Novel anthraimidazoledione-based compounds (1-3) are synthesized as selective colorimetric and fluorescent sensors for fluoride ion. The binding properties of the probes (1-3) are studied with different anions in acetonitrile solvent. Spectral red shifts in the absorption spectra and 'turn-off' emission are observed when fluoride is added to 1-3. The striking green to orange color change in the ambient light is thought to be due to the deprotonation of the N-H proton of the imidazole moiety of the probes by the basic F ion. Interestingly, in all three cases the nonfluorescent probe-F solutions, on treatment with copper perchlorate, show distinct color change from orange to golden yellow with resumption of fluorescence intensity. Furthermore, the reversibility of sensors (1-3) for the detection of F ion is tested for four cycles indicating that "ON-OFF-ON" mechanism is operative. Test strip based on sensor 2 acts as a reusable cost-effective F sensor.
Zinc amalgam mediated reduction of the title bis(benzylidene)cycloalkanes (I) and (V) affords exocyclic olefinic bond reduced compounds and corresponding β,β‐coupled dimers with intact carbonyl function.
One-pot protocol for anthra[1,2-d]imidazole-6,11-dione was developed via tandem cyclocondensation cum oxidation, catalyzed by phosphotungstic acid in PEG-400 support in open air. J-aggregation properties of products were confirmed by photophysical studies.
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