Tanushree Sen

Binding induced destruction of an excimer in anthracene-linked benzimidazole diamide: a case toward the selective detection of organic sulfonic acids and metal ions

A simple anthracene-linked benzimidazole diamide, 1, has been designed and synthesized. 1 was found to undergo a subtle change in conformation, followed by destruction of the inherently present excimer in the presence of organic sulfonic acids and selective metal ions. Destruction of the excimer did not take place in the presence of carboxylic acids and even stronger trifluroacetic acid. This finding was taken as a possible tool for distinguishing organic sulfonic acids from carboxylic acids. A similar situation arose in the presence of Cu2+, Co2+ and Ni2+, among the other metal ions studied, and the cleft was selective for Cu2+. The binding interaction was followed using 1H NMR, UV-vis and fluorescence spectroscopic methods.

Anthracene coupled adenine for the selective sensing of copper ions

Summary Anthracene-based adenines 1 and 2 have been designed and synthesized, and their metal ion recognition properties have been established fluorometrically. Both molecules exhibit Cu2+ induced ON-OFF type signaling patterns over the other representative metal ions studied. Compound 1 exhibits 97% quenching of emission in the presence of Cu2+ whilst derivative 2 shows 81% quenching under similar experimental conditions.

Naphthyridine-based symmetrical and unsymmetrical pyridinium amides in sensing of biotin salt

Two naphthyridine-based receptors have been designed and synthesised for biotin salt. The compounds serve as good hosts for the detection of biotin carboxylate rather than biotin ester. The correct dispositions of the binding groups under an isophthaloyl spacer enable the receptors to bind both the cyclic urea and the carboxylate ends simultaneously with moderate binding constant values. The receptors are effective for the binding of tetrabutylammonium salt of biotin with a concomitant increase in the fluorescence of naphthyridine and show appreciable binding of biotin salt in CH3CN containing 1.2% DMSO. The binding was monitored in CH3CN containing 1.2% DMSO and DMSO using 1H NMR, UV–vis and fluorescence spectroscopic methods.

trans-Pyridyl and Naphthyridyl Cinnamides as Alternatives for Urea in Complexation of Carboxylic Acid and Formation of Water-Templated Assemblies in the Solid State

A series of alpha,beta-unsaturated amides of pyridine and naphthyridine (1-4) derived from trans-cinnamic acid and its derivatives has been synthesized. The hydrogen-bonding behavior of these simple amides in the solid state has been established by solving X-ray structures. In solution and in the solid state, the above compounds 1-4 were found to bind carboxylic acid utilizing both conventional and unconventional hydrogen bonds. Hence, the possibility has been revealed of using this motif as an alternative of urea for the design of task-specific hosts. The experimental results have been rationalized with an accompanying theoretical study involving density functional calculations on the structure and the relative energies of different rotamers of the host systems as well as the binding energy of the complexes formed with trans-cinnamic acid. Generally, small binding energies (0.58-0.70 eV) are calculated for the complexes in the gas phase which become even smaller in chloroform solvent.