New gallium(III) corrole complexes as colorimetric probes for toxic cyanide anion

Demand for new colorimetric sensors for toxic anions has widely increased in the last ten years, because it is an inexpensive technique, in which the analyte is naked-eye detectable. Regarding this issue, two new corrole derivatives 2 and 3 were successfully synthetized and characterized by elemental analysis, 1H-NMR, MALDI-TOF-MS, UV–Vis absorption and emission spectra. β-Vinyl-corrole 1 was prepared by the Wittig reaction of β-formyl-corrole with phosphorus ylide. Subsequent treatment of β-vinyl-corrole with dimethyl acetylenedicarboxylate afforded compounds 2 and 3. The sensorial ability of the two new corrole derivatives towards fluoride, cyanide, acetate and phosphate anions was carried out by absorption and emission spectroscopy. Compound 2 shows to be colorimetric to cyanide, whereas a change of colour from green to colourless was visualized. In addition the highest association constants were obtained for compounds 2 and 3 in the presence of cyanide that are able to quantify a minor amount of cyanide (ca. 1.00 μM).