Dipodal Molecular Device as Fluorescent Sensor for Na(I) Detection
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Journal of Applied Spectroscopy, Vol. 87, No. 5, November, 2020 (Russian Original Vol. 87, No. 5, September–October, 2020)
DIPODAL MOLECULAR DEVICE AS FLUORESCENT SENSOR FOR Na(I) DETECTION V. Dangi,a M. Baral,a* and B. K. Kanungob
UDC 535.37
A novel dipodal fluorescent sensor, N 1,N 3-bis(2-(2,3,4-trihydroxybenzylidene)amino)ethylmalonamide (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 × 10 6 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. Keywords: dipodal chelator, pyrogallol, fluorescence, photoinduced electron transfer, sensor. Introduction. For physiological relevance, protons and metal ions such as sodium, potassium, calcium, and iron are the most popular targets for the development of new synthetic sensors. In the past decade, it is proved that sensors showed significant activity in the detection of biologically relevant metal ions and are well documented [1–3]. Many direct sensing schemes have been labeled for molecules in colorimetric and fluorescent chemosensors whose optical properties change upon binding with the cations [4–6]. These sensors need to show high selectivity for the metal ions over other interfering metal ions and to have a high association constant to enable metal chelation in the desired range. Sodium plays an important role in many physiological and pathological processes [7–10] and is known to be an essential alkali metal that is protuberant in extracellular fluids that controls the water level and electrolyte balance in the human body [11]. Any abnormality in its concentration may cause the risk of heart strokes or failure, diabetes, hyponatremia, and also kidney complications [12]. A large difference in the sodium concentration exists in between extracellular and intracellular compartments in animal cells. The range of concentration is 5–30 mM in intracellular sodium ions, and 100 mM in extracellular sodium ions, and these concentrations are maintained by their influx and efflux [13]. Also, sodium plays a major role in me
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