Journal of Physical and Theoretical Chemistry
Volume:3 Issue: 2, Summer 2006

Topological analysis has been performed on the total electron density of the two forms of Ozonemolecule,C2V and D3H ,to investigate the nature of chemical bonds ,molecular structure , atomiccharges and electrical properties. While these concepts have been completely discussed usingclassical models the emphasize in this work is based on Quantum Theory of Atoms in Molecules(QTAIM). Because the D3H form has not been observed experimentally a well defined chemicalmodel , i.e., QTAIM should be used to predict the above chemical properties for this species. Thecomparison between the atomic and molecular properties between the two forms has been done.Large π character has been assigned to the bonds in D3H form, classically. This latter concept hasalso been investigate using the ZZ component of atomic quadrupole moments.

The protonation of different species of glycylisoleucine were studied in the pH range of 1.5 - 10 at25 °C using potentiometric technique. Investigations were performed in sodium perchlorate andtetraethylammonium iodide as background electrolytes at I (0.1, 0.2, 0.3, 0.4, 0.5, and 0.6) moldm-3. The parameters based on the protonation constants were calculated, and their dependenceson ionic strength are described by a Debye-Huckel type equation. The dependence on ionicstrength of the protonation constants was also analyzed by the specific ion interaction theory (SIT)model. The constants at infinite dilution, obtained using this model, are logK°1 = 2.72 and logK°2= 8.24. The specific interaction coefficients are also reported.

Neutral bidentate N-O type complexe of VO(II) has been synthesized through condensation of Dpenicillamine,(D-H2Pen), with Bis(acetylacetonate)- oxovanadium(IV),[VO(acac)2], at neutralmedium . The established schiff base(NO type) complex was characterized on the basis of IR andmass spectroscopy techniques.Besides,D-H2Pen binding behavior to[VO(acac)2] has been studiedin thermodynamic viewpoint using Uv/Vis spectroscopy.The measurments were done in 5mMphosphate buffer,pH 7.0 and various temperatures.The optical absorption spectra of[VO(acac)2]were analyzed in order to obtain binding constants and stoichiometries using SQUADsoftware.The results show that the best fitting corresponds to 1:2 metal to ligand, complexbetween [VO(acac)2] and D-H2Pen.The estimation of binding constant at various temperaturesenabled us to calculate all of the thermodynamic parameters of binding using Van,t Hoff equation.

Ab initio calculation at HF/6-31G* level of theory for geometry optimization and MP2/6-31G*//HF/6-31G* for a single point total energy calculation are reported for the important energyminimumconformations and transition-state geometries of of cyclodeca-1,2,3-triene (1). The mostfavorable conformation of 1 is a unsymmetrical twist-chair (1-TC) structure. Degenerateinterconversion of 1-TC with itself can take place via Cs symmetric half-chair (1-HC, Cs). Thecalculated energy barrier for this processes is 30.3 kJ mol-1, respectively. The twist (1-Twist)conformation of the 1, with C2 symmetry, is calculated to be more unstable than the twist-chair(1-TC, C1) geometry by 12.4 kJ mol-1. Interconversion between 1-TC and 1-Twist conformationstakes place via the unsymmetrical transition state, which is 50.3 kJ mol-1 above 1-TC form. Theboat (C1) geometry of 1 is higher in energy by 19.1 kJ mol-1, respectively. Ring inversion in twistchairand boat conformations takes place via C2 symmetric 1-TB (1-HC, C2) form and requires65.6 kJ mol-1.

The synthesis of [Cu3O(OAc)6(H2O)3]Cl.CH3OH.6H2O is described. The X-ray crystallographic study of thecomplex revealed an isosceles triangle of copper atoms with a triply bridging oxo atom nearly in the plane of thetriangle. The coordination sphere around each metal center is close to distorted octahedral and the central{Cu3(μ3-O)} core is planar. Every two copper atoms were connected to each other, by two bridge of alkylacetate.The water molecule as a monodentate ligand is connected to every copper. Counter ion of this complexis a group that contain one atom of chlorine, one molecule of methanol and six molecule of water. Thiscompound crystallizes in the orthorhombic system, space group P21212, with four molecules per unit cell. Theunit cell dimension were a = 1359.3(1)Å, b = 2317.3(1)Å, c = 908.4(1) Å, α = 90°, β = 90°, γ = 90° and V =2861.4(4)106(pm3). The final R value is 0.0667 for 5321 measured reflections. The identification, IRinvestigation and elemental analysis data are consistent with a unit cell composed of[Cu3O(AcO)6(H2O)3]Cl.CH3OH.6H2O

A new poly(vinylchloride) membrane sensor for Cr3+ ions based on di (benzylamino)glyoxime asan ionophore was prepared. The electrode has a linear dynamic range 1×10-6-1×10-1 mol l-1,with aNernstian slope of 20.3 ± 0.5 mV per decade and a detection limit of 2×10-7. It has a fast responsetime of <15 s and can be used for at least 3 months without any considerable divergence inpotential. The proposed electrode revealed good sensitivity for Cr(III) over a wide variety of metalions and could be used in a pH range of 2-5.5. The proposed sensor was used for the determinationof Cr3+ ions in real samples such as tea leaves, coffee and cacao powder by direct potentiometry.

The potential energy surface of gaseous glycine determined years ago in the ab initio B3LYP/6-311++G** calculations is composed of thirteen stable conformers. We performed the ab initiomolecular orbital calculations as the starting point to carry out a force field and normal coordinatecalculation on the most stable conformer of non-zwitterionic glycine [conformer (I)]. Thecalculations were carried out at different levels of theory using two methods, namely, the Hartree-Fock (HF) and the Möller-Plesset second order perturbation (MP2) method (including electroncorrelation), and using the Pople’s basis sets, namely, STO-nG (n=2, 3 and 6), 3-21G, 6-21G, 6-31G, 6-311G and also cc-pVnZ to obtain HF limit. This different basis sets accompanied with thedifferent combinations of diffuse and polarization functions were used. Each level of theory, withno symmetry restrictions, did fully optimization of neutral glycine. The atomic chargedistributions were obtained using the Mulliken population analysis. The structural characteristicssuch as the total energies, the complete optimized geometrical parameters including bond lengths,normal and torsion angles, as well as dipole moments, rotational constants, atomic chargedistributions, vibrational frequencies and IR intensities of the equilibrium conformation of glycinein gas phase were calculated at a wide range of the levels of theory -as mentioned above- and theresults were compared together and with HF limit and the experimental data to examine thereliability of the applied basis sets and to introduce the most efficient ones. We also assayed howthe strength of internal H-bonds depended on the variant parameters of basis set via the calculatedatomic charges.