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41.
H. Raissi Abraham F. Jalbout B. Abbasi F. Fazli F. Farzad E. Nadim Aned de Leon 《International journal of quantum chemistry》2010,110(4):893-901
The molecular structure and intramolecular hydrogen bond energy of 18 conformers of 3‐imino‐propenyl‐amine were investigated at MP2 and B3LYP levels of theory using the standard 6‐311++G** basis set. The atom in molecules or AIM theory of Bader, which is based on the topological properties of the electron density (ρ), was used additionally and the natural bond orbital (NBO) analysis was also carried out. Furthermore calculations for all possible conformations of 3‐imino‐propenyl‐amin in water solution were also carried out at B3LYP/6‐311++G** and MP2/6‐311++G** levels of theory. The calculated geometrical parameters and conformational analyses in gas phase and water solution show that the imine–amine conformers of this compound are more stable than the other conformers. B3LYP method predicts the IMA‐1 as global minimum. This stability is mainly due to the formation of a strong N? H···N intramolecular hydrogen bond, which is assisted by π‐electrons resonance, and this π‐electrons are established by NH2 functional group. Hydrogen bond energies for all conformers of 3‐imino‐propenyl‐amine were obtained from the related rotamers methods. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 相似文献
42.
Synthesis and Characterization of Naphthalene‐Based Banana‐Shaped Liquid Crystals for Photoswitching Properties 下载免费PDF全文
Md Lutfor Rahman Mashitah Mohd Yusoff Gurumurthy Hegde Muhammad Nor Fazli Abdul Malek Nurlin Abu Samah H. T. Srinivasa Sandeep Kumar 《中国化学会会志》2014,61(5):571-577
A series of banana‐shaped monomers containing naphthalene as central units, azobenzene in side arms with terminal alkenes were synthesized and characterized. Polarizing optical microscopy, DSC and X‐ray diffraction measurements reveal that one compound processes a nematic phase while other four compounds exhibit B6 phase. The absorption spectrum of trans‐azobenzene displays high‐intensity π‐π* transition at 365 and low‐intensity n‐π* transition at 450 nm. These molecules exhibit strong photoisomerisation behaviour in solutions in which trans to cis isomerisation takes 55 seconds whereas reverse process takes about 32 hours. Such a long thermal back relaxation is useful for creation of optical image storage devices. 相似文献
43.
Khan A Khan MI Iqbal Z Shah Y Ahmad L Nazir S Watson DG Khan JA Nasir F Khan A Ismail 《Talanta》2011,84(3):789-801
A new, simple, economical and validated high-performance liquid chromatography linked with electrochemical detector (HPLC-ECD) method has been developed and optimized for different experimental parameters to analyze the most common monothiols and disulfide (cystine, cysteine, homocysteine, methionine, reduced (GSH) and oxidized glutathione (GSSG)) and ascorbic acid present in human plasma and erythrocytes using dopamine as internal standard (IS). Complete separation of all the targets analytes and IS at 35 °C on Discovery HS C18 RP column (250 mm × 4.6 mm, 5 μm) was achieved using 0.05% TFA:methanol (97:3, v/v) as a mobile phase pumped at the rate of 0.6 ml min−1 using electrochemical detector in DC mode at the detector potential of 900 mV. The limits of detection (3 S/N) and limits of quantification (10 S/N) of the studied compounds were evaluated using dilution method. The proposed method was validated according to standard guidelines and optimization of various experimental parameters and chromatographic conditions was carried out. The optimized and validated HPLC-ECD method was successfully applied for the determination of the abovementioned compounds in human plasma and erythrocytes. The method will be quite suitable for the determination of plasma and erythrocyte profile of ascorbic acid and aminothiols in oxidative stress and other basic research studies. 相似文献
44.
Faiza Naureen Yasar Shah Sayyed Ibrahim Shah Muhammad Abbas Inayat Ur Rehman Salar Muhammad Hamdullah Khang Wen Goh Fazli Khuda Amjad Khan Siok Yee Chan Mehwish Mushtaq Long Chiau Ming 《Molecules (Basel, Switzerland)》2022,27(13)
Mirtazapine is a tetracyclic anti-depressant with poor water solubility. The aim of this study was to improve the dissolution rate of mirtazapine by delivering the drug as a liquisolid compact. Central composite design (CCD) was employed for the preparation of mirtazapine liquisolid compacts. In this, the impacts of two independent factors, i.e., excipient ratio (carrier:coating) and different drug concentration on the response of liquisolid system were optimized. Liquisolid compacts were prepared using propylene glycol as a solvent, microcrystalline cellulose as a carrier, and silicon dioxide (Aerosil) as the coating material. The crystallinity of the formulated drug and the interactions between the excipients were examined using X-ray powder diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR), respectively. The dissolution study for the liquisolid compact was carried out as per FDA guidelines. The results showed loss of crystallinity of the mirtazapine in the formulation and was completely solubilized in non-volatile solvent and equally dispersed throughout the powder system. Moreover, drug dissolution was found to be higher in liquisolid compacts than the direct compressed conventional tablets (of mirtazapine). The liquisolid technique appears to be a promising approach for improving the dissolution of poorly soluble drugs like mirtazapine. 相似文献
45.
Surface tension of two ternary mixtures of water/acetonitrile/methanol and water/acetonitrile/ethanol, and their constituent binaries, were measured over the whole range of composition at 298.15 K and ambient pressure. The experimental data were used to calculate in the surface tension deviations (Δσ). The negative values of Δσ for the binary and ternary systems indicate the strong hydrogen bonding between unlike molecules of mixtures (particularly in the high concentration of water). Surface tension data of the binary systems were correlated with Fu et al., Wang–Chen, Redlich–Kister and Myers–Scott models. The mean standard deviation obtained from the comparison of experimental and calculated surface tension values for binary systems with four models is less than 0.42. Finally, the concentration dependence of the surface tension deviation of the ternary mixtures at 298.15 K was correlated using Pando et al. and Ku et al. models, with satisfactory results. 相似文献
46.
Fully biobased polylactide (PLA)/polyamide-11 (PA11) blends were prepared by melt mixing with an elastomer intermediate phase to address the low elasticity and brittleness of PLA blends. The incorporation of a biobased elastomer made of poly(butylene adipate-co-terephthalate) (PBAT) and polyethylene oxide (PEO) copolymers was found to change the rigid interface between PLA and PA11 into a much more elastic/deformable one as well as promote interfacial compatibility. The interfacial tension of the polymer pairs and spreading coefficients revealed a high tendency of PEO to spread at the PLA/PA11 interface, resulting in a complete wetting regime (interfacial tension of 0.56 mN/m). A fully percolated rubbery phase (PEO) layer at the PLA/PA11 interface with enhanced interfacial interactions and PLA chain mobility contributed to a better distribution of the stress around the dispersed phase, leading to shear yielding of the matrix. The results also show that both the morphological modification and improved compatibility upon PEO addition (up to 20 wt %) contributed to the improved elongation at break (up to 104%) and impact strength (up to 292%) of the ternary PLA/PA11/PEO blends to obtain a super-tough multiphase system. 相似文献
47.
Muhammad Imran Khan Zafar Iqbal Lateef Ahmad Yasar Shah Shabnam Nazir Abbas Khan Fazli Nasir 《Chromatographia》2011,73(9-10):929-939
A highly sensitive, precise, and accurate reversed-phase high-performance liquid-chromatography/electrochemical detection method for simultaneous determination of the endogenous free ??-lipoic acid and dihydrolipoic acid in biological matrices was developed and validated. The two analytes were extracted from the samples with acetonitrile/10% metaphosphoric acid solution(aqueous) (50/50 v/v). To determine the total lipoic acid, samples were treated with tris(2-carboxyethyl)phosphine solution in phosphate buffer, pH 2.5 with 85% orthophosphoric acid prior to deproteination. The two analytes were separated on a C18 (150 × 4.6 mm, 5 ??m) analytical column using acetonitrile-50 mM phosphate buffer, pH 2.5 with 85% orthophosphoric acid (35/65 v/v) as the isocratic mobile phase pumped at a flow rate of 2.0 mL min?1 at the column oven temperature of 35 °C. The column eluents were monitored at a potential of 0.9 V. These analytes were efficiently resolved in <7 min. The present method was sufficiently robust and specific for simultaneous determination of the two analytes and demonstrated acceptable values for linearity (r 2 = 0.999 in the range of 0.1?C500 and 0.25?C1,000 ng mL?1 for ??-lipoic acid and dihydrolipoic acid, respectively), recovery (>97%), precision (RSD% <2), and sensitivity (on column limit of detection, 150 and 375 fg for ??-lipoic acid and dihydrolipoic acid, respectively and limit of quantification: 0.5 and 1.25 pg for ??-lipoic acid and dihydrolipoic acid, respectively), indicating that the proposed method was more sensitive, precise, economical, and versatile, and has higher throughput than the previously reported methods for simultaneous determination of the two analytes. 相似文献
48.
Aziman Eli Syafiqah Ismail Aznan Fazli Jubri Siti Fatimah Rahmat Muhammad Abdullah Idris Wan Mohd Razi 《Journal of Radioanalytical and Nuclear Chemistry》2021,330(3):667-683
Journal of Radioanalytical and Nuclear Chemistry - Comprehensive radiological survey and evaluation of heavy metal contamination were conducted in Chini Lake, which has been awarded a pristine... 相似文献
49.
A. F. Jalbout M. Ali Naseri M. Fazli H. Raissi M. Rezaei A. Nowroozi A. de Leon 《International journal of quantum chemistry》2009,109(7):1481-1496
The intramolecular hydrogen bond, molecular structure, and vibrational frequencies of α‐chloro acetylacetone have been investigated. Fourier transform infrared and Fourier transform Raman spectra of this compound and its deuterated analogue were recorded in the regions 400–4,000 cm?1 and 50–4,000 cm?1, respectively. Rigorous normal coordinate analysis has been performed at the B3LYP/6‐311++G** level of theory for purposes of comparison. The complete vibrational assignment for TFAA has been made on the basis of the calculated potential energy distribution. We also applied the atoms in molecules theory and natural bond orbital method for the analysis of the hydrogen bond in α‐Chloro acetylacetone and acetylacetone. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 相似文献
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