Tanmay Sarkar

Rhodamine-based bis-sulfonamide as a sensing probe for Cu2+ and Hg2+ ions

A new rhodamine-based bis-sulfonamide 1 has been designed and synthesized. The receptor selectively recognizes Cu2+ and Hg2+ ions in CH3CN–water (4/1, v/v; 10 μM tris HCl buffer, pH 6.8) by showing different emission characteristics and color changes. While Cu2+ is sensed through increase in emission, Hg2+ is detected by a weak ratiometric change in emission of 1. The receptor shows in vitro detection of both the ions in human cervical cancer (HeLa) cells.

Selective sensing of Cu (II) by a simple anthracene-based tripodal chemosensor

A new and an easy-to-make simple tripodal shaped chemosensor 1 has been designed and synthesised for metal ions. In CH3CN containing 0.04% DMSO, upon excitation at 370 nm, chemosensor 1 exhibited structured emission centred at 418 nm, which increased to a significant extent upon complexation of Cu (II). The other metal ions except Zn2+ and Hg2+ examined in this study did not exhibit any marked change in emission of 1 under a similar condition. Although Cu2+ ion showed strong interaction with 1, Zn2+ and Hg2+ ions exhibited moderate binding.

Selective sensing of Al3+ by naphthyridine coupled rhodamine chemosensors

Napthyridine-based rhodamine chemosensors 1 and 2 are designed and synthesized. Both the chemosensors selectively recognize Al3+ ion over a series of other cations in CH3CN–H2O (4 : 1, v/v, 10 μM Tris–HCl buffer, pH = 7.0) by exhibiting change in color (colorless to pink) and emission at 588 nm in the turned on mode. Complexation is reversible and the ensembles of 1·Al3+ and 2·Al3+ selectively sense F− ion by discharging the pink color of the solutions and bringing a reverse change in both absorption and emission spectra.

Progress of 3-aminopyridinium-based synthetic receptors in anion recognition

This review describes the overall development on synthetic receptors built on the pyridinium motif with different functionalities at the 3-position in anion recognition. The review covers only the organic systems. In the designs, the pyridinium group along with the other functional motifs plays a crucial role in the binding of various anions of different shapes and sizes. Complexation characteristics are communicated through changes in 1H NMR, emission, color or gelation behaviours.

Rhodamine-labelled simple architectures for fluorometric and colorimetric sensing of Hg2+ and Pb2+ ions in semi-aqueous and aqueous environments

Triazole motif linked rhodamine derivatives 1 and 2 were synthesized. Chemosensor 1 recognizes both Hg2+ and Pb2+ ions in CH3CN–water (4/1, v/v; 10 μM tris HCl buffer, pH 7.0) both colorimetrically and fluorometrically. In addition, chemosensor 1 is cell permeable and detects intercellular Hg2+ and Pb2+ ions. The aqueous phase recognition of these ions was also studied with a resin bound sensor 2 which exhibits more sensitivity and selectivity towards Hg2+ over Pb2+ ion.

Rhodamine-linked pyridyl thiourea as a receptor for selective recognition of F–, Al3+ and Ag+ under different conditions

A new rhodamine-labelled pyridyl thiourea-based compound 1 has been designed and synthesised. While the receptor selectively recognises F– and Al3+ ions in CH3CN, Al3+ and Ag+ ions are selectively screened from other cations in CH3CN/water (4/1, v/v; 10 μM Tris–HCl buffer, pH 6.8) by observing different emission characteristics and colour changes. While Ag+ is sensed through an increase in emission at 416 nm, Al3+ is detected by a ratiometric change in emission of 1 with a band at 585 nm. The receptor shows in vitro detection of both the ions in human cervical cancer (HeLa) cells.

l-Valine-derived simple benzimidazole-based host in selective sensing of Hg(II) ions

A new and an easy-to-make simple benzimidazole-based chemosensor 1, derived from l -valine is reported. The chemosensor effectively recognises Hg2+ ion in the open cleft in CH3CN containing 0.2% DMSO by exhibiting significant enhancement in fluorescence emission. In the selectivity, the steric isopropyl groups in 1 play the key role as confirmed by considering the model compound 2. The ensemble of 1.Hg2+, on the other hand, shows the fluorescence sensing of l -cysteine, homocysteine, and glutathione over the other amino acids with no thiol group in aq. DMSO (DMSO:H2O = 4:1, v/v).

Coumarin-based symmetrical bisamide as fluorescent and colorimetric probes for copper ions

Coumarin-based new symmetrical bisamide 1 has been designed and synthesised. The bisamide 1 fluorometrically recognises Cu2+ in CH3CN containing 0.06% DMSO by exhibiting an increase in emission upon complexation. In comparison, the isomeric structure 2 also reports the selectivity for Cu2+ under identical condition by showing an opposite mode of emission. In addition, Cu2+ gives rise to a change in colour of the solution of 1, which is clearly visible to the naked eye.

Anthracene appended pyridinium amide-urea conjugate in selective fluorometric sensing of L-N-acetylvaline salt.

Summary A new anthracene labeled pyridinium amide–urea conjugate 1 has been designed and synthesized. The receptor shows a different fluorometric response with L-N-acetylvaline and L-N-acetylalanine salts in CH3CN in contrast to the other salts of L-N-acetyl α-amino acids and (S)-α-hydroxy acids studied. Upon complexation of the tetrabutylammonium salt of L-N-acetylvaline, the emission of 1 increases accompanied by the formation of a new band at higher wavelength and this characteristic change distinguishes it from other anionic substrates studied. The binding interaction has been studied by 1H NMR, fluorescence and UV titration experiments.