Dithiophosphinates of trivalent iron,ruthenium and osmium

Dithiophosphinates of Fe(III), Ru(III) and Os(III) have been prepared and their ESR studies indicate distortion from octahedral geometry. The tetragonal and rhombic splittings and the orbital reduction factors were calculated from the experimental g values for low-spin Ru(III) and Os(III) complexes. The metal-ligand covalency increases in the order Ru < Os.     

Synthesis of a novel class of steroidal tetrazolo[1,5-a]pyridines via intramolecular 1,3-dipolar cycloadditions

A facile synthesis of a novel class of steroidal A/B/D-ring annulated tetrazolo[1,5-a]pyridine derivatives has been accomplished via intramolecular 1,3-dipolar cycloaddition reaction of azide with nitrile in aprotic solvent. The synthesis of D-ring annulated tetrazolo[1,5-a]pyridine in alcohol showed incorporation of an alcohol molecule into the heterocyclic system.     

Synthesis of potassium 2,3,4-trihydroxy-2-methylbutanoate: a leaf-closing substance of Leucaena leucocephalam

Starting from citraconic anhydride (2), a six step synthesis of leaf closing substance (±)-erythro potassium 2,3,4-trihydroxy-2-methyl-butanoate (1) has been described with 29% overall yield via diesterification, OsO₄-dihydroxylation, acetonide protection, regioselective mono hydrolysis of unhindered ester moiety, borane-dimethylsulfide induced chemoselective reduction of carboxylic group and hydrolysis pathway. Surprisingly, the sodium borohydride reduction of monoester 5 and lithium borohydride reduction of 11 furnished the undesired regioisomer 7.     

Compounds of imidazoles with ruthenium(III) chloride

Summary Reaction of ruthenium(III) chloride with imidazole(Im) and different substituted imidazoles,viz. N-methylimidazole (N-MeIm), 2-methylimidazole(2-MeIm), 4-methylimidazole (4-MeIm),N-vinylimidazole(N-VIm), 2-methyl- 1-vinyl-imidazole(2-Me-1-VIm), 1,2-dimethylimidazole(1,2-Me,Im), 2-ethylimidazole(2-EtIm) and 2-ethyl-4(5)-methylimidazole (2-Et-4(5)-MeIm] yield products of the types [Ru₂L₄Cl₆] · 2 H₂O (L = N-VIm or 4-MeIm), [Ru₂L₄Cl₆] · 4 H₂O (L = Im or 2-Et-4(5)-MeIm), [Ru₂L ³ (H₂O)Cl₆] (L =N-MeIm or 2-MeIm), [Ru₂L ² (H₂O)₂Cl₆] (L = 1,2-Me₂Im or 4-MeIm), [Ru(2-Me-1-VIm)₃Cl₃] · H₂O and [Ru(2-EtIm)₃(H₂O)Cl₂]. These compounds were characterised by elemental analyses, conductometric measurements, i.r. and electronic spectral analyses. Magnetic moments range from 1.01 to 1.9 B.M. The e.s.r. spectra and g values of some of the compounds are indicative of high distortion.     

Dielectric Study on the Alignment or Orientation of N(4-n-heptyloxy benzylidene)4´-n-butylaniline and the Anomalous Dielectric Behavior in the Smectic G Phase

The present article reports on the alignment or orientation of a particular compound N(4-n-heptyloxy benzylidene)4´-n-butylaniline through dielectric study. The effect of using two different alignment layers (for homogenous alignment) and doping silver nanoparticles (0.25% by weight) on the behavior in dielectric property with varying temperature and biasing electric field was studied in terms of liquid crystal alignment or orientation using the mechanism proposed by earlier workers. The study includes the anomalous dielectric behavior in SmG phase by presenting a technique for the analysis of the absorption process, which exists only in SmG phase at fixed frequency while varying temperature, is also presented.     

Competitive anion binding aptitude of benzimidazole and amide functionality of a non-symmetrical receptor in solid state and solution phase

A novel non-symmetric tripodal receptor (L) with benzimidazole and amide –NH functionalities has been synthesised and a comparative study for anion binding aptitude of those functionalities has been performed in solid state and solution phase. The protonated receptors in solid state tend to form a pseudo-cavity around the octahedral hexafluorosilicate anion whilst in second complex, binding of one sulphate and two bisulphates in unison by two protonated units arises. The benzimidazole –NHs are the strongest hydrogen bond donors in both the crystals controlling dominance over amide –NHs. The neutral receptor being selective towards fluoride anion induces a naked eye visible colorimetric change. The ¹H NMR studies with the neutral and protonated form of the receptor suggest the strong involvement of amide –NH in anion binding in solution phase.     

Microwave assisted solid-state synthesis of functional organotin carboxylates from sterically encumbered 3,5-di-tert-butylsalicylic acid

Microwave assisted solid-state reaction between equimolar quantities of sterically encumbered 3,5-di-tert-butylsalicylic acid (H₂-DTBSA) and n-butylstannoic acid results in the formation of hexameric drum shaped stannoxane [ⁿBuSn(O)(H-DTBSA)]₆ (1). Synthesis of 1 could not be achieved under normal thermal conditions or mechanical grinding. However, the azeotropic removal of water produced in the reaction of ⁿBu₂SnO with 3,5-di-tert-butyl salicylic acid in benzene yielded the tetrameric ladder shaped stannoxane [{ⁿBu₂Sn(H-DTBSA)}₂O]₂ (2), which could also be synthesized in better yields by microwave irradiation as in the case of 1. Compounds 1 and 2 have been characterized by elemental analysis, IR, MALDI-MS and NMR (¹H and ¹³C) spectroscopy. The structures of compound 1 and 2 are determined by single crystal X-ray diffraction techniques. Compound 1 is hexameric with a Sn₆O₆ drum core while compound 2 forms a ladder structure with three Sn₂O₂ rings, both decorated with -OH functionalities on the exterior of the polyhedral structure. While the formation of 1 from n-butylstannoic acid is straightforward, the formation of 2 from nBu₂SnO (and not a cyclic structure similar to 3, where the phenolic oxygen also coordinates to tin) can be understood in terms of the increased steric hindrance in DTBSA for the phenolic protons to react with tin.     

Enantioselective Synthesis of C−O Axially Chiral Diaryl Ethers by NHC-Catalyzed Atroposelective Desymmetrization**

Axially chiral diaryl ethers, a distinguished class of atropisomers possessing unique dual C−O axis, hold immense potential for diverse research domains. In contrast to the catalytic enantioselective synthesis of conventional single axis bearing atropisomers, the atroposelective synthesis of axially chiral ethers containing flexible C−O axis remains a significant challenge. Herein, we demonstrate the first N-heterocyclic carbene (NHC)-catalyzed synthesis of axially chiral diaryl ethers via atroposelective esterification of dialdehyde-containing diaryl ethers. Mechanistically, the reaction proceeds via NHC-catalyzed desymmetrization strategy to afford the corresponding axially chiral diaryl ether atropisomers in good yields and high enantioselectivities under mild conditions. The derivatization of the synthesized product expands the utility of present strategy via access to a library of C−O axially chiral compounds. The temperature dependency and preliminary investigations on the racemization barrier of C−O bonds are also presented.     

Long Afterglow Room‐Temperature Phosphorescence from Nanopebbles: A Urea Pyrolysis Product

Materials having long afterglow are highly sought after for various applications such as light‐emitting diodes, security signs and bioimaging. Herein, we report a simple, low‐cost synthesis of a purely organic room‐temperature phosphorescent nanomaterial with a pebble‐like structure by heating urea, a biocompatible and easily available precursor, at 200 °C with a high phosphorescence lifetime of 1.0365 s and a visible afterglow for up to 10 s. This urea derived phosphorescent nanocomposite (UPNC) can be mixed with commercially available acrylic paint base and common gum, which can be readily used as a phosphorescent pigment.     

Transport and stability studies on high band gap a-Si:H films prepared by argon dilution

Device quality hydrogenated amorphous silicon films (a-Si:H) are deposited at a high deposition rate (4–5 Å/s) using a mixture of argon and hydrogen-diluted silane. The films exhibit good opto-electronic properties and show less degradation upon light soaking. Light-induced changes in conductivity could be annealed at much lower temperature. The presence of Ar^* and atomic hydrogen in plasma replaces the weak Si-Si bonds, which are responsible for light-induced degradation by strong Si-Si bonds. This results in the improved stability of the films.