Unexpected selectivity of a thioacetal-functionalized carbazole fluorophore toward Fe3+ ions in solution

A novel thioacetal-containing carbazole-based fluorescent sensor, 3-(5-(1,3-dithiolane-2-yl)pyridin-2-yl)-9-hexylcarbazole ( probe F ), was synthesized for the first time and exhibited remarkable and unexpected selectivity toward Fe3+ ions. Probe F showed a detection limit of 0.9 nM and retained its selectivity in the presence of competing analytes. Job's plot revealed a 1:1 binding stoichiometry, while HRMS and DFT studies indicated that both Fe-N and Fe-S coordination modes are feasible, with sulphur coordination being thermodynamically favoured under the experimental conditions. Practical application studies with satisfactory recovery values demonstrated the potential of probe F for Fe3+ detection.