Journal of Physical Chemistry & Electrochemistry
Volume:1 Issue: 1, 2010

In the present work, an extensive theoretical calculation study on Histidine-Histidine dipeptide in gas phase is done by using DFT method with Gaussian 98 program. Through investigations on the molecular geometries of this molecule it is found that there is six rings in the molecules not two rings. The presence of four intramolecular hydrogen bonds is responsible for the formation of additional four rings besides two imidazole rings which gives more stability to the molecule. The quantum theory of atoms in molecules (QTAIM) proves these strong intramolecular hydrogen bonds in the title dipeptide.

A PVC ion-selective membrane electrode based on Cd-tetraphenyl porphyrine as a carrier was prepared fordetermination of MnO4- ion. This electrode revealed good selectivity toward permanganate ion over a widevariety of anions. Effects of some experimental parameters such as nature of the plasticizer, the amounts ofcarrier and additive, and concentration of the internal solution on the potential response of the proposed sensorwere investigated. The electrode exhibited a sub-Nernstian slope of 51.0±1.0 mV per decade for MnO4- over aconcentration range of 3.3×10-6-7.5×10-2 M in the pH range 5.0-10.0. The detection limit and response time ofthe electrode were 1.7×10-6 M and 14 s, respectively. The electrode can be used within 3 days without anyconsiderable divergence in its potential. This electrode was successfully employed for indirect determinationof Mn(II).

Experimental results of dielectric investigations for binary mixtures of 2, 3-butanediol, 2, 3-BD, in2-ethyl-1-hexanol, 2EH, were reported for various mole fractions and temperatures (298.2-308.2) Kand they were used to calculate dielectric parameters such as Kirkwood correlation factor, excesspermittivity and Bruggeman parameter. These parameters were used to carry out temperaturedependent dielectric studies on the mixtures. The investigation showed a systematic change indielectric parameters of the systems with the change in concentration and temperature.

The crystal structure of the title Schiff base complex is obtained by single-crystal X-ray diffraction data.The solid state structure determination reveals that the coordination geometry around the copper(II) center istetrahedrally distorted square-planar. The crystal packing shows one dimensional infinite chains which arisesfrom the intermolecular interaction and stabilize the crystal packing.

In this work an analytical equation of state has been employed to calculate the PVT properties ofternary refrigerant mixtures. The theoretical EoS is that of Ihm, Song and Mason, which is based onstatistical-mechanical perturbation theory, and the two constants are enthalpy of vaporization ΔHvapand molar density ρnb, both at the normal boiling temperature. The following three temperaturedependentparameters are needed to use the EoS: the second virial coefficient, B2(T), an effectivevan der Waals covolume, b(T), and a scaling factor, α(T). The second virial coefficients arecalculated from a correlation based on the heat of vaporization, Hvap, and the liquid density at thenormal boiling point, ρnb. α(T) and b(T) can also be calculated from second virial coefficients byscaling rules. This procedure predicts liquid densities ofternary mixtures at saturated state with a temperature range from 173 K to 373 K and pressure up to4.0 MPa, with very good results.

An analytical equation of state by Song and Mason is developed to calculate the PVT properties ofmercury. The equation of state is based on the statistical-mechanical perturbation theory of hard convexbodies and can be written as a fifth-order polynomial in the density. There exists three temperaturedependentparameters in the equation of state; the second virial coefficient, an effective molecular volume,and a scaling factor for the average contact pair distribution function of hard convex bodies. Thetemperature-dependant parameters have been calculated using corresponding-states correlations based on theheat of vaporization and the liquid density at the melting point. The average absolute deviation for thecalculated density of mercury in the saturation and compressed state is 0.38 .

The major reason for the prediction of thermodynamic properties of mercury lies in the fact that itsintermolecular interactions highly depend on temperature and density. Internal pressure is a good criterion toinvestigate the density dependence of the interatomic interactions. Because its physical base is a forcetending to close together the molecules that is intermolecular interactions, and as well it can be calculatedfrom the experimental PVT data. In this study the behavior of the experimentally calculated internalpressure of the mercury demonstrates three different metallic, M-NMT and nonmetallic regions. Then toinvestigate these different states the general form of the Lennard-Jones potential function [LJ (m-n)] has beenchosen as the effective interaction potential and the experimentally calculated internal pressure has been usedto estimate the values of m and n in each state.

Nano-films consisting of an alternating sequence of positively and negatively charged polyelectrolyteshave been prepared by means of the electrostatic layer-by-layer sequential assembly technique on mildsteels. The mild steels were pretreated electrochemically to modify the mild steel surface. The modificationof the mild steel surface resulted in increasing the adhesion of the obtained nano-films and prevented thecorrosion attack during the coating processes. Different concentrations of Benzotriazole inhibitor wereencapsulated between cationic and anionic polyelectrolytes nano films. The encapsulation of benzotriazole inthe deposited nano-films was verified by U.V visible spectroscopy. The work mainly focuses on the effect ofthese nano-films of polyelectrolytes with inhibitor and without inhibitors on the corrosion protection. Tafel,corrosion potential, potentiostatic and Econ vs. time experiments were carried out in 0.7M NaCl solution.Weight loss method was used for measuring the corrosion rate of coated and uncoated mild steel substrate. Asignificant improvement in the corrosion protection was achieved especially in the case of electrochemicallymodifying the mild steel surface and encapsulating the inhibitors between the polyelectrolytes nano-films.