共查询到20条相似文献,搜索用时 15 毫秒
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Thomas K. Wood Warren E. Piers Brian A. Keay Masood Parvez 《Angewandte Chemie (International ed. in English)》2009,48(22):4009-4012
2009: A boraanthracene odyssey : General routes to boraanthracene derivatives—long proposed, but never observed—are disclosed, along with the structural and photophysical properties of these compounds and their remarkable reactivity towards oxygen.
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Valentina Cassinelli Dr. Birgit Oberleitner Jessica Sobotta Philipp Nickels Guido Grossi Dr. Susanne Kempter Dr. Thomas Frischmuth Prof. Tim Liedl Dr. Antonio Manetto 《Angewandte Chemie (International ed. in English)》2015,54(27):7795-7798
DNA‐based self‐assembled nanostructures are widely used to position organic and inorganic objects with nanoscale precision. A particular promising application of DNA structures is their usage as programmable carrier systems for targeted drug delivery. To provide DNA‐based templates that are robust against degradation at elevated temperatures, low ion concentrations, adverse pH conditions, and DNases, we built 6‐helix DNA tile tubes consisting of 24 oligonucleotides carrying alkyne groups on their 3′‐ends and azides on their 5′‐ends. By a mild click reaction, the two ends of selected oligonucleotides were covalently connected to form rings and interlocked DNA single strands, so‐called DNA catenanes. Strikingly, the structures stayed topologically intact in pure water and even after precipitation from EtOH. The structures even withstood a temperature of 95 °C when all of the 24 strands were chemically interlocked. 相似文献
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Molecular Design and Syntheses of Tetracyano‐5,10‐porphyrinquinodimethane Showing Stabilized LUMO 下载免费PDF全文
Ken‐ichi Yamashita Shino Sakamoto Akihiro Suzuki Prof. Ken‐ichi Sugiura 《化学:亚洲杂志》2016,11(7):1004-1007
An isomer of tetracyanoporphyrinquinodimethane (TCPQ), 5,10‐TCPQ, was designed, synthesized, and structurally characterized, and its basic properties were discussed with emphasis on comparison with those of reported 5,15‐TCPQ. The title compound was synthesized by a convenient cascade reaction involving a catalyst‐free aromatic nucleophilic substitution reaction and the Uno–Takahashi reaction. The obtained π‐expanded redox molecule acted as a Wurster‐type redox molecule that underwent not only reduction but also oxidation processes. Furthermore, its absorption spectrum showed a large bathochromic shift that extended to the near‐IR region, approximately 1150 nm. 相似文献
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Ágnes Kozma Jörg Rust Dr. Manuel Alcarazo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(30):10829-10834
The treatment of bis[(dialkylamino)cyclopropenimines] with dihalophosphines in the presence of trimethylsilyl trifluoromethanesulfonate (TMSOTf) to form diimine‐stabilized PIII‐centered dications is reported. The structures of the new compounds were determined by using X‐ray diffraction analysis and their donor abilities as ligands evaluated through electrochemical methods. Despite the two positive charges that they bear, these compounds depict intermediate behavior between that of phosphines and phosphites. The coordination of the [L2PR]2+ moiety to AuI and AgI is also reported. Even more surprisingly, these phosphorus centers can be oxidized to the corresponding PV dications in the presence of strong oxidants such as peroxides or XeF2. 相似文献
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Zhongshu Li Xiaodan Chen Liu Leo Liu Moritz Theodor Scharnhlz Hansjrg Grützmacher 《Angewandte Chemie (International ed. in English)》2020,59(11):4288-4293
In contrast to cyclic π‐conjugated hydrocarbons, the coordination chemistry of inorganic heterocycles is less developed. Dicarbondiphosphides stabilized by N‐heterocyclic carbenes (NHCs) NHC→C2P2←NHC ( 1 a , b ) (NHC=IPr or SIPr) contain a four‐membered C2P2 ring with an aromatic 6π‐electron configuration. These heterocycles coordinate to a variety of complex fragments with metals from groups 6, 9, and 10, namely [M0(CO)3] (M=Cr, Mo), [CoI(CO)2]+, or [NiIIBr2], through an η4‐coordination mode, leading to complexes 2 a , b , 3 a , b , 5 a , b , and 6 a , b , respectively. These complexes were characterized by X‐ray diffraction methods using single crystals, IR spectroscopy, and DFT calculations. In combination these methods indicate that 1 a , b behave as exceptionally strong 6π‐electron donors. 相似文献
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Oligomers of β‐substituted β‐amino acids (‘β3‐peptides') are known to adopt a helical secondary structure defined by 14‐membered ring hydrogen bonds ('14‐helix'). Here, we describe a deca‐β3‐peptide, 1 , that does not adopt the 14‐helical conformation and that may prefer an alternative secondary structure. β3‐Peptide 1 is composed exclusively of residues with side chains that are not branched adjacent to the β‐C‐atom (β3‐hLeu, β3‐hLys, and β3‐hTyr). In contrast, an analogous β‐peptide, 2 , containing β3‐hVal residues in place of the β3‐hLeu residues of 1 , adopts a 14‐helical conformation in MeOH, according to CD data. These results illustrate the importance of side‐chain branching in determining the conformational preferences of β3‐peptides. 相似文献
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A Square‐Planar Tetracoordinate Oxygen‐Containing Ti4O17 Cluster Stabilized by Two 1,1′‐Ferrocenedicarboxylato Ligands 下载免费PDF全文
Dr. Zhichang Liu Juying Lei Dr. Marco Frasconi Dr. Xiaohu Li Dennis Cao Dr. Zhixue Zhu Dr. Severin T. Schneebeli Prof. George C. Schatz Prof. J. Fraser Stoddart 《Angewandte Chemie (International ed. in English)》2014,53(35):9193-9197
By introducing steric constraints into molecular compounds, it is possible to achieve atypical coordination geometries for the elements. Herein, we demonstrate that a titanium‐oxo cluster [{Ti4(μ4‐O)(μ2‐O)2}(OPri)6(fdc)2], which possesses a unique edge‐sharing Ti4O17 octahedron tetramer core, is stabilized by the constraints produced by two orthogonal 1,1′‐ferrocenedicarboxylato (fdc) ligands. As a result, a square‐planar tetracoordinate oxygen (ptO) can be generated. The bonding pattern of this unusual anti‐van’t Hoff/Le Bel oxygen, which has been probed by theoretical calculations, can be described by two horizontally σ‐bonded 2px and 2py orbitals along with one perpendicular nonbonded 2pz orbital. While the two ferrocene units are separated spatially by the ptO with an Fe???Fe separation of 10.4 Å, electronic communication between them still takes place as revealed by the cluster’s two distinct one‐electron electrochemical oxidation processes. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(31):9136-9140
Protein nanobodies have been used successfully as surrogates for unstable G‐proteins in order to crystallize G‐protein‐coupled receptors (GPCRs) in their active states. We used molecular dynamics (MD) simulations, including metadynamics enhanced sampling, to investigate the similarities and differences between GPCR–agonist ternary complexes with the α‐subunits of the appropriate G‐proteins and those with the protein nanobodies (intracellular binding partners, IBPs) used for crystallization. In two of the three receptors considered, the agonist‐binding mode differs significantly between the two alternative ternary complexes. The ternary‐complex model of GPCR activation entails enhancement of ligand binding by bound IBPs: Our results show that IBP‐specific changes can alter the agonist binding modes and thus also the criteria for designing GPCR agonists. 相似文献
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Lauren N. Grant Prof. Balazs Pinter Brian C. Manor Prof. Dr. Hansjörg Grützmacher Prof. Dr. Daniel J. Mindiola 《Angewandte Chemie (International ed. in English)》2018,57(4):1049-1052
The first example of the OCPPCO ligand, diisophosphaethynolate, is reported via reductive coupling of a Sc?OCP precursor. Upon reduction with KC8, isolation of the dinuclear complex, namely [K(OEt2)]2[(nacnac)Sc(OAr)]2(OCPPCO), is observed, leading to a unique motif [OCPPCO]4?, stabilized by two scandium centers. Detailed NMR spectra of all complexes as well as IR and single crystal X‐ray studies were obtained to fully elucidate the nature of these complexes in solution as well as in the solid state. Theory is combined to probe the electronic structure and orbitals responsible for the bonding interactions in the Sc?OCPPCO?Sc skeleton but also to compare to the linear mode observed in the precursor. 相似文献
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Yuki Kataoka Naoya Kanbayashi Naoka Fujii Taka‐aki Okamura Takeharu Haino Kiyotaka Onitsuka 《Angewandte Chemie (International ed. in English)》2020,59(26):10286-10291
π‐Stacked polymers, which consist of layered π‐electron systems in a polymer, can be expected to be used in molecular electronic devices. However, the construction of a stable π‐stacked structure in a polymer is considerably challenging because it requires sophisticated designs and precise synthetic methods. Herein, we present a novel π‐stacked architecture based on poly(quinolylene‐2,3‐methylene) bearing alanine derivatives as the side chain, obtained through the living cyclo‐copolymerization of an o‐allenylaryl isocyanide. In the resulting polymer, the neighboring quinoline rings of the main chain form a layered structure with π–π interactions, which is stabilized by intramolecular hydrogen bonds. The vicinal quinoline units form two independent helices and the whole molecule is a twisted‐tape structure. This structure is established on the basis of UV/CD spectra, theoretical calculations, and atomic‐force microscopy. 相似文献
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Jiliang Zhou Liu Leo Liu Levy L. Cao Douglas W. Stephan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(16):5461-5466
Double chloride abstraction of Cp*AsCl2 gives the dicationic arsenic species [(η5‐Cp*)As(tol)][B(C6F5)4]2 ( 2 ) (tol=toluene). This species is shown to exhibit Lewis super acidity by the Gutmann–Beckett test and by fluoride abstraction from [NBu4][SbF6]. Species 2 participates in the FLP activation of THF affording [(η2‐Cp*)AsO(CH2)4(THF)][B(C6F5)4]2 ( 5 ). The reaction of 2 with PMe3 or dppe generates [(Me3P)2As][B(C6F5)4] ( 6 ) and [(σ‐Cp*)PMe3][B(C6F5)4] ( 7 ), or [(dppe)As][B(C6F5)4] ( 8 ) and [(dppe)(σ‐Cp*)2][B(C6F5)4]2 ( 9 ), respectively, through a facile cleavage of C?As bonds, thus showcasing unusual reactivity of this unique As‐containing compound. 相似文献
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Prof. Takanori Suzuki Yuto Sakano Dr. Tomohiro Iwai Dr. Shinichi Iwashita Dr. Youhei Miura Dr. Ryo Katoono Prof. Hidetoshi Kawai Prof. Kenshu Fujiwara Prof. Yasushi Tsuji Prof. Takanori Fukushima 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(1):117-123
When two benzene rings are fused to a tetraaryl‐o‐quinodimethane skeleton, sterically hindered helical molecules 1 acquire a high thermodynamic stability. Because the tetraarylbutadiene subunit contains electron‐donating alkoxy groups, 1 undergo reversible two‐electron oxidation to 2 2+, which can be isolated as deeply colored stable salts. Intramolecular transfer of the point chirality (e.g., sec‐butyl) on the aryl groups to helicity induces a diastereomeric preference in dications 2 b 2+ and 2 c 2+, which represents an efficient method for enhancing circular‐dichroism signals. Thus, those redox pairs can serve as new electrochiroptical response systems. X‐ray analysis of dication 2 2+ revealed π–π stacking interaction of the diarylmethylium moieties, which is also present in solution. The stacking geometry is the key contributor to the chirosolvatochromic response. 相似文献