Imidazole-coumarin containing D - A type fluorescent probe: Synthesis photophysical properties and sensing behavior for F- and CN- anion

A new class of D-A type intramolecular charge transfer (ICT) fluorescent probe, ICU has been designed and synthesized. The solvatochromic behavior, anion interaction and morphological features of the probe have been studied in detail. The molecular probe upon interaction with different class of anions showed good sensitivity for F- and CN- anions in organic medium with high detection limit and rapid response time. The time dependent fluorescence studies suggested about the dynamic and static fluorescence quenching with F- and CN- anions. The scanning electron microscopy (SEM) and diffraction light scattering (DLS) experiments have been performed to understand the morphological behavior and particle size of the probe to distinguish both anions. Upon interaction with F- and CN- the morphology of probe reveals a clear shape reconstruction from the initial aggregated spherical ball shape to fine leaf like and dumbbell like structures, respectively by disaggregation to form minimum energy structures. The photophysical and theoretical (DFT) studies all together suggested about the charge transfer process from imidazole (donor, D) to coumarin (acceptor, A) unit. The probe has been also utilized to detect the anions on test paper strips. The mechanism of interaction between probe and both the anions has been confirmed by (HNMR)-H-1 and HRMS spectral data analysis.