ACS Organic & Inorganic Au最新文献

A series of bis-phenolate saturated N-heterocyclic carbene (NHC) group 4 complexes ([κ³-O,C,O]-NHC)-M-(OiPr)-Cl-(THF) (M = Ti, 1; Zr, 2; Hf, 3) in the presence of [PPN]Cl as cocatalyst were investigated and showed high activity in the tandem terpolymerization of phthalic anhydride (PA), cyclohexene oxide (CHO) with CO₂. The resultant terpolymers revealed a diblock pattern leading selectively to poly-(ester-b-carbonate). Subsequently, other titanium complexes ([κ³-O,C,O]-NHC)-TiX₂ bearing various coligands (X = Cl, 4; OiPr, 5; OAc, 6; OAc^F, 7) also displayed high activity with a turnover frequency (TOF) up to 460 h^-1 that is comparable to 1. Using the same tandem approach, the nature of terpolymers was modulated with other mono- and tricyclic anhydrides alongside CHO with CO₂. Intrigued by the high rates of PA conversion observed experimentally in terpolymerization, complexes 1-3 as well as benzannulated and unsaturated NHC analogues of complex 1 were investigated as a stand-alone reaction for the copolymerization of PA and CHO. Complex 1/[PPN]Cl displayed excellent catalytic activity (TOF ∼ 1600 h^-1) and high selectivity (≥99%) toward polyesters comparable to other highly active heteronuclear (Al/K and Fe/K) catalysts and binary (salen)-MX systems. Kinetic studies performed on complexes 1 and 3 determined activation barriers (E _a) consistent with the observed catalytic trend, i.e., E _a: Ti < Hf.

Herein, we describe the photoredox activation of silanes under deep-red irradiation with or without osmium-based photocatalysts to generate silyl radicals. These radicals were further employed for achieving various reactivities previously unexplored in the red-light spectral region, such as hydrosilylation, hydrosulfonylation, and Giese reaction. Overall, the developed deep-red protocols allow for the preparation of a diverse array of high-value molecules.

This work reports on various physicochemical properties and energy conversion processes in phosphate glasses containing Sn²⁺ and Nd³⁺ ions of interest for luminescence-based applications. The glasses were prepared by melting with 50P₂O₅-(49 - x)-BaO-1Nd₂O₃-xSnO (x = 0, 1.0, 3.0, 5.0, 7.0, and 9.0 mol %) nominal compositions and characterized by X-ray diffraction, ¹¹⁹Sn Mössbauer spectroscopy, density and related physical properties, Raman spectroscopy, differential scanning calorimetry, dilatometry, optical absorption, and photoluminescence (PL) spectroscopy. X-ray diffraction confirmed the noncrystalline nature of the glasses. The ¹¹⁹Sn Mössbauer evaluation allowed for estimating the relative amounts of Sn²⁺ and Sn⁴⁺ in the glasses, which showed that Sn²⁺ occurrence was favored. The densities showed variations without definite trends; additional physical parameters were then determined such as Sn²⁺-Nd³⁺ distances based on ¹¹⁹Sn Mössbauer results. The characterization by Raman spectroscopy showed no significant structural variation was induced as SnO replaced BaO. The thermal properties of the codoped glasses assessed were however found to be impacted mostly by Sn²⁺ at high nominal SnO contents. Absorption spectra supported consistent occurrence of Nd³⁺ ions among the codoped glasses. The PL evaluation showed that exciting Sn²⁺ centers in the UV (e.g., near 290 nm) results in near-infrared emission from Nd³⁺, which was maximized for SnO added at 5 mol %. The visible PL data were consistent with the presence of Sn²⁺ in the glasses and showed dips in the emission spectra, indicating the energy transfer to Nd³⁺ ions. The Nd³⁺ decay times were however similar among the different samples.

Lithium garnets offer promising structural and electrochemical properties and could be used in all solid-state lithium batteries replacing liquid electrolytes. They can operate in a wide electrochemical voltage window and show high ionic conductivities (>10^-4 S cm^-1). The best-studied lithium garnet is Li₇La₃Zr₂O₁₂ (LLZO), which is known to undergo a transition from an ordered, tetragonal form to a disordered cubic modification at elevated temperatures. This is crucial, as the cubic modification offers about 2 orders of magnitude higher ionic conductivities. Applying the high-entropy concept to this material facilitates the stabilization of the cubic structure at ambient conditions. In this work, four different lithium garnet compositions based on Li₆La₃Zr_0.5Nb_0.5Ta_0.5Hf_0.5O₁₂ have been synthesized by mixing Zr⁴⁺, Nb⁵⁺, Ta⁵⁺, and Hf⁴⁺ by Sn⁴⁺, respectively, using two different solid-state approaches. They have been characterized by X-ray diffraction, energy-dispersive X-ray spectroscopy, and impedance spectroscopy to analyze the influence of synthesis parameters and composition on phase purity, elemental distribution, and ionic conductivity. It was found that combining calcination and sintering into one process yields a higher density and ionic conductivity than splitting it into two with intermediate regrinding of the material. Impedance data indicate an increase in ionic conductivity when substituting pentavalent ions for tetravalent ones due to the resulting higher concentration of mobile charge carriers in the structure, compared to Li₆La₃Zr_0.5Nb_0.5Ta_0.5Hf_0.5O₁₂.

We report a ligand-free, cerium-catalyzed decarboxylative fluorination of carboxylic acids via photoinduced ligand-to-metal charge transfer (LMCT) catalysis. This method utilizes readily available carboxylic acids as radical precursors, enabling the selective formation of alkyl fluorides under mild conditions. The protocol tolerates diverse carboxylic acids with a high functional group tolerance. Mechanistic studies confirm that the reaction proceeds via alkyl radical generation through light-induced LMCT of cerium-(IV) carboxylate followed by fluorine transfer. This efficient and cost-effective strategy provides a sustainable route to fluorinated molecules relevant to pharmaceuticals and agrochemicals.

The naturally low abundance of cysteine in proteins, combined with its propensity to undergo thiol–ene reactions, makes it a preferred amino acid for various bioconjugations. However, most of these methods rely on the use of UV radiation, radical initiators, or heavy-metal-based photocatalysts, which limits their applicability in complex biological environments. Herein, we report a photocatalyzed thiol–ene radical reaction that overcomes these limitations by employing a porphyrin-based photocatalyst and low-energy red light. This method operates under mild reaction conditions and can be expanded to a cysteinyl desulfurization reaction. As this approach proceeds in aqueous media and facilitates selective transformations of both simple free cysteine and cysteine residues within complex protein, it significantly expands the existing toolbox for cysteine bioconjugation.