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Chemistry: a European Journal

Masafumi Ueda, Akimi Tahara, Masashi Hasegawa, Takashi Shirahata, Yasuhiro Mazaki, Yohji Misaki
[5]Radialene with quintuple 4,5-benzo-1,3-dithiol-2-ylidenes (DTs) easily forms a stable polycationic salt (1)4+(BF4-)4 owing to its aromatic character in the central cyclopentadienide ring. However, we found that the polycationic salt (1)4+ underwent a hydration reaction in moist polar solvent to give several unexpected products, namely, an oxygen adduct dicationic salt (2)2+, a tetrathiafulvalene (TTF) vinylogous (3) with 1,4-dithiine-2(3H)-one moieties, and an oxygen adduct of π-extended TTF with a cyclopentenone core (4)...
January 12, 2019: Chemistry: a European Journal
Stefan Schoder, Hendrik V Schröder, Luca Cera, Rakesh Puttreddy, Arne Güttler, Ute Resch-Genger, Kari Rissanen, Christoph A Schalley
Organic fluorophores, particularly stimuli-responsive molecules, are very interesting for biological and material sciences applications, but frequently limited by aggregation- and rotation caused photoluminescence quenching. A series of easily accessible bipyridinium fluorophores is reported, whose emission is quenched by a twisted intramolecular charge transfer (TICT) mechanism. Encapsulation in a cucurbit[7]uril host yields a 1:1 complex exhibiting a moderate emission increase due to destabilization of the TICT state inside the apolar cucurbituril cavity...
January 12, 2019: Chemistry: a European Journal
Daniela Hermann, Heidi A Schwartz, Melanie Werker, Dominik Schaniel, Uwe Ruschewitz
Fifteen new photochromic hybrid materials were synthesized by gas phase loading of fluorinated azobenzenes, namely ortho-tetrafluoroazobenzene (tF-AZB), 4H,4H'-octafluoroazobenzene (oF-AZB), and perfluoroazobenzene (pF-AZB), into the pores of the well-known metal-organic frameworks MOF-5, MIL-53(Al), MIL-53(Ga), MIL-68(Ga), and MIL-68(In). Their composition was analysed by elemental (CHNS) and DSC/TGA analysis. For pF-AZB0.34@MIL-53(Al) a structural model based on high-resolution synchrotron powder diffraction data was developed and the host-guest and guest-guest interactions were elucidated from this model...
January 11, 2019: Chemistry: a European Journal
Shuang-Quan Zang, Jia-Yin Wang, Ren-Wu Huang, Zhong Wei, Xiao-Juan Xi, Xi-Yan Dong
Silver chalcogenolate clusters (SCCs) and silver cluster-assembled materials (SCAMs) are an important category of novel luminescent materials, whose emission can be modulated by variation of cluster nodes and linker's species. Here, we successfully synthesized two isostructural 2D SCAMs Ag12bpa and Ag12bpe using two linkers with different conformational freedom (bpa = 1,2-bis(4-pyridyl)ethane, bpe = trans-1,2-bis(4-pyridyl)ethylene), in which dodenuclear silver chalcogenolate clusters as secondary building units (SBUs)...
January 11, 2019: Chemistry: a European Journal
Yanhui Wang, Sanghoon Kim, Nicolas Louvain, Johan Alauzun, Hubert Mutin
An original, halide-free non-hydrolytic sol-gel route to mesoporous anatase TiO2 with hierarchical porosity and high specific surface area is reported. This route is based on the reaction at 200 °C of titanium (IV) isopropoxide with acetic anhydride, in the absence of a catalyst or of a solvent. NMR studies indicated that this method provides an efficient, truly non-hydrolytic and aprotic route to TiO2. Formation of the oxide involves acetoxylation and condensation successive reactions, both with ester elimination...
January 11, 2019: Chemistry: a European Journal
Pedro Ferreira, Barbara Ventura, Andrea Barbieri, José Paulo Da Silva, César Laia, A Jorge Parola, Nuno Basílio
The discovery of stimuli-responsive high affinity host-guest pairs with potential applications under biological relevant con-ditions is a challenging goal. Herein we report a high-affinity 1:1 complex formed between cucurbit[8]uril and a water soluble photochromic diarylethene derivative. We found that confining the open isomer within the cavity of the receptor induces a red-shift in the absorption spectrum and leads to an enhancement of the photocyclization quantum yield from Φ = 0.04 to Φ = 0.32. This improvement in the photochemical performance enables quantitative photocyclization with visible light that together with the near-infrared light induced ring-opening reaction and the 100-fold selectivity for the closed isomer confirms this as an outstanding light-responsive affinity pair...
January 11, 2019: Chemistry: a European Journal
Qi Yu, Briana Aguila, Jia Gao, Peixin Xu, Qizhe Chen, Jie Yan, Dong Xing, Yao Chen, Peng Cheng, Zhenjie Zhang, Shengqian Ma
Photomechanical molecular crystals are receiving great attention due to their efficient conversion of light into mechanical work and surpassing advantages including faster response time, higher Young's modulus and ordered structure measured by single-crystal X-ray. Recently, various photomechanical crystals with different motions (contraction, expansion, bending, fragmentation, hopping, curling and twisting) are springing up in the forefront of smart materials research. The photomechanical motions of these single crystals during irradiation is triggered by solid-state photochemical reactions and accompanied with phase transformation...
January 10, 2019: Chemistry: a European Journal
Rong Han, Yufei Yang, Shenlin Wang
Solid-state nuclear magnetic resonance (SSNMR) spectroscopy is a powerful technique for studying challenging biological systems, but it often suffers from low sensitivity. We report a longitudinal relaxation optimization scheme to enhance the signal sensitivity of heteronuclear single quantum coherence (HSQC) experiments in SSNMR. Under the proposed scheme, the 1H spins of 1H-X (15N or 13C) were selected for signal acquisition, while other vast 1H spins are flipped back to the axis of the static magnetic field to accelerate the spin recovery of the observed 1H spins, resulting in enhanced sensitivity...
January 10, 2019: Chemistry: a European Journal
James Edward Taylor, Susana Estopiñá-Durán, Liam J Donnelly, Euan B Mclean, Bryony M Hockin, Alexandra M Z Slawin
A combination of pentafluorophenylboronic acid and oxalic acid catalyses the dehydrative substitution of benzylic alcohols with a second alcohol to form new C-O bonds. This method has been applied to the intermolecular substitution of benzylic alcohols to form symmetrical ethers, intramolecular cyclisations of diols to form aryl-substituted tetrahydrofuran and tetrahydropyran derivatives, and intermolecular crossed-etherification reactions between two different alcohols. Mechanistic control experiments have identified a potential catalytic intermediate formed between the arylboronic acid and oxalic acid...
January 10, 2019: Chemistry: a European Journal
Matthias Lehmann, Moritz Dechant, Markus Hügel, Nikolai Scheuring, Tapas Ghosh
A series of shape-persistent star-shaped oligo(phenylenevinylene) liquid crystals and derivatives with fullerene tethered via spacers of different lengths to one arm have been successfully synthesized. Solution studies by NMR, UV-Vis and fluorescence spectroscopy reveal the preferential location of the C60 acceptor in the vicinity of the peripheral donor unit, which affects the quenching of the emission of the conjugated stilbenoid scaffold in the donor-acceptor dyad. The fluorescence is completely absent in the liquid crystal phase owing to the extraordinary hierarchical self-assembly...
January 9, 2019: Chemistry: a European Journal
Harry A Klein, Paul D Beer
Whilst the exploitation of interlocked host frameworks for anion recognition is widely established, examples incorporating halogen bond donor groups are still relatively rare. Through the integration of a novel tetra(iodotriazole)-pyridinium motif into macrocycle and axle components, a family of halogen bonding catenane and rotaxanes are constructed for anion recognition studies in a competitive aqueous-organic solvent mixture. Importantly, the degree of anion selectivity displayed is dictated by the topological nature and charged state of the respective interlocked host cavity...
January 9, 2019: Chemistry: a European Journal
Manuela Casutt, Benedikt Dittmar, Hanna Makowska, Tomasz Marszalek, Soh Kushida, Uwe H F Bunz, Jan Freudenberg, Daniel Jaensch, Klaus Müllen
1,4-Diketopyrrolo[3,4-c]pyrroles (DPPs) constitute a class of hydrogen-bonded pigments covering a color range from yellow-orange to dark violet. We report facile dimerization of a Boc-substituted 3,6-dithienyl-DPP. The formed dimer shows brilliantly blue color as a result of the expansion of the chromophore. The soluble dimer acts as latent pigment and is converted to the corresponding pigment either via thermocleavage or acidic deprotection of the Boc groups. The synthesized pigment is characterized by high migrational stability in a polymer matrix and a clear blue color...
January 9, 2019: Chemistry: a European Journal
Jia-Bin Han, Ao Guo, Xiangying Tang
A challenging deoxygenation of alkoxyl radicals from readily accessible alcohol derivatives was developed, affording facile synthesis of functionalized alkenes with good functional group tolerance under mild reaction conditions. Since alkoxyl radicals can easily undergo β-fragmentations or hydrogen abstractions, this new strategy for deoxygenation of alkoxyl radicals is highly valuable. Moreover, mechanistic studies revealed that the electron-neutral phosphine acts as the deoxygenation reagent.
January 9, 2019: Chemistry: a European Journal
Tobias Santowski, Alexander G Sturm, Max C Holthausen, Kenrick M Lewis, Thorsten Felder, Norbert Auner
The Müller-Rochow Direct Process (DP) for a multi ton production of methylchlorosilanes MenSiCl4-n (n=1-3) generates a disilane residue (MenSi2Cl6-n, n=1-6, DPR) in thousands of tons annually. In this contribution we report on methylchlorodisilane cleavage reactions using phosphonium chlorides as cleavage catalysts and reaction partners to preferably obtain bifunctional monosilanes MexSiHyClz (x=2, y=z=1; x, y=1, z=2; x=z=1, y=2). Product formation is controlled by reaction temperatures, the amount of phosphonium chlorides employed, the choice of substituents at phosphorus and optionally by the presence of hydrogen chloride, dissolved in ethers, in the reaction mixtures...
January 9, 2019: Chemistry: a European Journal
Helmut Schwarz, Knut R Asmis
Cryogenic ion trap vibrational spectroscopy paired with quantum chemistry currently represents the most generally applicable approach for the structural investigation of gaseous cluster ions that are not amenable to direct absorption spectroscopy. Here, we give an overview of the most popular variants of infrared action spectroscopy and describe the advantages of using cryogenic ion traps in combination with messenger tagging and vibrational predissociation spectroscopy. We then highlight a few recent studies that apply this technique to identify highly reactive ionic intermediates and to characterize their reactive sites...
January 9, 2019: Chemistry: a European Journal
Fabian O von Rohr, Alice Ryser, Huiwen Ji, Karoline Stolze, Jing Tao, Jessica J Frick, Greta R Patzke, Robert J Cava
The previously unreported oxygen excess hexagonal antimony tungsten bronze is reported, with a composition of Sb0.5 W3 O10 , in the following denoted as h-Sbx WO3+2x with x=0.167, to demonstrate its analogy to classical Ax WO3 tungsten bronzes. This compound forms in a relatively narrow temperature range between 580 °C<T<620 °C. It was obtained as a dark-blue polycrystalline powder, and as thin, needle-shaped, blue single crystals. h-Sbx WO3+2x crystallizes in the hexagonal space group P6/mmm with the cell parameters a=7...
January 9, 2019: Chemistry: a European Journal
Meng Liu, Hao Fan, Ou Zhuo, Xiao Du, Longqi Yang, Peng Wang, Lijun Yang, Qiang Wu, Xizhang Wang, Zheng Hu
Molybdenum disulfide (MoS2) are intensively studied anode materials for lithium-ion batteries (LIBs) owing to the high theoretical capacity, but still confront the severe challenges of unsatisfied rate capability and cycle life to date. Herein, few-layer MoS2 nanosheets are vertically grown on the hierarchical carbon nanocages (hCNC) via a facile hydrothermal method, which introduce pseudocapacitive lithium storage owing to the highly-exposed MoS2 basal planes, enhanced conductivity and facilitated electrolyte access arising from the well hybridization with hCNC...
January 9, 2019: Chemistry: a European Journal
Takeshi Naota, Ryo Inoue, Masaya Naito, Masahiro Ehara
Heat resistant properties towards thermal emission quenching of trans-bis[(β-iminomethyl)aryloxy]platinum(II) complexes 1-4, and a mechanistic rationale of these properties, are described in this report. Complex 1a exhibits intense red emission in 2-MeTHF at 298 K, whereas the analogues 2a-4a are less or non-emissive under the same measurement conditions. All four complexes are highly emissive at 77 K. The heat resistant properties toward thermal emission quenching (Φ298K/Φ77K) increase in the order 1a (0...
January 9, 2019: Chemistry: a European Journal
Yu Lu, Ruihua Zhao, Jiandong Guo, Zheyuan Liu, Wasihun Menberu Dagnaw, Zhixiang Wang
Acceptorless dehydrogenative couplings (ADCs) generally involve a nucleophile (e.g. amine) as a coupling partner. Intriguingly, it has been reported that nitrile could also act as a nucleophile to perform ADCs, achieving α-olefinations of nitriles with primary/secondary alcohols by employing Mn/Ru pincer complex as the catalyst. While different mechanisms were postulated for the two catalytic systems, our DFT mechanistic study allowed us to propose a unified mechanism to account for both nitrile α-olefinations...
January 8, 2019: Chemistry: a European Journal
Thomas Kader, Berthold Stöger, Johannes Fröhlich, Paul Kautny
The preparation and characterization of twelve azaindolo[3,2,1-jk]carbazoles is being presented. Ring closing C-H activation allowed for the convenient preparation of six mono and six twofold nitrogen substituted indolo[3,2,1-jk]carbazole derivatives whereupon ten of the materials have not been described in literature before. The detailed photophysical and electrochemical characterization of the developed materials revealed a significant impact of the incorporation of pyridine like nitrogen into the fully planar indolo[3,2,1-jk]carbazole backbone...
January 8, 2019: Chemistry: a European Journal
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