As the most abundant transition metal in biological systems, iron plays many significant roles. Both iron deficiency and high accumulation leads to major health problems. Exploration of real-time, ratiometric iron detection technique with high selectivity and sensitivity is important. Fluorescence technology is a very promising analytical tool for the detection of various species in biological systems. In this study three sulfonamide derivatives of dipicolylamine ligands were developed into fluorosensors for biological ferrous and ferric ion detection. The ligands bear three different R groups, biphenyl (L1=N(SO2biphenyldpa)), azobenzene (L2=N(SO2azobenzdpa)) and quinoline (L3=N(SO2quindpa)). All three ligands were soluble at 0.2%(v/v) methanol solutions. L1 had a lower detection limit of 0.674 µM and fluorescence increasing and decreasing mechanisms at 319 nm with Fe3+. L2 had fluorescence increasing mechanism at 458 nm with Fe3+ and a lower detection limit of 18.22 nM. Both ligands had minimum interferences from other common metal cations and had low pH sensitivity. L2 ligand had a relatively higher photostability and ability to visualize ferric iron under UV lamp with blue green fluorescence emission. L3, N(SO2quindpa), increased fluorescence intensity with Fe2+ ions at 399 nm wavelength. The ligand L3 had a good photostability, a lower detection limit of 1.05 µM and minimum interferences from other cations. The ligand displayed no significant change in pH range 5-10 and concluded as suitable for application in physiological conditions. UV-Visible absorbance spectra of all three ligand-metal complexes had higher intensity than their respective free ligands. With the addition of strong chelating agent such as ethylenediaminetetraacetic acid (EDTA), the ligands could be recovered from the metal complexes.

Novel fluorescent probes for determination of Fe3+/ Fe2+ ions in biological systems using sulfonamide derivatized dipicolylamine ligands

ACS Fall 2020 Virtual Meeting

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