One step synthesis of highly crystalline and high coercive cobalt-ferrite nanocrystals

Highly crystalline and almost monodisperse spinel cobalt-ferrite nanocrystals are synthesized in a one step process, which has very high coercivity at 10 K and exhibits superparamagnetic behaviour at 300 K.     

Trichosanthes dioica root possesses stimulant laxative activity in mice

Trichosanthes dioica Roxb. (Cucurbitaceae), named 'pointed gourd' in English, is a dioecious climber grown in India. This study was aimed at evaluating the laxative activity of the aqueous extract of T. dioica root (TDA) in Swiss albino mice. The laxative activity of TDA (100 and 200?mg?kg(-1) body weight per os) was evaluated by assessing the excretory bowel activities in naive (non-constipated) and in drug (loperamide)-induced constipation in mice. Further, the gastrointestinal transit was measured in both naive and in constipated mice. Castor oil (0.5?mL/mouse per os) was used as the reference. TDA significantly and dose-dependently increased all the excretory bowel activities and gastrointestinal transit in both naive and constipated mice. TDA at 200?mg?kg(-1) body weight was found to be the most active, causing diarrhoea in mice. Thus, T. dioica root demonstrated stimulant laxative activity in Swiss mice, validating its traditional usage in India.     

New iridoid from aerial parts of Mussaenda roxburghii

A new iridoid, shanzhiol (1), was isolated from the aerial parts of Mussaenda roxburghii. The structure was established by spectroscopic (including 2D NMR) and chemical methods. Shanzhiol (1) showed mild antibacterial activity against both Staphylococcus aureus and Escherichia coli with a MIC of 100 microg/mL by the broth dilution method.     

Lithium ion-ketocyanine dye interactions in the ground and excited states

Electronic absorption and emission spectral characteristics of a ketocyanine dye have been studied in solution in the presence of lithium perchlorate. Absorption spectral studies indicate complex formation between lithium ion and the dye in the ground state. The value of the equilibrium constant along with the molar absorbance of the absorbing species has been determined for the dye-cation interaction. The energy of maximum fluorescence shifts toward the red with the addition of LiClO(4). Steady-state emission studies point to the existence of two emitting species, viz., the solvated and the complexed dye in equilibrium. The values of the equilibrium constant for the process have been determined in acetone and acetonitrile. Time-resolved studies in the picosecond domain in pure solvents reveal that the lifetime (tau) value increases as the solvation interaction increases. Time-resolved studies also indicate the presence of two emitting species in equilibrium.     

A facile two-step chemoenzymatic access to natural germination inhibitor (+)-erigeronic acid A

A facile two-step synthesis of natural germination inhibitor 5-butyl-3-oxo-2,3-dihydrofuran-2-yl-acetic acid [(+)-erigeronic acid A, 1] has been described via highly regioselective ring opening of (R)-acetoxysuccinic anhydride with the primary enolate of butyl methyl ketone, followed by an enzymatic hydrolysis and an in situ dehydrative cyclization pathway with 77% overall yield. On the basis of the present chemoenzymatic approach, (R)-configuration has been assigned to the C-2 chiral centre of the natural erigeronic acid.     

Effects of axial coordination on the Ru-Ru single bond in diruthenium paddlewheel complexes

The 1,8-naphthyridine-based (NP-based) ligands with furyl, thiazolyl, pyridyl, and pyrrolyl attachments at the 2-position have been synthesized. Reactions of 3-MeNP (3-methyl-1,8-naphthyridine), fuNP (2-(2-furyl)-1,8-naphthyridine), tzNP (2-(2-thiazolyl)-1,8-naphthyridine), pyNP (2-(2-pyridyl)-1,8-naphthyridine), and prNP(-1) (2-(2-pyrrolyl)-1,8-naphthyridine) with [Ru2(CO)4(CH3CN)6]2+ lead to [Ru2(3-MeNP)2(CO)4(OTf)2] (1), [Ru2(fuNP)2(CO)4]2[BF4]2 (2), [Ru2(tzNP)2(CO)4][ClO4]2 (3), [Ru2(pyNP)2(CO)4][OTf]2 (4), and [Ru2(prNP)2(CO)4] (5). The molecular structures of complexes 1-5 have been established by X-ray crystallographic studies. The modulation of the Ru-Ru single-bond distances with axial donors triflates, furyls, thiazolyls, pyridyls, and pyrrolyls has been examined. A small and gradual increase in the Ru-Ru distance is measured with various donors of increasing strengths. The shortest Ru-Ru distance of 2.6071(9) angstroms is observed for the axially coordinated triflates in complex 1, and the longest Ru-Ru distance of 2.6969(10) angstroms is measured for axial pyrrolyls in complex 5. The Ru-Ru distances in complexes 3 (2.6734(7) angstroms) and 4 (2.6792(9) angstroms), having thiazolyls and pyridyls at axial sites respectively, are similar. The Ru-Ru distance for axial furyls in complex 2 (2.6261(9) angstroms) is significantly shorter than the corresponding distances in 3, 4, and 5. DFT calculations provide insight into the interaction of the Ru-Ru sigma orbital with axial donors. The Ru-Ru sigma orbital is elevated to a higher energy because of the interaction with axial lone pairs. The degree of destabilization depends on the nature of axial ligands: the stronger the ligand, higher the elevation of Ru-Ru orbital. The lengthening of Ru-Ru distances with respect to the axial donors in compounds 1-5 follows along the direction pyrrolyl > pyridyl approximately thiazolyl > furyl > triflate, and the trend correlates well with the computed destabilization of the Ru-Ru sigma orbitals.     

Radical-mediated opening of 2,3-epoxy alcohols using Cp2TiCl: stereoselective construction of quaternary chiral centers

Radical-mediated opening of chiral 2,3-epoxy alcohols regioselectively at the 2-position using Cp2TiCl and trapping the intermediate radical with methyl acrylate and acrylonitrile led to the stereoselective formation of tetrasubstituted chiral centers.     

Adaptive dendron: a bile acid oligomer behaving as both normal and inverse micellar mimic

[reaction: see text]. The normal and inverse micellar property of a bile-acid-based dendritic structure was established through dye solubilization studies in both polar and nonpolar media.     

Comparative photophysical behaviour of naphthalene-linked crown ethers and aza crown ethers of varying cavity dimensions

A comparative time-resolved emission studies of several naphtho-crown ethers I–V, where metal ions can be complexed in a predetermined orientation with respect to the naphthalene (Naph) π-plane and naphthalene-linked aza crown ethers (L1 and L2) have been presented. In both the systems, crown ethers and aza crown ethers, naphthalene fluorescence gets quenched. In the systems I to V, the quenching is mainly due to efficient spin-orbit coupling (SOC) leading to greater population of the lowest triplet state of naphthalene. This SOC depends on the orientation of the crown ring with respect to the Naph-π-plane. However, in the systems L1 and L2, the quenching is due to photoinduced electron transfer (PET) from nitrogen lone pair of the aza crown ring to naphthalene moiety and consequent exciplex formation. The results have been interpreted using the time-resolved emission studies of all the compounds in various solvents, their alkali metal ion complexes, and protonated ligands.