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排序方式: 共有171条查询结果,搜索用时 31 毫秒
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Dr. Rahul Kisan Kawade Chaowei Hu Nikolas R. Dos Santos Noelle Watson Dr. Xinsong Lin Dr. Kenneth Hanson Dr. Igor V. Alabugin 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(34):14458-14463
3-Point annulations, or phenalenannulations, transform a benzene ring directly into a substituted pyrene by “wrapping” two new cycles around the perimeter of the central ring at three consecutive carbon atoms. This efficient, modular, and general method for π-extension opens access to non-symmetric pyrenes and their expanded analogues. Potentially, this approach can convert any aromatic ring bearing a -CH2Br or a -CHO group into a pyrene moiety. Depending upon the workup choices, the process can be directed towards either tin- or iodo-substituted product formation, giving complementary choices for further various cross-coupling reactions. The two-directional bis-double annulation adds two new polyaromatic extensions with a total of six new aromatic rings at a central core. 相似文献
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Prof. Polly L. Arnold Dr. Alessandro Prescimone Dr. Joy H. Farnaby Dr. Stephen M. Mansell Prof. Simon Parsons Prof. Nikolas Kaltsoyannis 《Angewandte Chemie (International ed. in English)》2015,54(23):6735-6739
The diuranium(III) compound [UN′′2]2(μ‐η6:η6‐C6H6) (N′′=N(SiMe3)2) has been studied using variable, high‐pressure single‐crystal X‐ray crystallography, and density functional theory . In this compound, the low‐coordinate metal cations are coupled through π‐ and δ‐symmetric arene overlap and show close metal? CH contacts with the flexible methyl CH groups of the sterically encumbered amido ligands. The metal–metal separation decreases with increasing pressure, but the most significant structural changes are to the close contacts between ligand CH bonds and the U centers. Although the interatomic distances are suggestive of agostic‐type interactions between the U and ligand peripheral CH groups, QTAIM (quantum theory of atoms‐in‐molecules) computational analysis suggests that there is no such interaction at ambient pressure. However, QTAIM and NBO analyses indicate that the interaction becomes agostic at 3.2 GPa. 相似文献
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Anastasia Liakakou Apostolis Angelis Dimitrios P. Papachristos Nikolas Fokialakis Antonios Michaelakis Leandros A. Skaltsounis 《Molecules (Basel, Switzerland)》2021,26(11)
The present work describes the use of Centrifugal Partition Chromatography (CPC) for the bio-guided isolation of repellent active volatile compounds from essential oils. Five essential oils (EOs) obtained from three Pinus and two Juniperus species were initially analyzed by gas chromatography–mass spectrometry (GC/MS) and evaluated for their repellent properties against Aedes albopictus. The essential oil from needles of P. pinea (PPI) presented the higher activity, showing 82.4% repellency at a dose of 0.2 μL/cm2. The above EO, together with the EO from the fruits of J. oxycedrus subsp. deltoides (JOX), were further analyzed by CPC using the biphasic system n-Heptane/ACN/BuOH in ratio 1.6/1.6/0.2 (v/v/v). The analysis of PPI essential oil resulted in the recovery of (−)-limonene, guaiol and simple mixtures of (−)-limonene/β-pheladrene, while the fractionation of JOX EO led to the recovery of β-myrcene, germacrene-D, and mixtures of α-pinene/β-pinene (ratio 70/30) and α-pinene/germacrene D (ratio 65/45). All isolated compounds and recovered mixtures were tested for their repellent activity. From them, (−)-limonene, guaiol, germacrene-D as well the mixtures of (−)-limonene/β-pheladrene presented significant repellent activity (>97% repellency) against Ae. albopictus. The present methodology could be a valuable tool in the effort to develop potent mosquito repellents which are environmentally friendly. 相似文献
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Hang Xu Chun‐Shuai Cao Han‐Shi Hu Shi‐Bin Wang Jin‐Cheng Liu Peng Cheng Nikolas Kaltsoyannis Jun Li Bin Zhao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(18):6083-6088
Assembled from [Th48Ni6] nanocages, the first transition‐metal (TM)‐thorium metal–organic framework (MOF, 1 ) has been synthesized and structurally characterized. 1 exhibits high solvent and acid/base stability, and resistance to 400 kGy β irradiation. Notably, 1 captures ReO4? (an analogue of radioactive 99TcO4?, a key species in nuclear wastes) with a maximum capacity of 807 mg g?1, falling among the largest values known to date. Furthermore, 1 can enrich methylene blue (MB) and can also serve as an effective and recyclable catalyst for CO2 fixation with epoxides; there is no significant loss of catalytic activity after 10 cycles. Theoretical studies with nucleus‐independent chemical shifts and natural bond orbital analysis reveal that the [Th6O8] clusters in 1 have a unique stable electronic structure with (d–p)π aromaticity, partially rationalising 1 ′s stability. 相似文献
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Tao Xu Nikolas A. Savage Guangbin Dong 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(7):1922-1926
The rhodium‐catalyzed formation of all‐carbon spirocenters involves a decarbonylative coupling of trisubstituted cyclic olefins and benzocyclobutenones through C C activation. The metal–ligand combination [{Rh(CO)2Cl}2]/P(C6F5)3 catalyzed this transformation most efficiently. A range of diverse spirocycles were synthesized in good to excellent yields and many sensitive functional groups were tolerated. A mechanistic study supports a hydrogen‐transfer process that occurs through a β‐H elimination/decarbonylation pathway. 相似文献
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Georgia‐Paraskevi Nikoleli Muhammad Q. Israr Nikolaos Tzamtzis Dimitrios P. Nikolelis Magnus Willander Nikolas Psaroudakis 《Electroanalysis》2012,24(6):1285-1295
The present article describes a miniaturized potentiometric urea lipid film based biosensor on graphene nanosheets. Structural characterization of graphene nanosheets for miniaturization of potentiometric urea lipid film based biosensors have been studied through atomic force microscopy (AFM) and transmission electron microscopy (TEM) measurements. UV‐Vis and Fourrier transform IR (FTIR) spectroscopy have been utilized to study the pre‐ and postconjugated surfaces of graphene nanosheets. The presented potentiometric urea biosensor exhibits good reproducibility, reusability, selectivity, rapid response times (~4 s), long shelf life and high sensitivity of ca. 70 mV/decade over the urea logarithmic concentration range from 1×10?6 M to 1×10?3 M. 相似文献
10.
Nikolas R. Losse Rudibert King Marcus Zengl Ulrich Rist Bernd R. Noack 《Theoretical and Computational Fluid Dynamics》2011,25(1-4):167-178
Tollmien?CSchlichting waves are one of the key mechanisms triggering the laminar-turbulent transition in a flat-plate boundary-layer flow. By damping these waves and thus delaying transition, skin friction drag can be significantly decreased. In this simulation study, a wall segment is actuated according to a control scheme based on a POD-Galerkin model driven extended Kalman filter for state estimation and a model predictive controller to dampen TS waves by negative superposition based on this information. The setup of the simulation is chosen to resemble actuation with a driven compliant wall, such as a membrane actuator. Most importantly, a method is proposed to integrate such a localized wall actuation into a Galerkin model. 相似文献