Angelo Kirchon  Jialuo Li  Fangqing Xia  Gregory S. Day  Benjamin Becker  Wenmiao Chen  Hung‐Jue Sue  Yu Fang  Hong‐Cai Zhou 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(36):12555-12560

Modulation and templating are two synthetic techniques that have garnered significant attention over the last several years for the preparation of hierarchically porous metal–organic frameworks (HP‐MOFs). In this study, by using fatty acids with different lengths and concentrations as dual‐functional modulators/templates, we were able to obtain HP‐MOFs with tunable mesopores that exhibit different pore diameters and locations. We found that the length and concentration of the fatty acids can determine if micelle formation occurs, which in turn dictates the porosity of the resulting HP‐MOFs. The HP‐MOFs with different mesopores differed in their performance in gas uptake and dye adsorption, and the structure–performance relationships were ascribed to the pore diameters and locations. This approach could provide a potentially universal method to efficiently introduce hierarchal mesopores into existing microporous MOF adsorbents with tunable properties.  相似文献   

    

Xing Huang  Detre Teschner  Maria Dimitrakopoulou  Alexey Fedorov  Benjamin Frank  Ralph Kraehnert  Frank Rosowski  Harry Kaiser  Stephan Schunk  Christiane Kuretschka  Robert Schlgl  Marc‐Georg Willinger  Annette Trunschke 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(26):8688-8688

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Dr. Benjamin R. Lichman  Prof. Dr. Sarah E. O'Connor  Dr. Hajo Kries 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(28):6864-6877

Long sought after [4+2] cyclases have sprouted up in numerous biosynthetic pathways in recent years, raising hopes for biocatalytic solutions to cycloaddition catalysis, an important problem in chemical synthesis. In a few cases, detailed pictures of the inner workings of these catalysts have emerged, but intense efforts to gain deeper understanding are underway by means of crystallography and computational modelling. This Minireview aims to shed light on the catalytic strategies that this highly diverse family of enzymes employs to accelerate and direct the course of [4+2] cycloadditions with reference to small-molecule catalysts and designer enzymes. These catalytic strategies include oxidative or reductive triggers and lid-like movements of enzyme domains. A precise understanding of natural cycloaddition catalysts will be instrumental for customizing them for various synthetic applications.  相似文献   

    

Benjamin H. Strudwick  Mark A. J. Koenis  Hans J. Sanders  Valentin P. Nicu  Sander Woutersen  Prof. Wybren Jan Buma 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(54):12560-12566

Vibrational circular dichroism (VCD) studies are reported on a chiral compound in which a fullerene C₆₀ moiety is used as an electron acceptor and local VCD amplifier for an alanine-based peptide chain. Four redox states are investigated in this study, of which three are reduced species that possess low-lying electronic states as confirmed by UV/Vis spectroelectrochemistry. VCD measurements in combination with (TD)DFT calculations are used to investigate (i) how the low-lying electronic states of the reduced species modulate the amplification of VCD signals, (ii) how this amplification depends on the distance between oscillator and amplifier, and (iii) how the spatial extent of the amplifier influences amplification. These results pave the way for further development of tailored molecular VCD amplifiers.  相似文献   

    

Benjamin A. R. Günther  Dr. Sebastian Höfener  Dr. Ute Zschieschang  Prof. Dr. Hubert Wadepohl  Dr. Hagen Klauk  Prof. Dr. Lutz H. Gade 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(64):14669-14678

A new synthesis of tetraazaperopyrenes (TAPPs) starting from a halogenated perylene derivative 3,4,9,10- tetrabromo-1,6,7,12-tetrachloroperylene ( 1 ) gave access to bay-substituted TAPPs for the first time. Selective lithiation of the bromine-positions and subsequent addition of tosyl azide led to the formation of the tetraazidotetrachloroperylene ( 2 ), which was subsequently reduced by addition of sodium borohydride to the corresponding tetraaminotetrachloroperylene ( 3 ). Oxidation to its semiquinoidal form 4 and subsequent cyclization with acid chlorides gave rise to a series of bay-chlorinated TAPPs. Whereas the aromatic core of the previously studied ortho-substituted TAPPs was found to be planar, the steric pressure of the two chlorine substituents on each side leads to the twist of the peropyrene core of approximately 30 degrees, a structural feature also observed in other bay-substituted perylene derivatives. An experimental and computational analysis reveals that introducing chloride substituents at these positions leads to slightly increased electron affinities (EA) enabling the selective generation and characterization of the reduced mono-anionic radicals and closed shell di-anionic species. These anions were isolated and characterized by UV/Vis spectroscopy and EPR or NMR, respectively. Processing of the bay-chlorinated TAPPs in n-channel organic TFTs revealed electron mobilities of 0.001 to 0.003 cm² V⁻¹ s⁻¹. These reduced electron mobilities compared to the ortho-halogenated TAPPs are thought to be rooted in the less densely packed solid-state structures.  相似文献   

    

Durga D. Khanal  Yehia Z. Baghdady  Benjamin J. Figard  Kevin A. Schug 《Rapid communications in mass spectrometry : RCM》2019,33(9):821-830

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Lucas Schreyer  Roberta Properzi  Benjamin List 《Angewandte Chemie (International ed. in English)》2019,58(37):12761-12777

High acidity and structural confinement are pivotal elements in asymmetric acid catalysis. The recently introduced imidodiphosphorimidate (IDPi) Brønsted acids have met with remarkable success in combining those features, acting as powerful Brønsted acid catalysts and “silylium” Lewis acid precatalysts in numerous thus far inaccessible transformations. Substrates as challenging to activate as simple olefins were readily transformed, ketones were employed as acceptors in aldolizations allowing sub‐ppm level catalysis, whereas enolates of the smallest donor aldehyde, acetaldehyde, did not polymerize but selectively added a single time to a variety of acceptor aldehydes.  相似文献   

    

Benjamin M. Tansi  Matthew L. Peris  Oleg E. Shklyaev  Anna C. Balazs  Ayusman Sen 《Angewandte Chemie (International ed. in English)》2019,58(8):2526-2526

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Benjamin Schmidt  Benjamin Schrder  Karsten Sonnenberg  Simon Steinhauer  Sebastian Riedel 《Angewandte Chemie (International ed. in English)》2019,58(30):10340-10344

Pseudohalogens are defined as molecular entities that resemble the halogens in their chemistry. While our understanding of polyhalogen chemistry has increased over the last years, research on polypseudohalogen compounds is lacking. The pseudohalogen BrCN possesses a highly pronounced σ‐hole at the bromine side of the molecule, inducing strong halogen bonding. This allows the synthesis and characterization of new polypseudohalogen anions, as shown by the single‐crystal X‐ray diffraction of [PNP][Br(BrCN)] and [PNP][Br(BrCN)₃]. Both the nearly linear anion [Br(BrCN)]^? and the distorted pyramidal anion [Br(BrCN)₃]^? were characterized by Raman spectroscopy and quantum‐chemical calculations. The behavior of the polypseudohalogen compounds in solution and as room‐temperature ionic liquids (RT‐ILs) using the [NBu₄]⁺ cation was studied by ¹³C and ¹⁵N NMR spectroscopy. These types of ILs are capable of dissolving elemental gold and offer themselves as promising compounds in metal recycling.  相似文献   

    

Benjamin V. C. Collins 《International Journal of Mathematical Education in Science & Technology》2019,50(5):728-746

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