Physical Chemistry Research
Volume:6 Issue: 3, Summer 2018

With the aim of exploring the electronic and optical properties of some interesting conductive copolymers in view of potential applications, a regular oligomer systems made of aniline and three reference heterocyclic compounds (pyrrole, thiophene and furan) are studied using density functional theory (DFT) and time dependent density functional theory (TDDFT) calculations at B3LYP/6-31(d,p) level. It was found that poly (aniline-co-pyrrole) has the lowest ionization potential (4.48 eV) and electro affinity (0.77 eV) while poly (aniline-co-thiophene) has lowest band gap and longest (3.21 eV) wavelength of absorption (and then highest electronic conjugation) among the studied molecules. Comparison of the theoretical data and spectroscopic results obtained by DFT calculations with those experimentally obtained show very good agreement.

A dataset of (E)-N’-benzylideneisonicotinohydrazide derivatives as a potent anti-mycobacterium tuberculosis has been investigated utilizing Quantitative Structure-Activity Relationship (QSAR) techniques. Genetic Function Algorithm (GFA) and Multiple Linear Regression Analysis (MLRA) were used to select the descriptors and to generate the correlation QSAR models that relate the Minimum Inhibitory Concentration (MIC) values against mycobacterium tuberculosis with the molecular structures of the active molecules. The models were validated and the best model selected has squared correlation coefficient (R2) of 0.9202, adjusted squared correlation coefficient (Radj) of 0.91012, Leave one out (LOO) cross validation coefficient (Q_cv^2) value of 0.8954. The external validation set used for confirming the predictive power of the model has its R2pred of 0.8842. Stability and robustness of the model obtained by the validation test indicate that the model can be used to design and synthesis other (E)-N’-benzylideneisonicotinohydrazide derivatives with improved anti-mycobacterium tuberculosis activity.

In this manuscript, density functional theory was used to explore structural, vibrational and optical properties of the (Sc2O3)n (n=1-5) cluster systems using DFT/B3LYP/LanL2DZ level of computation. Different stable isomers were obtained and numerous chemical parameters such as HOMO-LUMO gap, ionization potential and electron affinity were calculated successfully. Stability of the clusters was investigated in terms of the total and binding energies. In order to determine the origin of the species, transition states or stationary points, vibrational frequencies were calculated for the most stable configurations of (Sc2O3)n (n=1-5) nanoclusters. Optical properties of scandium oxide nanoclusters were discussed by using time-dependent density functional theory methods.

N-Cyclohexyl-2,4,4-trimethyl-2,3,4,5-tetrahydro-1H-benzo[b][1,5]diazepine-2-carboxamide (5) was synthesized using an efficient, highly recyclable and eco-friendly catalyst heteropolyacid/triethoxysilyl)propyl]isonicotinamide (HPA/TPI-Fe3O4 nanoparticles) in one-pot. The compound 5 was characterized by FT-IR,1H NMR, 13C NMR, mass spectra, and elemental analysis. The theoretical calculations on 5 were carried out at the M062X and B3LYP methods with a 6-311(2d,p) basis set. The structural parameters and the IR data of 5 were analyzed and compared with the related experimental data. The results show fair correlation between the calculated 13C chemical shifts with B3LYP/6-311(2d,p) level and experimental data. Theoretical studies on the frontier molecular orbitals, mapped molecular electrostatic potential (MEP) and corresponding graphs and charge delocalization of 5 were also carried out.

In this research, biodiesel was produced using chicken fat in the presence of calcium oxide nano-catalyst. To do so, the effect of various parameters like temperature, reaction time, catalyst amount and methanol to oil ratio was investigated on the biodiesel production. The results showed that the best conditions for biodiesel production were obtained such as the temperature of 65oC, methanol to oil ratio of 1:9, the catalyst amount of 1 wt.% and reaction time of 5 h which in these conditions the biodiesel efficiency was determined 94.4%. Then, for improvement of fuel properties, they were mixed with diesel in different ratios (B25, B50, and B75) and their properties such as flash point, cloud point, pour point, kinematic viscosity and density were analyzed according to international standards. The results showed that the mixture ratio of B75 and B100 had density and viscosity in the range of standard. Additionally, this fuel should not be used in cold weather since its pour point is greater than zero.

This paper reports density and speed of sound data for solutions of the ionic liquids (ILs) [C4mim]Cl and [C4mim][CF3SO3] in aqueous solution of 0.05 w/w amino acids of alanine, serine and proline at T = (288.15, 298.15, 308.15 and 318.15) K. From the experimental data measured, the apparent molar volume (Vϕ), isentropic compressibility ( ), and apparent molar isentropic compression ( ) have been calculated. The Vϕ values of [C4mim]Cl and [C4mim][CF3SO3] in the investigated aqueous amino acid solutions decreased by increasing the hydrophobicity of the amino acid and follow the order: serine alanine proline. The apparent molar volume and isentropic compressibility values at infinite dilution of the investigated ILs in the aqueous amino acid solutions and their variations with temperature have been determined. The infinite dilution apparent molar volume and adiabatic compressibility for transfer of the studied ILs from water to aqueous solutions of the amino acids have been calculated and the results were discussed in terms of different interactions existing in these solutions.

In this study, a full-potential density functional theory was used to investigate the effects of Ti substitution by different cations. In both rutile and anatase, Ti atom was replaced by Ce, Au, Sn, Ag, Mo, Nb, Zr, and Y. Phase stability, electronic structure and formation energy of oxygen vacancy were compared for rutile and anatase. The results indicated that substitution of Ce and Zr increases anatase stability through which photocatalytic activity is enhanced. It seems that the cationic capacity and size play a critical role in anatase to rutile phase transition, where with an equi- or higher valence than Ti, larger cations increase the stability of anatase phase. Oxygen vacancy concentration, as a second factor of photocatalytic activity, was also studied by calculating its stability due to the cationic substitution. The data revealed that Au, Ag, Y, Ce and Sn effectively reduce oxygen-vacancy formation energy. Of the studied cations, Au and Ag had maximum reduction in band gap, by creating defect states in the middle of the band gap resulting from the overlaps of these elements d-orbitals and oxygen p-orbitals. Mo and Ce impurities did not have a significant effect on reducing gaps by creating defect states under the conduction band. Finally, Sn impurity also generated defect states in the middle of the gap merely with the lack of oxygen.

In this study, SBA-15-PAMAM mesoporous Nano-adsorbent was synthesized, characterized and applied for adsorption of Acid dyes (Acid Blue 62 (AB62) and Acid Red 266 (AR266)) from aqueous Medias. Adsorption of AB62 and AR266 on SBA-15 ordered mesoporous silica, polyamidoamine functionalized SBA-15(SBA-15-PAMAM), has been investigated. In order to assess the synthesized adsorbent constructional, FT-IR (Fourier transform infrared spectroscopy), TEM transmission electron microscopy images and XRD (X-ray diffraction) methods were utilized. In order to investigate and compare the adsorption of two acid dyes with each other, the chemical structure and molecular mass of two acid dyes on the synthesized Nano-adsorbent is compared with each other. The Acid Blue 62 dye with the structure of Anthrachinon (MW =422.43) and the Acid Red 266 dye with the structure of Azo (MW =467.78) is compared with each other. To appraise the proficiency of this Nano-adsorbent foradsrption of two acidic dyes from aqueous Medias, the efficacy of significant parameters comprising pH(2-10), adsorbent dosage(0.01-0.1g), dye concentration(200-600mg/g), contact time(10-120 min) and temperature(25-45°C) was investigated. The Langmuir, Freundlich, Tempkin and Dubin Radushkevich isotherms were perused. The empirical data were best demonstrated by the langmuir isotherm model with utmost adsorption valence of (1428.57 mg/g) for dye AB62 and (1111.11 mg/g) for dye AR266 at pH 2 and 25 °C and it is consented absolutely with the empirical data (R2 > 0.9933) for dye AB62 and (R2 > 0.9914) for dye AR266. It was concluded that SBA-15-PAMAM adsorbent could be applied as a significant adsorbent for acidic dyes removal.

Density functional theory (DFT) and time dependent DFT (TD-DFT) calculations were carried out for the oligomers of 3, 4- Ethylenedioxythiophene –Aniline (EDOT-Ani), 3, 4-Ethylenedithiafurane- Aniline (EDTF-Ani) and Thieno [3,4-b] benzene-Aniline (PITN-Ani). Structural parameters, electrical conductivity, spectral properties and electronic properties like ionization potential (IPs), (EAs), HOMO-LUMO isosurfaces and energy gaps of EDOT-Ani, EDTF-Ani and PITN-Ani were calculated and compared using density functional theory at B3LYP/6-31G(d) level which has been successful in predicting trends in conjugated systems. EDOT-Ani results show good correlation with our previous experimental data. The vibrational frequencies with their assignments are also in close agreement with experimental frequencies. The UV-vis spectra are simulated with TD-DFT/6-31G(d) level of theory and the Maximum wavelength (λmax), optical band gap (Egopt) and oscillator straight (f) of three oligomers were compared with each other and with experimental values. Among the studied copolymers, PITN-Ani shows the narrowest band gap which is attributed to its higher donor acceptor property compared to two other polymers.

In this article the behavior of tetrahydrofuran (THF) 2-alkanol namely 2-propanol, 2-butanol, 2-pentanol, 2-hexanol and 2-heptanol binary mixtures through the density and viscosity measurements have been studied as a function of composition and within the temperature range of 293.15–313.15 K. The excess molar volume, isobaric thermal expansivity, partial molar volumes, and viscosity deviations have been calculated. For all binary mixtures, values of excess molar volume are positive and viscosity deviations are negative while increasing with the alkyl chain of the alcohol. The results provide information on the interactions among the molecules in the pure state as well as the binary liquid mixtures. The measured densities and viscosities have been applied to test the applicability of the PC-SAFT model and friction theory coupled with the Peng–Robinson–Stryjek–Vera equation of state.

In this study, the main objective is the preparation and the characterization of a modified Algerian bentonite based adsorbent by intercalation with hexadecyltrimethylammonium bromide (HDTMA). Natural and modified bentonites were characterized using thermogravimetric analysis (TGA), X-ray diffraction (XRD) and infrared spectroscopy (FTIR). The X-ray results indicate that the geometry of the interlayer space was changed by the intercalation of HDTMA cations and the basal spacing was increased from 1.34 to 1.96 nm. The adsorption efficiency of natural and HDTMA-bentonite was examined for humic acid (HA) removal by batch adsorption experiments under different operating conditions. The maximum monolayer adsorption capacity qm of HA was found to be 54.80 mg/g and 330.34 mg/g for HDTMA-bentonite and natural bentonite respectively. The kinetic study indicated that HA adsorption followed the pseudo-first-order model. Both natural and HDTMA-bentonite showed quite good capabilities in removing HA from aqueous solutions.

This paper is designed to examine the binding behavior of Coumarin with bovine -casein (βCN) through fluorescence spectroscopy and molecular modeling techniques. The data analysis on fluorescence titration experiments at various temperatures represents the enthalpy driven nature for the formation of Coumarin–βCN complex and the prevailed role of hydrogen bonds and van der Waals interactions in the binding process. The results also represent the static quenching of tryptophan and dynamics quenching of tyrosine and phenylalanine residues due to the binding of Coumarin. It can be concluded from molecular docking studies that Coumarin binds to several polar and non-polar residues in the hydrophobic core of βCN with the binding energy of -6.96 kcal mol-1. Finally, analysis of molecular dynamics (MD) simulation results suggested that the interactions between βCN and Coumarin are very stable and the binding of Coumarin restricted the flexibility of important residues in the binding site of this protein.

In this investigation, the influence of doping graphene with silicon in the adsorption of alanine amino acid was inspected computationally. For this purpose, the structures of pure graphene, silicon doped graphene, alanine and 10 derived products of the alanine reaction with pure and silicon doped nano-adsorbents were optimized geometrically. Afterwards, the values of adsorption energy, formation enthalpy, gibbs free energy and thermodynamic constant for alanine adsorption procedures were determined at different situations. The obtained results demonstrate that pure graphene and also meta silicon doped graphenes do not have any interaction with alanine molecules due to their positive formation enthalpy and gibbs free energy values. But doping graphene with silicon in para situation can lead to the spontaneous and exothermic adsorption of alanine because of the achieved negative ΔHf (-4.4040 and -2.6881 eV) and ΔGf (-3.3973 and -1.6887 eV). The great acquired thermodynamic constants (1.689× 10 and 6.140× 10) have also confirmed this results. Some chemical properties such as HOMO and LOMO energy levels, energy gap, electrophilicity, chemical potential, maximum transmitted electron and dipole moment in the reactions were also evaluated. And the acquired HOMO–LUMO gap values indicate that silicon doped graphene can also be useful for sensing this amino acid. All calculations were applied by Density functional theory in the level of B3LYP / 6-31G(d) and the aqueous phase.

Nuclear quadrupole resonance (NQR) spectroscopy is an accurate method for determination of electric charge distribution around quadrupolar nuclei. Using ab initio computational methods, it is possible to calculate the Nuclear Quadrupole Coupling Constants (NQCCs) with high accuracy and obtain the useful structural information by using these parameters. Sodium Borohydride, NaBH4, is a metal hydride complex which is a good candidate for being applied in fuel cells as hydrogen storage material with high capacity of 10.6 wt %. Despite the high capacity of hydrogen storage, hydrogen desorption occurs at high temperatures due to high stability and strong bonds of this compound. This problem limits the practical usage of NaBH4 in fuel cells. One way to overcome this problem is applying the high-pressure techniques and using the pressure-induced NaBH4 structures. Under ambient conditions, NaBH4 has a cubic structure (α-NaBH4) that can be converted to β- and γ-NaBH4 by increasing the pressure. In the present research, charge distribution of α-NaBH4 nanocrystal has been compared to that of high-pressure structures using calculated NQCCs, to study the effect of pressure on different NaBH4 structures and hydrogen desorption ability of them. Our results show the smaller value of 2H–NQCCs and higher value of 11B-NQCCs for β-NaBH4 respect to other structures. In other words, the B-H bond is weaker in β-NaBH4 and it is expected that dehydrogenation occur more feasible and at lower temperature in β-phase compared to other phases. NBO results are in agreement with Calculated NQCCs. Calculations performed using Gaussian 09 program in B3LYP/6-311G*.

This work investigates the structural and nonlinear optical properties of a D-A type 1-[4-({(E)-[4-(methylsulfanyl)phenyl]methylidene}amino)phenyl]ethanone, MMP in which charge transfer occurs from -SCH3 donor to -COCH3 acceptor group through methylidene backbone; and some of its modeled analogues using quantum chemical calculations with pure BLYP and hybrid B3LYP correlation with high basis sets, 6-31G* and 6-31G* in gas phase in a bid to understand their structure-property relationship. The molecular properties like the FMOs energies, dipole moments (μ), polarizabilities (α), molecular first hyperpolarizabilities (β) were obtained. The results showed that the molecular properties were enhanced upon substitution with different groups. The β value is a measure of second order susceptibility of molecule; MMP has a β value of 2.44 x10-30 esu (B3LYP), 3.75 times of urea (0.65 x10-30 esu) and 2.61 x10-30(BLYP), 4.02 times that of urea. The experimental SHG efficiency of MMP is 4.13 times that of urea crystals of identical particle size, meaning that the BLYP correlation predicts the SHG efficiency and second order susceptibility more effectively than the B3LYP method. With 6-31*, B3LYP gave 2.83 x10-30 esu, 4.35 over urea’s (94.9%) while BLYP is 3.11 x10-30 esu, 4.78 times that of urea (84.3%). However, both basis sets gave expected results in the right order for the molecules however, all modeled analogues increased β value, confirming that they are better candidates for NLO applications than MMP. The electronic transitions were calculated with CAM-B3LYP.