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Saqib Kamal Arif I. Inamdar Kuan-Ru Chiou Batjargal Sainbileg Muhammad Usman Jenq-Wei Chen Tzuoo-Tsair Luo Michitoshi Hayashi Chen-Hsiung Hung Wen-Feng Liaw Kuang-Lieh Lu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(30):e202103905
The dielectric properties of coordination polymers has been a topic of recent interest, but the role of different functional groups on the dielectric properties of these polymers has not yet been fully addressed. Herein, the effects of electron-donating (R=NH2) and electron-withdrawing (R=NO2) groups on the dielectric behavior of such materials were investigated for two thermally stable and guest-free Zn-based coordination polymers, [Zn(L1)(L2)]n ( 1 ) and [Zn(L1)(L3)]n ( 2 ) [L1=2-(2-pyridyl) benzimidazole (Pbim), L2=5-aminoisophthalate (Aip), and L3=5-nitroisophthalate (Nip)]. The results of dielectric studies of 1 revealed that it possesses a high dielectric constant (κ=65.5 at 1 kHz), while compound 2 displayed an even higher dielectric constant (κ=110.3 at 1 kHz). The electron donating and withdrawing effects of the NH2 and NO2 substituents induce changes in the polarity of the polymers, which is due to the inductive effect from the aryl ring for both NO2 and NH2. Theoretical results from density functional theory (DFT) calculations, which also support the experimental findings, show that both compounds have a distinct electronic behavior with diverse wide bandgaps. The significance of the current work is to provide information about the structure-dielectric property relationships. So, this study promises to pave the way for further research on the effects of different functional groups on coordination polymers on their dielectric properties. 相似文献
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Simultaneous Determination of Pioglitazone and Glimepiride by High-Performance Liquid Chromatography
A rapid and accurate HPLC method has been developed for simultaneous determination of pioglitazone and glimepiride. Chromatographic separation of the two pharmaceuticals was performed on a Cosmosil C18 column (150 mm × 4.6 mm, 5 m) with a 45:35:20 (v/v) mixture of 0.01 m triammonium citrate (pH adjusted to 6.95 with orthophosphoric acid), acetonitrile, and methanol as mobile phase, at a flow rate of 1.0 mL min–1, and detection at 228 nm. Separation was complete in less than 10 min. The method was validated for linearity, accuracy, precision, limit of quantitation, and robustness [1, 2]. Linearity, accuracy, and precision were found to be acceptable over the ranges 2.50–30.00 g mL–1 for pioglitazone and 0.10–10.00 g mL–1 for glimepiride. 相似文献
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Band structure parameters such as the conduction band edge, the valence band edge and the quasi‐particle gap of diffusing CdSe quantum dots (Q‐dots) of various sizes were determined using cyclic voltammetry. These parameters are strongly dependent on the size of the Q‐dots. The results obtained from voltammetric measurements are compared to spectroscopic and theoretical data. The fit obtained to the reported calculations based on the semi‐empirical pseudopotential method (SEPM)—especially in the strong size‐confinement region, is the best reported so far, according to our knowledge. For the smallest CdSe Q‐dots, the difference between the quasi‐particle gap and the optical band gap gives the electron–hole Coulombic interaction energy (Je1,h1). Interband states seen in the photoluminescence spectra were verified with cyclic voltammetry measurements. 相似文献
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Chitosans with high degree of polymerization and molecular weight exhibit poor aqueous solubility which is an impediment in
their applicability. The low molecular weight chitosans (LMWCs) and chitooligosaccharides (COSs) can be used to avoid this
hurdle. The development of an efficient process for reducing the molecular weight of chitosan, without altering its chemical
structure, is of great interest to produce tailormade chitosans of varying Degree of Acetylation (DAs) and Degree of Polymerization
(DPs). The production of well-defined COS-mixtures, or even pure COS, is of great interest since these oligosaccharides are
thought to have several interesting bioactivities and applications. For this proper delineation of their characteristics is
needed. Hence it is our attempt to provide an overview of difffernt methods and techniques of their production and characterization.
Several methods viz. depolymerization under the action of reagents, enzymes, high energy impact and combinations thereof have
been employed to get COS by depolymerization of high molecular weight chitosans. Acid hydrolysis (hydrochloric, nitrous, phosphoric
acid, hydrogen fluoride) and oxidative reductive depolymerization (mediated by peroxide, ozone, and persulfate) are important
routes for synthesis of COSs. These oligomers can be produced from chitin or chitosan as a starting material by enzymatic
conversions. For this, numbers of enzymes have been used. Depolymerization under high energy impact and recombinant approaches
are also being tried for production of COSs. LMWC and COS, like parent chitosan, can be used for drug delivery and gene delivery.
The efficient and productive processes are needed for separation of COSs into its components or mixture of defined characters.
The characterization of COS can be carried out by chromatographic and spectroscopic techniques. Importantly COSs display an
array of biological activities as antimicrobial, anticancer/antimetastatic, wound healing acceleration, immunostimulation,
apoptosis induction or inhibiton, antioxidant, enzyme inhibiton, antihyperlipidemic, antidiabetic, chemoprevention, and many
more. A few of the biological actions are reported only sporadically where as some are persistently taken up by the scientific
fraternity to substantiate the claims and propose possible mechanisms of action. However there remains the disagreement of
results on COS activities. The disagreements can arise due to poor and variable reporting of the properties of COS such as
used in the studies as molecular weight, degree of acetylation, molecular weight distribution, and the pattern of N-acetylation
etc. With production of COS of well defined characters it might be possible to understand the modes of actions of COS in better
ways. 相似文献
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The time-resolved laser emission of coumarin 102 was investigated in various aprotic and protic solvents at picosecond resolution
by frequency upconversion technique. The spectral shift of the transient emission spectrum is attributed to solvent reorientation
and the results are discussed. 相似文献
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A model scheme incorporating reactant inhibition in the rate process has been analyzed with a view to study the instability of homogeneous solution due to diffusion. Conditions for the occurrence of Turing as well as phase instability are derived and show the existence of multiplicity in the parameter space. The Ginzburg-Landau equation for the system is developed and solved numerically in various regions of the parameter space. The simple model system shows the existence of very rich behavior including normal and inverted bifurcations in the super and subcritical regimes. The various results are analyzed and discussed. © 1993 John Wiley & Sons, Inc. 相似文献
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Applied Biochemistry and Biotechnology - 相似文献
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