Corroles as anion chemosensors: exploiting their fluorescence behaviour from solution to solid-supported devices

The reactivity of the new gallium(III) complex of 3-vinyl-5,10,15-tris(pentafluorophenyl) corrole 4, as a diene in Diels-Alder reactions was studied using 1,4-benzoquinone and 1,4-naphthoquinone as dienophiles. In these reactions only the dehydrogenated adducts 5 and 6 were isolated. All the new corrole derivatives 4-6 were fully characterized by elemental analysis, H-1-NMR, C-13-NMR, F-19-NMR, MALDI-TOF-MS, UV-Vis absorption and emission spectroscopy. The sensing ability of compounds 4-6 and of their precursors 1-3 was studied in solution towards the spherical halide ions F-, Cl-, Br-, I-, the linear anion CN- and the bulky anions CH3COO- and H2PO4-. This study was also realized in gas-phase with the anions F- and CN-. A red-shift in the absorption spectra and an enhancement in the emission intensity were observed, with compounds 1, 3 and 5 being strongly sensitive to fluoride. The highest association constant was obtained for 1 with F-, being able to quantify 0.69 ppm of this anion. On the other hand, compounds 1 and 2 present a high sensitivity towards cyanide anions, producing a red-shift in the absorption and emission spectra and an increase in the emission intensity, being able to quantify a minimal amount of 1.43 ppm. Moreover, compounds 1 and 5 were used to prepare two lowcost solid polymers, based on polymethylmethacrylate (PMMA) and polyacrylamide, the last one being very promising since it is able to detect ca. 70.0 ppb of CN- in water. Compounds 2a and 5 were also tested in the presence of 4,40-bipyridine, caffeine and nicotine and compound 2a proved to be very sensitive to 4,40-bipyridine, while compound 5 was really effective for detecting caffeine and nicotine.