Enoxacin trihydrate

The structure of the title compound, 1‐ethyl‐6‐fluoro‐1,4‐di­hydro‐4‐oxo‐7‐(piperazin‐4‐ium‐1‐yl)‐1,8‐naphthyridine‐3‐carb­oxylate trihydrate, C₁₅H₁₇FN₄O₃·3H₂O, has a zwitterion of enoxacin and three water mol­ecules in the asymmetric unit. The zwitterions form sheets lying parallel to each other and are hydrogen bonded in a head‐to‐tail manner. The crystal structure is stabilized by the involvement of O and H atoms from all the water mol­ecules in strong hydrogen bonds. The naphthyridine ring system is essentially planar, with the carboxyl­ate group lying out of this plane at an angle of 26.13 (6)° and the ethyl group oriented at approximately right angles to this plane. The piperazinium ring adopts a chair conformation.     

Effect of Aging on the Physico Chemical Properties of Glass Fiber under Different Environmental Conditions

Glass fibers were characterized for physical and chemical changes before and after subjecting to aging under different environmental conditions. The conditions selected were: low temperature, outdoor atmosphere, indoor atmosphere, chemical environment, 95% humidity & water soaking treatment. The results show that glass fiber is a good candidate to resist sunlight, corrosive atmosphere, low temperature and shady atmosphere. The influence of prolonged time exposure to water caused a detrimental effect on the properties of the glass fiber. Hence, prolonged exposure to water should be avoided for the integrity of the glass fiber under study.     

Supramolecular structures and properties models of macrocyclic polymer complexes

Two novel supramolecular complexes of types [Ru(L)(H₂L)Cl·OH₂] and [Ru(HL_n)Cl₃] (where H₂L is a potential tetradentate ligand derived from hydrazine hydrate and diethyl malonate, and HL_n is a potential bidentate ligand derived from coupling of allyl azo‐β‐diketone) have been synthesized and characterized by elemental analysis, conductance and magnetic measurements, followed by ¹H NMR, to determine the effect of substituents on the intramolecular hydrogen bond. The electronic properties and models of the bonding of ligands and complexes were investigated by UV–Vis and IR spectroscopies. The first type of complex contains terminal hydrazinic nitrogen atoms with an unshared electron pair and may take part in nucleophilic condensations. Therefore, the reactions of allyl‐β‐diketone complexes with malonic dihydrazide have also been studied, as these cause ring closure and formation of supramolecular macrocyclic ligand complexes. The wavelengths of the principal electronic absorption peaks have been accounted for quantitatively in terms of crystal field theory, and various parameters have been evaluated. On the basis of the electronic spectra, an octahedral geometry has been established for the polymer complexes C. The macrocyclic polymer complexes D are pentacoordinate, and a trigonal‐bipyramidal environment (D_3h) is suggested for the ruthenium(III) ion. The effect of the Hammett constant on the ligand field parameters is also discussed. Copyright © 2004 John Wiley & Sons, Ltd.     

<Superscript>13</Superscript>C-n.m.r. studies of the binding of 1,3-diazinane-2-selenone and 1,3-diazipine-2-selenone to gold(I) drugs

The interaction of gold(I) thiomalate, Myocrisin [(Autm)_n] with 1,3-diazinane-2-selenone (DiazSe) and 1,3-diazipine-2-selenone (DiapSe) has been studied in aqueous solution using ¹³C-n.m.r. spectroscopy. It is observed that ternary complexes, (DiazSe–Au–tm and DiapSe–Au–tm, respectively) are formed on coordination of these ligands to (Autm)_n. The ¹³C-n.m.r. data suggest that DiapSe binds more strongly to (Autm)_n than does DiazSe, which binds more strongly compared to its analogous thione, 1,3-diazinane-2-thione (Diaz). A similar observation was made for the gold(I) thioglucose (Autg) reaction with DiazSe.     

Effect of thiophene rings on UV/visible spectra and non‐linear optical (NLO) properties of triphenylamine based dyes: a quantum chemical perspective

In this study, density functional theory (DFT) and time‐dependent DFT (TD‐DFT) theory are use to shed light on how the number of thiophene rings in π‐conjugated system influence the absorption spectra and non‐linear optical (NLO) properties of dyes. The results of theoretical computation show that the absorption spectra are gradually broadened and red‐shifted (384–542 nm) with increasing number of thiophene units. The theoretical examination on non‐linear optical properties was performed on the key parameters of polarizabilty and hyperpolarizability. A remarkable increase in non‐linear optical response was observed on insertion of thiophene rings in π‐spacer. Copyright © 2015 John Wiley & Sons, Ltd.     

Investigation of the Electrochemical Behavior of Mesalazine on the Surface of a Glassy Carbon Electrode Modified with CNT/PPY Doped by 1,5‐Naphthalenedisulfonic Acid

A glassy carbon electrode (GCE) was modified with a thin layer of multiwalled carbon nanotubes (MWCNTs) and subsequently, electrochemically deposited poly‐pyrrole. The electrochemical behavior of mesalazine was studied on the surface of the modified electrode by applying linear sweep voltammetry (LSV). The electropolymerization process and the electrochemical response toward mesalazine were investigated in the presence of different aromatic anion dopants including, benzenesulfonic acid (BSA), 1,3‐benzenedisulfonic acid (1,3‐BDSA), 1,5‐naphthalenedisulfonic acid (1,5‐NDSA) and new coccine (NC). By using 1,5‐NDSA as dopant, a significant increase (～418 times) in the peak current of mesalazine was observed, in comparison to the bare GCE. Experimental variables such as drop size of the cast MWCNTs suspension, pH of the supporting electrolyte, accumulation conditions and the number of scans in the electropolymerization process were optimized by monitoring the LSV responses of mesalazine. Under the optimum conditions, two linear dynamic ranges of 0.01–0.1 µmol L^?1 and 0.1–1.0 µmol L^?1 with a detection limit of 3 nmol L^?1 were resulted for the voltammetric determination of mesalazine. The prepared electrode showed high sensitivity, stability and good reproducibility for determination of mesalazine. These properties made the prepared sensor suitable for the determination of mesalazine in pharmaceutical and clinical preparations.     

Polyimide-silica Hybrids: Structural and Morphological Investigations

Polyimide (PI) containing pendant hydroxyl functional groups have been employed for preparation of PI-silica hybrids through the sol-gel process. A stoichiometric amount of pyromellitic dianhydride (PMDA) was reacted with a mixture of oxydianiline (ODA) and 3,3′-diamino-4,4′-dihydroxybiphenyl (DAHP) in dimethylacetamide (DMAc) solvent to prepare the precursor poly(amic acid) (PAA) solution for the PI. Various proportions of tetraethoxysilane (TEOS) were mixed with PAA to prepare PI-silica hybrids through sol-gel process. The structure and morphology of these hybrids were investigated with field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), optical surface profilometery, and Fourier transform infrared (FTIR) spectroscopy and compared with the one in which the matrix was prepared from PMDA and ODA with no pendant hydroxyl functionalities. Formation of silica lean and silica rich phases (SLP and SRP) as a result of formation of nano-sized silica clusters with diffused boundaries, dispersed in the matrix and their agglomerates, respectively, along with totally different morphology suggest a strong influence of hydroxyl groups in controlling the morphology of PI-silica hybrids. A model namely “Retain and React” has been introduced to explain observed structure.     

Synthesis and Characterization of Hydrogel Nanoparticles Through Inverse Microemulsion Polymerization of 2-Acrylamido-2-methyl-1-propanesulfonic Acid

Nanosized hydrogel particles prepared through inverse microemulsion polymerization of 2-acrylamido-2-methyl-1-propanesulfonic acid, using the combination of an oil soluble emulsifier (SPAN80) with a water soluble emulsifier (TWEEN 80), and precise determination of HLB range related to the formation of stable single phase microemulsions.

The effect of crosslink density, water phase to oil phase ratio, and the hydrophilic-lipophilic balance (HLB) value on polymerization rate, particle size, and swelling ratio were investigated. It found that polymerization rate and particle size are strongly dependent on the water phase to oil phase ratio. Hydrogel samples prepared using oil soluble and water soluble initiators and the results showed that the initiator type had a great influence on monomer conversion and particle size. Effect of pH on equilibrium swelling of hydrogels was studied by dynamic light scattering and hydrogels showed pH-independent swelling behavior in a broad range of pH values. We also reported and discussed the crosslink density distribution in nanogels prepared by inverse microemulsion polymerization.     

Computational study of a latent heat thermal energy storage system enhanced by highly conductive metal foams and heat pipes

Numerical simulations are performed to analyze the thermal characteristics of a latent heat thermal energy storage system with phase change material embedded in highly conductive porous media. A network of finned heat pipes is also employed to enhance the heat transfer within the system. ANSYS-FLUENT 19.0 is used to create a transient multiphase computational model to simulate the thermal behavior of the storage unit. Copper foam is the porous medium used to enhance the heat transfer and is impregnated with the phase change material, potassium nitrate (KNO₃). The effects of the porosity of the metal foam and the quantity of heat pipes on the thermal characteristics of storage unit have been investigated. The results indicated that increasing the quantity of the embedded heat pipes leads to drastic acceleration of both charging and discharging process. Impregnating the copper foam with potassium nitrate phase change material significantly affects the total charging and discharging times of the storage unit. It was shown that the porosity of the metal foam plays a key role in the thermal behavior of the system during the charging and discharging processes.