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91.
Dirk Schlüter Florian Kleemiss Dr. Malte Fugel Dr. Enno Lork Prof. Dr. Kunihisa Sugimoto PD Dr. Simon Grabowsky Prof. Dr. Jeffrey R. Harmer Dr. Matthias Vogt 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(6):1335-1343
Derivatives of 1,2-dithienylethene (DTE) have superb photochromic properties due to an efficient reversible photocyclization reaction of their hexatriene structure and, thus, have application potential in materials for optoelectronics and (multi-responsive) molecular switches. Transition-metal complexes bearing switchable DTE motifs commonly incorporate their coordination site rather distant from the hexatriene system. In this work the redox active ligand 1,2-bis(2,5-dimethylthiophen-3-yl)ethane-1,2-dione is described, which reacts with [V(TMEDA)2Cl2] to give a rare non-oxido vanadium(IV) species 3(M,M/P,P) . This blue complex has two bidentate en-diolato ligands which chelate the VIV center and give rise to two five-membered metallacycles with the adjacent hexatriene DTE backbone bearing axial chirality. Upon irradiation with UVA light or prolonged heating in solution, the blue compound 3(M,M/P,P) converts into the purple atropisomer 4(para,M/para,P) . Both complexes were isolated and structurally characterized by single-crystal X-ray diffraction analysis (using lab source and synchrotron radiation). The antiparallel configuration (M or P helicity) present in both 3(M,M/P,P) and 4(para,M/para,P) is a prerequisite for (reversible) 6π cyclization reactions. A CW EPR spectroscopic study reveals the metalloradical character for 3(M,M/P,P) and 4(para,M/para,P) and indicates dynamic reversible cyclization of the DTE backbone in complex 3(M,M/P,P) at ambient temperature in solution. 相似文献
92.
Wenjun Yang Bo Ling Bowen Hu Haolin Yin Jianyou Mao Patrick J. Walsh 《Angewandte Chemie (International ed. in English)》2020,59(1):161-166
An umpolung 1,4‐addition of aryl iodides to enals promoted by cooperative (terpy)Pd/NHC catalysis was developed that generates various bioactive β,β‐diaryl propanoate derivatives. This system is not only the first reported palladium‐catalyzed arylation of NHC‐bound homoenolates but also expands the scope of NHC‐induced umpolung transformations. A diverse array of functional groups such as esters, nitriles, alcohols, and heterocycles are tolerated under the mild conditions. This method also circumvents the use of moisture‐sensitive organometallic reagents. 相似文献
93.
Ji‐Long Shi Rufan Chen Huimin Hao Cheng Wang Xianjun Lang 《Angewandte Chemie (International ed. in English)》2020,59(23):9088-9093
2D covalent organic frameworks (COFs) are receiving ongoing attention in semiconductor photocatalysis. Herein, we present a photocatalytic selective chemical transformation by combining sp2 carbon‐conjugated porphyrin‐based covalent organic framework (Por‐sp2c‐COF) photocatalysis with TEMPO catalysis illuminated by 623 nm red light‐emitting diodes (LEDs). Highly selective conversion of amines into imines was swiftly afforded in minutes. Specifically, the π‐conjugation of porphyrin linker leads to extensive absorption of red light; the sp2 ?C=C? double bonds linkage ensures the stability of Por‐sp2c‐COF under high concentrations of amine. Most importantly, we found that crystalline framework of Por‐sp2c‐COF is pivotal for cooperative photocatalysis with (2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl (TEMPO). This work foreshadows that the outstanding hallmarks of COFs, particularly crystallinity, could be exploited to address energy and environmental challenges by cooperative photocatalysis. 相似文献
94.
Yuanbin Zhang Jianbo Hu Rajamani Krishna Lingyao Wang Lifeng Yang Xili Cui Simon Duttwyler Huabin Xing 《Angewandte Chemie (International ed. in English)》2020,59(40):17664-17669
Separation of acetylene (C2H2) from carbon dioxide (CO2) or ethylene (C2H4) is important in industry but limited by the low capacity and selectivity owing to their similar molecular sizes and physical properties. Herein, we report two novel dodecaborate‐hybrid metal–organic frameworks, MB12H12(dpb)2 (termed as BSF‐3 and BSF‐3‐Co for M=Cu and Co), for highly selective capture of C2H2. The high C2H2 capacity and remarkable C2H2/CO2 selectivity resulted from the unique anionic boron cluster functionality as well as the suitable pore size with cooperative proton‐hydride dihydrogen bonding sites (B?Hδ????Hδ+?C≡C?Hδ+???Hδ??B). This new type of C2H2‐specific functional sites represents a fresh paradigm distinct from those in previous leading materials based on open metal sites, strong electrostatics, or hydrogen bonding. 相似文献
95.
Dr. Bence Kutus Jun Zhu Dr. Jian Luo Prof. Dr. Qi-Qiang Wang Dr. Alexandru Lupan Dr. Amr A. A. Attia Prof. Dr. De-Xian Wang Dr. Johannes Hunger 《Chemphyschem》2020,21(17):1957-1965
Tritopic ion-pair receptors can bind bivalent salts in solution; yet, these salts have a tendency to form ion-pairs even in the absence of receptors. The extent to which such receptors can enhance ion pairing has however remained elusive. Here, we study ion pairing of M2+ (Ba2+, Sr2+) and X− (I−, ClO4−) in acetonitrile with and without a dichlorooxacalix[2]arene[2]triazine-related receptor containing a pentaethylene-glycol moiety. We find marked ion association already in receptor-free solutions. When present, most of the MX+ ion-pairs are bound to the receptor and the overall degree of ion association is enhanced due to coordinative, hydrogen-bonding, and anion-π interactions. The receptor shows higher selectivity for iodides but also stabilizes perchlorates, despite the latter are often considered as weakly coordinating anions. Our results show that ion-pair binding is strongly correlated to ion pairing in these solutions, thereby highlighting the importance of taking ion association in organic solvents into account. 相似文献
96.
In this communication,we disclose the first example of metal-free and site-selective radical fluorination of readily available tertiary alkyl ethers,enabled by synergistic photocatalysis and organocatalysis.This catalytic combination allows for exclusive fluorination of tertiary C–O bonds under mild conditions even in the presence of competing reaction sites.The excellent functional group tolerance affords valuable access to sterically hindered alkyl fluorides through late-stage modification of complex molecules.The successful use of tertiary alkyl ethers in radical fluorination enhances the structural diversity of aliphatic fluorides that can be derived from naturally abundant alcohols. 相似文献
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