Synthesis of a cyclic dinuclear organotin carboxylate via simultaneous debenzylation and decarbonylation reactions: X-ray crystal structure of [(PhCH2)2{O2CC6H4{N(H)N(C6H3-4(O)-5-O)}-o}Sn]2

The complex, [(PhCH₂)₂{O₂CC₆H₄{N(H)N(C₆H₃-4(O)-5-O)}-o}Sn]₂ (1), is obtained as the exclusive reaction product from the reaction of sodium 2-[(E)-2-(3-formyl-4-hydroxyphenyl)-1-diazenyl]benzoate and (PhCH₂)₃SnCl. The reaction possibly proceeds via Dakin type rearrangements where arylazosalicylaldehyde is oxidized to arylazocatechol, followed by facile Sn-C bond cleavage. Complete assignments were achieved by ¹H, ¹³C, 2D ¹H-¹¹⁹Sn HMQC (¹¹⁹Sn chemical shift), 1D gs ¹H-¹⁵N HMQC (¹J(¹⁵N, ¹H) coupling constant) NMR and ESI-MS. The crystal structure of compound 1 as determined by X-ray diffraction analyses shows a cyclic centrosymmetric dinuclear moiety linked into extended chains by pairs of long Sn?O contacts of approximately 3.2 Å. Two polymorphs were identified and their structures differ primarily in the packing arrangement afforded by the benzyl groups. In one polymorph, when viewed along the Sn?Sn vector, the benzyl groups at each Sn-atom are oriented to form an S-shape, while they form a U-shape in the second polymorph.     

Synthesis of arene ruthenium triazolato complexes by cycloaddition of the corresponding arene ruthenium azido complexes with activated alkynes or with fumaronitrile

The neutral arene ruthenium azido complexes [(η⁶-p-cymene)Ru(LL)(N₃)], [LL = acetylacetonato (acac) (4), benzoylacetonato (bzac) (5) diphenylbenzoyl methane (dbzm) (6)] undergo [3+2] cycloaddition reaction with a series of activated alkynes and fumaronitrile to produce the arene ruthenium triazolato complexes: [(η⁶-p-cymene)Ru(LL){N₃C₂(CO₂R)₂}] [LL = (acac), R = Me (7); LL = (bzac), R = Me (8); LL = (dbzm), R = Me (9); LL = (acac), R = Et (10); LL = (bzac), R = Et (11); LL = (dbzm), R = Et (12) and [(η⁶-p-cymene)Ru(LL)(N₃C₂HCN)]; LL = acac (13), bzac (14); dbzm (15). However, cationic azido complexes, [(η⁶-p-cymene)Ru(dppe)(N₃)]⁺ and [(η⁶-p-cymene)Ru(dppm)(N₃)]⁺ do not undergo such cycloaddition reactions. The complexes were characterized on the basis of microanalyses, FT-IR and NMR spectroscopic data. Crystal structures of representative complexes were determined by single crystal X-ray diffraction.     

Temperature-dependent vibrational spectroscopic studies of pure and gold nanoparticles dispersed 4-n-Hexyloxy-4’-cyanobiphenyls

Raman spectra of pure and 2 wt.% gold nanoparticles (GNPs) dispersed liquid crystalline compound 4-n-Hexyloxy-4?- cyanobiphenyls (6OCB) has been recorded as a function of temperature from room temperature (solid crystal) to 80°C (isotropic liquid) in the spectral region of 500–2500 cm^?1. The variation of Raman spectral parameters (peak positions and line width) with temperature is used to explain the changes in molecular alignment and its effect on inter-/intra-molecular interactions at crystal-Nematic (K-N) transition. To understand the change in molecular structure during phase transition and on account of dispersion of gold nanoparticles in pure liquid crystal more precisely, two spectral regions 1000–1500 cm^?1 and 1500–2400 cm^?1 have been selected separately. From the detailed study, it is concluded that increased orientational/vibrational freedom of the molecules as well as delocalisation of electron clouds results in the spectral anomalies at K-N transition. The geometrical structure of 6OCB was optimised using density functional theory (DFT) and theoretical Raman spectra have been obtained for comparison with experimental spectra. The tentative assignment of vibrational modes observed in our region of study was calculated based on potential energy distribution (PED) using vibrational energy distribution analysis (VEDA) calculation.     

Withania somnifera root extracts induce skin darkening in wall lizard melanophores via stimulation of cholinergic receptors

The effects of the root extract of Withania somnifera and its active ingredient Withaferin A on the isolated melanophores of the wall lizard H. flaviviridis were studied in order to establish the mechanism of skin darkening at the cellular level. Significant skin darkening activity of the extract of W. somnifera and Withaferin A was observed on the isolated melanophores of the wall lizard. The melanin dispersal effects leading to the darkening of the skin were antagonised by atropine and hyoscine, and were also found to be highly potentiated by neostigmine. These findings suggest that the extract of W. somnifera, as well as its active principle, mimic the action of acetylcholine in melanin dispersion, thus leading to skin darkening via stimulation of cholinergic receptors of muscarinic nature within the melanophores of the wall lizard.     

Determination of antihelminthic drug pyrantel pamoate in bulk and pharmaceutical formulations using electro-analytical methods

Electrochemical behaviour of pyrantel pamoate has been studied by using different voltammetric and polarographic techniques in Britton Robinson buffer system. Differential pulse polarographic and cyclic voltammetric methods have been developed for the determination of drug in pharmaceutical formulation. A well-defined cathodic wave and one anodic peak were observed for the pyrantel pamoate in the entire pH range. Number of electrons transferred in the reduction process was calculated and the reduction mechanism postulated. The results indicate that the electrode process is reversible and diffusion controlled. The proposed method has been validated. The peak current is found to be linear over the concentration range 4 × 10⁻⁴ to 2 × 10⁻² mol L⁻¹. The lower detection limit (LOD) and lower limit of quantitation (LOQ) is found to be 2.45 × 10⁻⁵ and 8 × 10⁻⁵ mol L⁻¹.     

Mono and dinuclear arene ruthenium(II) triazoles by 1,3-dipolar cycloadditions to a coordinated azide in ruthenium(II) compounds

The dimeric η(6)-hexamethylbenzene ruthenium(II) triazole compounds of formulation [{(η(6)-C(6)Me(6))Ru(N(3)C(2)(CO(2)R)(2))}(2)(μC(2)O(4))] have been synthesized by 1,3-diploar cycloadditions of coordinated azido compound [{(η(6)-C(6)Me(6))Ru(L(1))N(3)}] (1) with substituted acetylene, RO(2)CC(2)CO(2)R via unexpected oxidation of the coordinated ligand to oxalate (where; L(1) = 5-hydroxy-2-(hydroxymethyl)-4-pyrone; R = Me, 3 or Et, 4). In contrast, a similar 1,3-dipolar cycloaddition reaction of [{(η(6)-C(6)Me(6))Ru(L(2))N(3)}] (2) (where; L(2) = tropolone) with acetylene yielded the monomeric triazole compound [(η(6)-C(6)Me(6))Ru(L(2)){N(3)C(2)(CO(2)R)(2)}] (where; R = Me, 5; Et, 6). The compounds were characterized by spectroscopy and the structures of representative compounds 4 and 6 have been determined by single crystal X-ray diffraction. The two ruthenium centres in the compound 4, are linked by a tetra-dentate oxalate group. Both compounds, 4 and 6, crystallized in a triclinic space group P-1.     

Temperature-dependent Raman study of pure and silver nanoparticles dispersed N-(4-n-heptyloxybenzylidene)-4’-n-butylaniline (7O.4)

Temperature-dependent micro-Raman study of C-H in-plane bending mode of aromatic rings, C-N and C=N stretching of linking group (-C(H)=N) and C=C stretching of rings of pure and silver nanoparticles dispersed (0.5% and 1% by weight) Schiff’s base liquid crystal (LC) compound, N-(4-n-heptyloxybenzylidene)-4’-n-butylaniline (7O.4) in 500–2250 cm^?1 region has been done. The change in Raman spectral parameters (peak position and linewidth) at crystal–smecticG (K–smG) and smecticG–smecticC (smG–smC) gives the evidence of charge shift at phase transition which is associated with changes in orientation and vibrational freedom of the molecules. The peak position of the Raman bands shows blue shift for 0.5 wt% dispersed sample, whereas it shows red shift for 1 wt% dispersed sample. The blue and red shifts of the Raman bands indicate an increase and decrease in the charge density, respectively. The optimised structure and theoretical room temperature Raman spectra of 7O.4 were obtained using density functional theory. The vibrational assignment using potential energy distribution is reported using vibrational energy distribution analysis (VEDA).     

Embryotoxicity studies of tri‐n‐butyltin(IV) complexes of 5‐[(E)‐2‐(aryl)‐1‐diazenyl]‐2‐hydroxybenzoic acid and 2‐[(E)‐2‐(3‐formyl‐4‐hydroxyphenyl)‐1‐diazenyl] benzoic acid on sea urchin development

The toxicity studies of free 5‐[(E)‐2‐(aryl)‐1‐diazenyl]‐2‐hydroxybenzoic acid and 2‐[(E)‐2‐(3‐formyl‐4‐hydroxyphenyl)‐1‐diazenyl]benzoic acid and their tri‐n‐butyltin(IV) complexes were evaluated by using sea urchin early developmental stages as recommended model organisms for toxicity tests. The novel complexes, as the parent tri‐n‐butyltin(IV) chloride (TBTCl), caused mitosis block and induced high embryonic mortality in sea urchin. Copyright © 2005 John Wiley & Sons, Ltd.     

Ruthenium(II)-catalyzed synthesis of 2-arylbenzimidazole and 2-arylbenzothiazole in water

Transition Metal Chemistry - Benzimidazoles/benzothiazoles are heterocyclic compounds which contain a five membered heteroatom and a benzene ring. They constitute a crucial structural unit of...     

Isolation and X-ray structure of deoxycholic acid from the sponge Ircinia sp

Ethyl acetate extract of the sponge Ircinia sp., collected by SCUBA divers off the coast of southern India, contained a cholest-based sterol of insignificant antimicrobial activity, with one carboxylic acid side chain (3alpha, 7beta-dihydroxy-5beta-cholan-24-oic acid, DCA). The structure of the compound was determined by spectroscopic data and single crystal X-ray diffraction studies. DCA crystallizes in the tetragonal space group P4(1)2(1)2, chirality documented by solution optical rotation [alpha]D = +67.4 degrees (c 0.16, CHCl3).