共查询到20条相似文献,搜索用时 15 毫秒
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Adam B. Braunschweig Dr. William R. Dichtel Dr. Ognjen Š. Miljanić Dr. Mark A. Olson Jason M. Spruell Saeed I. Khan Dr. James R. Heath Prof. Dr. J. Fraser Stoddart Prof. Dr. 《化学:亚洲杂志》2007,2(5):634-647
A series of donor–acceptor [2]‐, [3]‐, and [4]rotaxanes and self‐complexes ([1]rotaxanes) have been synthesized by a threading‐followed‐by‐stoppering approach, in which the precursor pseudorotaxanes are fixed by using CuI‐catalyzed Huisgen 1,3‐dipolar cycloaddition to attach the required stoppers. This alternative approach to forming rotaxanes of the donor–acceptor type, in which the donor is a 1,5‐dioxynaphthalene unit and the acceptor is the tetracationic cyclophane cyclobis(paraquat‐p‐phenylene), proceeds with enhanced yields relative to the tried and tested synthetic strategies, which involve the clipping of the cyclophane around a preformed dumbbell containing π‐electron‐donating recognition sites. The new synthetic approach is amenable to application to highly convergent sequences. To extend the scope of this reaction, we constructed [2]rotaxanes in which one of the phenylene rings of the tetracationic cyclophane is perfluorinated, a feature which significantly weakens its association with π‐electron‐rich guests. The activation barrier for the shuttling of the cyclophane over a spacer containing two triazole rings was determined to be (15.5±0.1) kcal mol?1 for a degenerate two‐station [2]rotaxane, a value similar to that previously measured for analogous degenerate compounds containing aromatic or ethylene glycol spacers. The triazole rings do not seem to perturb the shuttling process significantly; this property bodes well for their future incorporation into bistable molecular switches. 相似文献
3.
Hiroki Dobashi Lorenzo Catti Yuya Tanaka Munetaka Akita Michito Yoshizawa 《Angewandte Chemie (International ed. in English)》2020,59(29):11881-11885
To gain insight into the host functions of a nanocavity encircled by both polyaromatic panels and heteroatoms, nitrogen‐doped polyaromatic capsules were successfully synthesized from metal ions and pyridine‐embedded, bent anthracene‐based ligands. The new capsules display unique host–guest interactions in the isolated cavities, which are distinct from those of the undoped analogues. Besides the inclusion of Ag+ ions, the large absorption change of fullerene C60 and altered emission of a BODIPY dimer are observed upon encapsulation by the present hosts. Moreover, the N‐doped capsule exhibits specific binding ability toward progesterone and methyltestosterone, known as a natural female and synthetic male hormone, respectively, in water. 相似文献
4.
Biomimetic Donor–Acceptor Motifs in Conjugated Polymers for Promoting Exciton Splitting and Charge Separation 下载免费PDF全文
Honghui Ou Xinru Chen Lihua Lin Dr. Yuanxing Fang Prof. Xinchen Wang 《Angewandte Chemie (International ed. in English)》2018,57(28):8729-8733
Natural photosynthesis serves as a model for energy and chemical conversions, and motivates the search of artificial systems that mimic nature′s energy‐ and electron‐transfer chains. However, bioinspired systems often suffer from the partial or even large loss of the charge separation state, and show moderate activity owing to the fundamentally different features of the multiple compounds. Herein, a selenium and cyanamide‐functionalized heptazine‐based melon (DA‐HM) is designed as a unique bioinspired donor–acceptor (D‐A) light harvester. The combination of the photosystem and electron shuttle in a single species, with both n‐ and p‐type conductivities, and extended spectral absorption, endows DA‐HM with a high efficiency in the transfer and separation of photoexcited charge carriers, resulting in photochemical activity. This work presents a unique conjugated polymeric system that shows great potential for solar‐to‐chemical conversion by artificial photosynthesis. 相似文献
5.
Munechika Nakamura Yoshimi Tsukamoto Takuro Ueta Yoshihisa Sei Takanori Fukushima Kenji Yoza Kenji Kobayashi 《化学:亚洲杂志》2020,15(14):2218-2230
A 2 : 4 mixture of tetrakis[4‐(4‐pyridyl)phenyl]cavitand ( 1 ) or tetrakis[4‐(4‐pyridyl)phenylethynyl]cavitand ( 2 ) and Pd(dppp)(OTf)2 self‐assembles into a homocapsule { 1 2 ? [Pd(dppp)]4}8+ ? (TfO?)8 ( C1 ) or { 2 2 ? [Pd(dppp)]4}8+ ? (TfO?)8 ( C2 ), respectively, through Pd?Npy coordination bonds. A 1 : 1 : 4 mixture of 1 , 2 , and Pd(dppp)(OTf)2 produced a mixture of homocapsules C1 , C2 , and a heterocapsule { 1 ? 2 ? [Pd(dppp)]4}8+ ? (TfO?)8 ( C3 ) in a 1 : 1 : 0.98 mole ratio. Selective formation (self‐sorting) of homocapsules C1 and C2 or heterocapsule C3 was controlled by guest‐induced encapsulation under thermodynamic control. Applications of Pd?Npy coordination capsules with the use of 1 were demonstrated. Capsule C1 serves as a guard nanocontainer for trans‐4,4′‐diacetoxyazobenzene to protect against the trans‐to‐cis photoisomerization by encapsulation. A chiral capsule { 1 2 ? [Pd((R)‐BINAP)]4}8+ ? (TfO?)8 ( C5 ) was also constructed. Capsule C5 induces supramolecular chirality with respect to prochiral 2,2′‐bis(alkoxycarbonyl)‐4,4′‐bis(1‐propynyl)biphenyls by diastereomeric encapsulation through the asymmetric suppression of rotation around the axis of the prochiral biphenyl moiety. 相似文献
6.
Kaisa Helttunen Riia Annala Aku Suhonen Juho Iloniemi Elina Kalenius Gemma Aragay Pablo Ballester Heikki M. Tuononen Maija Nissinen 《化学:亚洲杂志》2019,14(5):647-654
The anion‐binding properties of three closely related oligoamide foldamers were studied using NMR spectroscopy, isothermal titration calorimetry and mass spectrometry, as well as DFT calculations. The 1H NMR spectra of the foldamers in [D6]acetone solution revealed partial preorganization by intramolecular hydrogen bonding, which creates a suitable cavity for anion binding. The limited size of the cavity, however, enabled efficient binding by the inner amide protons only for the chloride anion resulting in the formation of a thermodynamically stable 1:1 complex. All 1:1 chloride complexes displayed a significant favourable contribution of the entropy term. Most likely, this is due to the release of ordered solvent molecules solvating the free foldamer and the anion to the bulk solution upon complex formation. The introduction of electron‐withdrawing substituents in foldamers 2 and 3 had only a slight effect on the thermodynamic constants for chloride binding compared to the parent receptor. Remarkably, the binding of chloride to foldamer 3 not only produced the expected 1:1 complex but also open aggregates with 1:2 (host:anion) stoichiometry. 相似文献
7.
A. A. Stepanov 《Russian Journal of Electrochemistry》2003,39(11):1201-1202
Generation of a radical anion of a carbonyl compound in the presence of fluoroalkyltrimethylsilanes results in a chain reaction of addition to the carbonyl group with the generation of corresponding silyl ethers at a current efficiency of up to 7000%. A similar reaction is realized when zinc dust is used as the reductant. 相似文献
8.
Conner A. Hoelzel Hang Hu Charles H. Wolstenholme Basel A. Karim Kyle T. Munson Kwan Ho Jung Han Zhang Yu Liu Hemant P. Yennawar John B. Asbury Xiaosong Li Xin Zhang 《Angewandte Chemie (International ed. in English)》2020,59(12):4785-4792
While organic donor‐acceptor (D‐A) molecules are widely employed in multiple areas, the application of more D‐A molecules could be limited because of an inherent polarity sensitivity that inhibits photochemical processes. Presented here is a facile chemical modification to attenuate solvent‐dependent mechanisms of excited‐state quenching through addition of a β‐carbonyl‐based polar substituent. The results reveal a mechanism wherein the β‐carbonyl substituent creates a structural buffer between the donor and the surrounding solvent. Through computational and experimental analyses, it is demonstrated that the β‐carbonyl simultaneously attenuates two distinct solvent‐dependent quenching mechanisms. Using the β‐carbonyl substituent, improvements in the photophysical properties of commonly used D‐A fluorophores and their enhanced performance in biological imaging are shown. 相似文献
9.
Donor‐acceptor cyclopropanes not only participate in a broad range of ring openings with nucleophiles, electrophiles, radical and red‐ox agents, but also are excellent substrates for various (3+n)‐cycloaddition and (3+n)‐annulation processes. Moreover, under treatment with Lewis acid donor‐acceptor cyclopropanes can produce new ring systems via isomerization or cyclodimerization. Authors’ contribution to the synthesis of diverse carbocycles from donor‐acceptor cyclopropanes is summarized in this account. 相似文献
10.
Boron(III)‐Containing Donor–Acceptor Compound with Goldlike Reflective Behavior for Organic Resistive Memory Devices 下载免费PDF全文
Dr. Chun‐Ting Poon Dr. Di Wu Prof. Dr. Vivian Wing‐Wah Yam 《Angewandte Chemie (International ed. in English)》2016,55(11):3647-3651
A small‐molecule‐based boron(III)‐containing donor–acceptor compound has been designed and synthesized. Interesting goldlike reflective behavior was observed in the neat thin‐film sample from simple spin‐coating preparation, which can serve as a potential organic thin‐film optical reflector. The small thickness in nanometer range and the relatively smooth surface morphology, together with simple preparation and easy solution processability, are attractive features for opening up new avenues for the fabrication of reflective coatings. Moreover, this donor–acceptor compound has been employed in the fabrication of organic resistive memory device, which exhibited good performance with low turn‐on voltage, small operating bias, large ON/OFF ratio, and long retention time. 相似文献
11.
Dr. Thien H. Ngo David Zieba Whitney A. Webre Gary N. Lim Prof. Dr. Paul A. Karr Scheghajegh Kord Dr. Shangbin Jin Dr. Katsuhiko Ariga Marzia Galli Prof. Dr. Steve Goldup Dr. Jonathan P. Hill Prof. Dr. Francis D'Souza 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(4):1301-1312
An electron‐deficient copper(III) corrole was utilized for the construction of donor–acceptor conjugates with zinc(II) porphyrin (ZnP) as a singlet excited state electron donor, and the occurrence of photoinduced charge separation was demonstrated by using transient pump–probe spectroscopic techniques. In these conjugates, the number of copper corrole units was varied from 1 to 2 or 4 units while maintaining a single ZnP entity to observe the effect of corrole multiplicity in facilitating the charge‐separation process. The conjugates and control compounds were electrochemically and spectroelectrochemically characterized. Computational studies revealed ground state geometries of the compounds and the electron‐deficient nature of the copper(III) corrole. An energy level diagram was established to predict the photochemical events by using optical, emission, electrochemical, and computational data. The occurrence of charge separation from singlet excited zinc porphyrin and charge recombination to yield directly the ground state species were evident from the diagram. Femtosecond transient absorption spectroscopy studies provided spectral evidence of charge separation in the form of the zinc porphyrin radical cation and copper(II) corrole species as products. Rates of charge separation in the conjugates were found to be of the order of 1010 s?1 and increased with increasing multiplicity of copper(III) corrole entities. The present study demonstrates the importance of copper(III) corrole as an electron acceptor in building model photosynthetic systems. 相似文献
12.
Dynamic Covalent Synthesis of Donor–Acceptor Interlocked Architectures in Solution and at the Solution:Surface Interface 下载免费PDF全文
Despite advances in the range of mechanically interlocked architectures that can be synthesized and operated as supramolecular machines, motors and sensors in solution, in many cases their synthesis is laborious and expensive requiring long multistep pathways with extensive purification at each stage. Dynamic covalent chemistry has been shown to overcome problems with traditional kinetically controlled synthetic approaches that often afford low yields of interlocked architectures due to irreversible formation of non‐interlocked by‐products. Herein, we describe the use of reversible disulfide exchange reactions as a means to assemble catenanes and rotaxanes in organic solutions. Moreover, the application of this thermodynamic approach to assemble interlocked architectures at the solution:surface interface, specifically polymer resins, is discussed. 相似文献
13.
Modulating the Binding of Polycyclic Aromatic Hydrocarbons Inside a Hexacationic Cage by Anion–π Interactions 下载免费PDF全文
Dr. Nema Hafezi Dr. James M. Holcroft Dr. Karel J. Hartlieb Edward J. Dale Dr. Nicolaas A. Vermeulen Charlotte L. Stern Dr. Amy A. Sarjeant Prof. J. Fraser Stoddart 《Angewandte Chemie (International ed. in English)》2015,54(2):456-461
We report the template‐directed synthesis of BlueCage6+, a macrobicyclic cyclophane composed of six pyridinium rings fused with two central triazines and bridged by three paraxylylene units. These moieties endow the cage with a remarkably electron‐poor cavity, which makes it a powerful receptor for polycyclic aromatic hydrocarbons (PAHs). Upon forming a 1:1 complex with pyrene in acetonitrile, however, BlueCage?6 PF6 exhibits a lower association constant Ka than its progenitor ExCage?6 PF6. A close inspection reveals that the six PF6? counterions of BlueCage6+ occupy the cavity in a fleeting manner as a consequence of anion–π interactions and, as a result, compete with the PAH guests. This conclusion is supported by a one order of magnitude increase in the Ka value for pyrene in BlueCage6+ when the PF6? counterions are replaced by much bulkier anions. The presence of anion–π interactions is supported by X‐ray crystallography, and confirms the presence of a PF6? counterion inside its cavity. 相似文献
14.
Amrita Sikder Boyli Ghosh Saptarshi Chakraborty Dr. Ankan Paul Dr. Suhrit Ghosh 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(6):1908-1913
An adaptable and efficient molecular recognition pair has been established by taking advantage of the complementary nature of donor–acceptor interactions together with the strength of hydrogen bonds. Such distinct molecular recognition propagates in orthogonal directions to effect extended alternating co‐assembly of two different appended molecular entities. The dimensions of the assembled structures can be tuned by stoichiometric imbalance between the donor and acceptor building blocks. The morphology of the self‐assembled material can be correlated with the ratio of the two building blocks. 相似文献
15.
Yuan‐Bo Cai Dr. Jinhui Zhan Yang Hai Prof. Dr. Jun‐Long Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(14):4242-4249
There is widespread interest in non‐covalent bonding and weak interactions, such as electrostatic interactions, hydrogen bonding, solvophobic/hydrophobic interactions, metal–metal interactions, and π–π stacking, to tune the molecular assembly of planar π‐conjugated organic and inorganic molecules. Inspired by the roles of metal–aromatic interaction in biological systems, such as in ion channels and metalloproteins, herein, we report the first example of the use of Hg2+–aromatic interactions to selectively control the assembly and disassembly of zinc–salen complexes in aqueous media; moreover, this process exhibited significant “turn on” fluorescent properties. UV/Vis and fluorescence spectroscopic analysis of the titration of Hg2+ ions versus complex ZnL1 revealed that the higher binding affinity of Hg2+ ions (compared to 13 other metal ions) was ascribed to specific interactions between the Hg2+ ions and the phenyl rings of ZnL1 ; this result was also confirmed by 1H NMR spectroscopy and HRMS (ESI). Further evidence for this type of interaction was obtained from the reaction of small‐molecule analogue L1 with Hg2+ ions, which demonstrates the proximity of the N‐alkyl group to the aromatic protons during Hg2+‐ion binding, which led to the consequential H/D exchange reaction with D2O. DFT modeling of such interactions between the Hg2+ ions and the phenyl rings afforded calculated distances between the C and Hg atoms (2.29 Å) that were indicative of C? Hg bond‐formation, under the direction of the N atom of the morpholine ring. The unusual coordination of Hg2+ ions to the phenyl ring of the metallosalen complexes not only strengthened the binding ability but also increased the steric effect to promote the disassembly of ZnL1 in aqueous media. 相似文献
16.
《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(1):369-385
A range of covalently linked donor–acceptor compounds which contain 1) a hydroquinone (HQ) unit, 2) a 1,5‐dioxynaphthalene (DNP) ring system, or 3) a tetrathiafulvalene (TTF) unit as the π‐donor, and 4) cyclobis(paraquat‐p‐phenylene) (CBPQT4+) as the π‐accepting tetracationic cyclophane were prepared and shown to operate as simple molecular machines. The π‐donating arms can be included inside the cyclophane in an intramolecular fashion by virtue of stabilizing noncovalent bonding interactions. What amounts to self‐complexing/decomplexing equilibria were shown to be highly temperature dependent when the π‐donating arm contains either an HQ or DNP moiety. The thermodynamic parameters associated with the equilibria have been unraveled by using variable‐temperature 1H NMR spectroscopy. The negative ΔH° and ΔS° values account for the fact that the “uncomplexed” conformation becomes the dominant species, since the entropy gain associated with the decomplexation process overcomes the enthalpy loss resulting from the breaking of the donor–acceptor interactions. The arm's in‐and‐out movements with respect to the linked cyclophanes can be arrested by installing a bulky substituent at the end of the arm. In the case of compounds carrying a DNP ring system in their side arm, two diastereoisomeric, self‐complexing conformations are observed below 272 K in hexadeuterioacetone. By contrast, control over the TTF‐containing arm's movement is more or less ineffective through the thermally sensitive equilibrium although it can be realized by chemical and electrochemical ways as a result of TTF's excellent redox properties. Such self‐complexing compounds could find applications as thermo‐ and electroswitches. In addition, the thermochromism associated with the arm's movement could lead to some of the compounds finding uses as imaging and sensing materials. 相似文献
17.
Yannick Rio Dr. Wolfgang Seitz Andreas Gouloumis Dr. Purificacion Vázquez Prof. Jonathan L. Sessler Prof. Dr. Dirk M. Guldi Prof. Tomás Torres Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(6):1929-1940
A panchromatic 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene –zinc phthalocyanine conjugate (Bodipy–ZnPc) 1 was synthesized starting from phthalocyanine aldehyde 4 , via dipyrromethane 3 and dipyrromethene 2 . Conjugate 1 represents the first example in which a Bodipy unit is tethered to the peripheral position of a phthalocyanine core. Electrochemical and optical measurements provided evidence for strong electronic interactions between the Bodipy and ZnPc constituents in the ground state of 1 . When conjugate 1 is subjected to photoexcitation in the spectral region corresponding to the Bodipy absorption, the strong fluorescence characteristic of the latter subunit is effectively quenched (i.e., ≥97 %). Excitation spectral analysis confirmed that the photoexcited Bodipy and the tethered ZnPc subunits interact and that intraconjugate singlet energy transfer occurs with an efficiency of ca. 25 %. Treatment of conjugate 1 with N‐pyridylfulleropyrrolidine ( 8 ), an electron‐acceptor system containing a nitrogen ligand, gives rise to the novel electron donor–acceptor hybrid 1 ? 8 through ligation to the ZnPc center. Irradiation of the resulting supramolecular ensemble within the visible range leads to a charge‐separated Bodipy–ZnPc.+–C60.? radical‐ion‐pair state, through a sequence of excited‐state and charge transfers, characterized by a remarkably long lifetime of 39.9 ns in toluene. 相似文献
18.
《Angewandte Chemie (International ed. in English)》2017,56(45):14293-14296
Lewis‐acid‐catalyzed reactions of 2‐substituted cyclopropane 1,1‐dicarboxylates with thioketones are described. Highly substituted tetrahydrothiophenes with two adjacent quaternary carbon atoms were obtained in a stereospecific manner under mild conditions and in high yield when using AlCl3 as Lewis acid. Moreover, an intramolecular approach was successfully implemented to gain access to sulfur‐bridged [n .2.1] bicyclic ring systems. Conversion of selenoketones, the heavier analogues, under similar conditions resulted in the formation of various tetrahydroselenophenes. 相似文献
19.
Denis D. Borisov Dr. Roman A. Novikov Prof. Dr. Yury V. Tomilov 《Angewandte Chemie (International ed. in English)》2016,55(40):12233-12237
A new strategy for cascade assembly of substituted indenes and polycyclic lactones based on reactions of donor–acceptor cyclopropanes and styrylmalonates with aromatic aldehydes in the presence of GaCl3 has been developed. The use of GaCl3 makes it possible to principally change the direction of the reaction known in this series of substrates and to perform the process in a multicomponent version. Generation of formal 1,2‐zwitterionic intermediates owing to complexation of dicarboxylate groups with GaCl3 is the driving force of the reactions discovered. This method makes it possible to assemble indenylmalonates or indano[1′,2′:2,3]indano[2,1‐b]furan‐2‐ones in one synthetic stage from readily available starting compounds with high regio‐ and diastereoselectivity. A mechanism of the reactions has been suggested using the 18O label in benzaldehyde. 相似文献
20.
Tetsuya Doi Takumi Sakakibara Dr. Hiromu Kashida Dr. Yasuyuki Araki Prof. Dr. Takehiko Wada Prof. Dr. Hiroyuki Asanuma 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(45):15974-15980
We report on the characterization of a novel hetero‐selective DNA‐like duplex of pyrene and anthraquinone pseudo base pairs. The pyrene/anthraquinone pairs showed excellent selectivity in hetero‐recognition and even trimers were found to form a hetero‐duplex. Pyrene and anthraquinone moieties were tethered on acyclic D ‐threoninol linkers and linked to adjacent residues by using standard phosphoramidite chemistry. When pyrene and anthraquinone were incorporated at pairing positions in complementary strands of natural DNA oligonucleotides, the duplex was stabilized significantly. Moreover, a pyrene hexamer and an anthraquinone hexamer formed a stable artificial hetero‐duplex without the assistance of natural base pairs. The pyrene/anthraquinone pair was so stable that even trimers formed a hetero‐duplex under conditions in which natural DNA strands of three residues do not. 相似文献