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101.
Dr. Renata Kaczmarek Samuel Ward Dipra Debnath Taisiya Jacobs Alexander D. Stark Dariusz Korczyński Prof. Dr. Anil Kumar Prof. Dr. Michael D. Sevilla Dr. Sergey A. Denisov Dr. Viacheslav Shcherbakov Dr. Pascal Pernot Prof. Dr. Mehran Mostafavi Prof. Dr. Roman Dembinski Prof. Dr. Amitava Adhikary 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(43):9495-9505
The directionality of the hole-transfer processes between DNA backbone and base was investigated by using phosphorodithioate [P(S−)=S] components. ESR spectroscopy in homogeneous frozen aqueous solutions and pulse radiolysis in aqueous solution at ambient temperature confirmed initial formation of G.+-P(S−)=S. The ionization potential of G-P(S−)=S was calculated to be slightly lower than that of guanine in 5′-dGMP. Subsequent thermally activated hole transfer from G.+ to P(S−)=S led to dithiyl radical (P-2S.) formation on the μs timescale. In parallel, ESR spectroscopy, pulse radiolysis, and density functional theory (DFT) calculations confirmed P-2S. formation in an abasic phosphorodithioate model compound. ESR investigations at low temperatures and higher G-P(S−)=S concentrations showed a bimolecular conversion of P-2S. to the σ2-σ*1-bonded dimer anion radical [-P-2S 2S-P-]− [ΔG (150 K, DFT)=−7.2 kcal mol−1]. However, [-P-2S 2S-P-]− formation was not observed by pulse radiolysis [ΔG° (298 K, DFT)=−1.4 kcal mol−1]. Neither P-2S. nor [-P-2S 2S-P-]− oxidized guanine base; only base-to-backbone hole transfer occurs in phosphorodithioate. 相似文献
102.
Dr. Zheng-Guang Wu Xiang-Ji Liao Li Yuan Prof. Yi Wang Prof. You-Xuan Zheng Prof. Jing-Lin Zuo Prof. Yi Pan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(25):5694-5700
Click chemistry focuses on the development of highly selective reactions using simple precursors for the exquisite synthesis of molecules. Undisputedly, the CuI-catalyzed azide–alkyne cycloaddition (CuAAC) is one of the most valuable examples of click chemistry, but it suffers from some limitations as it requires additional reducing agents and ligands as well as cytotoxic copper. Here, we demonstrate a novel strategy for the azide–alkyne cycloaddition reaction that involves a photoredox electron-transfer radical mechanism instead of the traditional metal-catalyzed coordination process. This newly developed photocatalyzed azide–alkyne cycloaddition reaction can be performed under mild conditions at room temperature in the presence of air and visible light and shows good functional group tolerance, excellent atom economy, high yields of up to 99 %, and absolute regioselectivity, affording a variety of 1,4-disubstituted 1,2,3-triazole derivatives, including bioactive molecules and pharmaceuticals. The use of a recyclable photocatalyst, solar energy, and water as solvent makes this photocatalytic system sustainable and environmentally friendly. Moreover, the azide–alkyne cycloaddition reaction could be photocatalyzed in the presence of a metal-free catalyst with excellent regioselectivity, which represents an important development for click chemistry and should find versatile applications in organic synthesis, chemical biology, and materials science. 相似文献
103.
Mithilesh Kumar Nayak Jessica Stubbe Dr. Nicolás I. Neuman Dr. Ramakirushnan Suriya Narayanan Sandipan Maji Prof. Dr. Carola Schulzke Prof. Vadapalli Chandrasekhar Prof. Dr. Biprajit Sarkar Dr. Anukul Jana 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(19):4425-4431
This work presents a stepwise reversible two-electron transfer induced hydrogen shift leading to the conversion of a bis-pyrrolinium cation to an E-diaminoalkene and vice versa. Remarkably, the forward and the reverse reaction, which are both reversible, follow two completely different reaction pathways. Establishing such unprecedented property in this type of processes was possible by developing a novel synthetic route towards the starting dication. All intermediates involved in both the forward and the backward reactions were comprehensively characterized by a combination of spectroscopic, crystallographic, electrochemical, spectroelectrochemical, and theoretical methods. The presented synthetic route opens up new possibilities for the generation of multi-pyrrolinium cation scaffold-based organic redox systems, which constitute decidedly sought-after molecules in contemporary chemistry. 相似文献
104.
Matthias Müller Dr. Magnus R. Buchner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(44):9915-9922
The first synthesis of BePh2 was accomplished almost a century ago. However, its structure has remained unknown so far, while the corresponding aryls of the elements adjacent to beryllium in the periodic table are well investigated. Herein, we present an improved synthesis for diphenylberyllium and show by X-ray diffraction that it forms a trinuclear complex in the solid state. NMR spectroscopy revealed that this structure is also retained in solution but exhibits dynamic behavior. Its stability against heat and coordinating solvents is discussed and the possible obstacles to the synthesis of BePh2 from BeCl2 are examined. In the process of this study two ether adducts, BePh2⋅Et2O and Be2Ph4⋅Et2O, have been characterized as well as the previously unknown triphenylberyllate anion. From the latter several single-crystal structures were obtained under various conditions, in which [BePh3]− is either isolated or acts as a ligand for Li+. Furthermore, the crown ether induced selfionization of BePh2 is described and the resulting [(12-crown-4)BePh]+ cation was isolated, which shows an unusual 4+1 coordination around the Be atom. 相似文献
105.
Mathias Mallmann Sebastian Wendl Dr. Philipp Strobel Dr. Peter J. Schmidt Prof. Dr. Wolfgang Schnick 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(28):6257-6263
Nitridophosphates exhibit an intriguing structural diversity with different structural motifs, for example, chains, layers or frameworks. In this contribution the novel nitridophosphate Sr3P3N7 with unprecedented dreier double chains is presented. Crystalline powders were synthesized using the ammonothermal method, while single crystals were obtained by a high-pressure multianvil technique. The crystal structure of Sr3P3N7 was solved and refined from single-crystal X-ray diffraction and confirmed by powder X-ray methods. Sr3P3N7 crystallizes in monoclinic space group P2/c. Energy-dispersive X-ray and Fourier-transformed infrared spectroscopy were conducted to confirm the chemical composition, as well as the absence of NHx functionality. The optical band gap was estimated to be 4.4 eV using diffuse reflectance UV/Vis spectroscopy. Upon doping with Eu2+, Sr3P3N7 shows a broad deep-red to infrared emission (λem=681 nm, fwhm≈3402 cm−1) with an internal quantum efficiency of 42 %. 相似文献
106.
Dr. Timothy A. Barendt Dr. Melissa L. Ball Dr. Qizhi Xu Dr. Boyuan Zhang Dr. Brandon Fowler Ayden Schattman Virginia Cary Ritter Prof. Michael L. Steigerwald Prof. Colin Nuckolls 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(17):3744-3748
This work presents a synergy between organic electronics and supramolecular chemistry, in which a host–guest complex is designed to function as an efficacious electronic material. Specifically, the noncovalent recognition of a fullerene, phenyl-C61-butyric acid methyl ester ( PC61BM ), by an alternating perylene diimide ( P )-bithiophene ( B ) conjugated macrocycle ( PBPB ) results in a greater than five-fold enhancement in electron mobility, relative to the macrocycle alone. Characterization and quantification of the binding of fullerenes by host PBPB is provided alongside evidence for intermolecular electronic communication within the host–guest complexes. 相似文献
107.
Pim R. Linnebank Stephan Falcão Ferreira Alexander M. Kluwer Prof. Dr. Joost N. H. Reek 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(37):8214-8219
Regioselective catalytic transformations using supramolecular directing groups are increasingly popular as it allows for control over challenging reactions that may otherwise be impossible. In most examples the reactive group and the directing group are close to each other and/or the linker between the directing group is very rigid. Achieving control over the regioselectivity using a remote directing group with a flexible linker is significantly more challenging due to the large conformational freedom of such substrates. Herein, we report the redesign of a supramolecular Rh–bisphosphite hydroformylation catalyst containing a neutral carboxylate receptor (DIM pocket) with a larger distance between the phosphite metal binding moieties and the DIM pocket. For the first time regioselective conversion of internal and terminal alkenes containing a remote carboxylate directing group is demonstrated. For carboxylate substrates that possess an internal double bond at the Δ-9 position regioselectivity is observed. As such, the catalyst was used to hydroformylate natural monounsaturated fatty acids (MUFAs) in a regioselective fashion, forming of an excess of the 10-formyl product (10-formyl/9-formyl product ratio of 2.51), which is the first report of a regioselective hydroformylation reaction of such substrates. 相似文献
108.
Mark R. Bortolus Dr. Hélène P. A. Mercier Prof. Gary J. Schrobilgen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(41):8935-8950
The reactions of the fluoride-ion donor, XeF6, with the fluoride-ion acceptors, M′OF4 (M′=Cr, Mo, W), yield [XeF5]+ and [Xe2F11]+ salts of [M′OF5]− and [M2O2F9]− (M=Mo, W). Xenon hexafluoride and MOF4 react in anhydrous hydrogen fluoride (aHF) to give equilibrium mixtures of [Xe2F11]+, [XeF5]+, [(HF)nF]−, [MOF5]−, and [M2O2F9]− from which the title salts were crystallized. The [XeF5][CrOF5] and [Xe2F11][CrOF5] salts could not be formed from mixtures of CrOF4 and XeF6 in aHF at low temperature (LT) owing to the low fluoride-ion affinity of CrOF4, but yielded [XeF5][HF2]⋅CrOF4 instead. In contrast, MoOF4 and WOF4 are sufficiently Lewis acidic to abstract F− ion from [(HF)nF]− in aHF to give the [MOF5]− and [M2O2F9]− salts of [XeF5]+ and [Xe2F11]+. To circumvent [(HF)nF]− formation, [Xe2F11][CrOF5] was synthesized at LT in CF2ClCF2Cl solvent. The salts were characterized by LT Raman spectroscopy and LT single-crystal X-ray diffraction, which provided the first X-ray crystal structure of the [CrOF5]− anion and high-precision geometric parameters for [MOF5]− and [M2O2F9]−. Hydrolysis of [Xe2F11][WOF5] by water contaminant in HF solvent yielded [XeF5][WOF5]⋅XeOF4. Quantum-chemical calculations were carried out for M′OF4, [M′OF5]−, [M′2O2F9]−, {[Xe2F11][CrOF5]}2, [Xe2F11][MOF5], and {[XeF5][M2O2F9]}2 to obtain their gas-phase geometries and vibrational frequencies to aid in their vibrational mode assignments and to assess chemical bonding. 相似文献
109.
Dr. Qingcuomu De Prof. Xinxin Xu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(35):7923-7929
As promising fresh-water purification devices, solar steam generation systems have attracted significant attention recently. However, in practice, the approach often suffers from a poor solar energy conversion efficiency and a low water production rate due to poor material selection and inefficient microscopic structure design. Here, we fabricate an efficient solar steam generation system by “building” polyoxometalate “nano-walls” on rice paper-derived three-dimensional porous carbon paper. In this solar steam generation system, the height of the vertically aligned CoP4Mo6 “nano-walls” range from 100 to 150 nm with thicknesses about 15 to 25 nm. Under 1 sun irradiation (1 sun = 1 kW m−2), the surface temperature increases from 29 to 50 °C in a short time with a solar thermal conversion efficiency achieving 92.8 %. The stability and durability of this solar steam generation system, which withstands fifteen cycle continuous tests, also offer good prospects. Its attractive solar energy conversion performance originates from the intense sunlight absorption and high conversion ability of the CoP4Mo6 “nano-walls”, as well as extremely promising heat localization and water transportation properties of the three-dimensional porous carbon paper. This solar steam generation system, which has produced some inspiring results, is employed for seawater desalination and for purification of water polluted with organic dyes. 相似文献
110.
Henry Robinson Steven A. Oatley James E. Rowedder Pawel Slade Dr. Simon J. F. Macdonald Dr. Stephen P. Argent Prof. Dr. Jonathan D. Hirst Thomas McInally Prof. Dr. Christopher J. Moody 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(34):7678-7684
A late-stage functionalization of the aromatic ring in amino acid derivatives is described. The key step is a copper-catalysed diversification of a boronate ester by amination (Chan–Lam reaction) that can be carried out on a complex β-aryl-β-amino acid scaffold. This not only considerably extends the substrate scope of amination partners, but also delivers an array of potent and selective integrin inhibitors as potential treatment agents of idiopathic pulmonary fibrosis (IPF). This versatile chemical strategy, which is amenable to high-throughput-array protocols, allows the installation of pharmaceutically valuable heteroaromatic fragments at a late stage by direct coupling to NH heterocycles, leading to compounds with drug-like attributes. It thus constitutes a useful addition to the medicinal chemist's repertoire. 相似文献