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231.
Stefan Dix Paul Golz Jonas R. Schmid Prof. Dr. Sebastian Riedel Prof. Matthew N. Hopkinson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(45):11554-11558
Trifluoromethoxylated (hetero)arenes are of great interest for several disciplines, especially in agro- and medicinal chemistry. Radical C−H trifluoromethoxylation of (hetero)arenes represents an attractive approach to prepare such compounds, but the high cost and low atom economy of existing . OCF3 radical sources make them unsuitable for the large-scale synthesis of trifluoromethoxylated building blocks. Herein, we introduce bis(trifluoromethyl)peroxide (BTMP, CF3OOCF3) as a practical and efficient trifluoromethoxylating reagent that is easily accessible from inexpensive bulk chemicals. Using either visible light photoredox or TEMPO catalysis, trifluoromethoxylated arenes could be prepared in good yields under mild conditions directly from unactivated aromatics. Moreover, TEMPO catalysis allowed for the one-step synthesis of valuable pyridine derivatives, which have been previously prepared via multi-step approaches. 相似文献
232.
Sofia I. Bär Madeleine Gold Sebastian W. Schleser Dr. Tobias Rehm Alexander Bär Leonhard Köhler Lucas R. Carnell Dr. Bernhard Biersack Prof. Dr. Rainer Schobert 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(15):5003-5010
Three [1,3-diethyl-4-(p-methoxyphenyl)-5-(3,4,5-trimethoxyphenyl)imidazol-2-ylidene](L)gold(I) complexes, 4 a (L=Cl), 5 a (L=PPh3), and 6 a (L=same N-heterocyclic carbene (NHC)), and their fluorescent [4-(anthracen-9-yl)-1,3-diethyl-5-phenylimidazol-2-ylidene](L)gold(I) analogues, 4 b , 5 b , and 6 b , respectively, were studied for their localisation and effects in cancer cells. Despite their identical NHC ligands, the last three accumulated in different compartments of melanoma cells, namely, the nucleus ( 4 b ), mitochondria ( 5 b ), or lysosomes ( 6 b ). Ligand L was also more decisive for the site of accumulation than the NHC ligand because the couples 4 a / 4 b , 5 a / 5 b , and 6 a / 6 b , carrying different NHC ligands, afforded similar results in cytotoxicity tests, and tests on targets typically found at their sites of accumulation, such as DNA in nuclei, reactive oxygen species and thioredoxin reductase in mitochondria, and lysosomal membranes. Regardless of the site of accumulation, cancer cell apoptosis was eventually induced. The concept of guiding a bioactive complex fragment to a particular subcellular target by secondary ligand L could reduce unwanted side effects. 相似文献
233.
Julia Beerhues Maren Neubrand Dr. Sebastian Sobottka Dr. Nicolás I. Neuman Hannes Aberhan Shubhadeep Chandra Prof. Dr. Biprajit Sarkar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(21):6557-6568
Carbene-based radicals are important for both fundamental and applied chemical research. Herein, extensive electrochemical investigations of nine different 1,2,3-triazolylidene selenium adducts are reported. It is found that the half-wave potentials of the first reduction of the selones correlate with their calculated LUMO levels and the LUMO levels of the corresponding triazolylidene-based mesoionic carbenes (MICs). Furthermore, unexpected quasi-reversibility of the reduction of two triazoline selones, exhibiting comparable reduction potentials, was discovered. Through UV/Vis/NIR and EPR spectroelectrochemical investigations supported by DFT calculations, the radical anion was unambiguously assigned to be triazoline centered. This electrochemical behavior was transferred to a triazolylidene-type MIC-gold phenyl complex resulting in a MIC-radical coordinated AuI species. Apart from UV-Vis-NIR and EPR spectroelectrochemical investigations of the reduction, the reduced gold-coordinated MIC radical complex was also formed in situ in the bulk through chemical reduction. This is the first report of a monodentate triazolylidene-based MIC ligand that can be reduced to its anion radical in a metal complex. The results presented here provide design principles for stabilizing radicals based on MICs. 相似文献
234.
Lucas Ueberricke Dr. Bahiru Punja Benke Tobias Kirschbaum Dr. Sebastian Hahn Dr. Frank Rominger Prof. Dr. Uwe H. F. Bunz Prof. Dr. Michael Mastalerz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(6):2043-2049
A six-step synthesis towards a tribenzotriquinacene (TBTQ) bearing three quinoxalinophenanthrophenazine (QPP) units is presented. The optoelectronic properties are investigated and the effect of the three-dimensional arrangement of the individual QPP planes is examined using optical spectroscopy, electrochemical analysis and quantum-chemical calculations. 相似文献
235.
Dr. Ali Abdulkarim Marvin Nathusius Rainer Bäuerle Dr. Karl-Philipp Strunk Dr. Sebastian Beck Dr. Hans Joachim Räder Prof. Annemarie Pucci Dr. Christian Melzer Daniel Jänsch Dr. Jan Freudenberg Prof. Uwe H. F. Bunz Prof. Klaus Müllen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(1):281-288
The synthesis of unsubstituted oligo-para-phenylenes ( OPP ) exceeding para-hexaphenylene—in the literature often referred to as p-sexiphenyl—has long remained elusive due to their insolubility. We report the first preparation of unsubstituted para-nonaphenylenes ( 9PP s) by extending our precursor route to poly-para-phenylenes ( PPP ) to a discrete oligomer. Two geometric isomers of methoxylated syn- and anti-cyclohexadienylenes were synthesized, from which 9PP was obtained via thermal aromatization in thin films. 9PP was characterized via optical, infrared and solid-state 13C NMR spectroscopy as well as atomic force microscopy and mass spectrometry, and compared to polymeric analogues. Due to the lack of substitution, para-nonaphenylene, irrespective of the precursor isomer employed, displays pronounced aggregation in the solid state. Intermolecular excitonic coupling leads to formation of H-type aggregates, red-shifting emission of the films to greenish. 9PP allows to study the structure–property relationship of para-phenylene oligomers and polymers, especially since the optical properties of PPP depend on the molecular shape of the precursor. 相似文献
236.
Gene Senges Dr. Lin Li Dr. Artur Wodyński Dr. Helmut Beckers Dr. Robert Müller Prof. Dr. Martin Kaupp Prof. Dr. Sebastian Riedel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(54):13642-13650
Molecular platinum fluorides PtFn, n=1–6, are prepared by two different routes, photo-initiated fluorine elimination from PtF6 embedded in solid noble-gas matrices, and the reaction of elemental fluorine with laser-ablated platinum atoms. IR spectra of the reaction products isolated in rare-gas matrices under cryogenic conditions provide, for the first time, experimental vibrational frequencies of molecular PtF3, PtF4 and PtF5. Photolysis of PtF6 enabled a highly efficient and almost quantitative formation of molecular PtF4, whereas both PtF5 and PtF3 were formed simultaneously by subsequent UV irradiation of PtF4. The vibrational spectra of these molecular platinum fluorides were assigned with the help of one- and two-component quasirelativistic DFT computation to account for scalar relativistic and spin–orbit coupling effects. Competing Jahn-Teller and spin–orbit coupling effects result in a magnetic bistability of PtF4, for which a spin-triplet (3B2g, D2h) coexists with an electronic singlet state (1A1g, D4h) in solid neon matrices. 相似文献
237.
Sebastian Hamer Jan-Simon von Glasenapp Fynn Röhricht Dr. Chao Li Prof. Dr. Richard Berndt Prof. Dr. Rainer Herges 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(69):17452-17458
A set of dipolar molecular rotor compounds was designed, synthesized and adsorbed as self-assembled 2D arrays on Ag(111) surfaces. The title molecules are constructed from three building blocks: (a) 4,8,12-trioxatriangulene (TOTA) platforms that are known to physisorb on metal surfaces such as Au(111) and Ag(111), (b) phenyl groups attached to the central carbon atom that function as pivot joints to reduce the barrier to rotation, (c) pyridine and pyridazine units as small dipolar units on top. Theoretical calculations and scanning tunneling microscopy (STM) investigations hint at the fact that the dipoles of neighboring rotors interact through space through pairs of energetically favorable head-to-tail arrangements. 相似文献
238.
Influence of higher harmonics of the undulator in X‐ray polarimetry and crystal monochromator design 下载免费PDF全文
Berit Marx‐Glowna Kai S. Schulze Ingo Uschmann Tino Kämpfer Günter Weber Christoph Hahn Hans‐Christian Wille Kai Schlage Ralf Röhlsberger Eckhart Förster Thomas Stöhlker Gerhard G. Paulus 《Journal of synchrotron radiation》2015,22(5):1151-1154
The spectrum of the undulator radiation of beamline P01 at Petra III has been measured after passing a multiple reflection channel‐cut polarimeter. Odd and even harmonics up to the 15th order, as well as Compton peaks which were produced by the high harmonics in the spectrum, could been measured. These additional contributions can have a tremendous influence on the performance of the polarimeter and have to be taken into account for further polarimeter designs. 相似文献
239.
In solar cells fabricated from boron‐doped Cz‐Si wafers minority and majority carrier traps were detected by deep level transient spectroscopy (DLTS) after so‐called “light‐induced degradation” (LID). The DLTS signals were detected from mesa‐diodes with the full structure of the solar cells preserved. Preliminary results indicate metastable traps with energy levels positioned at EV + 0.37 eV and EC – 0.41 eV and apparent carrier capture cross‐sections in the 10–17–10–18 cm2 range. The concentration of the traps was in the range of 1012–1013 cm–3. The traps were eliminated by annealing of the mesa‐diodes at 200 °C. No traps were detected in Ga‐doped solar cells after the LID procedure or below the light protected bus bar locations in B‐doped cells. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
240.
Scalable bottom‐up assembly of suspended carbon nanotube and graphene devices by dielectrophoresis 下载免费PDF全文
Antonios Oikonomou Nick Clark Sebastian Heeg Andrey Kretinin Sarah Varey Geliang Yu Aravind Vijayaraghavan 《固体物理学:研究快报》2015,9(9):539-543
Bottom‐up assembly by dielectrophoresis (DEP) has emerged in recent years as a viable alternative to conventional top–down fabrication of electronic devices from nanomaterials, particularly carbon nanotubes and graphene. Here, we demonstrate how this technique can be extended to fabricate devices containing carbon nanotubes and graphene suspended between two electrodes over a back‐gate electrode. The suspended device geometry is critical for the development of nano‐electromechanical devices and to extract maximum performance out of electronic and optoelectronic devices. This technique allows for parallel assembly of devices over large scale. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献