Dipodal Molecular Device as Fluorescent Sensor for Na(I) Detection

Abstract

A novel dipodal fluorescent sensor, N1,N3-bis(2-(2,3,4-trihydroxybenzylidene)amino)ethylmalo namide (MEP), suitable for the practical measurement of sodium concentration has been successfully developed and characterized by several spectroscopic techniques. The design of the dipodal scaffold includes a central unit, spacer, and fluorophore moiety as structural key features. The fluorescence sensor MEP adopts a photoinduced electron transfer mechanism and shows excellent selectivity for Na(I) among other biologically and environmentally important metal ions, viz., Na(I), K(I), Al(III), Cr(III), Fe(III), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II) in DMSO by demonstrating a remarkable enhancement in the fluorescence intensity from 345.5 to 705.5 a.u. at λmax = 532.9 nm. The 1:2 binding stoichiometry between the ligand and Na(I) ion was confirmed by Stern–Volmer and Hill plots. The association constant determined for the ligand with the sodium metal ion is found to be very high, 7.7 × 106 M–2, which may be attributed to the trapping of sodium ions into the pseudo cavities of the ligand created by interaction of the ligand and sodium ions. The studies explore potential applications of the ligand for Na(I) ions detection in environmental and industrial applications.