Current Physical Chemistry - Volume 7, Issue 2, 2017

Objective: Based on the findings that the Conceptual Density Functional Theoretical descriptors have applications in the real world of chemistry and physics, in this paper, we applied the said descriptors to evaluate some very important atomic and molecular properties. Method: We proposed the methods of calculation of equalized molecular electronegativity, equalized molecular electrophilicity, and equalized molecular nucleophilicity. Conclusion: We computed the equalized molecular electronegativity and equalized molecular nucleophilicity of some heteronuclear diatomics under the assumption of charge equalization during molecule formation and by combining an electrostatic theorem and Conceptual DFT.

Background: The resultant measures of the information content in molecular electronic states are revisited. In these overall measures the current-related terms complement the probability functionals of classical Information Theory. The nonclassical Shannon entropy reflects the average magnitude of the state phase distribution, while the related current term in the complementary Fisher measure accounts for the average phase-gradient. Method: These generalized Fisher and Shannon descriptors of the information content in complex electronic states are applied to determine the phase-equilibria in molecules. The vertical and horizontal equilibria in molecules, which mark the extrema of the nonclassical and resultant entropy/information descriptors, respectively, are explored. The requirement, that the resultant measures have common solutions of the associated extreme entropy/information principles, calls for the negative sign of the nonclassical gradient measure. Conclusion: These extrema imply the phase-transformation of molecular electronic states. A separation of the density (modulus) and current (phase) factors in many-electron states is effected using the Harriman-Zumbach-Maschke construction of complex antisymmetric states yielding the specified electron density. A combined description of molecular systems, which accounts for the density and current degrees-of-freedom of electronic states is summarized and continuity equations for the state phase and resultant entropy are discussed.

Background: Excellent linear correlations exist between isoelectronic values of square root of the electronegativity measure i.e. {(I+A)/2}1/2 and the measure of hardness, (I-A)/2 in eight out of the first ten isoelectronic sequence (H-Ne); the determination coefficients are nearly one. Method: For He and Ne isoelectronic series, with inert gas configuration, the plots between {(I+A)/2}1/2 and (I-A)/2 are found to be nonlinear. For these two, linear plots exist between (I+A)/2 and (I-A)/2. Within the purview, the present study supports the recent suggestion that if (I+A)/2 and (I-A)/2 are to serve as the electronegativity and the hardness measure respectively, the mutual relation between electronegativity and hardness would depend on the electronic configuration of the neutral species. In majority of the cases, proportionality would exist between the square root of the electronegativity measure i.e. {(I+A)/2}1/2 and the hardness measure, (IA)/2, except for the species with inert gas configuration. Conclusion: The {(I+A)/2}1/2 vs. (I-A)/2 plots are very useful in pointing out the accuracy of listed ionization potentials. In Fluorine isoelectronic series, an abrupt inconsistency has been observed that has been linked up with incorrectly listed handbook value of VI ionization potential of Phosphorous.

Objective: In this work we have suggested the model for the evaluation of the proton affinity, PA of molecules and also calculated theoretical PA of some molecules using some CDFT descriptors. Method: A validity test of the model is performed by comparing the protonation energies of as many as 45 molecules computed using the model proposed in this work vis-is their corresponding experimental counterparts. Conclusion: The close agreement between the theoretically evaluated and experimentally determined PA's suggests that this modeling and the developed model for computing PA of molecules is efficacious and the hypothesis is scientifically acceptable.

The anharmonic chemical field potential, V (∅,χ ,η), is expressed in terms of the electrostatic potential, ∅, the electronegativity, χ, and the chemical hardness, η, density functionals, as they relate the electron density functional, ρ, and chemical bond formation by quantum field/operators [observable/measurable quantities (physical observables)].

Objective: In the present study, corrosion inhibition efficiencies of some molecules containing mercapto group (-SH) such as mercaptopryimidine (MP), 6-mercaptonicotinic acid (6-MN), thiophenol (TP), 3-mercaptobenzoic acid (3-MB), mercaptoacedic acid (MAA), mercaptopropionic acid (MPA) were investigated. Method: All calculations related to these molecules were performed in gas phase and at various level of B3LYP and HF method using Gaussian package program. Conclusion: As a result of examinations made considering quantum chemical parameters such as chemical hardness, electronegativity, chemical potential HOMO-LUMO energy gap (ΔE), it was suggested that 3-mercaptobenzoic acid (3-MB) is the best corrosion inhibitor among molecules considered in the study.

Objective: It is known that the electronegativities of functional groups can be significantly to used predict the reaction mechanisms and to explain inductive effects of chemical compounds. Method: Bratsch equation is one of the most important equations used to calculate the electronegativities of functional groups. Conclusion: In the present study, some important comments and contributions related to Bratsch's group electronegativity equation are presented. In addition, it is proposed that absolute electronegativity should be considered in comparison of inductive effects of functional groups.

Background: Chemical hardness is one of the most useful conceptual constructs of chemistry and physics and this quantity is an important tool in the understanding of behavior of chemical species. Method: In the present report, we have disclosed about the effect of molecular hardness on chemical properties like ionic character, bond length, bond force constant and melting point for alkali halides that are among the most familiar ionic crystals. Absolute hardness values of alkali halides have been calculated via molecular hardness equation published by us in the recent past. Conclusion: The results obtained and graphs plotted in the study demonstrated that ionic characters, bond lengths, bond strengths, bond force constants and melting points of alkali halides are closely associated with their absolute hardness values.

Objective: We show that anthocyanines extracted from 3 different local cultivar of grapes characteristic of the South Italian region named ″Salento″ can effectively act as naturefriendly and eco-sustainable sensitizers in Dye-sensitized Solar Cells (DSSC) type devices. Methods: The natural pigments have been extracted in a simple way immersing both the whole fruits and the fruit epicarps in methanol and in an ultrasonic bath, without any further purification step. Observation: The measured open circuit voltage and the fill factors are among the best values reported in literature. We compare the effectiveness of the extraction process from fermented and from fresh grapes, showing that the devices realized starting from the fresh fruit epicarps perform slightly better than those realized starting from the fermented fruit. Conclusion: We correlate this behavior with an interaction of different dye molecules in the device.

Objective: The reported work was aimed to remove methylene blue dye, a toxic chemical, from its aqueous solution by photo-catalytic degradation technique and to observe the effect of doping Mn and N on photo-catalytic activity of ZnS. Method: Nanosize ZnS, Mn-doped-ZnS, N-doped-ZnS and Mn-N co-doped ZnS were prepared by chemical co-precipitation method and characterized these using XRD, TEM and UV - visible spectroscopic techniques. Activity of as-synthesized photo-catalysts under UV and visible radiations were compared using degradation of methylene blue dye, as a probe. Results: The average crystallite size of above photo-catalysts, from XRD analysis, were: 7.8,7.5, 6.6 and 6.6 nm, respectively. Doping of N in ZnS caused a red shift of photo-absorption resulting in the decrease of band gap of ZnS. Co-doping of Mn and N in ZnS showed synergistic effect in enhancing oxidative degradation of the dye. The observed maximum degradation of 10 mg L-1 methylene blue at 3 hrs over Mn-N co-doped ZnS, separately, under UV and Visible radiations were: 55.6 % and 70.8%, respectively. Conclusion: Doping of Mn and N into ZnS exhibit synergism in increasing photo-catalytic activity of ZnS. The photo-catalytic degradation of methylene blue follows a pseudo first order kinetic under UV as well as visible radiation.