Metallophilic interactions are increasingly recognized as playing an important role in molecular assembly, catalysis, and bio‐imaging. However, present knowledge of these interactions is largely derived from solid‐state structures and gas‐phase computational studies rather than quantitative experimental measurements. Here, we have experimentally quantified the role of aurophilic (AuI⋅⋅⋅AuI), platinophilic (PtII⋅⋅⋅PtII), palladophilic (PdII⋅⋅⋅PdII), and nickelophilic (NiII⋅⋅⋅NiII) interactions in self‐association and ligand‐exchange processes. All of these metallophilic interactions were found to be too weak to be well‐expressed in several solvents. Computational energy decomposition analyses supported the experimental finding that metallophilic interactions are overall weak, meaning that favorable dispersion and orbital hybridization contributions from M⋅⋅⋅M binding are largely outcompeted by electrostatic or dispersion interactions involving ligand or solvent molecules. This combined experimental and computational study provides a general understanding of metallophilic interactions and indicates that great care must be taken to avoid over‐attributing the energetic significance of metallophilic interactions.
Rich phase behavior was observed in salt-free cationic and anionic (catanionic) mixtures of a double-tailed surfactant, di(2-ethylhexyl)phosphoric acid (abbreviated as DEHPA), and tetradecyldimethylamine oxide (C(14)DMAO) in water. At a fixed C(14)DMAO concentration, phase transition from L(1) phase to L(α) phase occurs with increasing amounts of DEHPA. Moreover, in the L(α) phase, with the increase in DEHPA concentration, a gradual transition process from vesicle phase (L(αv)) to stacked lamellar phase (L(αl)) was determined by cryo- and FF-TEM observations combining with (2)H NMR measurements. The rheological data show that the viscosity increases with DEHPA amounts for L(αv) phase samples because of the increase in vesicle density. At a certain molar ratio of DEHPA to C(14)DMAO, i.e., 80:250, the samples are with the highest viscoelasticity, indicating the existence of densely packed vesicles. While for L(αl) phase samples, with increasing DEHPA amount, a decrease of bilayer curvature was induced, leading to a decrease of viscosity obviously. Compared with general catanionic surfactant mxitures, in addition to the electrostatic interaction of ion pairs, the transition of the microstructures is also ascribed to the formation of the hydrogen bonding (-N(+)-O-H···O-N-) between C(14)DMAO molecules and protonated C(14)DMAOH(+), which induces the growth of aggregates and the decrease of aggregate curvatures.
An atom‐economic approach that has an unprecedented high selectivity for the synthesis of lactic acid (LA) based on a catalytic dehydrogenative cross‐coupling by using inexpensive bulk ethylene glycol and methanol is described. This method relies on the synthesis and utilization of a novel iridium catalyst bearing three N‐heterocyclic carbenes derived from 1,3‐dimethylbenzimidazolium salts, and exhibits outstanding activity in the production of LA [turnover frequency (TOF) up to 3660 h−1] owing to an elegant metal–ligand cooperation.
α-Hydroxy acids have attracted broad attention because of their prevalence in bioactive molecules and biodegradable polymers, but their conventional syntheses are usually restricted to aromatic substrates, especially, in a stepwise manner. Herein, we disclose the transformation of alkyl and aryl vicinal glycols to α-hydroxy acetates in water under the air atmosphere with our solid self-supported NHC-Ir single-site catalyst. Both aliphatic and aromatic glycols are compatible with a much higher catalytic efficiency in the presence of this solid single-site catalyst than other viable molecular catalysts (93% vs <35%) because of the “isolation effect”. Remarkably, our catalyst could be reused for 20 runs without an obvious loss in catalytic activity and selectivity. Control experiments and density functional theory calculations reveal that the reaction firstly undergoes a dehydrogenation facilitated by the catalyst, and then it proceeds through an unexpected oxidization relay step by oxygen in the air, leading to the α-hydroxy acetate formation. Our protocol can potentially contribute to the valorization of readily available and inexpensive diols.
The valorization of carbon dioxide (CO2) to fine chemicals is one of the most promising approaches for CO2 capture and utilization. Herein we demonstrated a series of porous organometallic polymers could be employed as highly efficient and recyclable catalysts for this purpose. Synergetic effects of specific surface area, iridium content, and CO2 adsorption capability are crucial to achieve excellent selectivity and yields towards N‐formylation of diverse amines with CO2 and H2 under mild reaction conditions even at 20 ppm catalyst loading. Density functional theory calculations revealed not only a redox‐neutral catalytic pathway but also a new plausible mechanism with the incorporation of the key intermediate formic acid via a proton‐relay process. Remarkably, a record turnover number (TON=1.58×106) was achieved in the synthesis of N,N‐dimethylformamide (DMF), and the solid catalysts can be reused up to 12 runs, highlighting their practical potential in industry.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.