The proton reduction activity of Orange protein (Orp), a small bacterial metalloprotein harboring a unique molybdenum/copper (Mo/Cu) heterometallic cluster [S2MoS2CuS2MoS2]3–, was investigated. It exhibits excellent photocatalytic activity in the presence of ascorbate as electron donor and [Ru(bpy)3]Cl2 as photosensitizer. Assembling synthetic dinuclear [S2MS2M′S2MS2](4n)– clusters in the active sites allows to tune the activity of the system, when the implementation of a Mo/Fe core led to a record activity among artificial hydrogenases.
The innovation is based on the nanostructuring of catalysts based on metals or metal oxides in a functionalized polymer film using a versatile electrochemical process. This offers numerous possibilities both in the composition of the catalyst/polymer matrix system and in the diversity of possible catalytic reactions.
We show that 2D solid-state NMR 13C–13C correlation spectra can be acquired at natural isotopic abundance with only milligram quantities of sample. These experiments combine fast Magic Angle Spinning of the sample, low-power dipolar recoupling, and dynamic nuclear polarization performed with AsymPol biradicals, a recently introduced family of polarizing agents. The approach is demonstrated on polyglutamine fibrils implicated in Huntington's disease and a microcrystalline antibiotic molecule.
This study reports the first non-toxic water-based synthesis method to effectively functionalize dextran with photo-sensitive methacrylate groups for photochemical cross-linking. The reaction presents unprecedented simplicity and efficiency. An unconventional solid-state photocross-linking method enabling the formation of strong cross-linked hydrogels was also developed with LAP (lithium phenyl-2,4,6-trimethylbenzoylphosphinate) as photoinitator. The green synthesis protocols developed to controllably obtain diverse dextran hydrogels open up new possibilities for biomedical applications including the fabrication of microneedles for drug delivery and electrochemical biosensing.
A thorough analytical treatment allows determining all thermodynamic and kinetic parameters of reversible electrocatalytic oxidation and production of dihydrogen mediated by the molecular DuBois/Shaw nickel bisdiphosphine complexes bearing pendant bases. This analysis shed light on the key activity descriptors responsible for reversible vs. bidirectional catalysis and paves the way towards rational optimization of such molecular catalysts.
Cellular reactive oxygen species levels must be regulated to avoid certain diseases, especially those associated with oxidative stress. One approach to antioxidant development is to model natural enzymes involved in ROS scavenging. We report Ni complexes with tripeptides derived from the ATCUN motif that mimics the active site of nickel superoxide dismutase, an enzyme that catalyzes the dismutation of the superoxide radical. A series of mononuclear NiII complexes was investigated, wherein the coordination sphere was varied from N3S to N2S2. The complexes were characterized in water, and all display a superoxide dismutase activity.
Studying the surface chemistry of functionalized cellulose nanofibrils at atomic scale is an ongoing challenge, mainly because FT-IR, NMR, XPS and RAMAN spectroscopy are limited in sensitivity or resolution. Herein, we show that dynamic nuclear polarization (DNP) enhanced 13C and 15N solid-state NMR is a uniquely suited technique to optimize the drug loading on nanocellulose using aqueous heterogeneous chemistry.
In this article, the synthesis and optoelectronic properties of a novel push–pull organic dye, pRK1, are reported. The photoelectrochemical activity for H2 production of NiO photocathodes sensitized with pRK1 (NiO|pRK1) was evaluated in combination with a cobalt tetrapyridyl catalyst in aqueous electrolyte. Comparison with two reference dyes from the literature shows that NiO|pRK1 is the most efficient photocathode. This study demonstrates that the chemical structure of dyes commonly used in DSSCs can be modified to meet the requirements for light-driven water splitting in DS-PECs.
The advent of high-field DNP-enhanced solid-state NMR has brought new challenges in the design of polarizing agents (PA) used to enhance sensitivity. Here, we present a trityl-nitroxide PA family, PyrroTriPol, based on a rigid piperazine linker. These new radicals can be readily synthesized and purified in large quantities. The rigid linker provides improved performance across a broad range of experimental conditions, while requiring reduced microwave power compared to bis-nitroxides.
A variety of 4-phosphinylpyrrolidin-3-ones was prepared in good yields and excellent diastereoselectivity via a [3+2] cycloaddition between aryl aldonitrones and phosphinylallenes. Under the reaction conditions, the cycloadducts directly undergo a rearrangement to afford selectively the corresponding pyrrolidin-3-ones. DFT calculations provide some insights into the mechanism.
Catalysis with G-quadruplexes (G4) has shown potential for asymmetric sulfoxidation of thioanisole derivatives. However, the mechanism of chiral regulation of sulfoxidation is yet unknown because G4 can adopt different topologies. To further understand the process underlying sulfoxidation, G4 was chemically constrained into a unique topology. It has been demonstrated that sulfoxidation can occur at the outside of tetrads or at the grooves, creating distinct enantiomers.
The mechanism of enantioselective sulfoxidation was clarified with the aid of these G4 mimics.