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991.
Kevin M. Szkop Dr. Andrew R. Jupp Hlib Razumkov Maotong Xu Prof. Dr. Douglas W. Stephan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(43):10084-10087
The phosphaketene Ph3GePCO is shown to react with the phosphide KP(tBu)2 to generate the anion [Ph3GePC(O)P(tBu)2]− 1 . This species reacts with CH3I or ClGePh3 to give the dissymmetric diphospha-ureas (tBu)2PC(O)P(GePh3)(CH3) 2 and (Ph3Ge)2PC(O)P(tBu)2 3 respectively. Sequential treatment of 2 with a base and CH3I affords a route to (tBu)2PC(O)P(CH3)2 5 . These species are products of the first modular diphospha-urea synthesis. The subsequent thermal and photochemical reactivity of these species was also probed and described. 相似文献
992.
Li-Dan Lin Prof. Dr. Dan Zhao Prof. Dr. Xin-Xiong Li Prof. Dr. Shou-Tian Zheng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(2):442-453
During the past decade, research on the design and synthesis of zeolite-like metal–organic frameworks (ZMOFs) has developed greatly. As an important subclass of ZMOFs, zeolite-like cluster organic frameworks (ZCOFs) built from 4-connected metal-cluster secondary building units (SBUs) and appropriate linear organic ligand bridges have attracted sustained interest, because such materials not only integrate the merits of inorganic zeolites, ZMOFs, and metal clusters, including interesting topologies, high surface areas, extra-large cavities and channels, structural tunability, and unique physicochemical properties from various metal clusters, but also open up a new avenue to design and fabricate hybrid zeolite-like materials that have many potential applications in material sciences. In this review, recent developments in ZCOFs are summarized by classifying the ZCOFs into four categories according to the composition of the SBUs: 1) ZCOFs based on metal–halide cluster SBUs, 2) ZCOFs based on metal–oxygen cluster SBUs, 3) ZCOFs based on metal–chalcogen cluster SBUs, and 4) ZCOFs based on mixed types of metal-cluster SBUs. Besides, challenges associated with the design and synthesis of ZCOFs and the vast potential of this area are also discussed. 相似文献
993.
Dr. Yunyi Gao Jiahui Chen Tong Zhang Jennifer E. S. Szymanowski Prof. Dr. Peter C. Burns Prof. Dr. Tianbo Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(69):15741-15745
An interesting phenomenon is reported when uranyl peroxide nanoclusters U60 (Li48+mK12(OH)m[UO2(O2)(OH)]60 (H2O)n, m≈20 and n≈310) interact with a small number of cationic surfactant molecules. Cationic surfactant molecules do not distribute evenly around the U60 clusters during the interaction as expected. Instead, a small fraction of U60 clusters attract almost all the surfactant molecules, leading to the self-assembly into supramolecular structures by using surfactant–U60 complexes as building locks, and later further aggregate and precipitate based on hydrophobic interaction, whereas the rest of the clusters remained unbounded soluble macroions in bulk dispersion. This phenomenon nicely demonstrates a unique feature of macroion solutions. Considering that Debye–Hückel approximation is no longer valid in such solutions, the competition between the local electrostatic interaction and hydrophobic interaction becomes important to regulate the solution behaviors of macroions. 相似文献
994.
Prof. Hisahiro Sasabe Prof. Yuki Kato Dr. Yuichiro Watanabe Tatsuya Ohsawa Dr. Naoya Aizawa Prof. Wataru Fujiwara Dr. Yong-Jin Pu Prof. Hiroshi Katagiri Prof. Junji Kido 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(71):16294-16300
Exploration of pure metal-free organic molecules that exhibit strong room-temperature phosphorescence (RTP) is an emerging research topic. In this regard, unveiling the design principles for an efficient RTP molecule is an essential, but challenging, task. A small molecule is an ideal platform to precisely understand the fundamental role of each functional component because the parent molecule can be easily derivatized. Here, the RTP behaviors of a series of 3-pyridylcarbazole derivatives are presented. Experimental studies in combination with theoretical calculations reveal the crucial role of the n orbital on the central pyridine ring in the dramatic enhancement of the intersystem crossing between the charge-transfer-excited singlet state and the locally excited triplet states. Single-crystal X-ray crystallographic studies apparently indicate that both the pyridine ring and fluorine atom contribute to the enhancement of the RTP because of the restricted motion owing to weak C−H⋅⋅⋅N and H⋅⋅⋅F hydrogen-bonding interactions. The single crystal of the fluorine-substituted derivative shows an ultra-long phosphorescent lifetime (τP) of 1.1 s and a phosphorescence quantum yield (ΦP) of 1.2 %, whereas the bromine-substituted derivative exhibits τP of 0.15 s with a ΦP of 7.9 %. We believe that this work provides a fundamental and universal guideline for the generation of pure organic molecules exhibiting strong RTP. 相似文献
995.
Dr. Patrick Feicht Dr. Johannes Biskupek Dr. Tatiana E. Gorelik Julian Renner Dr. Christian E. Halbig Maria Maranska Florian Puchtler Prof. Dr. Ute Kaiser Prof. Dr. Siegfried Eigler 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(38):8955-8959
Synthesis and studies of graphite oxide started more than 150 years ago and turned into a boom by the measurements of the outstanding physical properties of graphene. A series of preparation protocols emanated trying to optimize the synthesis of graphene oxide in order to obtain a less defective material, as source for graphene. However, over-oxidation of the carbon framework hampered establishing structure-property relationships. Here, the fact that two different synthetic methods for graphene oxide preparation lead to very similar types of graphene oxide with a preserved graphene lattice is demonstrated. Either sodium chlorate in nitric acid (similar to Brodie's method) or potassium permanganate in sulfuric acid (similar to Hummers’ method) treatment are possible; however, reaction conditions must be controlled. With a preserved carbon lattice analytical differences between the samples relate to the altered on-plane functionality. Consequently, terming preparation protocols “according to Brodie's/Hummers’ method” is not sufficient. 相似文献
996.
Prof. Jun Ishihara Fuma Usui Tomohiro Kurose Tomohiro Baba Yasunori Kawaguchi Yuki Watanabe Prof. Susumi Hatakeyama 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(6):1543-1552
The upper fragment of spirolides A and B, which are marine phycotoxins that exhibit strong antagonistic activities on nicotinic acetylcholine receptors, was constructed. The functionalized cyclohexene in spirolides was stereoselectively synthesized from the bicyclic lactone, which could be readily accessed by the Lewis acid template-catalyzed asymmetric Diels–Alder reaction of the pentadienol and methyl acrylate. 相似文献
997.
Dr. Lan Hu Prof. Dr. Yan Zhao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(32):7702-7710
Outcomes of chemical reactions are generally dominated by the intrinsic reactivities of reaction partners, but enzymes frequently override such constraints to transform less reactive molecules in the presence of more reactive ones. Despite the attractiveness of such catalysis, it is difficult to build synthetic catalysts with these features. Micellar imprinting is a powerful method to create template-complementary binding sites inside protein-sized water-soluble nanoparticles. When a photocleavable functional monomer was used to bind two phosphonate/phosphate templates as transition-state analogues, active sites with predetermined size and shape were formed inside doubly cross-linked micelles through molecular imprinting. Postmodification replaced the binding group with a catalytic pyridyl group, forming highly selective artificial esterases. The catalysts displayed enzyme-like kinetics and turnover numbers that were in the hundreds. The selectivity of the catalysts, derived from the substrate-complementary imprinted active sites, enabled transformation of less reactive esters in the presence of more reactive ones. 相似文献
998.
Ke Xu Evan T. Vickers Longshi Rao Dr. Sarah A. Lindley A'Lester C. Allen Prof. Binbin Luo Prof. Xueming Li Prof. Jin Zhong Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(19):5014-5021
CH3NH3PbBr3 perovskite quantum dots (PQDs) are synthesized by using four different linear alkyl phosphonic acids (PAs) in conjunction with (3-aminopropyl)triethoxysilane (APTES) as capping ligands. The resultant PQDs are characterized by means of XRD, TEM, Raman spectroscopy, FTIR spectroscopy, UV/Vis, photoluminescence (PL), time-resolved PL, and X-ray photoelectron spectroscopy (XPS). PA chain length is shown to control the PQD size (ca. 2.9–4.2 nm) and excitonic absorption band positions (λ=488–525 nm), with shorter chain lengths corresponding to smaller sizes and bluer absorptions. All samples show a high PL quantum yield (ca. 46–83 %) and high PL stability; this is indicative of a low density of band gap trap states and effective surface passivation. Stability is higher for smaller PQDs; this is attributed to better passivation due to better solubility and less steric hindrance of the shorter PA ligands. Based on the FTIR, Raman, and XPS results, it is proposed that Pb2+ and CH3NH3+ surface defects are passivated by R−PO32− or R−PO2(OH)−, whereas Br− surface defects are passivated by R−NH3+ moieties. This study establishes the combination of PA and APTES ligands as a highly effective dual passivation system for the synergistic passivation of multiple surface defects of PQDs through primarily ionic bonding. 相似文献
999.
Eunchan Jeong Joon Heo Dr. Sehoon Park Prof. Dr. Sukbok Chang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(25):6320-6325
While numerous organo(metallic)catalyst systems were documented for dearomative hydroboration of N-aromatics, alkoxide base catalysts have not been disclosed thus far. Described herein is the first example of alkoxide-catalyzed hydroboration of N-heteroaromatics including pyridines, providing a broad range of reduced N-heterocycles with high efficiency and selectivity. Mechanistic studies revealed an unprecedented counterintuitive dearomatization pathway, in which 1) pyridine-BH3 adducts undergo a hydride attack by alkoxyborohydrides, 2) in situ generated BH3 serves as a catalytic promoter, and 3) 1,4-dihydropyridyl borohydride is in a predominant resting state. 相似文献
1000.
Hedda Schrey Prof. Dr. Peter Spiteller 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(34):8035-8042
Fruiting bodies of Laccaria proxima were screened for the presence of new secondary metabolites by means of HPLC-UV and LC-HR-(+)-ESIMS. Thus, two isomeric alkaloids with a highly unusual core structure, E-proxamidine and its Z-isomer, were isolated from Laccaria proxima. The proxamidines consist of an eight-membered heterocyclic ring system with a formamidine unit. The structures were established by 2D NMR spectroscopic methods, HR-(+)-ESIMS, and HR-(+)-ESIMS/MS. The proxamidines are probably biosynthetically derived from tryptophan, dimethylallyl pyrophosphate, and S-adenosylmethionine and the eight-membered ring of the proxamidines is likely to be generated by a rearrangement of the tryptophan sceleton. Metabolic profiling of fruiting bodies of some other Laccaria species revealed that the proxamidines appear in significant amounts only in L. proxima making the compounds suitable as chemotaxonomic markers. E-Proxamidine exhibits herbicidal activity against Lepidium sativum. 相似文献