ABSTRACT
Coumarin carbamates with cholesteryl group 1 and 2 have been designed, synthesized and characterized. The isomeric compounds show different gelation behaviors in organic solvents such as toluene and CH3 CN. Rheological studies reveal the different viscoelastic properties of the gels. Gels of the isomers differ in morphology. While an intertwined fibre-like structure is noted for the toluene gel of 1, rod like fibres are observed for toluene gel of 2. The positional alteration of carbamate group around coumarin changes the polarity of the isomers and hence influences the packing of molecules to establish different 3D networks for gel formation as explained by DFT study. Gels of the isomers show multiple applications with different attributes. Toluene gel of 1 is found to be F- -responsive and undergoes gel-to-sol phase transition due to the disruption of intermolecular hydrogen bonding through deprotonation. Under the condition, toluene gel of 2 is anion stable. Compound 1 also shows measurable interaction with F- over other anions in CH3 CN as interpreted by UV-vis and emission spectral changes. Based on phase-selective gelation (PSG) property, both 1 and 2 is deployed to remove cationic dye from water. Further, only gelator 2 is useful for oil spill recovery, whereas isomer 1 is not suitable in this regard.
Subject(s)
Petroleum Pollution , Carbamates , Coumarins , Gels/chemistry , Solvents/chemistry , Toluene/chemistry , Water/chemistryABSTRACT
Visible light is used to generate heat from gold nanoparticles wrapped in an amphiphilic polymer shell and trigger a reverse Diels-Alder reaction of a 'caged' tyrphostin therapeutic agent. The hydrophilic nature of the released agent results in it travelling from the polymer to the bulk medium, while the byproduct of the reaction is trapped in the hydrophobic layer of the nano-assembly.
ABSTRACT
Hydrazine (N2H4) is one of the commonly used chemical reagents in numerous industries and applications but its toxicity to humans poses a need to develop simple visual detection methods. Herein, we demonstrate a novel dual-mode system to detect and simultaneously consume hydrazine in vapour and solution by using a small photoresponsive molecule that has altered optical response (both colourimetric and fluorescent) after reacting with hydrazine.
ABSTRACT
Compounds 1, 2 and 3 with a common strategy of variation of substituent at the 4-position of naphthalimide have been designed and synthesized. Of the three structures, compound 1 has been established as F- sensor in CH3CN involving a color change from colorless to pink. The pink color is discharged in the presence of water or any polar protic solvent. By comparison, while compound 3 did not show any response towards anions, compound 2 under identical conditions exhibited color change from light yellow to pink in presence of several basic anions such as F-, AcO- and H2PO4-. This emphasizes the importance on structural tuning in establishing a new effective sensor for a particular anion. F--induced deprotonation of 1 and its reprotonation with water has been employed as the working principle to detect the moisture content in various organic solvents. In addition, F--activated CO2 sensing via color and fluorescence changes have been demonstrated using chemosensor 1. Compound 1 and F- coated paper exhibit color change on heating and cooling. Writing on this 1.F- coated paper using AcO- ion as ink and its appearance/disappearance on heating/cooling has been possible successfully.
ABSTRACT
Dinitrobenzenesulfonyl-protected naphthyl azo pyridine conjugate 1 has been designed and synthesized. Compound 1 acts as a nongelator in dimethyl sulfoxide (DMSO)-H2O (1:1, v/v) while its hydroxy counterpart 2 can form a nice gel in the same solvent. In the presence of sulfide, compound 1 undergoes rapid sulfonate ester hydrolysis and results in the formation of azo-naphthol 2 that responds in instant gelation. Such deprotection was extremely selective to sulfide; other analytes did not show measurable response. The sensing mechanism has been established by various spectroscopic techniques. Compound 1 in solution (DMSO-H2O) also shows a selective response toward sulfide over a series of other anions with a color change. Preparation of test kit with compound 1 allows detection of sulfide in solution and vapor states. Such kind of dosimetric sensing of chemical analytes by improvising the protection/deprotection of functional groups in gelator structure is rare in the literature, and to the best of our knowledge, this is the first example of a stimuli-responsive low-molecular-weight gelator which dosimetrically senses sulfide over other nucleophilic substrates.
