A new class of alkyl-chain-appended pyrene derivatives 4-14 were synthesized and evaluated for their gelation abilities. Depending on the nature of the linking group, these compounds gelated a number of organic solvents, either in the presence or in the absence of the acceptor molecule 2,4,7-trinitrofluorenone (TNF). Compounds with ester, ether, or alkyl linkages gelated a number of hydroxylic and hydrocarbon solvents by means of a charge-transfer interaction with TNF, while compounds with amide, urethane and urea linkers formed gels on their own in a variety of solvents by means of pi-pi stacking and hydrogen-bonding interactions. The Xray crystal structure of urethane (S)-12 showed hydrogen-bonding and stacking features, as suggested by the model. The gels obtained were investigated by spectroscopic and electron microscopic techniques which provided structural insights.
Summary: This article describes some of the exciting results obtained during the study of the gelation behavior of bile acid derivatives in the authors laboratory. The serendipitous discovery of charge-transfer interaction promoted gelation of organic solvents by (steroid)pyrene derivatives/TNF is presented. In this class of molecules, the effect of the location of the chiral center in chiral gelators on the overall chirality of the aggregates in the gel was studied. Also described are the aggregation behavior of bile acid based aqueous gelators which led us to postulate design principals to obtain bile acid based aqueous/organogelators.
Rechargeable magnesium batteries
are of considerable interest due
to their high theoretical capacity, and they are projected as good
alternates for stationary energy storage and electric vehicles. Sluggish
Mg2+ kinetics and scarce availability of suitable cathode
materials are major issues hindering the progress of rechargeable
magnesium batteries. Herein, a conjugated, off-planar, two-dimensional
(2D) polymer is explored for reversible magnesium storage. The polymer
cathode reveals high capacity and high cycling stability with high
rate capability. Replacing the Mg metal anode with the Mg alloy, AZ31
further enhances the ion storage performance. At a high current density
of 2 A g–1, stable capacity is shown for almost
5000 cycles with 99% Coulombic efficiency. A composite of carbon nanotube
with the polymer delivers capacity values higher (>1.5 times) than
that of a pristine polymer at a current density of 2 A g–1 and shows cycling up to 5 A g–1. Electrokinetic
studies reveal a contribution of pseudocapacitive nature, and the
mechanism is investigated by ex situ X-ray photoelectron spectroscopy
and infrared spectroscopy. The use of 2D polymer electrodes opens
up opportunities for developing high-rate, high-capacity, and stable
rechargeable magnesium ion batteries.
A new class of 23- and 24-phosphonobile acids have been synthesized from bile acid and their in vitro cholesterol-dissolving efficiency have been estimated. 24-Phosphonobile salts (PBSs) are slightly more efficient in solubilizing cholesterol than 23-PBSs and natural bile salts. The cholesterol solubilizing power is influenced by the structure of PBSs, and is considerably reduced with an increase in the bulk pH.
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