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, ¹H-NMR, ¹³C-NMR, ¹⁹F-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 low-cost 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 4,4′-bipyridine, caffeine and nicotine and compound 2a proved to be very sensitive to 4,4′-bipyridine, while compound 5 was really effective for detecting caffeine and nicotine.

Carbon nanodots (Cdots) are now emerging as promising nonlinear fluorophores for applications in biological environments. A thorough and systematic approach to the two-photon induced emission of Cdots that could provide design guidelines to control their nonlinear emission properties is still missing. In this work, we address the nonlinear optical spectroscopy of Cdots prepared by controlled chemical cutting of graphene oxide (GO). The two-photon absorption in the 700–1000 nm region and the corresponding emission spectrum are carefully investigated. The highest two-photon absorption cross-section estimated was 130 GM at 720 nm. This value is comparable with the one reported for graphene nanoribbons with push–pull architecture. The emission spectrum depends on the excitation mode. At the same excitation energy, nonlinear excitation results in excitation-wavelength independent emission, while upon linear excitation the emission is excitation-wavelength dependent. The biphotonic interaction seems to be selective towards sp² clusters bearing electron donor and acceptor groups found in push–pull architectures. Both linear and nonlinear emission can be understood based on the existence of isolated sp² clusters involved in π–π stacking interactions with clusters in adjacent layers.