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Literature 07-04-15 Literature 07-04-15 Expanding the scope of strained-alkyne chemistry: a protection–deprotection strategy via the formation of a dicobalt–hexacarbonyl complex 1 Gobbo, P.; Romagnoli, T.; Barbon, S. M.; Price, J. T.; Keir, J.; Gilroy, J. B.; Workentin, M. S. Chem. Commun. 2015, 51, 6647-6650. Abstract: A protection–deprotection strategy for strained alkynes used for bioorthogonal chemistry is reported. A strained alkyne can be protected with dicobalt–octacarbonyl and we demonstrate for the first time that a strained alkyne can be re-formed and isolated under mild reaction conditions for further bioorthogonal reactivity. The protection–deprotection strategy herein reported will expand the versatility of strained alkynes for the preparation of substrates in chemical biology and materials applications. Visible light photooxidation of nitrate: the dawn of a nocturnal radical Hering, T.; Slanina, T.; Hancock, A.; Wille, U.; König, B. Chem. Commun. 2015, 51, 6568-6571. Abstract: Highly oxidizing nitrate radicals (NO3˙) are easily accessed from readily available nitrate salts by visible light photoredox catalysis using a purely organic dye as the catalyst and oxygen as the terminal oxidant. The interaction of the excited catalyst and nitrate anions was studied by spectroscopic methods to elucidate the mechanism, and the method was applied to the NO3˙ induced oxidation of alkynes and alcohols. Big, Strong, Neutral, Twisted, and Chiral π Acids Zhao, Y.; Huang, G.; Besnard, C.; Mareda, J.; Sakai, N.; Matile, S. Chem. Eur. J. 2015, 21, 6202–6207. Abstract: Literature 07-04-15 2 General synthetic access to expanded π-acidic surfaces of variable size, topology, chirality, and π acidity is reported. The availability of π surfaces with these characteristics is essential to develop the functional relevance of anion–π interactions with regard to molecular recognition, translocation, and transformation. The problem is that, with expanded π surfaces, the impact of electron-withdrawing substituents decreases and the high π acidity needed for strong anion–π interactions can be more difficult to obtain. To overcome this problem, it is herein proposed to build large surfaces from smaller fragments and connect these fragments with bridges that are composed only of single atoms. Two central surfaces for powerful anion–π interactions, namely, perfluoroarenes and naphthalenediimides (NDIs), were selected as fragments and coupled with through sulfide bridges. Their oxidation to sulfoxides and sulfones, as well as fluorine substitution in the peripheral rings, provides access to the full chemical space of relevant π acidities. According to cyclic voltammetry, LUMO levels range from −3.96 to −4.72 eV. With sulfoxide bridges, stereogenic centers are introduced to further enrich the intrinsic planar chirality of the expanded surfaces. The stereoisomers were separated by chiral HPLC and characterized by X-ray crystallography. Their topologies range from chairs to π boats, and the latter are reminiscent of the cation–π boxes in operational neuronal receptors. With pentafluorophenyl acceptors, the π acidity of NDIs with two sulfoxide groups in the core reaches −4.45 eV, whereas two sulfone moieties give a value of −4.72 eV, which is as low as with four ethyl sulfone groups, that is, a π superacid near the limit of existence. Beyond anion–π interactions, these conceptually innovative π-acidic surfaces are also of interest as electron transporters in conductive materials. Oxidized Carbon Nitrides: Water-Dispersible, Atomically Thin Carbon Nitride-Based Nanodots and Their Performances as Bioimaging Probes Oh, J.; Yoo, R. J.; Kim, S. Y.; Lee, Y. J.; Kim, D. W.; Park, S. Chem. Eur. J. 2015, 21, 6241–6246. Abstract: Three-dimensional (3D) carbon nitride (C3N4)-based materials show excellent performance in a wide range of applications because of their suitable band structures. To realize the great promise of two- dimensional (2D) allotropes of various 3D materials, it is highly important to develop routes for the Literature 07-04-15 production of 2D C3N4 materials, which are one-atom thick, in order to understand their intrinsic properties and identify their possible applications. In this work, water-dispersible, atomically thin, 3 and small carbon nitride nanodots were produced using the chemical oxidation of graphitic C3N4. Various analyses, including X-ray diffraction, X-ray photoelectron, Fourier-transform infrared spectroscopy, and combustion-based elemental analysis, and thermogravimetric analysis, confirmed the production of 3D oxidized C3N4 materials. The 2D C3N4 nanodots were successfully exfoliated as individual single layers; their lateral dimension was several tens of nanometers. They showed strong photoluminescence in the visible region as well as excellent performances as cell-imaging probes in an in vitro study using confocal fluorescence microscopy. Shape-Reprogrammable Polymers: Encoding, Erasing, and Re-Encoding Kohlmeyer, R. R.; Buskohl, P. R.; Deneault, J. R.; Durstock, M. F.; Vaia, R. A.; Chen, J. Adv. Mater. 2014, 26, 8114–8119. Abstract: Shape-reprogramming in a polymer is demonstrated, where prescribed 3D geometric information can be encoded, decoded, erased, and re-encoded. In essence, the shape-reprogrammable polymer (SRP) acts as computer hardware that can be reformatted and reprogrammed repeatedly. Such SRPs have the potential to be repurposed directly without going through material disposal and recycling. Highly Thermal Stable and Efficient Organic Photovoltaic Cells with Crosslinked Networks Appending Open-Cage Fullerenes as Additives Chen, C.-P.; Huang, C.-Y.; Chuang, S.-C. Adv. Funct. Mater. 2015, 25, 207–213. Abstract: Literature 07-04-15 Highly thermal stable organic bulk heterojunction (OBHJ) photovoltaic cells are demonstrated with crosslinkable open-cage fullerenes (COF) as additives in the active layer. Partial incorporation of COF, 4 ≈10–15 wt% with weight ratio of P3HT:PC61BM = 1:0.9, builds up three-dimensional local borders upon heating treatment at 150 °C for 10 min. This process induces crosslinking chemical reaction through activating the styryl moiety in COF and reduces phase aggregation rates of fullerenes materials. Supported by statistics of devices degradation data analysis and optical microscopy study, the devices with COF show longer lifetime with keeping their efficiency (t = 144 h) under accelerated heating test at 150 °C, while PCE of normal devices without COF drop dramatically. These results demonstrate that the thermally crosslinkable COF is an excellent additive for highly thermal stable and durable OPVs applications. Programming macro-materials from DNA-directed self-assembly Zhang, X.; Wang, R.; Xue, G. Soft Matter 2015, 11, 1862-1870. Abstract: DNA is a powerful tool that can be attached to nano- and micro-objects and direct the self-assembly through base pairing. Since the strategy of DNA programmable nanoparticle self-assembly was first introduced in 1996, it has remained challenging to use DNA to make powerful diagnostic tools and to make designed materials with novel properties and highly ordered crystal structures. In this review, we summarize recent experimental and theoretical developments of DNA-programmable self- assembly into three-dimensional (3D) materials. Various types of aggregates and 3D crystal structures obtained from an experimental DNA-driven assembly are introduced. Furthermore, theoretical calculations and simulations for DNA-mediated assembly systems are described and we highlight some typical theoretical models for Monte Carlo and Molecular Dynamics simulations. Enzyme-responsive protein/polysaccharide supramolecular nanoparticles Hou, X.-F.; Chen, Y.; Liu, Y. Soft Matter 2015, 11, 2488-2493. Abstract: Literature 07-04-15 5 Biocompatible and enzyme-responsive supramolecular assemblies have attracted more and more interest in biomaterial fields, and find many feasible applications especially in the controlled drug release at specific sites where the target enzyme is located. In this work, novel supramolecular nanoparticles were successfully constructed from two biocompatible materials, i.e. a cyclic polysaccharide named sulfato-β-cyclodextrin (SCD) and a protein named protamine, through non- covalent association, and fully characterized by means of atomic force microscopy (AFM) and high- resolution transmission electron microscopy (TEM). Significantly, the disassembly of the resulting nanoparticles can respond especially to trypsin over other enzymes. Owing to their trypsin-triggered disassembly behaviors, these nanoparticles can efficiently release the encapsulated model substrate in a controlled manner. That is, the model substrate can be encapsulated inside the nanoparticles with a high stability and released when treated with trypsin. Synthesis of Cysteine-Rich Peptides by Native Chemical Ligation without Use of Exogenous Thiols Tsuda, S.; Yoshiya, T.; Mochizuki, M.; Nishiuchi, Y. Org. Lett. 2015, 17, 1806–1809. Abstract: Native chemical ligation (NCL) performed without resorting to the use of thiol additives was demonstrated to be an efficient and effective procedure for synthesizing Cys-rich peptides. This method using tris(2-carboxyethyl)phosphine (TCEP) as a reducing agent facilitates the ligation reaction even at the Thr-Cys or Ile-Cys site and enables one-pot synthesis of Cys-rich peptides throughout NCL and oxidative folding Tetrahydropyranyl, a Nonaromatic Acid-Labile Cys Protecting Group for Fmoc Peptide Chemistry Ramos-Tomillero, I.; Rodríguez, H.; Albericio,
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