Indrajit Saha

A new ortho-phenylenediamine-based cleft for selective sensing of H2PO4− and ATP

Ortho-phenylenediamine based chemosensor 1 has been designed and synthesized. The chemosensor 1 selectively binds H2PO4− in CH3CN showing excimer emission at 456 nm due to π–π stacking between the pendant naphthalene units. The sensor 1 also fluorometrically distinguishes ATP from ADP and AMP in CH3CN–H2O (1 : 1, v/v) at pH = 6.5.

A new benzimidazolium receptor for fluorescence sensing of iodide

A new anthracene-appended benzimidazolium-based receptor 1 has been designed and synthesised. The receptor shows selective recognition of iodide in the excited state by exhibiting quenching of emission of anthracene. In the ground state, receptor 1 shows different selectivity and prefers to bind bromide with higher binding constant value as established from NMR titration experiment. Other anions in the study indicated weak or no interaction. Hydrogen bonding and charge–charge interactions are the forces responsible for strong binding. The interaction properties of the new receptor were evaluated by 1H NMR, UV–vis and fluorescence spectroscopic methods.

Benzimidazolium-based flexible tripodal fluorescent chemosensor for selective sensing of dihydrogenphosphate and ATP

A new anthracene-coupled benzimidazolium-based tripodal, tricationic fluorescent chemosensor 1 was designed and synthesised. Receptor 1 exhibits high degree of selectivity towards in CH3CN through anion-induced quenching of emission along with the formation of a weak excimer complex in the excited states. Furthermore, receptor 1 shows selective sensing of ATP over ADP and AMP by exhibiting an increase in emission in aqueous CH3CN (CH3CN:H2O = 3:2 v/v). The electrostatic charge–charge interaction along with both conventional (N–H…X; X = O, halides) and unconventional (C+–H…X; X = O, halides) hydrogen bonding between the host and the guest molecule synergistically interplays in the complexation. The anion-binding properties of receptor 1 were understood by 1H NMR, UV–vis and fluorescence spectroscopic methods.