MNDO Method Research Articles

Antimicrobial Properties Of Pyrazolone Compounds With Their Qsar Investigations

The present paper reports the analysis and the antimicrobial activity viz. antifungal activity of some pyrazolone compounds which were performed against Alternaria solani using disc diffusion method on nutrient agar and nutrient broth media. The compounds were characterized by elemental analysis and spectral studies. Result of antimicrobial screening indicated that compounds 4-Amino antipyrine thiosemicarbazone, 1-(2-Chloro-5-sulfophenyl)-3-methyl-5-pyrazolone and 1-(4 -Sulfoamidophenyl)-3-methyl-5-pyrazolone were found to be the most potent/active against A. solani. Correlation studies between different computed properties of the compounds with their biological activity, QSAR (Quantitative Structure Activity Relationship) investigations with a stepwise linear regression analysis were conducted. The studies are carried out using Hyperchem 8.0 version software using AM1, PM3, MNDO and ZINDO methods. Selected QSAR/ 3D-QSAR equations including different physical parameters of these series are reported.

Механизм взаимодействия и технология нанесения нового сверхтонкого лекарственного покрытия медицинских билиарных стентов

Several years ago, there were no effective methods for treating bile tract structures, but the situation changed significantly with the invention of the stent. The use of biliary stents for the treatment of mechanical jaundice made it easier to remove them from the body. However, it was not possible to stop the appearance of restenosis and thrombosis. To prevent such complications, drug coatings, which are a polymer matrix with drugs introduced into it, began to be applied to the stent surface. At present, despite the rather wide range of drug coatings, the search for new biodegradable carrier polymers that provide a high-quality and inexpensive coating of biliary stents remains relevant. The paper considers the technology of creating a new ultra-thin drug coating for these stents based on polyvinylpyrrolidone with the addition of doxorubicin and carbon nanotubes. The invention proposes the use of carbon nanotubes based on their unique sorption properties. Steps of application of drug coating on stent surface and selection of optimal content of carbon nanotubes in coating composition are described. Theoretical studies of the interaction processes of drug coating components using the quantum-chemical method MNDO have been carried out. GAMESS, Gaussian, GaussView software packages were used for calculations.

ON THE ELECTRONIC AND GEOMETRIC STRUCTURE OF GRAPHENE OXIDE IN THE FRAMEWORK OF THE HOFFMAN AND RESS MODELS

For the first time, the geometric and electronic structure of graphene oxide was calculated within the framework of the Hoffman and Ress models by the quantum-chemical method MNDO. Optimized structures of this compound are obtained. The acidic strength (pKa = 28 and pKa = 14) was theoretically estimated in the Hoffman and Ress model, respectively.

Исследование взаимодействия кислорода с поверхностью боросодержащих нанотрубок

Studies of semiconductor carbon nanotubes show that they are extremely sensitive to the chemical environment, and the effects of oxygen drastically change their properties. It has been found that narrow-zone semiconductor carbon tubes can be converted into an apparent metal by such action. Since other types of nanotubes, such as boron-carbon nanotubes of the BC3 type and boron-nitride BN nanotubes, are of great interest, it seems important to investigate whether they are capable of absorbing atomic and molecular oxygen. The study was conducted using the MNDO calculation method within molecular and ion-nested covalent-cyclic cluster models. The results of the study of the interaction of atomic and molecular oxygen with the external surfaces of boron-carbon (BC3), boron-nitride (BN) and boron nanotubes are considered: chair (n, n) and zigzag (n, 0) type. The study was performed by the MNDO method as part of a covalent-cyclic cluster model with embedded ions. Optimal geometry of adsorption complexes is determined and their main electronic and energy properties are described. Boron-carbon nanotubes have been shown to be better oxygen adsorbents than other types of nanotubes considered.

Mathematical modeling of the process of interaction of sulfur dioxide with pyrolyzed polyacrylonitrile

The paper presents a study of the interaction of sulfur dioxide with a polymer-pyrolyzed polyacrylonitrile (PPAN). The possibility of using PPAN as an element of an electronic sensor device for recording the presence and identification of sulfur dioxide in the atmosphere is shown. The results of the established geometric and electron-energy characteristics of the polymer interacting with gas are described. Theoretical calculations were performed using the molecular cluster model and the quantum-chemical MNDO method.

Quantum-chemical calculation of antiviral dexamethasone medication by mndo, ab initio and dft methods

Quantum-chemical calculation of antiviral dexamethasone medication by mndo, ab initio and dft methods

Simulation of pyrolysed polyacrylonitrile based composite with amorphising boron additives

The paper deals with the possibility of modifying pyrolyzed polyacrylonitrile with amorphizing additives. Adsorption features of the boron atom on the surface of the monolayer of polymer are studied, and the geometric and electron-energy characteristics of the composite obtained are established. The calculations were performed using the semi-empirical MNDO method within the framework of the molecular cluster model.

Walter Thiel (1949-2019).

On August 23, 2019 Walter Thiel passed away suddenly and unexpectedly. Thiel was a giant in the field of Theoretical Chemistry and has left deep marks as an outstanding scientist and as a wonderful human being. With Walter Thiel, the scientific community has lost a visionary scientific leader and an important voice of reason.

Comparative Studies of Infrared Spectral Simulation of Some Benzoyl Derivatives of N-Heterocyclic Compounds Using Semi-Empirical Methods

Simulation studies based on ab initio, semi-empirical or density functional (DFT) calculations are now becoming common among the researchers who are pursuing their intereset in theoretical chemistry. These studies are based on quantum chemical softwares. These studies provide better insight for the structural and other parameters of the compounds. The present paper includes the studies on synthesis or procurement along with the simulated IR spectra of some benzoyl derivatives of N-heterocyclic compounds viz. 2-aminopyridine, 4-aminoantipyrine, 2-aminopyrimidine or 3-aminopyridine using four different AM1, PM3, MNDO and ZINDO1 semi-empirical methods. Among the methods used for the study, AM1 method is more reliable and more accurate so far as the prediction of spectral results is concerned.

Quantum-Chemical Study of the Protonation Mechanism of P-Fluorostyrol by the MNDO Method

Quantum-Chemical Study of the Protonation Mechanism of P-Fluorostyrol by the MNDO Method

On the mechanism of pore formation in pyrolized polyacrylonitrile

The paper presents a study of the possibilities and mechanisms of pore formation (based on vacancy defects) in single-layer and two-layer pyrolyzed polyacrylonitrile. The geometrical and electronic-energy characteristics are described, the effect of the number of PPAN layers on the processes under consideration is studied. Theoretical calculations were performed using the molecular cluster model and the quantum chemical method MNDO.

Vacancy Transport Properties in Boron-Carbon BC3 Nanotubes

The paper presents results of theoretical research into vacancy formation in B type of boron-carbon nanotubes ВСn, where n = 3. The research was performed using the MNDO method within the framework of an ionic-embedded covalent-cyclic cluster model, molecular cluster model and DFT method. We found that when a V-defect (vacancy) is introduced in a boron-carbon nanotube, the band gap of the defective tubules increases. It means that physical properties of materials can be purposefully changed by introducing defects. Vacancy migration along the atomic bonds in the tubule was simulated and vacancy transport properties were studied. It was found that the defect migration along different bonds actually represents the process of carbon or boron ions hopping between their stable states on the nanotube surface. The calculated activation energy values revealed dependence of ionic conductivity in boron-carbon tubules on temperature.

SENSOR PROPERTIES OF CARBON NANOTUBES

A review of publications over the last years dealing with the development of gas and electrochemical sensors, including biosensors, on the basis of carbon nanotubes is provided. Results of the experimental and theoretical study of their principles and operation mechanisms are provided. The structure of carbon nanotubes has been described. The main regularities of the structure, energetic characteristics and sensor properties of the modified semiconducting systems on the basis of carbon nanotubes have been studied. Analysis of the mechanisms of the interaction between nanotubes and the functional groups (including carboxyl and amino ones), metal nanoparticles and polymers for the formation of chemically active sensors has been reported. The possibility of application of the boundary modified monolayer carbon nanotubes for the identification of metals is discussed. Results of simulation of the interaction between nanotubes boundary modified by —COOH and —NH2 groups with atoms and ions of potassium, sodium and lithium obtained using the molecular cluster model and the MNDO and DFT calculation methods are provided. The sensors synthesized in this way will be used for establishment of the existence and identification of metal atoms and their ions included in salts and alkalis.

COMPARISON OF SENSOR ACTIVITY IN CARBON NANOTUBES MODIFIED WITH FUNCTIONAL GROUPS

This article presents a theoretical study of sensor activity of nanosystems based on carbon nanotubes modified with functional groups (carboxyl, aminogen, nitrogroup) for some metal atoms and ions. Calculations have been performed within the frameworks of a molecular cluster model with the use of the semiempirical MNDO method and the density functional theory DFT. The mechanism of functional group binding to the open border of single−walled zig− zag carbon nanotubes leading to the formation of chemically active sensors on their basis has been investigated. Main geometric and electron energy characteristics of the resultant systems have been defined. Interaction of the sensors so synthesized with atoms and ions of some metals, e.g. potassium, sodium and lithium, has been analyzed.

Surface Activities and Quantum Chemical Calculations for Different Synthesized Cationic Gemini Surfactants

Abstract Three series of cationic gemini surfactants were prepared and characterized using elemental analysis and 1H-NMR spectroscopy. The surface properties of them, critical micelle concentration (CMC), surface excess concentration (Γmax) and minimum surface area per molecule (Amin) were evaluated via surface tension measurements. Quantum chemical parameters, such as the energy of the highest occupied molecular orbital (EH), the energy of the lowest unoccupied molecular orbital EL, the energy gap (ΔEg), dipole moment (μ), electronegativity (χ), hardness (η), electrophilicity (ω), hydrophobicity (Log P), approximated surface area (A) and the total energy of the optimized structure (ΔET), were theoretically calculated using the MNDO method.

Ionic conductivity in BC3 type boron carbon nanolayers

Studies of ionic conductivity and structuresf in which it can be achieved are of great importance for the development of modern batteries. The use of new materials will allow avoiding such typical disadvantages of batteries as short service life, low capacity and leaks. In this article we present the results of our study of the ionic conductivity in boron carbon nanolayers. We have simulated three types of boron carbon nanolayers containing different amounts of boron. The studies have been carried out using the MNDO method within the framework of the molecular cluster model and the DFT method with the B3LYP functional and the 6–31G basis. To study the ion conduction process we have simulated vacancy formation for each type of the nanolayers and studied the energy and electronic characteristics of these processes. We show that 25% boron substitution is the most energetically favorable for vacancy formation. We have also simulated vacancy migration and determined the thermal conductivity as a function of temperature.

Study of vacancy migration as a function of boron substitution in carbon nanolayers

Studies of ionic conductivity and structures in which it can be achieved are of great importance for the development of modern batteries. The use of new materials will allow avoiding such typical disadvantages of batteries as short service life, low capacity and leaks. In this article we present the results of our study of the ionic conductivity in boron carbon nanolayers. We have simulated three types of boron carbon nanolayers containing different amounts of boron. The studies have been carried out using the MNDO method within the framework of the molecular cluster model and the DFT method with the B3LYP functional and the 6−31G basis. To study the ion conduction process we have simulated vacancy formation for each type of the nanolayers and studied the energy and electronic characteristics of these processes. We show that 25 % boron substitution is the most energetically favorable for vacancy formation. We have also simulated vacancy migration and determined the thermal conductivity as a function of temperature.

Carbon nanotubes: Sensor properties. A review

Recent publications dealing with dealing with the fabrication of gas and electrochemical biosensors based on carbon nanotubes have been reviewed. Experimental and theoretical data on the working principles of nanotubes have been presented. The main regularities of the structure, energy parameters and sensor properties of modified semiconducting systems on the basis of cabon nanotubes have been studied by analyzing the mechanisms of nanotubule interaction with functional groups (including carboxyl and amino groups), metallic nanoparticles and polymers leading to the formation of chemically active sensors. The possibility of using boundary modified nanotubes for the identification of metals has been discussed. Simulation results have been reported for the interaction of nanotubes boundary modified by –СООН and –NH2 groups with atoms and ions of potassium, sodium and lithium. The simulation has been carried out using the molecular cluster model and the MNDO and DFT calculation methods. Sensors fabricated using this technology will find wide application for the detection of metallic atoms and their ions included in salts and alkali.

Simulation of a vacancy defect at the C(111)–2 × 1 surface

The configurations of a vacancy defect on the C(111)–2 × 1 surface, containing atoms with one or two dangling bonds, possessing a high adsorption activity, are calculated. We study the configurations of the vacancy defect at the surface of diamond C(111)–2 × 1 using the semiempirical MNDO method (MOPAC) and the ab initio Hartree–Fock method (PC GAMESS). We calculate the energies of clusters, the orders of atomic bonds, the populations of atomic orbitals, and the localized molecular orbitals.

Phase stability and ordering of nematogen at molecular level: A computer-aided modeling

ABSTRACTThe present article deals with the phase stability and ordering of nematogen, viz., 6-octyloxy-2-naphthylyl-4-octoxybenzoate (ONOB) at molecular level. A comparative picture has been given between molecular charge distribution, and phase stability based on AM1, PM3, CNDO, and MNDO methods. The modified Rayleigh–Schrodinger perturbation method along with multicentered-multipole expansion method has been employed to evaluate the long-range intermolecular interactions, while a “6-exp” potential function has been assumed for the short-range interactions. The total interaction energy values obtained through these computations have been used to calculate the probability of each configuration at room temperature, nematic-isotropic transition temperature, and above transition temperature using the Maxwell–Boltzmann formula. Further, the entropy of each configuration has been computed during the different modes of interactions. An effort has been made to develop a computational model at molecular level based on configurational entropy, and translational rigidity parameters introduced in this article.