Electrochemical Diselenation of BODIPY Fluorophores for Bioimaging Applications and Sensitization of 1 O2.

We report a rapid, efficient, and scope-extensive approach for the late-stage electrochemical diselenation of BODIPYs. Photophysical analyses reveal red-shifted absorption - corroborated by TD-DFT and DLPNO-STEOM-CCSD computations - and color-tunable emission with large Stokes shifts in the selenium-containing derivatives compared to their precursors. In addition, due to the presence of the heavy Se atoms, competitive ISC generates triplet states which sensitize 1 O2 and display phosphorescence in PMMA films at RT and in a frozen glass matrix at 77 K. Importantly, the selenium-containing BODIPYs demonstrate the ability to selectively stain lipid droplets, exhibiting distinct fluorescence in both green and red channels. This work highlights the potential of electrochemistry as an efficient method for synthesizing unique emission-tunable fluorophores with broad-ranging applications in bioimaging and related fields.

Electrochemical Diselenation of BODIPY Fluorophores for Bioimaging Applications and Sensitization of 1 O2.

Invited for the cover of this issue are the groups of Holger Braunschweig at the Julius-Maximilians-Universität Würzburg, Germany and Eufrânio N. da Silva Júnior at the Universidade Federal de Minas Gerais, UFMG, Brazil. The image depicts the electrochemical synthesis of selenium-containing BODIPY molecules with lightning symbolizing the electrifying synthetic process, while the surrounding elemental chaos hints at the red-shifted absorption and emission and the transformative photophysical properties of these new compounds. Read the full text of the article at 10.1002/chem.202303883.

It Takes Two to Tango, Part II: Synthesis of A-Ring Functionalised Quinones Containing Two Redox-Active Centres with Antitumour Activities.

In 2021, our research group published the prominent anticancer activity achieved through the successful combination of two redox centres (ortho-quinone/para-quinone or quinone/selenium-containing triazole) through a copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction. The combination of two naphthoquinoidal substrates towards a synergetic product was indicated, but not fully explored. Herein, we report the synthesis of 15 new quinone-based derivatives prepared from click chemistry reactions and their subsequent evaluation against nine cancer cell lines and the murine fibroblast line L929. Our strategy was based on the modification of the A-ring of para-naphthoquinones and subsequent conjugation with different ortho-quinoidal moieties. As anticipated, our study identified several compounds with IC50 values below 0.5 µM in tumour cell lines. Some of the compounds described here also exhibited an excellent selectivity index and low cytotoxicity on L929, the control cell line. The antitumour evaluation of the compounds separately and in their conjugated form proved that the activity is strongly enhanced in the derivatives containing two redox centres. Thus, our study confirms the efficiency of using A-ring functionalized para-quinones coupled with ortho-quinones to obtain a diverse range of two redox centre compounds with potential applications against cancer cell lines. Here as well, it literally takes two for an efficient tango!

Combination of Aryl Diselenides/Hydrogen Peroxide and Carbon-Nanotube/Rhodium Nanohybrids for Naphthol Oxidation: An Efficient Route towards Trypanocidal Quinones.

This work reports a combination of aryl diselenides/hydrogen peroxide and carbon-nanotube (CNT)/rhodium nanohybrids (RhCNT) for naphthol oxidation towards the synthesis of 1,4-naphthoquinones and evaluation of their relevant trypanocidal activity. Under a combination of (PhSe)2 /H2 O2 in the presence of O2 in iPrOH/hexane, several benzenoid (A-ring)-substituted quinones were prepared in moderate to high yields. We also studied the contribution of RhCNT as co-catalyst in this process and, in some cases, yields were improved. This method provides an efficient and versatile alternative for preparing A-ring-modified naphthoquinonoid compounds with relevant biological profile.

Solvent-free hydroboration of alkenes and alkynes catalyzed by rhodium-ruthenium nanoparticles on carbon nanotubes.

A heterogeneous catalyst consisting of bimetallic rhodium-ruthenium particles immobilized on carbon nanotubes was used in the hydroboration reaction and proved highly effective for a variety of alkenes and alkynes. The reactions were carried out with low catalytic loadings (0.04 mol%), under solvent-free conditions, and at room temperature. In addition, to demonstrate its recyclability, the catalyst was recovered by a simple centrifugation process and reused over 5 consecutive cycles without losing any activity.

Aryl-Phenanthro[9,10-d]imidazole: A Versatile Scaffold for the Design of Optical-Based Sensors.

Fluorescent and colorimetric sensors are important tools for investigating the chemical compositions of different matrices, including foods, environmental samples, and water. The high sensitivity, low interference, and low detection limits of these sensors have inspired scientists to investigate this class of sensing molecules for ion and molecule detection. Several examples of fluorescent and colorimetric sensors have been described in the literature; this Review focuses particularly on phenanthro[9,10-d]imidazoles. Different strategies have been developed for obtaining phenanthro[9,10-d]imidazoles, which enable modification of their optical properties upon interaction with specific analytes. These sensing responses usually involve changes in the fluorescence intensity and/or color arising from processes like photoinduced electron transfer, intramolecular charge transfer, intramolecular proton transfer in the excited state, and Förster resonance energy transfer. In this Review, we categorized these sensors into two different groups: those bearing formyl groups and their derivatives and those based on other molecular groups. The different optical responses of phenanthro[9,10-d]imidazole-based sensors upon interaction with specific analytes are discussed.

Use of activated carbon as a reactive support to produce highly active-regenerable Fe-based reduction system for environmental remediation.

Composites based on iron supported on high surface area activated carbon were prepared and characterized with (57)Fe Mössbauer spectroscopy, X-ray diffraction, saturation magnetization measurements and temperature-programmed reduction. Upon thermal treatment, the supported iron oxides react with carbon to yield reduced chemical species, i.e. Fe(3)O(4) and Fe(0). This so produced composite was found to be highly efficient in two environmental applications: (i) degradation of textile dye and (ii) reduction of Cr(VI) in aqueous medium. Sequential reuses evidenced a progressive chemical deactivation of the composites due to a corresponding oxidation of the reactive species. Even after being virtually deactivated, the initial chemical reducing ability of the composites can be regenerated by heating at 800 degrees C under N(2) atmosphere, and then reused for several consecutive times.

Investigation of reaction mechanisms by electrospray ionization mass spectrometry: characterization of intermediates in the degradation of phenol by a novel iron/magnetite/hydrogen peroxide heterogeneous oxidation system.

Electrospray ionization (ESI) mass spectrometry (MS) and tandem mass spectrometry (MS/MS) were used to monitor the oxidation of phenol by a novel heterogeneous Fenton system based on a Fe(0)/Fe(3)O(4) composite and H(2)O(2). On-line ESI-MS(/MS) shows that this heterogeneous system promotes prompt oxidation of phenol to hydroquinone, which is subsequently oxidized to quinone, other cyclic poly-hydroxylated intermediates and an acyclic carboxylic acid. A peroxide-type intermediate, probably formed via an electrophilic attack of HOO(.) on the phenol ring, was also intercepted and characterized. ESI-MS(/MS) monitoring of the oxidation of two other model aromatic compounds, benzene and chlorobenzene, indicates the participation of analogous intermediates. These results suggest that oxidation by the heterogeneous system is promoted by highly reactive HO(.) and HOO(.) radicals generated from H(2)O(2) on the surface of the Fe(0)/Fe(3)O(4) composite via a classical Fenton-like mechanism.

The iodide-catalyzed decomposition of hydrogen peroxide: Mechanistic details of an old reaction as revealed by electrospray ionization mass spectrometry monitoring

A espectrometria de massas com ionização electrospray no modo negativo, ESI(-)-MS, foi usada para investigar a decomposição da água oxigenada catalisada por iodeto em meio aquoso. O monitoramento por ESI(-)-MS revelou a presença de um ânion intenso de m/z 287, o qual foi sugerido possuir a estrutura [I-IOOH]­ em solução aquosa, através de uma interação entre o íon iodeto e a espécie neutra e instável IOOH. Evidências da estrutura proposta para tal ânion foram obtidas através de sua fragmentação por colisão com hélio, a qual forneceu, exclusivamente, um íon-produto de m/z 254 (I2 •­), através de uma perda de radical peroxila (HOO• , 33 Da). Cálculos teóricos ab initio revelaram que a formação do ânion [I-IOOH]­ , a partir da interação entre IOOH e I­ , é um processo termodinamicamente favorável, enquanto que sua fragmentação levando a I2 • e HOO• , é o canal de dissociação mais provável. Deste modo, foi proposto um novo mecanismo para a decomposição da H2 O2 catalisada por iodeto para gerar H2 O e O2 tendo como base a participação do intermediário-chave IOOH.