Arijit Chakraborty

In(OTf)3—A New Efficient Lewis Acid Catalyst for Stereoselective C-Glycosylation Reactions of Glycal Derivatives

Abstract A variety of glycal derivatives reacted smoothly with allyltrimethylsilane and trimethylsilylcyanide in neat condition as well as in dichloromethane in the presence of 2–5 mol% of In(OTf)3 affording the corresponding 2,3-unsaturated C-glycosides in excellent yields and moderate to excellent α-selectivities.

Aryl 4,6-O-arylidene-1-thio-β-d-glycopyranoside-based new organogelators and their gels

Aryl 4,6-O-arylidene-1-thio-beta-d-glycopyranosides based on glucose and galactose form organogels in benzene, toluene, o- and p-xylene and 1,2,3,4-tetrahydronaphthalene. The gel morphologies of micro and nano dimensions were studied using SEM and TEM. Absorption spectroscopic studies of two organogels in benzene revealed that CH-pi or pi-stacking along with intermolecular H-bonding is responsible for the gel assembly.

Coumarin based colorimetric and fluorescence on-off chemosensor for F−, CN− and Cu2 + ions

(E)-4-Chloro-3-[{2-(4-nitrophenyl)hydrazono}methyl]-2H-chromen-2-one (C), a coumarin derivative has been studied toward its ion sensing properties for F-, CN- and Cu2+. A proton-transfer mechanism for F- sensing has been deduced with the help of 1H NMR titration alongwith from the changes in the absorption and emission spectra of C in the presence of F-. C formed 1:1 stoichiometric complex with each of these analytes. Sensing of C toward Cu2+ is poor, but interestingly in the presence of F-or CN- the sensing ability of Cu2+ gets enhanced many folds, and C can act as F-or CN- mediated off-on sensor for Cu2+. Moreover, colorimetric strip (pre-coated with the coumarin derived compound) tests for F-and CN- from their DMSO solution at high temperature (~100°C) opens up the door for easiest naked eye recognition and distinction of these ions, and also for naked-eye detection of F- and CN- from its aqueous solution at high temperature (~100°C).

Perimidine based selective colorimetric and fluorescent turn-off chemosensor of aqueous Cu2+: studies on its antioxidant property along with its interaction with calf thymus-DNA

We have developed a perimidine based simple and easily synthesised chemosensor, 1,3-bis(2,3-dihydro-1H-perimidin-2-yl)benzene (1), which exhibits selective colorimetric and fluorescence “turn off” response toward nano molar Cu2+. This method allows a sensitive readout of chemosensor 1 within a wide linear range of (5–2771) × 10−8 M at λmax 346 nm, and with limit of detection (LOD) 6.19 × 10−8 M. Moreover, 1 exhibits free radical scavenging ability, six times better than that of L-ascorbic acid. The binding interaction studies of 1 with calf-thymus DNA (CT-DNA) indicate a groove binding mode.

Carbohydrate Derived Organogelators and the Corresponding Functional Gels Developed in Recent Time

Owing to their multifarious applicability, studies of molecular and supramolecular gelators and their corresponding gels have gained momentum, particularly in the last two decades. Hydrophobic–hydrophilic balance, different solvent parameters, gelator–gelator and gelator–solvent interactions, including different noncovalent intermolecular interactive forces like H-bonding, ionic interactions, π–π interactions, van der Waals interactions, etc., cause the supramolecular gel assembly of micro and nano scales with different types of morphologies, depending on the gelator, solvent, and condition of gelation. These gel structures can be utilized for making template inorganic superstructures for potential application in separation, generation of nanocomposite materials, and other applications like self-healing, controlled drug encapsulation, release and delivery, as structuring agents, oil-spill recovery, for preparation of semi-conducting fabrics, and in many other fields. Sugars, being easily available, inexpensive, and nontoxic natural resources with multi functionality and well-defined chirality are attractive starting materials for the preparation of sugar-based gelators. This review will focus on compilation of sugar derived organogelators and the corresponding gels, along with the potential applications that have been developed and published recently between January 2015 and March 2018.