No abstract

The optical sensing and supramolecular cyanide recognition sites of two dipodal Schiff bases having conjugated to catecols (1) and phenols (2) (namely, salophenes 1 and 2) have been studied. In the case of optical sensing, both probes recognized only cyanide (CN¯) ions in 30% PBS buffer CH3CN (pH 7.4) as confirmed from the changes of absorption and emission bands, resulting in color changes. From the supramolecular recognition point of view, probes 1 and 2 show the different recognition bahaviour toward CN¯, as evidenced by the fluoroscence and NMR data, as well the OH¯ and reversibility experiments. While 1 recognizes CN¯ via deprotonation, that of 2 is the first example of Schiff base which senses CN¯ through an intramolecular aldimine condensation cyclization, leading to formation of dihydroxyquinoxaline 4. In general, probes 1, 2 and 4 are promising on-site optical sensors in terms of easy prepared, selectivity, sensitivity (1–10 nM), ease of use, rapid response (< 5 s) and test kits.