The structural identities of monomeric and dimeric Cr(II) sites, and the dimeric Cr(III)-hydride site, were validated, and their structures were fully determined.
Carboamination of olefins, an intermolecular process, presents a powerful platform for the rapid construction of structurally complex amines from abundant sources. However, the occurrences of these reactions are often tied to transition-metal catalysis, and primarily limited to 12-carboamination. This study details a novel 14-carboimination radical relay across two different olefins, employing bifunctional oxime esters derived from alkyl carboxylic acids, achieved through energy transfer catalysis. A highly chemo- and regioselective reaction resulted in the formation of multiple C-C and C-N bonds in a single, concerted operation. Employing a mild, metal-free approach, this method exhibits remarkably broad substrate compatibility, tolerating sensitive functional groups exceptionally well. This characteristic allows straightforward access to structurally diverse 14-carboiminated products. LF3 The obtained imines could, furthermore, be effortlessly converted into significant biologically relevant free amino acids.
A remarkable and demanding defluorinative arylboration process has been successfully executed. An intriguing defluorinative arylboration procedure of styrenes, facilitated by a copper catalyst, has been established. The methodology, built upon polyfluoroarenes as the starting materials, affords flexible and straightforward access to a diverse array of products under moderate reaction conditions. A chiral phosphine ligand enabled the enantioselective defluorinative arylboration process, generating a selection of chiral products with unparalleled enantioselectivity.
In cycloaddition and 13-difunctionalization reactions, the transition-metal-catalyzed functionalization of acyl carrier proteins (ACPs) has been a significant area of study. Although theoretically possible, nucleophilic reactions of ACPs catalyzed by transition metals are a topic of limited documentation in the scientific literature. LF3 A novel method for the synthesis of dienyl-substituted amines, utilizing palladium and Brønsted acid co-catalysis, has been developed in this article, achieving enantio-, site-, and E/Z-selectivity in the addition of ACPs to imines. The preparation of a range of synthetically valuable dienyl-substituted amines was accomplished with good to excellent yields and outstanding enantio- and E/Z-selectivities.
Polydimethylsiloxane (PDMS), possessing distinctive physical and chemical attributes, is extensively employed across numerous applications, where the process of covalent cross-linking is frequently used to cure this fluidic polymer. A non-covalent network formation in PDMS, brought about by the incorporation of terminal groups with substantial intermolecular interaction capabilities, has also been shown to enhance its mechanical properties. We recently developed a method of inducing long-range structural order in PDMS by utilizing a terminal group design facilitating two-dimensional (2D) assembly, instead of the typical multiple hydrogen bonding motifs. This approach led to a noteworthy shift in the polymer's behavior, transitioning from a fluid to a viscous solid. We demonstrate a surprising terminal-group effect: the replacement of a hydrogen atom with a methoxy group produces an extraordinary enhancement in the mechanical properties, creating a thermoplastic PDMS material devoid of covalent cross-links. The general perception that less polar and smaller terminal groups have minimal influence on polymer properties will be revised by this finding. In a detailed examination of terminal-functionalized PDMS's thermal, structural, morphological, and rheological characteristics, we observed the 2D assembly of terminal groups creating PDMS chain networks. These networks are structured into domains displaying a long-range one-dimensional (1D) periodic arrangement, ultimately leading to the storage modulus of the PDMS exceeding its loss modulus. At 120 degrees Celsius, the one-dimensional periodic arrangement dissolves, yet the two-dimensional configuration persists until 160 degrees Celsius. The two and one-dimensional structures reappear in succession during the cooling process. Due to the thermally reversible, stepwise structural disruption/formation and the absence of covalent cross-linking, the terminal-functionalized PDMS possesses thermoplastic behavior and self-healing properties. A 'plane'-forming terminal group, outlined in this report, has the potential to influence the self-assembly of other polymers into a periodic network structure, thereby significantly modifying their mechanical properties.
Advancements in material and chemical research are anticipated to arise from the accurate molecular simulations executed by near-term quantum computers. LF3 Recent progress has underscored the capacity of current quantum devices to determine the precise ground-state energies of small molecules. The significance of electronically excited states in chemical processes and applications is undeniable, yet the need for a robust and practicable method for routine excited-state computations on near-term quantum platforms continues. Based on excited-state methods in unitary coupled-cluster theory from quantum chemistry, we develop an equation-of-motion method for calculating excitation energies, analogous to the variational quantum eigensolver algorithm for determining ground-state energies on a quantum processor. Employing H2, H4, H2O, and LiH molecules as test cases, we numerically simulate these systems to evaluate our quantum self-consistent equation-of-motion (q-sc-EOM) method and compare its results with those from other contemporary leading-edge methods. To guarantee accurate calculations, q-sc-EOM leverages self-consistent operators to uphold the vacuum annihilation condition, a critical necessity. It conveys real and substantial energy discrepancies linked to vertical excitation energies, ionization potentials, and electron affinities. Implementation of q-sc-EOM on NISQ devices is anticipated to be more robust against noise than existing methods, making it a more suitable choice.
Phosphorescent Pt(II) complexes, built with a tridentate N^N^C donor ligand and a monodentate ancillary ligand, were chemically bonded to DNA oligonucleotides. Three attachment methods involving a tridentate ligand, represented as a synthetic nucleobase, connected through either 2'-deoxyribose or propane-12-diol chains, were researched, and the ligand was positioned within the major groove by connection to a uridine's C5 position. The complexes' photophysical properties are a function of the method of attachment and the nature of the monodentate ligand, either iodido or cyanido. All cyanido complexes, when integrated into the DNA's structural framework, exhibited a substantial stabilization of the duplex. The degree of luminescence is significantly impacted by the presence of a single complex compared to two adjacent ones; the latter scenario gives rise to an additional emission band, characteristic of excimer formation. Oligonucleotides, doubly platinated, could prove valuable as ratiometric or lifetime-based oxygen sensors, because the photoluminescence intensities and average lifetimes of the monomeric species dramatically increase when oxygen is removed. Conversely, the red-shifted excimer phosphorescence is virtually unaffected by the presence of dissolved triplet dioxygen.
While transition metals exhibit a high capacity for lithium storage, the underlying mechanism remains unclear. The origin of this anomalous phenomenon is revealed by in situ magnetometry, utilizing metallic cobalt as a model system. The lithium storage phenomenon in metallic cobalt is found to occur through a two-stage mechanism: injection of spin-polarized electrons into the cobalt 3d orbital, followed by the transfer of these electrons to the surrounding solid electrolyte interphase (SEI) at lower voltages. Electrode interfaces and boundaries create space charge zones with capacitive behavior, leading to the rapid storage of lithium. Hence, a transition metal anode, in contrast to existing conversion-type or alloying anodes, maintains exceptional stability while significantly increasing the capacity of common intercalation or pseudocapacitive electrodes. These results are crucial for deciphering the unique lithium storage properties of transition metals, and for the development of high-performance anodes with improved capacity and sustained long-term durability.
The in situ immobilization of theranostic agents within cancer cells, manipulated spatiotemporally, is crucial yet complex for enhancing their bioavailability in tumor diagnosis and treatment. This proof-of-concept study details the first report of a tumor-specific near-infrared (NIR) probe, DACF, possessing photoaffinity crosslinking properties, aimed at improving both tumor imaging and therapeutic outcomes. With exceptional tumor-targeting properties, this probe generates robust near-infrared/photoacoustic (PA) signals and a dominant photothermal effect, leading to high-resolution imaging and successful photothermal therapy (PTT) of tumors. Covalent attachment of DACF within tumor cells was observed following exposure to a 405 nm laser. This attachment arose from the photocrosslinking reaction of photolabile diazirine groups with surrounding biomolecules. Consequently, improved tumor accumulation and retention were achieved, thus leading to significant enhancements in in vivo tumor imaging and photothermal therapy. Accordingly, we anticipate that our current strategy will yield novel insights for the precise diagnosis and treatment of cancer.
Employing 5-10 mol% of -copper(II) complexes, the first catalytic enantioselective aromatic Claisen rearrangement of allyl 2-naphthyl ethers is presented. A Cu(OTf)2 complex, incorporating an l,homoalanine amide ligand, was found to generate (S)-products with an enantiomeric excess of up to 92%. Differently, a Cu(OSO2C4F9)2 complex bound to an l-tert-leucine amide ligand gave rise to (R)-products, with enantiomeric excesses reaching up to 76%. Computational studies employing density functional theory (DFT) indicate that these Claisen rearrangements proceed through a stepwise mechanism involving close-contact ion pairs. The (S)- and (R)-products are obtained with enantioselectivity via staggered transition states that govern the cleavage of the C-O bond, which is the rate-controlling step.