-D/6-31G(d,p) level, including solvent effects with the polarizable continuum solvation approach. The experimental data supported the Z to E isomerization of γ-alkylidenebutenolides under acid catalysis. Newly prepared samples have predominantly Z configuration, which partially isomerizes to the E isomer under acidic conditions. Density functional theory studies corroborate the experimental findings. While neutral γ-alkylidenebutenolides are more stable in the Z form, protonation of the γ-lactone carbonyl group results in preferential stabilization of the E isomer.

Based on the data about structure and antidiabetic activity of twenty seven vanadium and zinc coordination complexes collected from literature we developed QSAR models using the GUSAR program. These QSAR models were applied to 10 novel vanadium coordination complexes designed in silico in order to predict their hypoglycemic action. The five most promising substances with predicted potent hypoglycemic action were selected for chemical synthesis and pharmacological evaluation. The selected coordination vanadium complexes were synthesized and tested in vitro and in vivo for their hypoglycemic activities and acute rat toxicity. Estimation of acute rat toxicity of these five vanadium complexes was performed using a freely available web-resource (). It has shown that the selected compounds belong to the class of moderate toxic pharmaceutical agents, according to the scale of Hodge and Sterner. Comparison with the predicted data has demonstrated a reasonable correspondence between the experimental and predicted values of hypoglycemic activity and toxicity. Bis{tert-butyl[amino(imino)methyl]carbamato}oxovanadium (IV) and sodium(2,29-Bipyridyl)oxo-diperoxovanadate(V) octahydrate were identified as the most potent hypoglycemic agents among the synthesized compounds.

This work is a continuation of our pilot study on the use of off‐center s‐type Gaussian functions in noncovalent interaction calculations. A grid of s‐type Gaussians surrounding the molecule is intended to substitute for the presence of diffuse basis functions, which are important for accurate description of noncovalent interactions. The advantage over the use of diffuse functions is reduction or elimination of linear dependency issues in the atomic orbital basis set, which often causes convergence problems. Placement of a grid of s‐functions on the surface of the molecule allows more favorable scaling of the total number of basis functions with the molecular size to be achieved. In this article, we present several innovations on the concept, namely the parametrization and assessment of grids with triple‐ζ quality basis set; use in post‐second‐order correlation treatment (methods such as Møller–Plesset third‐order or coupled‐cluster); and combination with modified virtual orbital ap...

Intermetallic Fe-Li interaction likely occurs during some stereoselective lithiation reactions of ferrocene derivatives. The nature of this interaction was assessed on a model system of ferrocenemethyl lithium complex using coupled cluster methods CCSD(T). CCSD(T) calculations predicted interaction energy of -38.0 kJ.mol -1 and Fe-Li distance of 2.75 Å. The ability of commonly used DFT functionals to describe this interaction was also screened. The best agreement of structural parameters (energy, and Fe-Li distance) with the CCSD(T) calculated results was achieved by dispersion corrected TPSS functional. DFT calculations were also used for natural bond orbital analysis of the intramolecular Fe-Li interaction in benzylferrocene ortho-lithiated on the phenyl ring. This bimetallic bond can be explained as a donor-acceptor orbital interactions between the iron lone pair or C-Fe bonding electrons with the empty orbitals of lithium.

Dipole polarizabilities of fluorinated C2 and C3 hydrocarbons have been studied using Coupled Cluster theory including single, double and non-iterative triple substitutions (CCSD(T)) -in conjunction with three basis sets: Pol, Z3Pol and HyPol. All molecular geometries were optimized at the MP2/aug-cc-pVTZ level. We have found only small effects of electron correlation on electric properties in fluorinated species. The dipole polarizabilities increase slightly with the increasing fluorination of ethene and propene. For fluorinated ethenes Pol and Z3Pol basis sets give polarizabilities in very good agreement with the literature data.

Some of the new unique features of the MOLCAS quantum chemistry package version 7 are presented in this report. In particular, the Cholesky decomposition method applied to some quantum chemical methods is described. This approach is used both in the context of a straight forward approximation of the two‐electron integrals and in the generation of so‐called auxiliary basis sets. The article describes how the method is implemented for most known wave functions models: self‐consistent field, density functional theory, 2nd order perturbation theory, complete‐active space self‐consistent field multiconfigurational reference 2nd order perturbation theory, and coupled‐cluster methods. The report further elaborates on the implementation of a restricted‐active space self‐consistent field reference function in conjunction with 2nd order perturbation theory. The average atomic natural orbital basis for relativistic calculations, covering the whole periodic table, are described and associated u...

Proper description of noncovalent interactions requires, among other things, the use of diffuse atomic orbital (AO) basis sets. However, the presence of diffuse functions, especially in extended molecular systems, can lead to linear dependent AO basis sets. This in turn results, for example, in molecular orbital optimization problems or, when dependencies are removed in unpredictable and possibly geometrydependent accuracy fluctuations. In this work, an alternative approach is proposed which suffers no linear dependence problems and delivers comparably accurate noncovalent interaction energies. An algorithm is proposed and implemented to construct a grid of off-center s-type Gaussian functions surrounding the molecule; substituting the presence of atomcentered diffuse basis functions. While the number of basis functions in the grid is comparable to the number of diffuse basis functions in aug-cc-pVXZ (for each cardinality number "X") basis sets for small molecular systems, the ratio becomes more favorable with increasing system size. The grid is constructed in a way that it is unique for a molecule (monomer) and, thus, independent of noncovalent complex/cluster geometry. The grid parameters, such as the density of grid points and s-function exponents, are obtained via optimization toward the S22 data set on the MP2 level. The quality, transferability, and versatility of the grid is tested on the S66 data set as well as on several cuts through the potential energy surface for noncovalent complexes, such as methyl-guanine•••methyl-cytosine conversion from stacked to hydrogen-bonded structure.

The program system MOLCAS is a package for calculations of electronic and structural properties of molecular systems in gas, liquid, or solid phase. It contains a number of modern quantum chemical methods for studies of the electronic structure in ground and excited electronic states. A macromolecular environment can be modeled by a combination of quantum chemistry and molecular mechanics. It is further possible to describe a crystalline material using model potentials. Solvent effects can be treated using continuum models or by combining quantum chemical calculations with molecular dynamics or Monte-Carlo simulations. MOLCAS is especially adapted to treat systems with a complex electronic structure, where the simplest quantum chemical models do not work. These features together with the inclusion of relativistic effects makes it possible to treat with good accuracy systems including atoms from the entire periodic system. MOLCAS has effective methods for geometry optimization of equilibria, transition states, conical intersections, etc. This facilitates studies of excited state energy surfaces, spectroscopy, and photochemical processes.

Dipole moments of a series of radicals, OH, NO, NS, SF, SO, PO, ClO, CN, LiO, NO2, and ClO2 were calculated by the Coupled Cluster CCSD(T) method with the single determinant restricted open shell Hartree-Fock (ROHF) reference. For all molecules theoretical dipole moments were carefully compared to experimental values. The size and the quality of the basis set were systematically improved. Spin adaptation in the ROHF-CCSD(T) method, largest single and double excitation amplitudes and the T1 diagnostics were considered as indicators in the quality assessment of calculated dipole moments. For most molecules the accuracy within 0.01-0.03 D was readily obtained. For ClO and CN the spin adaptation was necessary - its contribution was as large as 0.03-0.045 D. Large deviation from experiment is observed for OH in its A2Σ+ excited state (0.135 D) and especially for LiO in its 2Π ground state (0.22 D). No indication of the failure of theoretical calculations was found which leads to the conc...

In the title compound, [Yb(C24H40BN6)2]·C7H8, the Yb atom is coordinated by two tris(3-tert-butyl-5-methylpyrazol-1-yl)hydridoborate [TptBu,Me] ligands. One ligand binds in the κ3mode, throuh three N atoms of the pyrazolyl rings, the other ligand coordinates through two N atoms of the pyrazolyl rings and the H atom attached to the central Bviaan agostic-type interaction through the B—H group of the second TptBu,Meligand, giving an overall distorted octahedral geometry. One of thetert-butyl groups is disordered over two sites, with occupancies of 0.65 and 0.35.

Thirty-six stable complexes of formic acid with formaldehydes and thioformaldehydes were determined on the potential energy surface, in which the XCHOÁÁÁHCOOH complexes are found to be more stable than the XCHSÁÁÁHCOOH counterparts, with X = H, F, Cl, Br, CH 3 , NH 2 . All complexes are stabilized by hydrogen bonds, and their contribution to the total stabilization energy of the complexes increases in going from C-HÁÁÁS to C-HÁÁÁO to O-HÁÁÁS and finally to O-HÁÁÁO. Remarkably, a significant blueshift of C sp2 -H bond by 81-96 cm -1 in the C sp2 -HÁÁÁO hydrogen bond has hardly ever been reported, and a considerable redshift of O-H stretching frequency by 206-544 cm -1 in the O-HÁÁÁO/S hydrogen bonds is also predicted. The obtained results in our present work and previous literatures support that a distance contraction and a stretching frequency blueshift of C-H bond involving hydrogen bond depend mainly on its polarity and gas phase basicity of proton acceptor, besides the rearrangement of electron density due to complex formation. Markedly, we suggest the ratio of deprotonation enthalpy to proton affinity (R c ) as an indicator to prospect for classification of hydrogen bonds. The symmetry adapted perturbation theory results show a larger role of attractive electrostatic term in XO-n as compared to that in XS-n and the electrostatic interaction is overwhelming dispersion or induction counterparts in stabilizing XO-n and XS-n, with n = 1, 2, 3.

Density functional theory (DFT) calculations using numerical basis sets were employed to predict the solvation energies, Gibbs free energies and pKa values of a series of 5-substituted uracil derivatives. Obtained results show that solvation energies are not significantly different between DFT methods using the numerical (DNP) and Gaussian basis set (aug-cc-pVTZ). It is noteworthy that the independent and suitable solvation energy of proton of -258.6 kcal/mol has been proposed for the evaluation of pKa values in conjunction with the numerical basis set. In addition, the calculated pKa values suggest that the anti-conformation of 5-formyluracil is the most stable form in the aqueous solution. 

The aim of this study is to find the relationship between HIV-1 activity and chemical structure for 2-Pyridinone derivatives by using the Electron-Topological Method (ETM). Data for ETM were obtained quantum mechanical calculations. Quantum chemical calculations were performed after the conformational analysis. By using the data obtained from quantum chemical calculation results ETM were perfomed and pharmacophere and anti-pharmacophere fragments for the HIV-1specific Reverse Transcriptase inhibitors were explained. Conformational analysis and quantum-chemical calculations of 2-pyridinone derivatives were carried out by using B3LYP method with basis set of the 6-311G(d,p) in order to determine molecular properties. The descriptors of HOMO, LUMO, HOMO-LUMO energy gap, chemical hardness, chemical softness, electro-negativity, chemical potential, dipole moment etc. were calculated and tabulated in order to employed in statistical analyses that are Linear Discriminant Analysis (LDA) and Artificial Neural Networks (ANNs). By doing so, the linear and non-linear sections of data structure are investigated and their corresponding descriptors having impact on dependent variable has been found. We see from the fragment properties atoms found in benzoxazole groups give rise to activity of the molecules, and atoms in the naphthyl groups causes breaking the activity.

Cellular membrane affinity chromatography is a technique that is based on the immobilization of a target trans-membrane protein onto a stationary phase. The target protein is isolated by homogenization and solubilization of a source (e.g., cell line) followed by immobilization on either the immobilized artificial membrane-phosphatidyl choline (IAM-PC) stationary phase or the surface of an open tubular capillary during a dialysis step. The procedure typically takes 3-4 d for the IAM-PC stationary phase, whereas the open-tubular method takes an extra week for the preparation of the capillary. The resulting columns can then be used to characterize binding sites on the target protein through frontal chromatographic and/or nonlinear chromatographic studies using a wide variety of ligands including small molecules and polypeptides. The columns have been used in drug discovery as well as in the screening of tobacco smoke condensates.

Using the Kirkwood-Buff theory of solutions, the preferential solvation of the N-methylacetamide (NMA), N-methylformamide, (NMF), and N,N-dimethylformamide, (DMF), molecule has been investigated in the binary famide+methanolg mixtures at 313.15 K. Moreover, for the famide+methanolg mixtures, where amide = NMF, DMF, and NMA, the molecular dynamics calculations at x amide = 0.518 were performed. From the obtained molecule-molecule radial distribution functions, (rdf), and atom-atom rdf, it was possible to estimate the local mole fractions around the amide molecule, the orientation effects of molecules within the solvation shell, and a possibility of the formation of complexes. The general picture obtained from analysis of the molecular dynamics results is consistent with the deductions derived from thermodynamic data.

New crown ether styryl dyes (trans-lc,d) containing the 18-crown-6 ether fragment were synthesized. Interaction of trans-lc0d dyes, as well as their analogs, trans-la,b containing the |5-crown-5 ether fragment, with Ca(CIO4) 2 in MeCN afforded supramolecular structures (dimeric complexes). Competing reactions, trans-cis-photoisomerization with the formation of anion-"capped" complexes of c/s-la--d and {2+2] autophotocycloaddition with the formation of cyclobutane derivatives 8a--d and 9¢, were observed on photolysis of solutions of complexes of trans-la--d with Ca 2+. Preorganization of tram-isomers in dimeric complexes with Ca 2÷ determined the regio-and stereoselectivity of each of the two directions of the photocycloaddition and the efficiency of the reaction.

The electronic absorption and fluorescence spectra of newly synthesized indole derivatives viz., 1) 5-methyl-3-phenyl–2–[4′–amino-s-triazolo- 3′-yl] indole-5′-hydrazide, (MPATIH) 2) 3-[5′-methyl-3′-phenylindol-2′- yl] -s-triazolo[3,4-b][1,3,4] thiadiazol-6(5H) -thione (MPITTT) and 3) 5-methyl-3-phenyl-2- [s-oxadiazol-2′-thione-5′-yl] indole (MPOTI) have been measured at 1×10-5 M concentration in various solvents at room temperature. The ground state dipole moment (μg) and first excited singlet state dipole moment (μe) have been estimated from solvatochromic shifts of absorption and fluorescence spectra as a function of the dielectric constant (D) and refractive index (n), and also by utilizing the microscopic solvent polarity parameter ( NT E ). These indole derivatives have shown greater dipole moment in the excited state than the ground state. The results indicate that the observed band in these compounds may be attributed to π→ π* transition.

This study finds the equilibrium configuration, vibrational analysis, thermodynamic properties, and electronic properties of formaldehyde and its derivatives, namely acetone, acetyl chloride, and methyl acetate, using First Principles Analysis. It emphasizes the impact of substituents on the carbonyl group and the need for this comprehensive analysis. The computational methods employed in this work are

A cyclodextrin derivative 1 possessing multiple pnitrophenylamide groups, which is a strong hydrogen-bond donor, encapsulates phosphodiester anions in two recognition modes. One is the 'threading' mode, in which the phosphodiester passes through the cyclodextrin cavity. The other is the 'folding' mode, in which the included phosphodiester is bent inside the cyclodextrin cavity. The tendency between the two recognition modes depends on the substituents on the phosphodiesters.

NMR chemical shifts have been experimentally measured and theoretically estimated for all the carbon atoms of (1R,3S,4S,8S)-p-menthane-3,9-diol in chloroform solution. Theoretical estimations were performed using a combination of molecular dynamics simulations and quantum mechanical calculations. Molecular dynamics simulations were used to obtain the most populated conformations of the (1R,3S:4S,8S)-p-menthane-3,9-diol as well as the distribution of the solvent molecules around it. Quantum mechanical calculations of NMR chemical shifts were performed on the most relevant conformations employing the GIAO-DFT formalism. A special emphasis was put in evaluating the effects of the surrounding solvent molecules. For this purpose, supermolecule calculations were performed on complexes constituted by the solute and n chloroform molecules, where n ranges from 3 to 16. An excellent agreement with experimental data has been obtained following this computational strategy.

ABSTRACTFirst principles calculations using density functional theory (DFT) are reported for two layers of methane adsorbed on the (100) surface of MgO. The lowest energy structure determined has a first layer with C2v methanes adsorbed above magnesium atoms, with hydrogen atoms pointed towards neighboring oxygen atoms, and a rotation of 90° in between each neighboring methane. The second layer methane layer has a similar structure, except the hydrogen atoms are directed towards nearest neighbor magnesium atoms. It is found that the structure of the first layer has a large effect on the relative energies of proposed bilayer structures, as does the calculated separation between the two layers of methane. Competing roles of surface-adsorbate and adsorbate-adsorbate interactions are also discussed.

We describe some recent mathematical results in constructing computational methods that lead to the development of fast and accurate multiresolution numerical methods for solving quantum chemistry and nuclear physics problems based on Density Functional Theory (DFT). Using low separation rank representations of functions and operators in conjunction with representations in multiwavelet bases, we developed a multiscale solution method for integral and dierential equations and integral transforms. The Poisson equation, the Schrodinger equation, and the projector on the divergence free functions provide important examples with a wide range of applications in computational chemistry, nuclear physics, computational electromagnetic and uid dynamics. We have implemented this approach along with adaptive representations of operators and functions in the multiwavelet basis and low separation rank (LSR) approximation of operators and functions. These methods have been realized and implemented in a software package called Multiresolution Adaptive Numerical Evaluation for Scientic Simulation (MADNESS). .

Using first principles density functional theory in combination with the nonequilibrium Green's function formalism, we study the effect of derivatization on the electronic and transport properties of C 60 fullerene. As a typical example, we consider [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM), which forms one of the most efficient organic photovoltaic materials in combination with electron donating polymers. Extra peaks are observed in the density of states (DOS) due to the formation of new electronic states localized at/near the attached molecule. Despite such peculiar behavior in the DOS of an isolated molecule, derivatization does not have a pronounced effect on the electronic transport properties of the fullerene molecular junctions. Both C 60 and PCBM show the same response to finite voltage biasing with new features in the transmission spectrum due to voltage induced delocalization of some electronic states. We also study the diffusive motion of molecular fullerenes in ethanol solvent and inside poly(3-hexylthiophene) lamella using reactive molecular dynamics simulations. We found that the mobility of the fullerene reduces considerably due to derivatization; the diffusion coefficient of C 60 is an order of magnitude larger than the one for PCBM. V

The focus of this study is to determine the conformational, structural and vibrational properties of Methionyl-Serine dipeptide (L-Methionyl-L-Serine, Met-Ser), a biological active molecule. To investigate their energetically preferred conformations, molecular mechanics methods were utilized to determine the optimal conformations of the 3402 different dihedral angle values of the backbone and side chains. It was found that the extended (e) backbone shape in the LB conformational range was the most stable L-Methionyl-L-Serine dipeptide conformation, with 3.12 kcal/mol of energy. Density Functional Theory (DFT) was used to determine the optimized geometry, the vibrational wavenumbers and modes of the title dipeptide values, with 6-31G (d,p) and 6-311++G (d,p) basis sets. The potential energy distribution data was used to carry out the assignment of the bands. In addition, the vibrational spectra of the most stable conformer and its dimer form were determined and the obtained results were compared with the experimental IR and Raman spectra in the solid phase. To determine the presence of intramolecular charge transfer, molecular dipole moment, polarizability and hyperpolarizability, the Natural Bond Orbital (NBO) , HOMO-LUMO calculations, the linear polarizability (α) and the first order hyperpolarizability (β 0 ) value analyses of the investigated molecule were carried out using the DFT with the B3LYP/6-31++G(d,p) basis set. This study aims to determine a relatively stable conformation of antioxidant dipeptide and to investigate the molecular geometry, molecular

The theoretical vibrational spectral features of 2,3,5,6 Tetrafluoro-4-pyridinecarbonitrile were explored and compared with experimental results. The geometrical parameters, vibrational wavenumbers, bonding features and Energies were calculated at the B3LYP level with the basis set 6-311++G(d,p) levels. The calculated wavenumbers, vibrational energy distribution Analysis (VEDA), potential energy distributions (PEDs), and vibrational spectra were used to suggest reliable vibrational assignments. Molecular Electrostatic Potential investigations revealed the reactive zones around the molecule. The computed HOMO-LUMO energies were -8.369 and -3.380 eV, respectively, indicating charge transfer inside the molecule. The charge transfer of charge due to intra molecule interactions has been explained using naturalbond orbital analysis. The ELF and LOL calculations were provide a visual aid for interpreting the results of electronic structure. The molecular docking approach was used to find t...

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

The [3+2] cycloaddition reactions on citral which is the mixture of geranial 1 and neral 2 isomers have been performed to obtain interesting varieties of its derivatives. The probable 1,3-dipolar cycloaddition reactions between citral mixture (1 and 2) with trimethylsilylazide (TMS), the comparison of the citral mixture in the kinetic and thermodynamic reactions, the structural studies of the 1,2,3-triazoline products, carbine reactive intermediates and transition states are investigated. The reactions are studied and discussed by B3LYP/6-31G* method. The main configurations are performed with less steric restraint effects. The HOMO and LUMO orbital levels, ∆ΕHOMO-LUMO gaps, dipole moments, Mulliken charges, thermodynamic and kinetic stabilities in vacuum are investigated for the components by the density functional theory (DFT) B3LYP/6-31G* method. The elimination reactions of N2 molecule from the 1,2,3-triazolines to produce aziridine products, the mechanisms, the biradical interm...

Recently, a multitude number of studies have paid attention to organic solar cells due to their advantages such as flexibility, long life and low cost. In this research, a Donor-Acceptor (D-A) system using dipyrido[3,2-a:2',3'-c]phenazine (A) as an acceptor and α-sexithiophene (D) as a donor are designed using DFT and TDDFT computational methods. The effect of acceptor complex of Mg, Ca, and Be on the system function is investigated. The complexation of dipyrido[3,2-a:2',3'-c]phenazine with Mg, Ca, and Be has reduced its orbital energy level. In addition, this complexation has a relatively good performance as A for the introduced D-A system. Computations at the ground state by investigating HOMO&LUMO orbital energy and electron density have been done. This indicates the efficiency of acceptor complex of Ca, which has an energy gap of 0.92 eV, after optimal function of Mg acceptor. The Charge Transfer (CT) at excited state for different acceptors in D-A system is explained by using electron-hole theory and computations. CT results demonstrates that the best function is related to the Ca-acceptor complex, which has the greatest amount of CT with a length of 17.82 Å.

This research paper clearly identifies the problems of data transmission traffic, erratically slow data and video streaming on the World Wide Web internet through the network interface cards (NICs). It also provides the reliable solutions and appropriate means to address these perennial problems of ICT-Based institutions and organisations. The entire wired or wireless internet data network connectivity of an institution is sustained by the standard of installed Network Interface Cards (NICs). The standard and the relative performance metrics of NIC types such as 1Gbps, 10Gbps and 100Gbps were adequately examined using different information data sizes of 20MB, 40MB, 60MB, 80MB and 100MB which is either meant for data upload or download on the internet network. Specifically, the paper categorically discusses the parameters for performance metrics of each of these Ethernet card which include the data transmission time, data total time delay and throughput. The research work accurately established the active features of the NICs as the major backbone of the Internet network and the transmission control protocol (TCP) which is designed for reliable transmission of data over the internet. TCP as a connectionless protocol of the NIC is majorly used for surfing webs, downloading and uploading files. In practical terms, the TCP is able to dynamically adapt its packet sending rate to the network conditions in order to achieve the highest possible throughput. In a nutshell , this research paper proposes an upgrade to 100Gbps Ethernet card on the Internet infrastructures of ICT-Based institutions in order to ensure reliable, efficient, sustainable, fast and effective internet data access in all internet devices connected to their networks.

The essential oils of Inula viscosa have been commonly worldwide
employed as a crude drug by people in Asia, the Middle East and Africa. Due
to the development of antimicrobial resistance by the use of antibiotics among
pathogenic bacteria, natural products extracted from the plants can be used as
alternative strategies to reduce pathogenic bacteria from foods and patients.
The main aim of the present work was the extraction of essential oils from the
leaves of Inula viscosa, an aromatic plant harvested in full bloom (March)
from the mountainous region of Tessalah of Sidi Bel-Abbes (northwest
Algeria) and the evaluation of their antibacterial properties against some
bacteria such as E. coli, Ps. aeruginosa ATCC 27853, and St. aureus ATCC
25923, B. subtilus by using agar well diffusion method and by the study of
bacterial growth in the absence and the presence of essential oils.
The quantitative analyzes of essential oils of Inula viscosa by
hydrodistillation showed a low yield with a value of 0.23% and the
antibacterial activity of essential oils of Inula viscosa, different concentrations
(1, 2, 4, 6, 8, 12 μl), which was emulsified with Tween 80 and by using agar
well diffusion method has indicated an excellent antibacterial activity by E.
coli, S. aureus ATCC 25923, Ps. aeruginosa ATCC 27853 and Ba. cereus
with a maximal diameter of inhibition zone 24, 13, 32, 22 mm respectively.
Furthermore, the study of Ps. aeruginosa ATCC 27853 and S.
aureus ATCC 25923 growth in the absence (Control) and in the presence of
the essential oils of Inula viscosa, has manifested a considerable biomass
reduction accompanied by unbalanced growth after adding of essential oils of
Inula viscosa.