ACS Organic & Inorganic Au最新文献

In the past 5 years, hexafluoroisopropanol (HFIP) has been used as a unique solvent or additive to enable challenging transformations through substrate activation and stabilization of reactive intermediates. In this Review, we aim at describing difunctionalization processes which were unlocked when HFIP was involved. Specifically, we focus on cyclizations and additions to alkenes, alkynes, epoxides, and carbonyls that introduce a wide range of functional groups of interest.

Molybdenum(III) complexes bearing pincer-type ligands are well-known catalysts for N₂-to-NH₃ reduction. We investigated herein the impact of an anionic PNP pincer-type ligand in a Mo(III) complex on the (electro)chemical N₂ splitting ([LMoCl₃]⁻, 1^–, LH = 2,6-bis((di-tert-butylphosphaneyl)methyl)-pyridin-4-one). The increased electron-donating properties of the anionic ligand should lead to a stronger degree of N₂ activation. The catalyst is indeed active in N₂-to-NH₃ conversion utilizing the proton-coupled electron transfer reagent SmI₂/ethylene glycol. The corresponding Mo(V) nitrido complex 2H exhibits similar catalytic activity as 1H and thus could represent a viable intermediate. The Mo(IV) nitrido complex 3^– is also accessible by electrochemical reduction of 1^– under a N₂ atmosphere. IR- and UV/vis-SEC measurements suggest that N₂ splitting occurs via formation of an “overreduced” but more stable [(L(N₂)₂Mo⁰)₂μ-N₂]^2– dimer. In line with this, the yield in the nitrido complex increases with lower applied potentials.

A recent reinvestigation of the gas-phase photoelectron spectra of Group 6 metal–metal quadruple-bonded complexes with scalar-relativistic DFT calculations showed that common exchange-correlation functionals reproduce the lowest ionization potentials in a semiquantitative manner. The finding encouraged us to undertake a DFT study of metal–metal quintuple bonds in a set of bisamidinato complexes with the formula M^I₂[HC(NR)₂]₂ (M = Cr, Mo, W; R = H, Ph, 2,6-iPr₂C₆H₃) and idealized D_2h symmetry. Scalar-relativistic OLYP/STO-TZ2P calculations indicated significant shifts in valence orbital energies among the three metals, which translate to lower first ionization potentials, higher electron affinities, and lower HOMO–LUMO gaps for the W complexes relative to their Cr and Mo counterparts. These differences are largely attributable to substantially larger relativistic effects in the case of tungsten relative to those of its lighter congeners.

As the SIRTi analogue series (HL1–HL6) show potent antitumor activity in vitro, we synthesized their corresponding zinc(II) complexes (ZnL1–ZnL6) and investigated their potential as anticancer agents. The Zn(II) complexes showed substantially greater cytotoxicity than HL1–HL6 alone in several cancer cell-types. Notably, distinct structure–activity relationships confirmed the significance of tert-butyl (ZnL2) pharmacophore inclusion in their activity. ZnL2 complexes were found to transmetalate with copper ions inside cells, causing the formation of redox-active copper complexes that induced reactive oxygen species (ROS) production, mitochondrial membrane depolarization, ATP decay, and cell death. This is the first study to exhibit Zn(II) complexes that mediate their activity via transmetalation with copper ions to undergo paraptosis cell death pathway. To further confirm if the SIRT1/2 inhibitory property of SIRTi analogues is conserved, a docking simulation study is performed. The binding affinity and specific interactions of the Cu(II) complex obtained after transmetalation with ZnL2 were found to be higher for SIRT2 (K_i = 0.06 μM) compared to SIRT1 (K_i = 0.25 μM). Thus, the concurrent regulation of several biological targets using a single drug has been shown to have synergistic therapeutic effects, which are crucial for the effective treatment of cancer.

Electrochemical water oxidation is known as the anodic reaction of water splitting. Efficient design and earth-abundant electrocatalysts are crucial to this process. Herein, we report a family of catalysts (1–3) bearing bis(benzimidazole)pyrazolide ligands (H₂L1–H₂L3). H₂L3 contains electron-donating substituents and noninnocent components, resulting in catalyst 3 exhibiting unique performance. Kinetic studies show first-order kinetic dependence on [3] and [H₂O] under neutral and alkaline conditions. In contrast to previously reported catalyst 1, catalyst 3 exhibits an insignificant kinetic isotope effect of 1.25 and zero-order dependence on [NaOH]. Based on various spectroscopic methods and computational findings, the L3Co₂^III(μ-OH) species is proposed to be the catalyst resting state and the nucleophilic attack of water on this species is identified as the turnover-limiting step of the catalytic reaction. Computational studies provided insights into how the interplay between the electronic effect and ligand noninnocence results in catalyst 3 acting via a different reaction mechanism. The variation in the turnover-limiting step and catalytic potentials of species 1–3 leads to their catalytic rates being independent of the overpotential, as evidenced by Eyring analysis. Overall, we demonstrate how ligand design may be utilized to retain good water oxidation activity at low overpotentials.

During the last years, the development of more sustainable and straightforward methodologies to minimize the generation of waste organic substances has acquired high importance within synthetic organic chemistry. Therefore, it is not surprising that many efforts are devoted to ameliorating already well-known successful methodologies, that is, the case of the asymmetric allylic allylation reaction of carbonyl compounds. The use of free alcohols as alkylating agents in this transformation represents a step forward in this sense since it minimizes waste production and the substrate manipulation. In this review, we aim to gather the most recent methodologies describing this strategy by paying special attention to the reaction mechanisms, as well as their synthetic applications.

The industrial production of methanol through CO hydrogenation using the Cu/ZnO/Al₂O₃ catalyst requires harsh conditions, and the development of new catalysts with low operating temperatures is highly desirable. In this study, organic biomimetic FLP catalysts with good tolerance to CO poison are theoretically designed. The base-free catalytic reaction contains the 1,1-addition of CO into a formic acid intermediate and the hydrogenation of the formic acid intermediate into methanol. Low-energy spans (25.6, 22.1, and 20.6 kcal/mol) are achieved, indicating that CO can be hydrogenated into methanol at low temperatures. The new extended aromatization–dearomatization effect involving multiple rings is proposed to effectively facilitate the rate-determining CO 1,1-addition step, and a new CO activation model is proposed for organic catalysts.

The present review summarizes important aspects of the crystal chemistry of ytterbium-based intermetallic compounds along with a selection of their outstanding physical properties. These originate in many cases from the ytterbium valence. Different valence states are possible here, divalent (4f¹⁴), intermediate-valent, or trivalent (4f¹³) ytterbium, resulting in simple diamagnetic, Pauli or Curie–Weiss paramagnetic, or valence fluctuating behavior. Especially, some of the Yb³⁺ intermetallics have gained deep interest due to their Kondo or heavy Fermion ground states. We have summarized their property investigations using magnetic and transport measurements, specific heat data, NMR, ESR, and Mössbauer spectroscopy, elastic and inelastic neutron scattering, and XAS data as well as detailed thermoelectric measurements.

The combination of visible light catalysis and Ni catalysis has enabled the synthesis of indolyl phenyl diketones through the cyclization/oxidation process of ynones. This reaction proceeded under mild and base-free conditions and showed a broad scope and feasibility for gram-scale synthesis. Several natural products and biologically interesting molecules could be readily postfunctionalized by this method.