Joana F. B. Barata

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, 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.

Strategies for Corrole Functionalization

This review covers the functionalization reactions of meso-arylcorroles, both at the inner core, as well as the peripheral positions of the macrocycle. Experimental details for the synthesis of all known metallocorrole types and for the N-alkylation reactions are presented. Key peripheral functionalization reactions such as halogenation, formylation, carboxylation, nitration, sulfonation, and others are discussed in detail, particularly the nucleophilic aromatic substitution and the participation of corroles in cycloaddition reactions as 2π or 4π components (covering Diels-Alder and 1,3-dipolar cycloadditions). Other functionalizations of corroles include a large diversity of reactions, namely Wittig reactions, reactions with methylene active compounds, formation of amines, amides, and imines, and metal catalyzed reactions. At the final section, the reactions involving oxidation and ring expansion of the corrole macrocycle are described comprehensively.

A green method for the preparation of fluorescent hybrid structures of gold and corrole

Gold/soap nanostructures were prepared by a green methodology using saponified household sunflower oil, as reducing and organic dispersing agent of auric acid. The incorporation of hydrophobic molecules on the novel water-soluble gold nanoparticles was followed by fluorescence lifetime imaging microscopy, using as model hydrophobic compound 5,10,15-tris-(pentafluorophenyl)corrolatogallium(III)(pyridine) (GaPFC), a highly fluorescent corrole. The results showed the hydrophobic GaPFC located between the organic bilayer surrounding several Au nanoparticles, which in turn were coated with fatty acids salts anchored by the double bond at the gold’s surface.Graphical Abstract

Corrole and corrole functionalized silica nanoparticles as new metal ion chemosensors: a case of silver satellite nanoparticles formation.

Corrole macrocycles are very appealing dyes for incorporation into light harvesting devices. This work shows the sensorial ability of 5,10,15-tris(pentafluorophenyl)corrole 1 and its monoanionic species toward Na(+), Ca(2+), Cu(2+), Cd(2+), Pb(2+), Hg(2+), Ag(+), and Al(3+) metal ions in toluene and acetonitrile. The photophysical studies toward metal ions were carried out by absorption and emission spectroscopy. From all metal ions studied, corrole 1 shows to be colorimetric for Hg(2+) allowing a naked-eye detection of Hg(2+) through a change of color from purple to blue in acetonitrile and from green to yellow in toluene. In addition a new β-imine corrole 4 was successful synthesized and further functionalized with 3-isocyanatopropyl-trimethoxysilane resulting in an alkoxysilane derivative 5. The grafting of alkoxysilane derivative 5 with optically transparent silica nanoparticles (SiNPs) was achieved succesfully. The new-coated silica nanoparticles with corrole 5 were studied in the presence of Cu(2+), Hg(2+), and Ag(+) as metal ion probes. Interestingly, upon addition of Ag(+), groups of satellite AgNPs were formed around the SiNPs and were checked by transmission electron microscopy (TEM). At same time, a change of color from green to yellow was observed.

Corrole-silica hybrid particles: synthesis and effects on singlet oxygen generation

The present study describes the first example of hybrid particles composed of amorphous silica and corrole. The hybrid particles were obtained by covalent linking of the gallium(III)(pyridine) complex of 5,10,15-tris(pentafluorophenyl)corrole (GaPFC) at the surface of functionalized silica spheres. The functionalization step was achieved by a nucleophilic substitution reaction between corrole and 3-aminopropyltriethoxysilane previously grafted at the silica surfaces. The hybrids were morphologically and chemically characterized and the results have confirmed covalent linkages between corrole molecules and the silica particles. Preliminary studies on the capacity of corrole and hybrid particles to generate singlet oxygen was evaluated by a chemical method in which 1,3-diphenylisobenzofuran was used to trap singlet oxygen. The new corrole-silica hybrid particles have shown lower efficiency to generate singlet oxygen as compared to the pure corrole precursor. This effect was interpreted as a consequence of interparticle interactions mediated by the corrole molecules grafted at the silica surfaces that result in their clustering. Taken together, these findings demonstrate that despite lower efficiency in terms of singlet oxygen generation, the hybrid materials offer an alternative route to develop new platforms with potential for photodynamic therapy.

Corroles in 1,3-dipolar cycloaddition reactions

The azomethine ylide generated from the reaction of a corrole-3-carbaldehyde and N-methylglycine was trapped with dimethyl fumarate, dimethyl acetylenedicarboxylate and fullerene C60 in 1,3-dipolar cycloadditions. A similar azomethine ylide generated from a corrole-2-carbaldehyde was trapped with 1,4-naphthoquinone, yielding the expected dehydrogenated 1,3-dipolar cycloadduct and a quinone-fused corrole derivative. A detailed synchrotron single-crystal X-ray diffraction analysis of the gallium(III)(pyridine) complex of 5,10,15-tris(pentafluorophenyl)corrole-3-carbaldehyde is also presented.

Fluorescent Bioactive Corrole Grafted-Chitosan Films.

Transparent corrole grafted-chitosan films were prepared by chemical modification of chitosan with a corrole macrocycle, namely, 5,10,15-tris(pentafluorophenyl)corrole (TPFC), followed by solvent casting. The obtained films were characterized in terms of absorption spectra (UV-vis), FLIM (fluorescence lifetime imaging microscopy), structure (FTIR, XPS), thermal stability (TGA), thermomechanical properties (DMA), and antibacterial activity. The results showed that the chemical grafting of chitosan with corrole units did not affect its film-forming ability and that the grafting yield increased with the reaction time. The obtained transparent films presented fluorescence which increases with the amount of grafted corrole units. Additionally, all films showed bacteriostatic effect against S. aureus, as well as good thermomechanical properties and thermal stability. Considering these features, promising applications may be envisaged for these corrole-chitosan films, such as biosensors, bioimaging agents, and bioactive optical devices.

Recent advances in the functionalization of meso-triarylcorroles via cycloaddition reactions

With reference to the Portugal-Spain Special Issue of the Journal of Porphyrins and Phthalocyanines, this highlight is mainly concerned with the contribution by the University of Aveiro group on the functionalization of the β-pyrrolic positions of triarylcorroles via cycloaddition reactions.

New platinum(II)-bipyridyl corrole complexes: Synthesis, characterization and binding studies with DNA and HSA.

A simple methodology giving access to the metal-free corroles of trans-A2B type, 5,15-bis(pentafluorophenyl)-10-{3-[2-(pyridin-4-yl)vinyl]phenyl}corrole and 5,15-bis(pentafluorophenyl)-10-{4-[2-(pyridin-4-yl)vinyl]phenyl}corrole, and to the corresponding bipyridyl platinum(II) complexes is described. These new positional isomers were fully characterized and spectroscopic studies demonstrated the ability of Pt(II)-corrole complexes to establish non-covalent interactions with calf-thymus DNA (ct-DNA) and human serum albumin (HSA). Additionally, gel electrophoresis experiments demonstrated that Pt(II)-corrole complexes are able to bind plasmid pMT123 DNA, inducing alterations on its secondary structure.

Revisiting Heck–Mizoroki reactions in ionic liquids

The use of ionic liquids as an alternative to conventional organic solvents has been an important research topic in order to answer economic and environmental challenges. This critical review revisits the different approaches and achievements on the use of ionic liquids as solvents in Heck–Mizoroki coupling reactions; a brief reference to supported ionic liquids will be also highlighted.