Study of half sandwich platinum group metal complexes containing tetradentate N-donor ligand bearing two di-pyridylamine units linked by an aromatic spacer

A general approach for the preparation of dinuclear η⁵- and η⁶-cyclic hydrocarbon platinum group metal complexes, viz. [(η⁶-arene)₂Ru₂(NN∩NN)Cl₂]²⁺ (arene = C₆H₆, 1; p-ⁱPrC₆H₄Me, 2; C₆Me₆, 3), [(η⁵-C₅Me₅)₂M₂(NN∩NN)Cl₂]²⁺ (M = Rh, 4; Ir, 5), [(η⁵-C₅H₅)₂M₂(NN∩NN)(PPh₃)₂]²⁺ (M = Ru, 6; Os, 7), [(η⁵-C₅Me₅)₂Ru₂(NN∩NN)(PPh₃)₂]²⁺ (8) and [(η⁵-C₉H₇)₂Ru₂(NN∩NN)(PPh₃)₂]²⁺ (9), bearing the bis-bidentate ligand 1,2-bis(di-2-pyridylaminomethyl)benzene (NN∩NN), which contains two chelating di-pyridylamine units connected by an aromatic spacer, is reported. The cationic dinuclear complexes have been isolated as their hexafluorophosphate or hexafluoroantimonate salts and characterized by use of a combination of NMR, IR and UV-vis spectroscopic methods and by mass spectrometry. The solid state structure of three derivatives, [2][SbF₆]₂, [3][PF₆]₂ and [4][PF₆]₂, has been determined by X-ray structure analysis.     

Synthesis and properties of amphiphilic photoresponsive gelators for aromatic solvents

A sugar-based photoresponsive supergelator, N-glycosylazobenzene that shows selective gelation of aromatic solvents is described. The partial trans-cis isomerization of the azobenzene moiety allows photoinduced chopping of the entangled gel fibers to short fibers, resulting in controlled fiber length and gel-sol transition. The gelator is useful for the selective removal of toxic aromatic solvents from water.     

Micellization behavior of aromatic moiety bearing hybrid fluorocarbon sulfonate surfactants

Aggregation behavior and thermodynamic properties of two novel homologous aromatic moiety bearing hybrid fluorocarbon surfactants, sodium 2-(2-(4-ethylphenyl)-1,1,2,2-tetrafluoroethoxy)-1,1,2,2-tetrafluoroethanesulfonate (1) and sodium 2-(1,1,2,2-tetrafluoro-2-(4-vinylphenyl)ethoxy)-1,1,2,2-tetrafluoroethanesulfonate (2) were studied using surface tension measurements and isothermal titration calorimetry (ITC) in dilute aqueous solutions at room temperature. Because of the aromatic group in the hydrophobic tail, both surfactants are soluble at room temperature unlike their starting precursor, 5-iodooctafluoro-3-oxapentanesulfonate as well as several other fluorocarbon sulfonic acid salts. Moreover, the surfactant 2 has the ability that it can be polymerized once microemulsions are formed with it. The ionic conductivity measurements of 1 at five different temperatures from 288 to 313 K were carried out to study the effect of temperature on the micellization and its thermodynamics. The pseudophase separation model was applied to estimate thermodynamic quantities from conductivity data. The Gibbs energy of micellization versus temperature exhibited the characteristic U-shaped behavior with a minimum at 306 K. The micellization process was found to be largely entropy driven. Because of its hybrid structure, the entropy change of micellization for 1 was larger than what is common for hydrocarbon surfactants like SDS but less than for fully fluorinated surfactants like NaPFO. The micellization process was found to be following the entropy-enthalpy compensation phenomena.     

Phenolic compounds from the aerial parts of Diplomorpha canescens

One new C-methyl flavanone glucoside, farrerol 4'-O-β-D-glucopyranoside (1) was isolated from the aerial parts of Diplomorpha canescens (MEISN.) C. A. MEYER. Fourteen known phenolic compounds such as farrerol (2), luteolin 7-methyl ether 5-O-β-D-glucopyranoside (3), (-)-pinoresinol (4), (-)-lariciresinol (5), (-)-dihydrosesamin (6), (±)-dehydrodiconiferyl alcohol (7), rutarensin (8), umbelliferone (9), coniferyl aldehyde (10), sinapyl aldehyde (11), p-coumaric acid methyl ester (12), p-hydroxybenzaldehyde (13), p-hydroxyacetophenone (14) and syringaldehyde (15) were also isolated for the first time from this plant. Structure of 1 was determined on the basis of spectroscopic data including two dimensional (2D)-NMR, circular dichroism (CD) and by the application of Klyne's rule.     

Identification and structural elucidation of two process impurities and stress degradants in darifenacin hydrobromide active pharmaceutical ingredient by LC-ESI/MS(n)

The present study describes the identification and characterization of two process impurities and major stress degradants in darifenacin hydrobromide using high performance liquid chromatography (HPLC) analysis. Forced degradation studies confirmed that the drug substance was stable under acidic, alkaline, aqueous hydrolysis, thermal and photolytic conditions and susceptible only to oxidative degradation. Impurities were identified using liquid chromatography coupled with ion trap mass spectrometry (LC-MS/MS(n)). Proposed structures were unambiguously confirmed by synthesis followed by characterization using nuclear magnetic resonance spectroscopy (NMR), infrared spectroscopy (IR) and elemental analysis (EA). Based on the spectroscopic, spectrometric and elemental analysis data, the unknown impurities were characterized as 2-{1-[2-(2,3-dihydrobenzofuran-5-yl)-2-oxo-ethyl]-pyrrolidin-3-yl}-2,2-diphenylacetamide (Imp-A), 2-[1-(2-benzofuran-5-yl-ethyl)-pyrrolidin-3-yl]-2,2-diphenylacetamide (Imp-B), 2-{1-[2-(2,3-dihydrobenzofuran-5-yl)-ethyl]-1-oxy-pyrrolidin-3-yl}-2,2-diphenylacetamide (Imp-C) and 2-{1-[2-(7-bromo-2,3-dihydrobenzofuran-5-yl)-ethyl]-pyrrolidin-3-yl}-2,2-diphenylacetamide (Imp-D). Plausible mechanisms for the formation and control of these impurities have also been proposed. The method was validated as per regulatory guidelines to demonstrate specificity, sensitivity, linearity, precision, accuracy and the stability-indicating nature. Regression analysis showed a correlation coefficient value greater than 0.99 for darifenacin hydrobromide and its impurities. The accuracy of the method was established based on the recovery obtained between 86.6 and 106.7% for all impurities.     

Comparative Study of Natural Terpenoid Precursors in Reactive Plasmas for Thin Film Deposition

If plasma polymer thin films are to be synthesised from sustainable and natural precursors of chemically heterogeneous composition, it is important to understand the extent to which this composition influences the mechanism of polymerisation. To this end, a well-studied monoterpene alcohol, terpinen-4-ol, has been targeted for a comparative study with the naturally occurring mix of terpenes (viz. Melaleuca alternifolia oil) from which it is commonly distilled. Positive ion mode mass spectra of both terpinen-4-ol and M. alternifolia oil showed a decrease in disparities between the type and abundance of cationic species formed in their respective plasma environments as applied plasma power was increased. Supplementary biological assay revealed the antibacterial action of both terpinen-4-ol and M. alternifolia derived coatings with respect to S. aureus bacteria, whilst cytocompatibility was demonstrated by comparable eukaryotic cell adhesion to both coatings. Elucidating the processes occurring within the reactive plasmas can enhance the economics of plasma polymer deposition by permitting use of the minimum power, time and precursor pre-processing required to control the extent of monomer fragmentation and fabricate a film of the desired thickness and functionality.     

Synthesis and biological evaluation of some new class of benzothiazole–pyrazole ligands containing arene ruthenium,rhodium and iridium complexes

Transition Metal Chemistry - Metal complexes 1–9 have been synthesized by reacting the benzothiazole–pyrazole derivative ligands (L1, L2 and L3) with the metal precursors of ruthenium...     

Heteropoly acid catalyzed synthesis of 8-methyl-2-aryl/alkyl-3-oxabicyclo[3.3.1]non-7-ene derivatives through (3,5)-oxonium-ene reaction

A variety of aldehydes undergo a smooth coupling with (4-methylcyclohex-3-en-1-yl)methanol in the presence of 2 mol % of phosphomolybdic acid in dichloromethane to afford 3-oxabicyclo[3.3.1]non-7-ene in good yields through 3,5-oxonium-ene cyclization under mild conditions. The use of inexpensive, nontoxic, and readily available heteropoly acid catalyst makes this method simple, convenient, and environmental-friendly.     

Synthesis of thiadiazoles,triazoles and oxadiazoles from sulfonyl acetic acids via a common route

A new class of five membered heterocycles, thiadiazoles, triazoles and oxadiazoles were prepared from sulfonyl acetic acids via acid hydrazides.     

Novel deoxygenation reaction of epoxides by indium

[reaction: see text] A novel, mild, ecofriendly protocol for the deoxygenation of epoxides to alkenes using indium metal and indium(I) chloride or ammonium chloride in alcohol has been developed. It was necessary for the presence of good radical-stabilizing groups adjacent to the oxirane ring for the deoxygenation reaction to occur. It is proposed that this reaction occurs through an SET process with indium as an electron donor.