Azomesogens with methoxyethyl tail: Synthesis and characterization

Two new mesogenic homologous series are synthesized from methoxyethyl 4-(4′-hydroxyphenylazo) benzoate. In series I the phenolic -OH group is alkylated, whereas in series II it is esterified with 4-n-alkoxybenzoyl group. In series I, all the nine members synthesized exhibit only enantiotropic smectic A mesophase. In series II, all the twelve homologues exhibit enantiotropic nematic mesophase. Smectic A mesophase appears from then-decyloxy derivative as a enantiotropic phase and persists till the last n-hexadecyloxy member. The mesomorphic properties of both the series are compared with each other and also with the properties of other structurally related series to evaluate the effect of the methoxyethyl tail on mesomorphism.     

Metal–organic frameworks (MOFs) constructed from Zn/Cd-2,2′-bipyridines and polycarboxylic acids: Synthesis,characterization and microstructural studies

Metal–organic frameworks with the compositions [Zn(bpy)(bdc)(H₂O)]_n1, [Zn(bpy)(btec)_1/2(H₂O)]_n2, [Cd(bpy)(bdc)(H₂O)]_n3 and Cd(bpy)(btec)_1/2(H₂O)]_n4 (H₂bdc = 1,4-benzenedicarboxylic acid = terephthalic acid, H₄btec = 1,2,4,5-benzenetetracarboxylic acid and bpy = 2,2′-bipyridine) have been synthesized and characterized using spectroscopic and single-crystal X-ray diffraction techniques. In these complexes, Zn^II/Cd^II-2,2′-bipyridine units and carboxylate anions exists as nodes and spacers respectively. An infinite 1D zig-zag chain structure is observed for both complexes 1 and 3, whereas complexes 2 and 4 display a 3D supramolecular architecture. The complexes are found to be photoluminescent, porous and show significant thermal stability.     

A rapid and specific approach for direct measurement of donepezil concentration in human plasma by LC-MS/MS employing solid-phase extraction

A selective, rapid and simple liquid chromatography-tandem mass spectrometry (LC-MS/MS) method is described for assay of donepezil in human plasma using escitalopram as an internal standard. Chromatographic separation was achieved on a Betabasic-C(8), 5 microm, 100 x 4.6 mm column using methanol:water:formic acid (90:9.97:0.03, v/v/v) as mobile phase. Detection of donepezil and internal standard was achieved by ESI MS/MS in positive ion mode using 380.20/91.10 and 325.13/262.00 transitions, respectively. The linearity over the concentration range of 0.15-50 ng/mL for donepezil was obtained and the lower limit of quantification was 0.15 ng/mL. For each level of quality control samples, inter-day and intra-day precisions (RSD) were < or =8.92 and 10.35% and accuracy (%RE) were < or =7.33% and 9.33%, respectively. The recovery was more than 88.50% for both donepezil and internal standard by solid-phase extraction, eliminating evaporation and reconstitution steps.     

Zinc triflate: a highly efficient reusable catalyst in the synthesis of functionalized quinolines via Friedlander annulation

An environmentally friendly and highly efficient procedure for the preparation of quinolines and fused polycyclic quinolines has been developed by a simple Friedlander annulation reaction of 2-aminoaryl ketone with carbonyl compounds in presence of zinc triflate under microwave irradiation and solvent-free conditions. The reaction also proceeds effectively when In(OTf)₃ was used in lieu of Zn(OTf)₂ as the catalyst. The catalyst can be recovered after the reaction and reused efficiently in subsequent runs.     

Synthesis and study of mesomorphic properties of unsymmetrical cyclohexanone-derived bis-chalcones

A series of (2E,6E)-2-(4-n-alkoxybenzylidene)-6-((benzo[d][1,3]dioxol-6-yl)methylene)cyclohexanones were synthesised by stepwise condensation reactions from cyclohexanone. The optical and thermal analysis of the series indicated the mesomorphic properties of some derivatives. The compounds with C7–C16 substituents showed the nematic phases in the range of 90–73°C. The single crystal X-ray analysis confirms the head to tail packing arrangement.     

Studies on 6-[(dimethylamino)methylene]aminouracil: a facile one-pot synthesis of novel pyrimido[4,5-d]pyrimidine derivatives

The reactions of 6-[(dimethylamino)methylene]aminouracil 1, with various heterocumulenes such as aryl isocyanates and isothiocyanates give rise to novel pyrimido[4,5-d]pyrimidines in excellent yields, after elimination of dimethylamine from the (1:1) cycloadducts and tautomerisation. This procedure provides a convenient method for direct synthesis of pyrimido[4,5-d]pyrimidine derivatives under thermal conditions.     

Mixed-ligand Ru(II) complexes with 2,2'-bipyridine and tetradentate Schiff bases auxiliary ligands: Synthesis, physico-chemical study, DFT analysis, electrochemical and Na+ binding properties

cis-Bis(2,2'-bipyridyl)dichlororuthenium(II)dihydrate complexed with Schiff bases salen (L1H2) and salophen (L2H2) provides complexes of compositions [Ru(L1)(bpy)2] 1 and [Ru(L2)(bpy)2] 2, respectively with cavity. The structure of these complexes characterized by spectroscopic studies were supported by their optimized geometries based on DFT calculations. Complexes 1 and 2 were then allowed to interact with methanolic solution of sodium perchlorate separately providing corresponding complexes 3 and 4 with the compositions 1.NaClO4 and 2.NaClO4, respectively. The formation constants were then evaluated by monitoring the changes in their UV-visible spectral features upon addition of different amount of sodium salts in the presence of a fixed concentration of the ruthenium complexes at a wavelength 294 nm. Emission (solution), luminescence microscopic and cyclic voltammetric studies of these complexes have also been made.     

Sustainable Synthesis of 2-Hydroxymethylbenzimidazoles using D-Fructose as a C2 Synthon

D-fructose, a biomass-derived carbohydrate has been identified as an environmentally benign C₂ synthon in the preparation of synthetically useful 2-hydroxymethylbenzimidazole derivatives by coupling with 1,2-phenylenediamines. Proof of concept was established by synthesizing 23 examples using BF₃.OEt₂ (20 mol%), TBHP (5.5 M, decane) (1.0 equiv.) in CH₃CN at 90 °C for 1 h. The pivotal features of this method include metal-free conditions, short time, good functional group tolerance, gram scale feasibility and the synthesis of benzimidazole fused 1,4-oxazine. Control studies with conventional C₂ synthons did not produce the desired product, thus suggesting a new reaction pathway from D-fructose.     

Correction: Effects of novel intake manifold design and investigation of diesel engine operating on different alternative fuels

Journal of Thermal Analysis and Calorimetry -