A sensitive molecular probe exhibiting significant change in their photophysical and morphological behavior upon interaction with Fe³⁺ ion

An efficient molecular probe 8 has been designed and synthesized. The photophysical, electrochemical and morphological behavior of the probe has been examined in the absence and presence of different ions. The probe 8 at 90 % water fraction in acetonitrile showed aggregation induced emission (AIE). Probe 8 upon interaction with ions binds with Fe³⁺ ion selectively in a 1:1 stoichiometry and showed fluorescence "turn-Off" response with good limit of detection (LOD = 92.2 nM). The particle size (DLS method) of probe upon increasing water fraction in acetonitrile showed a gradual increase while upon formation of a stable complex, 8 + Fe³⁺ particle size decreased along with change in morphology of the probe. SEM and TEM studies showed that in pure acetonitrile probe self-assemble into a sheet like structure of uneven surface. While in aggregated state (fw, 90 %) it changes to a uniform hollow rectangular rod shape structure. Further interaction of the probe with Fe³⁺ ions in aggregated state acquired a well-defined smooth sheet. Electrochemical (CV) studies suggested that the redox property of the probe incurred a marginal change in band gap upon complexation with Fe³⁺. The cell imaging studies were performed to detect Fe³⁺ in HeLa cells. The paper strip test and real water sample analysis showed the potential analytical application of probe to detect Fe³⁺ with a naked-eye sensitive visible color change. The formation of a complex, 8 + Fe³⁺ involving N and O atoms of the probe molecule was confirmed by ¹HNMR and HRMS data.