JOURNAL OF PHYSICAL AND THEORETICAL CHEMISTRY
Year:2018 | Volume:14 | Issue:4|Papers Count:9

In this study, samples of coastal waters of Kiashahr port were collected. Magnetic desalination involves exposing the sample to a magnetic field and putting the water in physical contact with magnetic nanoparticles which were synthesized with the co-precipitation method. X-ray diffraction, Fourier transform infrared spectroscopy and field-emission scanning electron microscopy were used for the characterization of nanoparticles. The results showed that nanoparticles have a spherical shape and a diameter of less than 20 nm. After modifying the surface of Fe3O4 nanoparticles with SiO2, they maintained their uniform distribution and spherical shape but their size increased by 20 nm. The salinity and electrical conductivity of the sample was measured prior to and following the magnetic treatment. Maximum reduction in the level of salt and electrical conductivity was achieved when 0. 1 g of nanoparticles was placed in contact with sea water for 2 h and also when sea water at a flow of 50 ml/min was introduced to a magnetic field of 30 mT for 20 s. The amount of salt in the sample was reduced to 9. 65 g/l using the above-mentioned method-having an initial value of 11. 6 g/l.

2-(3-indolyl) – 4, 5 di phynyl imidazole. (IDPI) was used as a complexing agent in cloud point extraction for the first time and applied for selective pre-concentration of trace amounts of cadmium. The method is based on the extraction of cadmium at pH= 7. 0 by using non-ionic surfactant Triton-X114 and 2-(3-indolyl) – 4, 5 di phynyl imidazole. (IDPI) as a chelating agent. The adopted concentrations for IDPI, Triton X-114 and HNO3, bath temperature were optimized, The response are linear over concentration range of 8. 0-90 (ng mL-1) for Cd2+ and RSD % (n =5) 1. 8 for Cd2+, Detection limits (3SDb/m, n =10, m = slope of calibration) of 2. 8 (ng. mL-1) for Cd2+ respectively. The enrichment factors was 33 for Cd2+. the preconcentration factors was 39 for Cd2+ respectively. The high efficiency of cloud point extraction to carry out the determination of analytes in complex matrices was demonstrated. The proposed method was successfully applied to the ultra-trace determination of cadmium in real and water samples.

The application of many hetero-aromatic compounds in pharmaceutical and dye industries make the theoretical study of their dipole moment (μ ) oscillator strength (f) and other photo-physical properties worthwhile. These properties determine the solubility of many compounds; predict the relationship between their structures, properties and performance. The f, μ , α , transition dipole moment (Δ μ ), vertical Excitation Energies (EE) and the frontier orbitals energy gap (Δ ELUMO-HOMO) of the optimized structures of 3, 4-diphenylthiophene (DPT); 3, 4-dicarboxylic-2, 5-diphenylthiophene (DCDPT); and benzo[b] thiophene (BT) were determined in solvents of different polarity functions (Δ P) by Time-Dependent Density Functional Theory, using Becke’ s three parameter with Lee-Yang-Parr modification and 6-31G* basis set theory (TD-DFT-B3LYP/6-31G*). The associated quantum chemical descriptors of Δ ELUMO-HOMO such as: Ionization Potential (IP) and global hardness (ƞ ) for the compounds were also determined with the same level of theory. The μ of the molecules increases with increasing Δ P, but highest for DCDPT. Bathochromic shifts associated with decreasing EE were recorded for the electronic transitions in DCDPT compare with those observed for DPT and BT. The IP and ƞ increased as Δ P increases, suggesting high stability of these compounds in polar solvents. The energy gaps, its associated parameters and positive Δ μ suggested strong activity of the molecules, with DCDPT being the highest. This is in reasonable agreement with the experimental results for the molecules particularly if the experimental uncertainties are considered.

A theoretical study at the B3LYP/6-31++G(d, p) level was performed on the tatumerization of 7H-purine-2, 6-diamine into 9H-purine-2, 6-diamine. Such a tautomerism can take place via three different pathways namely A, B, and C. The energetic results associated with the gas phase reveal that pathways A, B, and C display a very high activation Gibbs free energy of 45. 1, 68. 6 and 48. 9 kcal/mol, respectively, indicating this process cannot take place in the gas phase. When solvent effects of water are taken into account through a continuum of a uniform dielectric constant, the gas phase activation Gibbs free energies increase to 58. 8, 70. 6, and 52. 4 kcal/mol along pathway A, B, and C, respectively, emphasizing long range solute-solvent interactions do not play a key role in the considered tautomerization. The studied process can easily take place by inclusion of three molecules of water in which a significantly reduced activation Gibbs free energy of 24. 8 kcal/mol indicates the predominance of short range solute-solvent interactions over the long range ones. Combination of short range and long range solute-solvent interactions lead to an activation Gibbs free energy of 23. 5 kcal/mol for tatumerization of 7H-purine-2, 6-diamine into 9H-purine-2, 6-diamine. This value clearly points out that employing a polar and protic solvent is able to noticeably reduce the barrier of tatomerization.

The solvatochromic behaviour of two ketonic derivatives of benzodiazepine namely 7-chloro-1-methyl-5-phenyl-1, 5-benzodiazepine-2, 4-dione (Clobazam® ) and 5, (2-chlorophenyl)-7-nitro-2, 3-dihydro-1, 4-benzodiazepine-2-one (Clonazepam® ) were analysed in some selected solvents of different polarities using UV-Visible spectroscopy and DFT computational techniques. The solute-solvent interactions were evaluated by means of Kamlet-Taft’ s Linear Solvation Energy Relationship (LSER) concept. The results show that electronic absorption properties of the compounds depend on the solvent polarity and both specific and non-specific interactions between solute and solvent. Also, the spectral properties show satisfactory correlation with solvatochromic parameters (α , β and π ). The plot of ῡ max calculated against ῡ max observed in the representative solvents gives a good linear regression value of R2=0. 998. The results of Frontier Orbital calculations showing the differences between HOMO and LUMO of the ground states and various excited states of Clobazam® and Clonazepam® are-5. 15eV and-4. 20eV respectively and both are in good agreement with the most important transitions observed in the two compounds.

Thymus is regarded as one of the medicinal species, which according to obtained chromatograms of floral water of Thymus; one of the main components is thymol as strong antioxidant. In this study the appropriate and physically powerful correlation was found between the anti-radical and oxidation potentials. The antioxidant activity of the Thymus was measured by using square wave and cyclic voltammetry methods and 2, 2-diphenyl-1-picrylhydrazyl hydrate (DPPH) method in the concentration range of 1% to 2. 5% V/V. Electrochemical methods are used based on the relationship between oxidation power and antioxidant strength, which compared with ascorbic acid as standard. Based on the results of electrochemical methods, these methods have several advantages over the DPPH∙ method such as simplicity, cheaper operating costs, short integration time, high speed, low solvent and sample usage. Moreover, the square wave voltammetry method is more sensitive method for evaluation the antioxidant activities compared to DPPH and cyclic voltammetry methods.

Ajwain is one of the medicinal plants, which the highest composition is thymol, as a strong antioxidant respect to the obtained chromatograms of GC/MS. The antioxidant activity of the Ajwain is measured by square wave voltammetry method and cyclic voltammetry method and 2, 2-Diphenyl-1-picrylhydrazyl (DPPH) method in at the specific concentrations of 1%, 1. 5%, 2% and 2. 5% and constant pH. The results of the present study indicated that the antioxidant activity of Ajwain obtained from cyclic voltammetry and square wave is almost equal to the results of the DPPH method, which can be used to measure the antioxidant activity. Compared to DPPH method, electrochemical method involves a number of advantages such as simplicity, cheap operating costs, fastness, low amount of solvent, and no need for chemical reagents. Furthermore, based on the results obtained, the square wave method includes a higher sensitivity and accuracy than cyclic voltammetry method and DPPH method.

Density functional theory methods(DFT) and natural bond orbital (NBO) analysis were used to investigate the effects of isomerism and side chain mutation at a microscopic level on the stability, binding energy and NMR/NQR tensors of structural isomers, L-methionylasparagine (Met-Asn) and L-asparagylmethionine (Asn-Met) in the gas phase. The results represented that the isomerism and side chain mutation were caused to change the relative stability, binding energy and the thermodynamics parameters of peptide bond in the considered compounds. Therefore, Asn-Met had higher binding energy and relative stability than Met-Asn. On the other hand, NMR and NQR calculations at B3LYP/6-311+G (d, p) level of theory on the optimized structures of Met-Asn and Asn-Met indicated that the isotropic chemical shielding (σ iso) values of oxygen and nitrogen nuclei in two structures with similar positions were different considerably and nitrogen nuclei were more shielded than oxygen nuclei in both dipeptides. In addition, amino nitrogens (N10 nuclei) had the highest values of chemical shielding (σ iso) and the nuclear quadrupole coupling constant (χ ) among nitrogen nuclei and the order of chemical shielding values of nitrogen nuclei in two structural isomers was amino nitrogen> amidic nitrogen> peptide nitrogen (N10>N9>N1). The mentioned order for chemical shielding values was exactly the opposite of the order of resonance energies values of nitrogen lone pair electrons in two dipeptides. In other words, by increasing contribution of nitrogen lone pair electrons in intra-molecular resonance interactions, NMR chemical shielding around nitrogen nuclei were decreased.

A simple, sensitive and feasible cloud-point extraction (CPE) methodology has been developed for the separation and preconcentration of cadmium and lead ions in real samples. The metals in the aqueous solution were complexes with 2-(3-indolyl)-4, 5 di phynyl imidazole. (IDPI), at pH = 7. 0 and Triton X-114 was added as surfactant. The variables effecting like concentration of Triton X-114 and HNO3, bath temperature, centrifuge rate and time on the cloud-point extraction were optimized. Under optimum conditions, the response are linear over concentration range of 0. 077-1. 29 (μ g mL-1) for Zn2+ and RSD % (n =5) 1. 6 for Zn2+, Detection limits (3SDb/m, n = 10, m = slope of calibration) of 0. 14 (μ g. mL-1) Zn2+ respectively. The enrichment factors was 33, the preconcentration factors was 27 for Zn2+ respectively. The high efficiency of cloud point extraction to carry out the determination of analytes in complex matrices was demonstrated. The proposed method was successfully applied to the ultra-trace determination of cadmium in real samples.