Interaction of anions with thiourea-linked acridinedione fluorophore was studied by absorption, 1H NMR, steady-state and time-resolved fluorescence techniques. Addition of AcO and H2PO4 shows a genuine H-bonded complex with thiourea receptor; whereas, F shows stepwise H-bonding and deprotonation of thiourea NH as confirmed by 1H NMR titration. Free receptor 1 shows emission maximum at 418 nm; whereas, Hbonded complex of 1·F shows a new redshifted emission maximum at 473 nm and the deprotonated 1 exhibits an emission peak at 502 nm. Presence of these three different emitting species was probed by 3D emission spectroscopic studies. Equilibrium between the free receptor 1, 1·F H-bonded complex and deprotonated 1 was confirmed by time-resolved fluorescence studies. Time-resolved area normalised emission spectra (TRANES) of 1 in the presence of F shows two isoemissive points at 456 and 479 nm between time delays of 0–0.5 ns and 1–20 ns, respectively, due to the existence of three emitting species in equilibrium. Observation of such an equilibrium based on fluorescence spectroscopic studies further proves the earlier reported absorption and 1H NMR spectroscopic studies of H-bonding and deprotonation processes and also illustrates the dynamics of anion-receptor interactions
Chem. Eur. J. 2010, 16, 13271 – 13277