Sebastian Beil
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[ASAP] Visible Light Induced Cu-Catalyzed Asymmetric C(sp3)–H Alkylation
Double-anonymised peer review: a new option for authors at Chemical Science
DOI: 10.1039/D1SC90122B, Editorial
Introducing double-anonymised peer review in Chemical Science. Graphical abstract image adapted from © Shutterstock/M-SUR.
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Good research begins long before papers get written
Nature, Published online: 29 April 2021; doi:10.1038/d41586-021-01167-9
Publishers are redoubling their commitment to transparency and reproducibility — but they can’t bring about change alone.[ASAP] Mechanically Responsive Luminescent Polymers Based on Supramolecular Cyclophane Mechanophores
[ASAP] Synthesis of Enynic and Allenic Orthoesters via Defluoromethoxylation of 2-Trifluoromethyl-1,3-enynes
Masked Alkyne Equivalents for the Synthesis of Mechanically Interlocked Polyynes**
Active‐metal‐template synthesis has been used to prepare a [2]rotaxane in which the whole dumbbell component is a masked C16H2 polyyne. t‐Butyl substituents make the photo‐labile terminal groups bulky enough to act as stoppers and prevent unthreading of the macrocycle. Rotaxanes of this type are promising intermediates in the synthesis of mechanically interlocked carbon‐rich architectures, such as cyclocarbon catenanes and carbyne polyrotaxanes.
Abstract
Polyyne polyrotaxanes, encapsulated cyclocarbon catenanes and other fascinating mechanically interlocked carbon‐rich architectures should become accessible if masked alkyne equivalents (MAEs) can be developed that are large enough to prevent unthreading of a macrocycle, and that can be cleanly unmasked under mild conditions. Herein, we report the synthesis of a new bulky MAE based on t‐butylbicyclo[4.3.1]decatriene. This MAE was used to synthesize a polyyne [2]rotaxane and a masked‐polyyne [3]rotaxane by Cadiot–Chodkiewicz coupling. Glaser cyclo‐oligomerization of the [2]rotaxane gave masked cyclocarbon catenanes. The unmasking behavior of the catenanes and rotaxanes was tested by photolysis at a range of UV wavelengths. Photochemical unmasking did not proceed cleanly enough to prepare extended encapsulated polyyne polyrotaxanes. We highlight the scope and challenges involved with this approach to interlocked carbon‐rich architectures.
Dimeric Cycloparaphenylenes with Rigid Aromatic Linker
Dimeric cycloparaphenylene (CPP) architectures with well‐defined flipping motion are constructed taking advantage of an efficient cyclocondensation reaction. Variable‐temperature nuclear magnetic resonance (VT‐NMR) analyses and theoretical calculations indicate rapid interconversion of cis and trans conformers at room temperature, while energetically favorable trans conformer exists at low temperature with the metastable cis conformer hidden. The trihexylsilylethynyl‐substituted dimer exhibits bright emission in solution at 616 nm with quantum yield up to 80%, representing the brightest CPP‐based emitter beyond 600 nm. A 1:2 host‐guest complex of the dimer and C60 is established with negative cooperativity, demonstrating the first example of 1:2 complex from CPP derivatives.
[ASAP] Selective Anion Binding Drives the Formation of AgI8L6 and AgI12L6 Six-Stranded Helicates
Synthesis of i‐Corona[6]arenes for Selective Anion Binding: Interdependent and Synergistic Anion–π and Hydrogen‐Bond Interactions
i‐Corona[3]arene[3]tetrazines were synthesized straightforwardly from the nucleophilic aromatic substitution reaction of resorcinol and its derivatives with 3,6‐dichlorotetrazine in a one‐pot fashion under mild conditions. They can regulate their macrocyclic conformation and cavity structures to recognize anions by forming interdependent and synergistic anion–π/and hydrogen bond interactions.
Abstract
i‐Corona[3]arene[3]tetrazines were synthesized from the nucleophilic aromatic substitution reaction of resorcinol and its derivatives with 3,6‐dichlorotetrazine in a one‐pot fashion under mild conditions. All of the resulting macrocycles adopted 1,3,5‐alternate conformation irrespective of the nature of the substituents on both upper‐ and lower‐rims. i‐Corona[3]arene[3]tetrazine was found to self‐regulate its macrocyclic conformation and cavity to recognize anions with binding constants spanning from 26 M−1 to 2.2×103 M−1 depending on the structure of the anions. The selective binding resulted from a significant interdependent and synergistic effect between multiple tetrazine π/anion and Caryl–H/anion hydrogen bond interactions. Taking advantage of synergistic effect revealed, a cyanobenzene‐embedded i‐corona[3]arene[3]tetrazine was designedly synthesized and highly selective and very strong affinity toward nitrate with a binding constant of 2.2×105 M−1 was achieved.
A Green and Wide‐Scope Approach for Chiroptical Sensing of Organic Molecules through Biomimetic Recognition in Water
Optical chirality sensing of a wide scope of organic molecules, including common products in asymmetric catalysis, natural products, and chiral drugs, has been achieved using amide naphthotubes in water. The use of water as solvent and the possibility to readily recover the sensors makes this method environmentally friendly.
Abstract
Optical chirality sensing has attracted a lot of interest due to its potential in high‐throughput screening in chirality analysis. A molecular sensor is required to convert the chirality of analytes into optical signals. Although many molecular sensors have been reported, sensors with wide substrate scope remain to be developed. Herein, we report that the amide naphthotube‐based chirality sensors have an unprecedented wide scope for chiroptical sensing of organic molecules. The substrates include, but are not limited to common organic products in asymmetric catalysis, chiral molecules with inert groups or remote functional groups from their chiral centers, natural products and their derivatives, and chiral drugs. The effective chirality sensing is based on biomimetic recognition in water and on effective chirality transfer through guest‐induced formation of a chiral conformation of the sensors. Furthermore, the sensors can be used in real‐time monitoring on reaction kinetics in water and in determining absolute configurations and ee values of the products in asymmetric catalysis.
Molecular Cages Self‐Assembled by Imine Condensation in Water
By taking advantage of multivalence and ligand preorganization, a series of basket‐shaped cages are self‐assembled by imine condensation in water. These cages are rather stable and inert against hydrolysis, and therefore they are able to take advantage of the hydrophobic effect for guest recognition.
Abstract
Self‐assembly by imine condensation in aqueous media is a formidable task because of the labile nature of imines in the presence of water. Here, by taking advantage of multivalence and ligand preorganization, basket‐shaped triscationic cage molecules are self‐assembled in high yields in both water and organic solvent, by condensing a hexaformyl and bisamine. These cages, especially the chiral ones, are stable or inert in aqueous solution, that is, no decomposition was observed upon dilution, precipitation, or exposure to competitive amines or aldehydes. Such water‐compatibility allows the hosts to take advantage of the hydrophobic effect to accommodate hydrophobic guests. The chiral cage S‐2 3+ selectively binds and distinguishes one of two enantiomers, opening up opportunities for applications such as chiral compound separation. Chiral narcissistic self‐sorting and sergeants‐and‐soldiers effects occur during cage formation when two amino precursors are involved in self‐assembly.
Competition between chiral solvents and chiral monomers in the helical bias of supramolecular polymers
Nature Chemistry, Published online: 30 November 2020; doi:10.1038/s41557-020-00583-0
Mirror-symmetry breaking in chiral systems by a chiral solvent has remained poorly understood for decades. Now, the supramolecular polymerization of triphenylene derivatives has shown that—through the additive effects of polymerization—the cumulative entropic effects of the interactions between chiral solvents and solutes create measurable differences in free enthalpy.Why your scientific presentation should not be adapted from a journal article
Nature, Published online: 20 November 2020; doi:10.1038/d41586-020-03300-6
In trying to be rigorous, scientists frequently pack presentations with content from journal articles. The result can be incomprehensible and a lost opportunity.[ASAP] Rotaxanating Metallo-supramolecular Nano-cylinder Helicates to Switch DNA Junction Binding
Postdoc survey reveals disenchantment with working life
Nature, Published online: 18 November 2020; doi:10.1038/d41586-020-03191-7
The second article in a series on Nature’s inaugural survey of postdocs in academia worldwide uncovers a sense of instability among the research precariat.[ASAP] The Chemistry and Applications of Heteroisoindigo Units as Enabling Links for Semiconducting Materials
Tetra‐benzothiadiazole‐based [12]Cycloparaphenylene with Bright Emission and Its Supramolecular Assembly
A benzothiadiazole‐based [12]cycloparaphenylene (TB[12]CPP) is obtained and characterized. TB[12]CPP exhibits a lime to orange emission with a quantum yield up to 98 %, ranking it as one of the brightest CPPs. As a supramolecular host, TB[12]CPP is bright as well, showing adaptable ring structure. A ternary assembly between TB[12]CPP, fullerene, and buckybowl is realized.
Abstract
The radial conjugated π‐system of cycloparaphenylenes (CPPs) makes them intriguing fluorophores and unique supramolecular hosts. However, the bright photoluminescence (PL) of CPPs was limited to the blue light and the supramolecular assembly behavior of large CPPs was rarely investigated. Here we present the synthesis of tetra‐benzothiadiazole‐based [12]cycloparaphenylene (TB[12]CPP), which exhibits a lime to orange PL with an excellent quantum yield up to 82 % in solution. The PL quantum yield of TB[12]CPP can be further improved to 98 % in polymer matrix. Benefiting from its enlarged size, TB[12]CPP can accommodate a fullerene derivative or concave–convex complexes of fullerene and buckybowl through the combined π–π and C−H⋅⋅⋅π interactions. The latter demonstrates the first case of a ternary supramolecule of CPPs.
[ASAP] Shape-Selective Synthesis of Pentacene Macrocycles and the Effect of Geometry on Singlet Fission
[ASAP] Unexpected Influence of Substituents on the Binding Affinities of Polycyclic Aromatic Hydrocarbons with a Tetra-Au(I) Metallorectangle
Spin‐Crossover Properties of an Iron(II) Coordination Nanohoop
Addition of a bipyridyl embedded cycloparaphenylene (CPP) nanohoop to [Fe{H2B(pyz)2}] (pyz=pyrazolyl) produces the distorted octahedral complex [Fe(bipy[9]CPP){H2B(pyz)2}2]. Its spin‐crossover (SCO) properties are strongly influenced by a distortion associated with the nanohoop, implying that variations in nanohoop size may provide a way of tuning the SCO properties of iron compounds.
Abstract
Addition of the bipyridyl‐embedded cycloparaphenylene nanohoop bipy[9]CPP to [Fe{H2B(pyz)2}] (pyz=pyrazolyl) produces the distorted octahedral complex [Fe(bipy[9]CPP){H2B(pyz)2}2] (1). The molecular structure of 1 shows that the nanohoop ligand contains a non‐planar bipy unit. Magnetic susceptibility measurements indicate spin‐crossover (SCO) behaviour with a T 1/2 of 130 K, lower than that of 160 K observed with the related compound [Fe(bipy){H2B(pyz)2}2] (2), which contains a conventional bipy ligand. A computational study of 1 and 2 reveals that the curvature of the nanohoop leads to the different SCO properties, suggesting that the SCO behaviour of iron(II) can be tuned by varying the size and diameter of the nanohoop.
Fluorescent Self‐Threaded Peptide Probes for Biological Imaging
A fluorophore buried inside a self‐threaded peptide probe will promote high water solubility, lower the propensity for probe self‐aggregation, and greatly enhance probe stability. The peptide loops determine the affinity and selectivity for targets within complex biological samples such as cell culture, tissue histology slices, or living subjects.
Abstract
A general synthetic method creates a new class of covalently connected, self‐threaded, fluorescent molecular probes with figure‐eight topology, an encapsulated deep‐red fluorophore, and two peripheral peptide loops. The globular molecular shape and rigidified peptide loops enhance imaging performance by promoting water solubility, eliminating probe self‐aggregation, and increasing probe stability. Moreover, the peptide loops determine the affinity and selectivity for targets within complex biological samples such as cell culture, tissue histology slices, or living subjects. For example, a probe with cell‐penetrating peptide loops targets the surface of cell plasma membranes, whereas, a probe with bone‐targeting peptide loops selectively stains the skeleton within a living mouse. The unique combination of bright deep‐red fluorescence, high stability, and predictable peptide‐based targeting is ideal for photon intense fluorescence microscopy and biological imaging.
A BN‐Doped Cycloparaphenylene Debuts
The introduction of a 1,2‐azaborine ring into a CPP scaffold enables new chemical reactivity associated with the BN heterocycle that cannot be accomplished with carbonaceous CPP compounds.
Abstract
The first example of a BN‐doped cycloparaphenylene BN‐[10]CPP was synthesized and characterized. Its reactivity and photophysical properties were evaluated in direct comparison to its carbonaceous analogues Mes‐[10]CPP and [10]CPP. While the photophysical properties of BN‐[10]CPP remains similar to its carbonaceous analogues, the electronic structure changes associated with the introduction of a 1,2‐azaborine BN heterocycle into a CPP scaffold enables facile and selective late‐stage functionalizations that cannot be accomplished with carbonaceous CPPs. Specifically, Ir‐catalyzed hydrogenation of BN‐[10]CPP selectively reduces the BN heterocyclic ring, which upon hydrolysis produces a rare example of a macrocyclic paraphenylene 6 incorporating the versatile ketone functionality within the macrocyclic ring.
Synthesis and Properties of a Cyclohexa‐2,7‐anthrylene Ethynylene Derivative
The synthesis of a cyclohexa‐2,7‐anthrylene ethynylene derivative was achieved for the first time. This macrocycle possesses a planar conformation and an inner cavity that includes [9]cycloparaphenylene through an aromatic edge‐to‐face CH‐π interaction.
Abstract
The synthesis of a cyclohexa‐2,7‐(4,5‐diaryl)anthrylene ethynylene (1) was achieved for the first time by using 1,8‐diaryl‐3,6‐diborylanthracene and 1,8‐diaryl‐3,6‐diiodoanthracene as key synthetic intermediates. Macrocycle 1 possesses a planar conformation of approximately D 6h symmetry, because of the triple‐bond linker between the anthracene units at the 2,7‐positions. It was confirmed that macrocycle 1, bearing bulky substituents at the outer peripheral positions, behaves as a monomeric form in solution without π‐stacking self‐association. Macrocycle 1 has an inner‐cavity size that allows specific inclusion of [9]cycloparaphenylene ([9]CPP), but not [8]CPP or [10]CPP, through an aromatic edge‐to‐face CH‐π interaction.
[ASAP] A Synthetic Approach to Dimetalated Arenes Using Flow Microreactors and the Switchable Application to Chemoselective Cross-Coupling Reactions
Conjugated Nanohoops Incorporating Donor‐, Acceptor‐, Hetero‐ or Polycyclic Aromatics
In the last 12 years several synthetic strategies have been developed that provide access to [ n ]cycloparaphenylenes ([ n ]CPPs) and related conjugated nanohoops. A number of potential applications have emerged, including optoelectronic devices and their use as templates for carbon nanomaterials and in supramolecular chemistry. To tune the structural or optoelectronic properties of carbon nanohoops beyond the size‐dependent effect known for [ n ]CPPs , a variety of aromatic rings other than benzene have been introduced. In this review, we provide an overview over the syntheses, properties and applications of conjugated nanohoops beyond [ n ]CPPs with intrinsic donor/acceptor structure or such that contain acceptor‐, donor‐, heteroaromatic or polycyclic aromatic units within the hoop as well as conjugated nanobelts.
Redox-controlled chalcogen and pnictogen bonding: the case of a sulfonium/stibonium dication as a preanionophore for chloride anion transport
DOI: 10.1039/D0SC04417B, Edge Article
We describe a sulfonium/stibonium dication that behaves as a preanionophore activatable by glutathione (GSH). Indeed, this dication is reduced by GSH to yield a thioether/stibonium monocation that readily transports Cl− across phospholipid membranes.
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Solvent-controlled E/Z isomerization vs. [2 + 2] photocycloaddition mediated by supramolecular polymerization
DOI: 10.1039/D0SC03442H, Edge Article
Controlled supramolecular polymerization is used to switch the photoresponsive behaviour of cyanostilbenes from a reversible E/Z photoisomerization in organic solvents to a highly efficient and selective [2 + 2] photocycloaddition in aqueous media.
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A New Mechanically‐Interlocked [Pd2L4] Cage Motif by Dimerization of two Peptide‐based Lemniscates
Most metallo‐supramolecular assemblies of low nuclearity adopt simple topologies, with bridging ligands spanning neighboring metal centers in a direct fashion. Here we contribute a new structural motif to the family of host compounds with low metal count (two) that consists of a pair of doubly‐interlocked, figure‐eight‐shaped subunits, also termed “lemniscates”. Each metal is chelated by two chiral bidentate ligands, composed of a peptidic macrocycle that resembles a natural product with two pyridyl‐terminated arms. DFT calculation results suggest that dimerization of the mononuclear halves is driven by a combination of 1) Coulomb interaction with a central anion, 2) π‐stacking between intertwined ligand arms and 3) dispersive interactions between the structure’s compact inner core bedded into an outer shell composed of the cavitand‐type macrocycles. The resulting cage‐like architecture was characterized by NMR, MS and X‐ray structure analyses. This new mechanically bonded system highlights the scope of structural variety accessible in metal‐mediated self‐assemblies composed of only a few constituents.
[ASAP] Linking Molecular Behavior to Macroscopic Properties in Ideal Dynamic Covalent Networks
Heparin reversal by an oligoethylene glycol functionalized guanidinocalixarene
DOI: 10.1039/D0SC03922E, Edge Article
An oligoethylene glycol functionalized guanidinocalix[4]arene was developed as a safe antidote against heparin, via specific recognition and neutralization of heparin in vitro and in vivo.
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