A Di-Copper-Peptoid in a Noninnocent Borate Buffer as a Fast Electrocatalyst for Homogeneous Water Oxidation with Low Overpotential

Water electrolysis is a promising approach toward low-cost renewable fuels; however, the high overpotential and slow kinetics limit its applicability. Studies suggest that either dinuclear copper (Cu) centers or the use of borate buffer can lead to efficient catalysis. We previously demonstrated the ability of peptoids-N-substituted glycine oligomers-to stabilize high-oxidation-state metal ions and to form self-assembled di-copper-peptoid complexes. Capitalizing on these features herein we report on a unique Cu-peptoid duplex, Cu₂(BEE)₂, that is a fast and stable homogeneous electrocatalyst for water oxidation in borate buffer at pH 9.35, with low overpotential and a high turnover frequency of 129 s^-1 (peak current measurements) or 5503 s^-1 (FOWA); both are the highest reported for Cu-based water electrocatalysts to date. BEE is a peptoid trimer having one 2,2'-bipyridine ligand and two ethanolic groups, easily synthesized on solid support. Cu₂(BEE)₂ was characterized by single-crystal X-ray diffraction and various spectroscopic and electrochemical techniques, demonstrating its ability to maintain stable in four cycles of controlled potential electrolysis, leading to a high overall turnover number of 51.4 in a total of 2 h. Interestingly, the catalytic activity of control complexes having only one ethanolic side chain is 2 orders of magnitude lower than that of Cu₂(BEE)₂. On the basis of this comparison and on mechanistic studies, we propose that the ethanolic side chains and the borate buffer have significant roles in the high stability and catalytic activity of Cu₂(BEE)₂; the -OH groups facilitate protons transfer, while the borate species enables oxygen transfer toward O-O bond formation.

Molecular and heterogeneous water oxidation catalysts: recent progress and joint perspectives

The recent synthetic and mechanistic progress in molecular and heterogeneous water oxidation catalysts highlights the new, overarching strategies for knowledge transfer and unifying design concepts.

Designed Metal-ATCUN Derivatives: Redox- and Non-redox-Based Applications Relevant for Chemistry, Biology, and Medicine

The designed "ATCUN" motif (amino-terminal copper and nickel binding site) is a replica of naturally occurring ATCUN site found in many proteins/peptides, and an attractive platform for multiple applications, which include nucleases, proteases, spectroscopic probes, imaging, and small molecule activation. ATCUN motifs are engineered at periphery by conjugation to recombinant proteins, peptides, fluorophores, or recognition domains through chemically or genetically, fulfilling the needs of various biological relevance and a wide range of practical usages. This chemistry has witnessed significant growth over the last few decades and several interesting ATCUN derivatives have been described. The redox role of the ATCUN moieties is also an important aspect to be considered. The redox potential of designed M-ATCUN derivatives is modulated by judicious choice of amino acid (including stereochemistry, charge, and position) that ultimately leads to the catalytic efficiency. In this context, a wide range of M-ATCUN derivatives have been designed purposefully for various redox- and non-redox-based applications, including spectroscopic probes, target-based catalytic metallodrugs, inhibition of amyloid-β toxicity, and telomere shortening, enzyme inactivation, biomolecules stitching or modification, next-generation antibiotic, and small molecule activation.

Copper Containing Molecular Systems in Electrocatalytic Water Oxidation—Trends and Perspectives

Molecular design represents an exciting platform to refine mechanistic details of electrocatalytic water oxidation and explore new perspectives. In the growing number of publications some general trends seem to be outlined concerning the operation mechanisms, with the help of experimental and theoretical approaches that have been broadly applied in the case of bioinorganic systems. In this review we focus on bio-inspired Cu-containing complexes that are classified according to the proposed mechanistic pathways and the related experimental evidence, strongly linked to the applied ligand architecture. In addition, we devote special attention to features of molecular compounds, which have been exploited in the efficient fabrication of catalytically active thin films.

On the copper(ii) binding of asymmetrically functionalized tripodal peptides: solution equilibrium, structure, and enzyme mimicking

The increasing histidyl functionalisation of tren results in the fundamental impact on the structure, stability and catecholase activity of its copper(ii) complexes.

Electrocatalytic water oxidation by Cu(ii) ions in a neutral borate buffer solution

Herein we report that a Cu(ii) salt can efficiently catalyze water oxidation in a neutral borate buffer.