Journal of Physical and Theoretical Chemistry
Volume:12 Issue: 1, Spring 2015

The physicochemical properties of solute in solutions provide valuable information on solute –solvent, solute – solute and solvent – solvent interactions. The intermolecular forces between theliquids molecules and solvent molecules affect the viscosity of the solution. Information regardinginter and intra molecular interactions can be obtained from volumetric, and viscometric data in asolute solvent system. This study reports the volumetric and viscometric properties of solution of :-alanine at the concentration range of 0.05 - 0.5 mol dm-3 in water and liquid ammonia at temperaturerange of 293 - 313K. Apparent molar volume at infinite dilution ( ov
) was estimated from the leastsquare fit of v
vs concentration. Viscosity coefficients A and B were calculated from the viscositydata Jones–Dole equation. Viscosity coefficients A and B were calculated from the viscosity dataJones–Dole equation. The activation parameters for viscous flow #1#2#μ1 ,μ ,S and #1 H werealso estimated using Eyring equation. The data are explained vis-à-vis structure making or breakingeffect of : - Alanine in the solvents under conditions of investigation.

With the aim of recognizing the steric effects on the silylenic R2C6H6Si structures, DFT calculationsare carried out on 8 structures of R2C6H6Si (where R is hydrogen (H), methyl (Me), isopropyl (i-pro),and tert-butyl (tert-Bu)). These species are at either triplet (t) or singlet (s) states. Singlet–tripletenergy separations (<Gt-s) and relative energies for the above structures are acquired at B3LYP/6-31G** levels of theory. The <Gt–s of R2C6H6Si was increased in the order (in kcal/mol): H (23.73) >i-Pr (20.56) > Me (20.32) > t-Bu (15.92).all singlet states of R2C6H6Si, are more stable than theircorresponding triplet states. linear correlations are encountered between the LUMO–HOMO energygaps of the singlet(stable) states of R2C6H6Si compounds, and their corresponding singlet–tripletenergy separations are calculated at B3LYP/6-311++G∗∗ level of theory. Other geometricalparameters such as bond angles, dihedral angles, bond lengths, NBO charge at atoms, dipolemoments (D), (HOMO), (LUMO), chemical hardness (F), chemical potential (G), electrophilicity (H)and the maximum amount of electronic charge, <Nmax were calculated and discussed.

The formation constants of the species formed in the systems H+ + Mo(VI) + histidine and H+ +histidine have been determined at different aqueous solutions of methanol (0 - 45 % v/v) at 25 °C andconstant ionic strength (0.1 mol dm-3 sodium perchlorate), using a combination of spectrophotometricand potentiometric techniques. The composition of the complex species was determined by thecontinuous variations method (Job). It was shown that molybdenum (VI) forms a mononuclear 1:1complex with histidine of the type MoO3L- at pCH 5.8. The protonation of histidine and the formationconstant of the formed complex species in various media were analyzed in terms of Kamlet, Abboud,and Taft (KAT) parameters. Single-parameter correlation of the formation constant versus (hydrogen-bond donor acidity),  (hydrogen-bond accepter basicity) and * (dipolarity/polarizability)are poor in all solutions, but dual-parameter correlation represents significant improvement withregard to the single or multi-parameter models. Linear correlation is observed when the experimentallog KS values are plotted versus the calculated ones while the KAT parameters are considered.Finally, the results are discussed in terms of the effect of solvent on protonation and complexation.

Tetrazole-containing compounds have been the subject of much recent research because of theirpotential as high energy density materials (HEDMs). In this work, theoretical studies on the 1Htetrazolylderivatives of tetrahedrane were done at the density functional theory (DFT) method withthe 6-31G(d) basis set without any symmetrical restrictions in order to find the structural andenergetically properties. Geometric and electronic structures, natural bond orbitals (NBOs)population, aromaticity of tetrazole rings, thermodynamic properties and detonation performances ofthese molecules have been studied using mentioned level of theory. Nucleus independent chemicalshift (NICS) calculations show the tetrazole rings on the tetrahedrane system are aromatic. The heatof formation (HOF) values of all structures has been calculated by a proper isodesmic reaction. TheHOFs are found to be correlative with the number of tetrazole groups. According to the results of thecalculations, only tri-substituted derivative of tetrahedrane can be a viable candidate of high energymaterials.

To get a mole of a gas, it is necessary to calculate the intermolecular interaction. Theseintermolecular interactions can be depicted by drawing the potential energy of a pair molecule inrelation to the distance. The intermolecular potential energy surface in the mixtures of CH4-H2COgases from ab initio calculations has been explored. In ab initio calculations the basis setsuperposition error (BSSE) is important. This error can be eliminated to some extent by using thecounterpoise correction method (CPC). In this work ab initio calculation performed at the secondorderMoller-Plesset theory, MP2, with the 6-311+G(2df,2pd) basis set, for six relative orientations oftwo CH4- H2CO molecules as a function of CH4-H2CO separation distance. Then, the adjustableparameters of Buckingham potential energy function are fitted to the ab initio MP2/6-311+G(2df,2pd)interaction energies for six different orientations. Assuming a given set of parameters, we obtainedtheoretically second virial coefficients for CH4- H2CO system in different temperatures.

The binding, release and oxidation of oxygen occur at the heme group iron ion. Hemoglobinoxidation-reduction studies have been previously performed using spectroelectrochemistry (SEC) andhave provided insight into the hemoglobin electron transfer process and more specifically, into theheme group electronic factor and subunit interaction influences. In this study, the number of fullerenecarbon atoms was used as an index to establish a relationship between the structures of hemoglobin Aand - and -fumarate crosslinked hemoglobins, which were designated as HbA, XL and XL-[HbA] 1-3, respectively. These compounds represent the most well-known blood molecular systemsand fullerenes (Cn, where n = 60, 70, 76, 82 or 86), which generated the following complexes:Cn@[HbA], A-1 to A-5; Cn@DXL-[HbA], B-1 to B-5 and Cn@EXL-[HbA], C-1 to C-5. Therelationship between the carbon atom number and electron transfer free energies (Get) were assessedusing the Rehm-Weller equation for A-1 to A-5, B1 to B-5 and C-1 to C-5 supramolecular Cn@X-[HbA] (where HbA = hemoglobin A; X = - and -fumarate crosslinked hemoglobins (XL & XL))and complexes 4-57, which possessed different electrochemical properties. Calculations werepresented for the first Cn oxidation potentials (Ox.E1). The results were used to calculate the electrontransfer first free energies (Get(1)) of supramolecular complexes A-1 to A-5, B1 to B-5 and C-1 to C-5 for fullerenes C60 to C300. The first free activation energies and kinetic rate constants of the electrontransfers, G#et(n) (Get(1)#) and ket, respectively, were also calculated in this study for A-1 to A-7, B1to B-7 and C-1 to C-7 (compounds 4-24) in accordance with the Marcus theory.

Tacrine (9-amino-1,2,3,4-tetrahydroacridine) as a reversible inhibitor of acetylcholinesterase (AChE),was the first drug for the symptomatic treatment of Alzheimer’s disease (AD). NMR structuredetermination still presents some considerable challenges: the method is limited to systems ofrelatively small molecular mass, data collection times are long, data analysis remains a lengthyprocedure, and it is difficult to evaluate the quality of the final structures but calculation of a structureitself has become extremely rapid, and new labeling methods have significantly improved bothspectral quality and automated analysis, whilst rigorous standards and data formats affordcompatibility of different software packages. In this theoretical study, we used HF and DFT (BLYP,B3LYP) method for chemical shift nucleus magnetic resonance DFT-NMR. The basis set used were6–31G, 6–31G** and 6-31G++. The results show a reasonably good correlation between calculatedand experimental chemical shifts. Agreement of experiment and calculated data suggesting thatstudies of drug structures can be pursued with some degree of confidence with this level of theory.

In this study, Monte Carlo statistical mechanical simulations for vinblastine and vincristine werecarried out in standard manner using the Metropolis sampling technique in canonical (T, V, N)ensemble., Geometrical optimizations of vinblastine and vincristine were carried out with the HFmethod coupled to 6-31G(d) basis sets for all atoms. Simulation was done by four force fields ofMM+, BIO+, AMBER and OPLS. Some important energy parameters such as Potential Energy andTotal Energy in ten different simulating temperatures (300, 302, 304, 306, 308, 310, 312, 314, 316and 318 Kelvin) were used for computation.