Large N-Heteroacenes: New Tricks for Very Old Dogs? Bunz, Uwe H. F.; Engelhart, Jens U.; Lindner, Benjamin D. ...
Angewandte Chemie (International ed.),
April 2, 2013, Letnik:
52, Številka:
14
Journal Article
Recenzirano
Azaacenes have been known for a very long time, either as N,N′‐dihydro compounds or in their oxidized form as 4 n+2π systems, but only recently have processable and charcterizable derivatives been ...sought. In the last three years synthetic routes to large N‐heteroacenes have been developed. In particular, the Pd‐catalyzed coupling of aromatic diamines with activated aromatic dihalogenides has enabled simple access to numerous new azaacenes. Since 2010, azapentacene and stabile oligoazahexacene have been synthesized, as well as a symmetrical tetraazapentacene, which acts as an excellent electron‐transport material for thin‐film transistors.
Electron‐transporting alternatives to pentacene? Since 2010, several research groups have succeeded in synthesizing substituted diaza‐ and tetraazapentacenes as well as structurally similar tetraaza‐ and hexaazahexacenes. The symmetrical tetraazapentacene (see structure; C gray, H white, N blue, Si tan) has been investigated as an electron‐transporting material in thin‐film transistors.
Often, the interpretation of experiments concerning the manipulation of the energy distribution of laser-accelerated ion bunches is complicated by the multitude of competing dynamic processes ...simultaneously contributing to recorded ion signals. Here we demonstrate experimentally the acceleration of a clean proton bunch. This was achieved with a microscopic and three-dimensionally confined near critical density plasma, which evolves from a 1 µm diameter plastic sphere, which is levitated and positioned with micrometer precision in the focus of a Petawatt laser pulse. The emitted proton bunch is reproducibly observed with central energies between 20 and 40 MeV and narrow energy spread (down to 25%) showing almost no low-energetic background. Together with three-dimensional particle-in-cell simulations we track the complete acceleration process, evidencing the transition from organized acceleration to Coulomb repulsion. This reveals limitations of current high power lasers and viable paths to optimize laser-driven ion sources.
A negatively charged poly(para‐phenyleneethynylene) (PPE) forms electrostatic complexes with four positively charged antimicrobial peptides (AMP). The AMPs partially quench the fluorescence of the ...PPE and discriminate fourteen different bacteria in water and in human urine by pattern‐based fluorescence recognition; the AMP‐PPE complexes bind differentially to the components of bacterial surfaces. The bacterial species and strains form clusters according to staining properties (Gram‐positive and Gram‐negative) or genetic similarity (genus, species, and strain). The identification and data treatment is performed by pattern evaluation with linear discriminant analysis (LDA) of the collected fluorescence intensity data.
Discriminated! Electrostatic complexes formed from four cationic antimicrobial peptides (AMPs) and one anionic poly(para‐phenylene‐ethynylene) (PPE) were examined as a new type of an array‐based sensor. The array identifies and discriminates 14 different types of bacteria according to Gram status and their genetic relationship in human urine by subjecting the obtained fluorescence response patterns to linear discriminant analysis.
In the past years, the interest in the laser-driven acceleration of heavy ions in the mass range of Formula: see text has been increasing due to promising application ideas like the fission-fusion ...nuclear reaction mechanism, aiming at the production of neutron-rich isotopes relevant for the astrophysical r-process nucleosynthesis. In this paper, we report on the laser acceleration of gold ions to beyond 7 MeV/u, exceeding for the first time an important prerequisite for this nuclear reaction scheme. Moreover, the gold ion charge states have been detected with an unprecedented resolution, which enables the separation of individual charge states up to 4 MeV/u. The recorded charge-state distributions show a remarkable dependency on the target foil thickness and differ from simulations, lacking a straight-forward explanation by the established ionization models.
Accessible azaacenes: Pd‐catalyzed coupling reactions between aromatic diamines and unactivated aromatic dibromides furnish N,N′‐dihydrodiazapentacenes, ‐hexacenes, and ‐heptacenes (see scheme; ...TIPS=triisopropylsilyl). Oxidation of these products led to diazapentacenes and a diazahexacene. The existence of a diazaheptacene intermediate was proven by solving the single‐crystal structure of its (4+4) dimerization product.
Age-related macular degeneration (AMD) is the leading cause of severe vision impairment in Western populations over 55 years. A growing number of gene variants have been identified which are strongly ...associated with an altered risk to develop AMD. Nevertheless, gene-based biomarkers which could be dysregulated at defined stages of AMD may point toward key processes in disease mechanism and thus may support efforts to design novel treatment regimens for this blinding disorder. Circulating microRNAs (cmiRNAs) which are carried by nanosized exosomes or microvesicles in blood plasma or serum, have been recognized as valuable indicators for various age-related diseases. We therefore aimed to elucidate the role of cmiRNAs in AMD by genome-wide miRNA expression profiling and replication analyses in 147 controls and 129 neovascular AMD patients. We identified three microRNAs differentially secreted in neovascular (NV) AMD (hsa-mir-301-3p, pcorrected = 5.6*10-5, hsa-mir-361-5p, pcorrected = 8.0*10-4 and hsa-mir-424-5p, pcorrected = 9.6*10-3). A combined profile of the three miRNAs revealed an area under the curve (AUC) value of 0.727 and was highly associated with NV AMD (p = 1.2*10-8). To evaluate subtype-specificity, an additional 59 AMD cases with pure unilateral or bilateral geographic atrophy (GA) were analyzed for microRNAs hsa-mir-301-3p, hsa-mir-361-5p, and hsa-mir-424-5p. While we found no significant differences between GA AMD and controls neither individually nor for a combined microRNAs profile, hsa-mir-424-5p levels remained significantly higher in GA AMD when compared to NV (pcorrected<0.005). Pathway enrichment analysis on genes predicted to be regulated by microRNAs hsa-mir-301-3p, hsa-mir-361-5p, and hsa-mir-424-5p, suggests canonical TGFβ, mTOR and related pathways to be involved in NV AMD. In addition, knockdown of hsa-mir-361-5p resulted in increased neovascularization in an in vitro angiogenesis assay.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A series of bis-triazolyl benzochalcogendiazoles was synthesized to investigate their metal-binding capabilities. These fluorophores were formed through the cycloaddition of an ethynylated ...benzochalcogendiazole and a water-soluble azide. Variation of the chalcogen heteroatom was seen to affect the photophysical properties as well as the metal-binding activity. These cycloadducts exhibited a distinct response to Cu2+, Ni2+, and Ag+ in water. The binding affinity for the copper and nickel ions increased moving the chalcogen atom from O to Se. Statistical analysis of the spectral data enabled differentiation of Ag+, Cu2+, and Ni2+ ions.
A series of functionalized diaza‐ and tetraazatetracenes was synthesized, either by condensation of an aromatic diamine with an ortho‐quinone/diethyloxalate followed by chlorination with POCl3 to ...give diazatetracenes or by palladium‐catalyzed coupling of a phenylenediamine with various 2,3‐dichloroquinoxalines to give tetraazatetracenes (after oxidation with MnO2). Representative examples included halogenated and nitrated derivatives. The optical properties of these azatetracenes were discussed with respect to their molecular structures and substitution patterns. The diazatetracenes and tetraazatetracenes formed two different groups that had significantly different electronic structures and properties. Furthermore, 1,2,3,4‐tetrafluoro‐6,11‐bis((triisopropylsilyl)ethynyl)benzobphenazine was synthesized, which is the first reported fluorinated diazatetracene. Single‐crystal X‐ray analysis of this compound is reported.
A colorful bunch of heteroacenes were prepared by direct condensation of diamines with ortho‐quinones or by Pd‐catalyzed coupling of diamines to dichloroquinoxalines. The oligoazatetracenes displayed different colors depending upon their substitution patterns.
The fission-fusion reaction mechanism was proposed in order to generate extremely neutron-rich nuclei close to the waiting point N = 126 of the rapid neutron capture nucleosynthesis process ...(r-process). The production of such isotopes and the measurement of their nuclear properties would fundamentally help to increase the understanding of the nucleosynthesis of the heaviest elements in the Universe. Major prerequisite for the realization of this new reaction scheme is the development of laser-based acceleration of ultra-dense heavy ion bunches in the mass range of A 200 and above. In this paper, we review the status of laser-driven heavy ion acceleration in the light of the fission-fusion reaction mechanism. We present results from our latest experiment on heavy ion acceleration, including a new milestone with laser-accelerated heavy ion energies exceeding 5 MeV u−1.
Stable Hexacenes through Nitrogen Substitution Lindner, Benjamin D.; Engelhart, Jens U.; Tverskoy, Olena ...
Angewandte Chemie (International ed.),
September 5, 2011, Letnik:
50, Številka:
37
Journal Article
Recenzirano
Give me an N: Tetraazahexacenes (see picture, N blue, Si brown) are easily prepared in high yields. Their modular synthesis allows the introduction of any substituent by the choice of suitable ...quinoxaline derivatives.
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