Dioxygen Activation by Gold(I)-Distorted Porphyrin Dinuclear Complexes

Interactions between gold-based materials and dioxygen (O2) have motivated researchers to understand reaction mechanisms for O2 activation by homo- and heterogeneous gold catalysts. In this work, gold(I) porphyrin dinuclear complexes were synthesized with a saddle-distorted porphyrin ligand. The gold(I) porphyrin complexes showed unprecedented O2 activation in the presence of protic solvents to form gold(III) tetradentate porphyrin complexes. Mechanistic insights into the O2 activation by the gold(I) center were elucidated by spectroscopic measurements and theoretical calculations, revealing that dissociation of halides on the gold(I) center by alcohol solvents and hydrogen bonding of an N-H proton in the distorted porphyrin with dioxygen played important roles in establishing the unique reactivities of gold(I) complexes.

Valence Tautomerism Induced Proton Coupled Electron Transfer:X-H Bond Oxidation with a Dinuclear Au(II) Hydroxide Complex

We report the preparation and characterization of the dinuclear AuII hydroxide complex AuII 2(L)2(OH)2 (L=N,N'-bis (2,6-dimethyl) phenylformamidinate) and study its reactivity towards weak X-H bonds. Through the interplay of kinetic analysis and computational studies, we demonstrate that the oxidation of cyclohexadiene follows a concerted proton-coupled electron transfer (cPCET) mechanism, a rare type of reactivity for Au complexes. We find that the Au-Au σ-bond undergoes polarization in the PCET event leading to an adjustment of oxidation levels for both Au centers prior to C(sp3)-H bond cleavage. We thus describe the oxidation event as a valence tautomerism-induced PCET where the basicity of one reduced Au-OH unit provides a proton acceptor and the second more oxidized Au center serves as an electron acceptor. The coordination of these events allows for unprecedented radical-type reactivity by a closed shell AuII complex.

A Cavity-Shaped Gold(I) Fragment Enables CO2 Insertion into Au-OH and Au-NH Bonds

A cavity-shaped linear gold(I) hydroxide complex acts as a platform to access unusual gold monomeric species. Notably, this sterically crowded gold fragment enables the trapping of CO₂ via insertion into Au-OH and Au-NH bonds to form unprecedented monomeric gold(I) carbonate and carbamate complexes. In addition, we succeeded in the identification of the first gold(I) terminal hydride bearing a phosphine ligand. The basic nature of the Au(I)-hydroxide moiety is also explored through the reactivity toward other molecules containing acidic protons such as trifluoromethanesulfonic acid and terminal alkynes.

An overview of blockchain efficient interaction technologies

The successful operation of Bitcoin has made its underlying blockchain technology receive wide attention. As the application scenarios of blockchain technology are enriched, the requirements for its performance are getting higher. Therefore, it is of utmost importance to effectively solve the problem of high-performance data interaction in the blockchain. In this paper, based on relevant domestic and foreign research literature, we start from the development history of blockchain technology and review the relevant research work on improving the performance of blockchain from three perspectives: on-chain interaction technology, off-chain interaction technology, and cross-chain interaction technology in turn. The on-chain and off-chain interaction technologies improve performance by improving the architecture of the blockchain system. The performance improvement solution of on-chain interaction technology is to modify and optimize the basic protocol and architecture of the blockchain itself to achieve a performance improvement. Still, the impact of this approach is limited in terms of performance improvement. The performance improvement solution of off-chain interaction technology is to transfer part of the data processing to off-chain and only return the final result to on-chain for storage and recording, which reduces the burden of on-chain operation and improves the efficiency of data processing. In terms of cross-chain interaction technology, this paper analyses four mainstream technology, namely, Notary Scheme, Side chain and Chain relay, Hash-Locking, and Distributed Private Key Control, and ultimately concludes through comparative analysis that cross-chain technology has a significant impact on improving blockchain performance. Finally, the paper provides a systematic overview of the above and an outlook on the possible future development of technologies related to enhancing blockchain performance.

Understanding the Surprising Oxidation Chemistry of Au-OH Complexes

Au is known to be fairly redox inactive (in catalysis) and bind oxygen adducts only quite weakly. It is thus rather surprising that stable Au-OH complexes can be synthesized and used as oxidants for both one- and two-electron oxidations. A charged AuIII -OH complex has been shown to cleave C-H and O-H bonds homolytically, resulting in a one-electron reduction of the metal center. Contrasting this, a neutral AuIII -OH complex performs oxygen atom transfer to phosphines, resulting in a two-electron reduction of the hydroxide proton to form a AuIII -H rather than causing a change in oxidation state of the metal. We explore the details of these two examples and draw comparisons to the more conventional reactivity exhibited by AuI -OH. Although the current scope of known Au-OH oxidation chemistry is still in its infancy, the current literature exemplifies the unique properties of Au chemistry and shows promise for future findings in the field.

Direct oxygen atom transfer versus electron transfer mechanisms in the phosphine oxidation by nonheme Mn(iv)-oxo complexes

Direct oxygen atom transfer from Mn(iv)-oxo to Ph₃P occurs, exhibiting significant steric effects of the ortho-substitution of the phenyl group, whereas in the presence of HOTf, the mechanism is switched to electron transfer from Ph₃P to Mn(iv)-oxo, exhibiting no steric effects.

An element through the looking glass: exploring the Au-C, Au-H and Au-O energy landscape

Gold, the archetypal "noble metal", used to be considered of little interest in catalysis. It is now clear that this was a misconception, and a multitude of gold-catalysed transformations has been reported. However, one consequence of the long-held view of gold as inert metal is that its organometallic chemistry contains many "unknowns", and catalytic cycles devised to explain gold's reactivity draw largely on analogies with other transition metals. How realistic are such mechanistic assumptions? In the last few years a number of key compound classes have been discovered that can provide some answers. This Perspective attempts to summarise these developments, with particular emphasis on recently discovered gold(iii) complexes with bonds to hydrogen, oxygen, alkenes and CO ligands.

Gold-acetonyl complexes: from side-products to valuable synthons

A new synthetic strategy was devised leading to the formation of complexes, such as [Au(IPr)(CH2 COCH3)]. The approach capitalizes on the formation of a decomposition product observed in the course of the synthesis of [Au(IPr)(Cl)]. A library of gold acetonyl complexes containing the most common N-heterocyclic carbene (NHC) ligands has been synthesized. These acetonyl complexes are good synthons for the preparation of numerous organogold complexes. Moreover, they have proven to be precatalysts in common gold(I)-catalyzed reactions.

Enhanced π-backdonation from gold(I): isolation of original carbonyl and carbene complexes

The specific electronic properties of bent o-carborane diphosphine gold(I) fragments were exploited to obtain the first classical carbonyl complex of gold [(DPCb)AuCO](+) (ν(CO)=2143 cm(-1) ) and the diphenylcarbene complex [(DPCb)Au(CPh2 )](+) , which is stabilized by the gold fragment rather than the carbene substituents. These two complexes were characterized by spectroscopic and crystallographic means. The [(DPCb)Au](+) fragment plays a major role in their stability, as substantiated by DFT calculations. The bending induced by the diphosphine ligand substantially enhances π-backdonation and thereby allows the isolation of carbonyl and carbene complexes featuring significant π-bond character.

Trapping atmospheric CO2 with gold

The ability of gold-hydroxides to fix CO2 is reported. [Au(IPr)(OH)] and [{Au(IPr)}2(μ-OH)][BF4] react with atmospheric CO2 to form the trigold carbonate complex [{Au(IPr)}3(μ(3)-CO3)][BF4]. Reactivity studies revealed that this complex behaves as two basic and one cationic Au centres, and that it is catalytically active. DFT calculations and kinetic experiments have been carried out.