Carla I. M. Santos

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.

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.

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.

Copper(II) Coordination Polymers Self-Assembled from Aminoalcohols and Pyromellitic Acid: Highly Active Precatalysts for the Mild Water-Promoted Oxidation of Alkanes

Three novel water-soluble 2D copper(II) coordination polymers-[{Cu2(μ2-dmea)2(H2O)}2(μ4-pma)]n·4nH2O (1), [{Cu2(μ2-Hedea)2}2(μ4-pma)]n·4nH2O (2), and [{Cu(bea)(Hbea)}4(μ4-pma)]n·2nH2O (3)-were generated by an aqueous medium self-assembly method from copper(II) nitrate, pyromellitic acid (H4pma), and different aminoalcohols [N,N-dimethylethanolamine (Hdmea), N-ethyldiethanolamine (H2edea), and N-benzylethanolamine (Hbea)]. Compounds 2 and 3 represent the first coordination polymers derived from H2edea and Hbea. All the products were characterized by infrared (IR), electron paramagnetic resonance (EPR), and ultraviolet-visible light (UV-vis) spectroscopy, electrospray ionization-mass spectroscopy (ESI-MS(±)), thermogravimetric and elemental analysis, and single-crystal X-ray diffraction (XRD), which revealed that their two-dimensional (2D) metal-organic networks are composed of distinct dicopper(II) or monocopper(II) aminoalcoholate units and μ4-pyromellitate spacers. From the topological viewpoint, the underlying 2D nets of 1-3 can be classified as uninodal 4-connected layers with the sql topology. The structures of 1 and 2 are further extended by multiple intermolecular hydrogen bonds, resulting in three-dimensional (3D) hydrogen-bonded networks with rare or unique topologies. The obtained compounds also act as highly efficient precatalysts for the mild homogeneous oxidation, by aqueous H2O2 in acidic MeCN/H2O medium, of various cycloalkanes to the corresponding alcohols and ketones. Overall product yields up to 45% (based on cycloalkane) were attained and the effects of various reaction parameters were investigated, including the type of precatalyst and acid promoter, influence of water, and substrate scope. Although water usually strongly inhibits the alkane oxidations, a very pronounced promoting behavior of H2O was detected when using the precatalyst 1, resulting in a 15-fold growth of an initial reaction rate in the cyclohexane oxidation on increasing the amount of H2O from ∼4 M to 17 M in the reaction mixture, followed by a 2-fold product yield growth.

Turn-on selective vitamin B6 derivative fluorescent probe for histidine detection in biological samples

A new compound L soluble in water derived from vitamin B6 was successfully synthesized and characterized. The complex LAl(3+) is a turn-on selective fluorescent probe for histidine in HEPES buffer, with detection and quantification limits of 0.3 μM and 0.6 μM, respectively. The application of the complex LAl(3+) in real urine samples is reported.

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.

New aqua-soluble dicopper(II) aminoalcoholate cores for mild and water-assisted catalytic oxidation of alkanes

Two new dicopper(II) aminoalcoholate compounds, namely a discrete 0D complex [{Cu(Hdea)(H2dea)}2(μ2-H2pma)]·3H2O (1) and a 1D coordination polymer [Cu2(μ2-H2tea)2(μ2-nda)]n·2nH2O (2), were self-assembled from copper(II) nitrate, an aminoalcohol {diethanolamine (H2dea) or triethanolamine (H3tea)} and carboxylic acid {pyromellitic (H4pma) or 2,6-naphthalenedicarboxylic (H2nda)} building blocks. Both products were isolated as stable and water-soluble microcrystalline solids and fully characterized by IR spectroscopy, ESI-MS(±), elemental analysis and single-crystal X-ray diffraction, revealing distinct types of dicopper(II) units. The structures of 1 and 2 are further extended by intermolecular hydrogen bonds giving rise to 3D or 2D H-bonded nets with a pcu and sql topology, respectively. Both compounds act as efficient pre-catalysts for the mild homogeneous oxidation, by aqueous H2O2 in MeCN/H2O medium, of different cycloalkanes to the corresponding cyclic alcohols and ketones, which are obtained in up to 34% total yields (based on alkanes). The influence of various reaction parameters such as the amount and type of pre-catalyst and acid promoter, solvent composition and substrate scope were investigated, which also show that the oxidation of cycloalkanes and the activity of a catalytic system can be restarted upon addition of new portions of oxidant and substrate. Besides, an unusual promoting role of water was found when using both pre-catalysts 1 and 2. The bond-, regio- and stereoselectivity parameters were established using different alkane substrates, supporting a free radical oxidation mechanism. The model 1/H+/H2O2 and 2/H+/H2O2 solutions were investigated by ESI-MS(±), allowing us to propose some possible catalytically active species.

Self-assembly generation, structural features, and oxidation catalytic properties of new aqua-soluble copper(II)-aminoalcohol derivatives

Self-assembly reactions of copper(II) nitrate with aminoalcohols {bis(2-hydroxyethyl)amino-tris(hydroxymethyl)methane (H5bis-tris) or 1,3-bis(tris(hydroxymethyl)methylamino)propane (H6bis-tris-propane)} as main N,O-building blocks, and isonicotinic acid (Hinic) or sodium azide (NaN3) as ancillary ligand sources resulted in two new copper(II) compounds [{Cu(H4.5bis-tris)(inic)}2](NO3)·2H2O (1) and [Cu(H5bis-tris-propane)(N3)]·2H2O (2). The obtained products were isolated as stable microcrystalline solids and fully characterized including by single-crystal X-ray diffraction, which disclosed the six-coordinate copper(II) centers with distorted octahedral {CuN2O4} or {CuN3O3} environments. The structures of 1 and 2 feature the formation of complex 3D H-bonded networks that were topologically classified as cbs-3,4-Cmmm-2 and sxd underlying nets, respectively. Both compounds 1 and 2 are soluble in water (S25 °C ≈ 6–12 mg mL−1) and act as efficient homogeneous catalysts for the mild and acid-promoter-free oxidation, by aqueous hydrogen peroxide, of C5–C8 cycloalkanes (cyclopentane, cyclohexane, cycloheptane, and cyclooctane) to give the corresponding cyclic alcohols and ketones. The influence of various reaction parameters (time, solvent composition, loading of substrate, oxidant, and catalyst, presence of a radical trap), bond- and regioselectivity features, and substrate scope were investigated and discussed in detail. A notable feature of the present catalysts concerns their high activity without the requirement for any promoter or co-catalyst, resulting in up to 46% total product yields based on cycloalkane.