Orthogonal joints, understood as connections with an angle of 90°, were introduced in the design of the “Geländer” model compounds 1 and 2 . The banister, consisting of a conjugated carbazole dimer linked by either 1,3-butadiyne ( 2 ) or a single thiophene ( 1 ), wraps around an axis composed of a phthalimide dimer due to the dimensional mismatch of both subunits, which are interconnected by phenylene rungs. The “Geländer” structure was assembled from a monomer comprising the 1,4-diaminobenzene rung with one amino substituent as part of a 4-bromo phthalimide subunit forming the orthogonal junction to the axis, and the other as part of a masked 2-ethynyl carbazole as orthogonal joint to the banister. The macrocycle was obtained by two sequential homocoupling steps. A first dimerization by a reductive homocoupling assembled the axis, while an oxidative acetylene coupling served as ring-closing reaction. The formed butadiyne was further derivatized to a thiophene, rendering all carbons of the model compound sp2 hybridized. Both helical structures were fully characterized and chirally resolved. Assignment of the enantiomers was achieved by simulation of chiroptical properties and enantiopure synthesis. 相似文献
The novel diacetylene bridged terphenylic macrocycle 1 is presented and discussed in the context of rotationally restricted “Geländer” oligomers. The 1,4-bis(phenylbuta-1,3-diyn-1-yl) benzene bridge of diacetylene 1 is significantly longer than its terphenyl backbone, forcing the bridge to bend around the central pylon. The synthesis of molecule 1 is based to a large extent on acetylene scaffolding strategies, profiting from orthogonal alkyne protection groups to close both macrocyclic subunits by oxidative acetylene coupling sequentially. The spatial arrangement and the dynamic enantiomerization process of the bicyclic target structure 1 are analyzed. In-depth NMR investigations not only reveal an unexpected spatial arrangement with both oligomer strands bent alongside the backbone, but also display the limited stability of the model compound in the presence of molecular oxygen. 相似文献
Summary: A new kind of aniline oligomer with a “dumbbell” shape was synthesized through a simple oxidative coupling reaction with a new rigid aromatic amine as starting material. The oligomer was characterized with mass spectrometry, IR and NMR spectroscopies. Its redox property was checked by cyclic voltammetry and chemical oxidation/reduction process was monitored by UV spectroscopy. We found it has a reversible electrochemical property like common oligoanilines. Combined with its well‐defined structure, it is expected to act as a model compound for a molecular electronic switch.
The “dumbbell‐shaped” oligoaniline compound synthesized here. 相似文献
A new Friedländer synthon, 2,3‐diaminobenzene‐1,4‐dicarbaldehyde, was prepared from p‐xylene in 4 steps, of which the Friedländer reaction with acetaldehyde and acetone in a Schulenk bottle afforded 1,10‐phenathroline and neocuprine in 44% and 82% yield, respectively. The scope of the Friedländer reactions of 2,3‐diaminobenzene‐1,4‐dicarbaldehyde, including the synthesis of hexaazacyclic cyclophane with 1,10‐phenanthroline and pyridine units, was described 相似文献
A new type of “Geländer” molecule based on a ortho-tetraphenylene core is presented. The central para-quaterphenyl backbone is wrapped by a 4,4’-di((Z)-styryl)-1,1’-biphenyl banister, with its aryl rings covalently attached to all four phenyl rings of the backbone. The resulting helical chiral bicyclic architecture consists exclusively of sp2-hybridized carbon atoms. The target structure was assembled by expanding the central ortho-tetraphenylene subunit with the required additional phenyl rings followed by a twofold macrocyclization. The first macrocyclization attempts based on a twofold McMurry coupling were successful but low yielding; the second strategy, profiting from olefin metathesis, provided satisfying yields. Hydrogenation of the olefins resulted in a saturated derivative of similar topology, thereby allowing the interdependence between saturation and physico-chemical properties to be studied. The target structures, including their solid-state structures, were fully characterized. The helical chiral bicycle was synthesized as a racemate and separated into pure enantiomers by HPLC on a chiral stationary phase. Comparison of recorded and simulated chiroptical properties allowed the enantiomers to be assigned. 相似文献
Inspired by hydrophobic interface, a novel design of “polysulfide‐phobic” interface was proposed and developed to restrain shuttle effect in lithium–sulfur batteries. Two‐dimensional VOPO4 sheets with adequate active sites were employed to immobilize the polysulfides through the formation of a V?S bond. Moreover, owing to the intrinsic Coulomb repulsion between polysulfide anions, the surface anchored with polysulfides can be further evolved into a “polysulfide‐phobic” interface, which was demonstrated by the advanced time/space‐resolved operando Raman evidences. In particular, by introducing the “polysulfide‐phobic” surface design into separator fabrication, the lithium–sulfur battery performed a superior long‐term cycling stability. This work expands a novel strategy to build a “polysulfide‐phobic” surface by “self‐defense” mechanism for suppressing polysulfides shuttle, which provides new insights and opportunities to develop advanced lithium–sulfur batteries. 相似文献
Summary: The synthesis and self‐assembly of a comb oligomer having rigid racemic binaphthyl macrocyclic pendant groups are described. The coupling of two structural motifs at the molecular level, e.g., a nanometer‐size chiral cavity, and a flexible polymeric backbone, could lead to new opportunities in molecular recognition and separation. The macrocyclic monomers were synthesized followed by introduction of an acrylate side‐group, and through free‐radical polymerization, they yielded a comb oligomer. Most importantly, this novel oligomer can self‐assemble into solid or hollow spheres when tetrahydrofuran (THF) solutions of the oligomer at different concentrations are dropped onto the surface of water. The morphology of the solid or hollow spheres was observed by TEM, ESEM and DLS.
A schematic illustration of the processes of self‐assembly of the oligomer. 相似文献
Organic azides have been somewhat popularized due to their pivotal role in the emerging field of “click chemistry”. A simple approach has been used for the synthesis of uniform nano Fe‐MIL‐88B‐NH2, and a generic postsynthetic modification route has been developed for the synthesis of azide‐modified nano Fe‐MIL‐88B‐N3. The approach also has been used to synthesize the azide‐modified IRMOF‐3(‐N3). These new azide‐modified Fe‐MIL‐88B‐N3 nanocrystals hold promising potential for the applications in the fields of “click chemistry”, nanotechnology devices and nano composite membranes. 相似文献
A series of degradable branched PDMAEMA copolymers were investigated with the linear PDMAEMA counterpart as gene‐delivery vectors. The branched PDMAEMA copolymers were synthesized by controlled radical cross‐linking copolymerization based on the “vinyl oligomer combination” approach. Efficient degradation properties were observed for all of the copolymers. The degree of branching was found to have a big impact on performance in transfection when tested on different cell types. The product with the highest degree of branching and highest degree of functionality had a superior transfection profile in terms of both transfection capability and the preservation of cell viability. These branched PDMAEMA copolymers show high potential for gene‐delivery applications through a combination of the simplicity of their synthesis, their low toxicity, and their high performance. 相似文献
The first example of core cross‐linked star (CCS) polyrotaxane was prepared using the poly(ϵ‐caprolactone) (PCL) CCS three‐dimensional (3D) scaffold. The 3D CCS polymer was firstly prepared through the “arm‐first” approach. Then, the “arms” of the resultant PCL CCS polymer were threaded with α‐cyclodextrins (α‐CDs). The threaded α‐CDs were permanently locked by the “click” reaction of terminal alkyne functionalities of the star polymers with the azide‐functionalized end caps to afford the CCS polyrotaxanes. All analytical results confirm the formation of the CCS polyrotaxanes and reveal their characteristics, including fluorescence under UV, a channel‐type crystalline structure, a two‐step thermal decomposition, and a unique core‐shell structure in great contrast to the polymer precursors. 相似文献
A modified Friedländer conversion of the cyclocondensation of aromatic o‐aminonitriles with carbonyl compounds was discovered. Systematic studies reveal that both the new transformation and the classic Friedländer annulation in the presence of ZnCl2 constitute a pair of divergent reaction, and thecontrolled PDF transformation of this divergent reaction was achieved in the present of bases. 相似文献
In this work, an “on–off–on” switch system has been successfully applied through the construction of an electrochemiluminscent biosensor for copper ion (Cu2+) detection based on a new electrochemiluminescence (ECL) emitter of supramolecular nanorods, which was achieved through supramolecular interactions between 3,4,9,10‐perylenetetracarboxylic acid (PTCA) and aniline. The initial “signal‐on” state with strong and stable ECL emission was obtained by use of the supramolecular nanorods with a new signal amplification strategy involving a co‐reaction accelerator. In addition, ECL quencher probes (Fc‐NH2/Cu‐Sub/nano‐Au) were fabricated by immobilizing aminoferrocene (Fc‐NH2) on Cu‐substrate strand modified Au nanoparticles. The quencher probes were hybridized with the immobilized Cu‐enzyme strand to form Cu2+‐specific DNAzyme. Similarly, the “signal‐off” state was obtained by the high quenching effect of Fc‐NH2 on the ECL of the excited‐state PTCA (1PTCA*). As expected, the second “switch‐on” state could achieved by incubating with the target Cu2+, owing to the Cu2+‐specific DNAzyme, which was irreversibly cleaved, resulting in the release of the quencher probes from the sensor interface. Herein, on the basis of the ECL intensity changes (ΔIECL) before and after incubating with the target Cu2+, the prepared Cu2+‐specific DNAzyme‐based biosensor was used for the determination of Cu2+ concentrations with high sensitivity, excellent selectivity, and good regeneration. 相似文献
We designed, synthesized, and characterized two types of dimeric forms of monocarba‐closo‐dodecaborate, namely, a “dumbbell”‐shaped dianion having a C?C bond and a “clackers”‐shaped monoanion having an iodonium linker. The unique architectures of these anionic molecules were established by X‐ray analysis. Spectroscopic analysis, DFT calculations, and reactivity experiments revealed high anionic and chemical stability of both anions, which are crucial properties for weakly coordinating anions. 相似文献
Large Stokes‐shift coumarin dyes with an O‐phosphorylated 4‐(hydroxymethyl)‐2,2‐dimethyl‐1,2,3,4‐tetrahydroquinoline fragment emitting in the blue, green, and red regions of the visible spectrum were synthesized. For this purpose, N‐substituted and O‐protected 1,2‐dihydro‐7‐hydroxy‐2,2,4‐trimethylquinoline was oxidized with SeO2 to the corresponding α,β‐unsaturated aldehyde and then reduced with NaBH4 in a “one‐pot” fashion to yield N‐substituted and 7‐O‐protected 4‐(hydroxymethyl)‐7‐hydroxy‐2,2‐dimethyl‐1,2,3,4‐tetrahydroquinoline as a common precursor to all the coumarin dyes reported here. The photophysical properties of the new dyes (“reduced coumarins”) and 1,2‐dihydroquinoline analogues (formal precursors) with a trisubstituted C=C bond were compared. The “reduced coumarins” were found to be more photoresistant and brighter than their 1,2‐dihydroquinoline counterparts. Free carboxylate analogues, as well as their antibody conjugates (obtained from N‐hydroxysuccinimidyl esters) were also prepared. All studied conjugates with secondary antibodies afforded high specificity and were suitable for fluorescence microscopy. The red‐emitting coumarin dye bearing a betaine fragment at the C‐3‐position showed excellent performance in stimulation emission depletion (STED) microscopy. 相似文献