A simple and efficient fluorophoric probe for dual sensing of Fe3+ and F-: application to bioimaging in native cellular iron pools and live cells

A new quinoline functionalized fluorophoric Schiff base L-1 was synthesized and its colorimetric and fluorescence responses toward various metal ions in mixed aqueous media were explored. The ligand exhibited high selectivity towards Fe3+ in the presence of a large excess of other competing ions with certain observable optical and fluorescence changes. These spectral changes are significant enough in the visible region of the spectrum and thus enable naked eye detection. The efficiency of L-1 in detecting Fe3+ ions was also checked in the presence of relevant complex biomacromolecules viz. methaemoglobin, fetal bovine serum and human serum albumin. L-1 was also found to be sensitive enough for visual detection of Fe3+ ions in native iron pools of banana pith. Studies revealed that L-1-Fe complex formation is fully reversible in the presence of the fluoride anion with very high selectivity. Furthermore, fluorescence microscopic studies demonstrated that compound L-1 could also be used as an imaging probe for detection of uptake of these ions in model human cells. This selective sensing behaviour of L-1 towards Fe3+ was explained via the CHEF process where theoretical calculations also supported the premise.