Anupam Majumdar

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.

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.

Dipicolylamine coupled rhodamine dyes: new clefts for highly selective naked eye sensing of Cu2+ and CN− ions

The dipicolylamine (DPA) motif which is known as a binder of Zn(II) ions, has been utilized in devising rhodamine labelled compounds 1 and 2. Compound 1 acts as a FRET sensor and shows excellent selectivity for Cu(II) ions over a series of other cations in CH3CN/H2O by exhibiting a colour change (colourless to pink) of the solution. The spectral and colour changes are recovered in the presence of CN− ions and thus, the ensemble 1·Cu2+ in CH3CN/H2O is established as the medium for selective detection of CN− ions. In contrast, the modified compound 2 with the dipicolylamine motif as the principal binding site has been established as the colorimetric sensor of Cu(II) ions and the fluorometric sensor of Hg(II), Zn(II) and Cd(II) ions. Both the compounds 1 and 2 are cell permeable and are successfully employed for the detection of intercellular metal ions through bright field and fluorescence imaging.

L-Amino acid derived pyridinium-based chiral compounds and their efficacy in chiral recognition of lactate

A series of pyridinium-based chiral compounds 1–6 have been designed and synthesized. L-Amino acids have been used as the chiral source in the molecules. Among the chiral compounds, an L-valine derived compound 1 was found to exhibit enantioselective recognition of D-lactate in fluorescence. Structural tuning of this derivative, either by replacing L-valine with L-alanine or L-phenylglycine or by reducing the number of chiral centres around the binding site, does not result in any significant change in enantioselectivity in the recognition process. Change of the urea site to amide introduces compound 6 that displays good enantiodiscrimination for lactate (enantiomeric fluorescence difference ratio ef = 28.33 for D-lactate), even better than that of the L-valine derived compound 1 and of other reported structures in the literature.