Our findings confirmed the presence of monomeric and dimeric Cr(II) species, as well as dimeric Cr(III) hydride centers, and their structures were elucidated.
The rapid construction of complex amines from plentiful feedstocks is facilitated by intermolecular carboamination of olefins. However, the occurrences of these reactions are often tied to transition-metal catalysis, and primarily limited to 12-carboamination. A novel radical relay 14-carboimination process, operating across two distinct olefins and utilizing alkyl carboxylic acid-derived bifunctional oxime esters, is presented, demonstrating energy transfer catalysis. Multiple C-C and C-N bonds emerged in a single, meticulously orchestrated chemo- and regioselective reaction. 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. click here In addition, the synthesized imines could be effortlessly converted to valuable free amino acids with biological significance.
In a groundbreaking endeavor, defluorinative arylboration, though challenging, has been realized. The defluorinative arylboration of styrenes, facilitated by a copper catalyst, has been established as an interesting procedure. The methodology, built upon polyfluoroarenes as the starting materials, affords flexible and straightforward access to a diverse array of products under moderate reaction conditions. Using a chiral phosphine ligand, an enantioselective defluorinative arylboration was carried out, producing a series of chiral products with unprecedented degrees of enantioselectivity.
In cycloaddition and 13-difunctionalization reactions, the transition-metal-catalyzed functionalization of acyl carrier proteins (ACPs) has been a significant area of study. Transition metal catalysis of nucleophilic reactions on ACPs has, unfortunately, not been frequently observed in the literature. click here This article details a palladium- and Brønsted acid co-catalyzed method for the enantio-, site-, and E/Z-selective addition of ACPs to imines, yielding dienyl-substituted amines. With good to excellent yields and remarkable enantio- and E/Z-selectivities, a series of synthetically valuable dienyl-substituted amines were effectively prepared.
Polydimethylsiloxane (PDMS), owing to its distinctive physical and chemical characteristics, finds extensive application in diverse fields, where covalent cross-linking is a prevalent method for curing the polymer. The creation of a non-covalent network within PDMS, driven by the incorporation of terminal groups with robust intermolecular interaction strengths, has also been documented as improving the mechanical properties. A terminal group design enabling two-dimensional (2D) assembly, contrasting with the standard multiple hydrogen bonding motifs, recently enabled our demonstration of a strategy to induce extensive structural order in PDMS, resulting in a pronounced transition from a fluid state to a viscous solid. A novel terminal-group effect is presented: the simple substitution of a hydrogen atom for a methoxy group results in an exceptional strengthening of the mechanical properties, yielding a thermoplastic PDMS material that is not crosslinked covalently. The generally accepted view that the effects of less polar and smaller terminal groups on polymer properties are negligible will be modified by this observation. 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. Heating leads to the loss of the one-dimensional periodic pattern near 120 degrees Celsius, in contrast to the two-dimensional organization, which endures until 160 degrees Celsius. Both structures re-emerge during cooling, first two-dimensional, then one-dimensional. The absence of covalent cross-linking, combined with the thermally reversible, stepwise structural disruption and formation, leads to thermoplastic behavior and self-healing properties in the terminal-functionalized PDMS. Herein presented is a terminal group capable of 'plane' formation. This group may also direct the assembly of other polymers into a periodically structured network, thus significantly altering their mechanical properties.
Advancements in material and chemical research are anticipated to arise from the accurate molecular simulations executed by near-term quantum computers. click here Profound progress in quantum computing has already exhibited the aptitude of present-day devices to calculate accurate ground-state energies for small molecules. Although essential to chemical reactions and applications, the quest for a trustworthy and practical method for common excited-state computations on near-future quantum processors continues. Inspired by excited-state approaches from the unitary coupled-cluster framework in quantum chemistry, we develop an equation-of-motion method for computing excitation energies, compatible with the variational quantum eigensolver algorithm for determining ground-state energies on a quantum computer. To evaluate our quantum self-consistent equation-of-motion (q-sc-EOM) method, numerical simulations are carried out on H2, H4, H2O, and LiH molecules, juxtaposing its results with those obtained from other cutting-edge methods. In q-sc-EOM, self-consistent operators are instrumental in fulfilling the vacuum annihilation condition, an essential aspect of accurate computational work. Energy differences, substantial in their impact and real in nature, are presented for vertical excitation energies, ionization potentials, and electron affinities. The expected noise resistance of q-sc-EOM makes it a preferable choice for NISQ device implementation, superior to the currently available methodologies.
DNA oligonucleotides were functionalized with phosphorescent Pt(II) complexes, which incorporated a tridentate N^N^C donor ligand and a monodentate ancillary ligand for enhanced properties. 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 behavior is determined by the attachment approach and the kind of monodentate ligand present, being iodido or cyanido. All cyanido complexes demonstrated a substantial stabilization of the DNA duplex when their structures were bound to the DNA backbone. A single complex or a pair of adjacent complexes leads to differing luminescence levels; the latter setup displays a supplementary emission band, a clear indication of excimer formation. As oxygen sensors, doubly platinated oligonucleotides could be promising ratiometric or lifetime-based tools, as the deoxygenation dramatically increases the green photoluminescence intensities and average lifetimes of the monomeric species, contrasting with the nearly insensitive red-shifted excimer phosphorescence to the presence of triplet dioxygen in the solution.
Although transition metals effectively accommodate substantial lithium storage, the explanation for this characteristic is not yet entirely known. In situ magnetometry, using metallic cobalt as a test system, discerns the origin of this anomalous phenomenon. Studies demonstrate that lithium storage in metallic cobalt proceeds through a two-stage mechanism, characterized by spin-polarized electron injection into the cobalt 3d orbital and subsequent electron transfer to the surrounding solid electrolyte interphase (SEI) at reduced electrochemical potentials. Space charge zones, exhibiting capacitive behavior, form at the electrode interface and boundaries, facilitating rapid lithium storage. In conclusion, transition metal anodes elevate the capacity of common intercalation or pseudocapacitive electrodes, showing markedly superior stability than existing conversion-type or alloying anodes. These findings lay the groundwork for understanding the peculiar lithium storage mechanisms of transition metals, and for the design of high-performance anodes with improved capacity and endurance.
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 initial report details a near-infrared (NIR) probe, DACF, specifically designed for tumor targeting and equipped with photoaffinity crosslinking characteristics, leading to enhanced tumor imaging and therapeutic applications. The probe, featuring significant tumor-targeting ability, is equipped with intense near-infrared/photoacoustic (PA) signals and a marked photothermal effect, enabling accurate tumor imaging and efficient photothermal therapy (PTT). In a significant observation, a 405 nm laser triggered the covalent bonding of DACF to tumor cells. This bonding occurred through photocrosslinking reactions between photolabile diazirine groups and adjacent biomolecules. The result was a simultaneous increase in tumor uptake and prolonged retention, markedly improving both in vivo tumor imaging and photothermal therapy efficacy. Subsequently, we are of the opinion that our current methodology furnishes a new perspective for achieving precise cancer theranostics.
Employing 5-10 mol% of -copper(II) complexes, the first catalytic enantioselective aromatic Claisen rearrangement of allyl 2-naphthyl ethers is presented. Enantiomeric excesses of up to 92% were observed in (S)-products resulting from the reaction of an l,homoalanine amide ligand with a Cu(OTf)2 complex. 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%. Density functional theory (DFT) calculations show that these Claisen rearrangements occur through a sequential mechanism facilitated by closely bound ion pairs. Enantioselective production of (S)- and (R)-products originates from staggered transition states affecting the C-O bond scission, which is the rate-limiting step in the process.