An official website of the United States government
Abstract Photoredox nickel catalysis has emerged as a powerful strategy for cross-coupling reactions. Although the involvement of paramagnetic Ni(I)/Ni(III) species as active intermediates in the catalytic cycle has been proposed, a thorough spectroscopic investigation of these species is lacking. Herein, we report the tridentate pyridinophane ligandsRN3 that allow for detailed mechanistic studies of the photocatalytic C–O coupling reaction. The derived (RN3)Ni complexes are active catalysts under mild conditions and without an additional photocatalyst. We also provide direct evidence for the key steps involving paramagnetic Ni species in the proposed catalytic cycle: the oxidative addition of an aryl halide to a Ni(I) species, the ligand exchange/transmetalation at a Ni(III) center, and the C–O reductive elimination from a Ni(III) species. Overall, the present work suggests theRN3 ligands are a practical platform for mechanistic studies of Ni-catalyzed reactions and for the development of new catalytic applications.
more »
« less
In‐vitro and In‐vivo Photocatalytic Cancer Therapy with Biocompatible Iridium(III) Photocatalysts
Abstract Photocatalytic anticancer profile of a IrIIIphotocatalyst (Ir3) with strong light absorption, high turnover frequency, and excellent biocompatibility is reported.Ir3showed selective photo‐cytotoxicity against cisplatin‐ and sorafenib‐resistant cell lines while remaining dormant to normal cell lines in the dark.Ir3exhibited excellent photo‐catalytic oxidation of cellular co‐enzyme, the reduced nicotinamide adenine dinucleotide phosphate (NADPH), and amino acids via a single electron transfer mechanism. The photo‐induced intracellular redox imbalance and change in mitochondrial membrane potential resulted in necrosis and apoptosis of cancer cells. Importantly,Ir3exhibited high biocompatibility and photo‐catalytic anticancer efficiency as evident from in vivo zebrafish and mouse cancer models. To the best of our knowledge,Ir3is the first IrIIIbased photocatalyst with such a high biocompatibility and photocatalytic anticancer therapeutic effect.
more »
« less
- Award ID(s):
- 1764264
- PAR ID:
- 10237077
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Angewandte Chemie International Edition
- Volume:
- 60
- Issue:
- 17
- ISSN:
- 1433-7851
- Format(s):
- Medium: X Size: p. 9474-9479
- Size(s):
- p. 9474-9479
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract A series of new isoxazole‐substituted aryl iodides1 a–1 dhave been synthesized by DIB‐mediated [3+2] cycloaddition reaction of 2‐iodo‐1,3‐bis(prop‐2‐yn‐1‐yloxy) benzene (4) with corresponding benzaldehyde oximes5 a–5 d. Structure of the synthesized aryl iodides1were characterized by IR,1H NMR,13C NMR and HRMS. The structure of1 awas also confirmed by single‐crystal X‐ray crystallography. Further, catalytic activity of iodoarenes1 a–1 dwas screened for the oxidation of hydroquinones and sulfides. On oxidation using aryl iodides1withm‐CPBA as terminal oxidant, hydroquinones afforded benzoquinones while sulfides gave corresponding sulfoxides in good to excellent yields. Iodoarene1 bshowed the best catalytic activity for the oxidation of sulfides and hydroquinones. Moreover, iodoarene1 b, was also utilized for α‐oxytosylation of acetophenones.more » « less
-
Abstract A series of molecular Mn catalysts featuring aniline groups in the second‐coordination sphere has been developed for electrochemical and photochemical CO2reduction. The arylamine moieties were installed at the 6 position of 2,2’‐bipyridine (bpy) to generate a family of isomers in which the primary amine is located at theortho‐(1‐Mn),meta‐(2‐Mn), orpara‐site (3‐Mn) of the aniline ring. The proximity of the second‐sphere functionality to the active site is a critical factor in determining catalytic performance. Catalyst1‐Mn, possessing the shortest distance between the amine and the active site, significantly outperformed the rest of the series and exhibited a 9‐fold improvement in turnover frequency relative to parent catalyst Mn(bpy)(CO)3Br (901 vs. 102 s−1, respectively) at 150 mV lower overpotential. The electrocatalysts operated with high faradaic efficiencies (≥70 %) for CO evolution using trifluoroethanol as a proton source. Notably, under photocatalytic conditions, a concentration‐dependent shift in product selectivity from CO (at high [catalyst]) to HCO2H (at low [catalyst]) was observed with turnover numbers up to 4760 for formic acid and high selectivities for reduced carbon products.more » « less
-
Abstract Redox flow batteries (RFBs) with high energy densities are essential for efficient and sustainable long‐term energy storage on a grid scale. To advance the development of nonaqueous RFBs with high energy densities, a new organic RFB system employing a molecularly engineered tetrathiafulvalene derivative ((PEG3/PerF)‐TTF) as a high energy density catholyte was developed. A synergistic approach to the molecular design of tetrathiafulvalene (TTF) was applied, with the incorporation of polyethylene glycol (PEG) chains, which enhance its solubility in organic carbonate electrolytes, and a perfluoro (PerF) group to increase its redox potential. When paired with a lithium metal anode, the two‐electron‐active(PEG3/PerF)‐TTFcatholyte produced a cell voltage of 3.56 V for the first redox process and 3.92 V for the second redox process. In cyclic voltammetry and flow cell tests, the redox chemistry exhibited excellent cycling stability. The Li|(PEG3/PerF)‐TTFbatteries, with concentrations of 0.1 M and 0.5 M, demonstrated capacity retention rates of ~94 % (99.87 % per cycle, 97.52 % per day) and 90 % (99.93 % per cycle, 99.16 % per day), and the average Coulombic efficiencies of 99.38 % and 98.35 %, respectively. The flow cell achieved a high power density of 129 mW/cm2. Furthermore, owing to the high redox potential and solubility of(PEG3/PerF)‐TTF, the flow cell attained a high operational energy density of 72 Wh/L (100 Wh/L theoretical). A 0.75 M flow cell exhibited an even higher operational energy density of 96 Wh/L (150 Wh/L theoretical).more » « less
-
Abstract Manganese catalysts that activate hydrogen peroxide have seen increased use in organic transformations, such as olefin epoxidation and alkane C−H bond oxidation. Proposed mechanisms for these catalysts involve the formation and activation of MnIII‐hydroperoxo intermediates. Examples of well‐defined MnIII‐hydroperoxo complexes are rare, and the properties of these species are often inferred from MnIII‐alkylperoxo analogues. In this study, we show that the reaction of the MnIII‐hydroxo complex [MnIII(OH)(6Medpaq)]+(1) with hydrogen peroxide and acid results in the formation of a dark‐green MnIII‐hydroperoxo species [MnIII(OOH)(6Medpaq)]+(2). The formulation of2is based on electronic absorption,1H NMR, IR, and ESI‐MS data. The thermal decay of2follows a first order process, and variable‐temperature kinetic studies of the decay of2yielded activation parameters that could be compared with those of a MnIII‐alkylperoxo analogue. Complex2reacts with the hydrogen‐atom donor TEMPOH two‐fold faster than the MnIII‐hydroxo complex1. Complex2also oxidizes PPh3, and this MnIII‐hydroperoxo species is 600‐fold more reactive with this substrate than its MnIII‐alkylperoxo analogue [MnIII(OOtBu)(6Medpaq)]+. DFT and time‐dependent (TD) DFT computations are used to compare the electronic structure of2with similar MnIII‐hydroperoxo and MnIII‐alkylperoxo complexes.more » « less
