Sebastian Beil

Rewired: A versatile rewiring mechanism leading to the emergence of constitutional dynamic networks is introduced (see picture). DNAzymes associated with the network constituents provide reporters to quantify the adaptive properties of the networks and guide emerging catalytic functions of the networks. The relevance of the study to the evolution of life is discussed.

Abstract

The evolution of networks is a fundamental unresolved issue in developing the area of systems chemistry. We introduce a versatile rewiring mechanism that leads to the emergence of nucleic‐acid‐based constitutional dynamic networks (CDNs). A two‐component constituent AA′ functionalized with a Mg²⁺‐ion‐dependent DNAzyme activator unit forms a complex with an intact hairpin H_BB′ composed of B and B′ sequences. Cleavage of H_BB′ leads to the two‐component constituent BB′, and its rewiring with AA′ yields CDN X composed of the equilibrated constituents AA′, AB′, BA′, and BB′. In analogy, subjecting AA′ to an intact hairpin H_CC′ leads to the formation of CDN Y consisting of AA′, AC′, CA′, and CC′. Subjecting AA′ to the mixture of H_BB′ and H_CC′ evolves the [3×3] CDN Z, composed of nine constituents, thus demonstrating hierarchical adaptive properties. Furthermore, the DNAzyme units associated with the constituents are applied to tailor emerging catalytic functions from the different CDNs.

Photoexcited electron-hole pairs on a semiconductor surface can engage in redox reactions with two different substrates. Similar to conventional electrosynthesis, the primary redox intermediates afford only separate oxidized and reduced products or, more rarely, combine to one addition product. Here, we report that a stable organic semiconductor material, mesoporous graphitic carbon nitride (mpg-CN), can act as a visible-light photoredox catalyst to orchestrate oxidative and reductive interfacial electron transfers to two different substrates in a two- or three-component system for direct twofold carbon–hydrogen functionalization of arenes and heteroarenes. The mpg-CN catalyst tolerates reactive radicals and strong nucleophiles, is straightforwardly recoverable by simple centrifugation of reaction mixtures, and is reusable for at least four catalytic transformations with conserved activity.

Nature Communications, Published online: 25 July 2019; doi:10.1038/s41467-019-11285-8

Nature, Published online: 23 July 2019; doi:10.1038/d41586-019-02277-1

Nature Chemistry, Published online: 22 July 2019; doi:10.1038/s41557-019-0301-2

Bowl inversion: A series of exo‐type buckybowl‐supramolecules are obtained using a concave nanographene acceptor. The reversible bowl inversion in the solid state is realized in the complex with the weakest binding strength by heating and cooling cycles and is unambiguously observed by single‐crystal X‐ray diffraction.

Abstract

Bowl inversion is a unique property of buckybowls. The polarity and assembly configuration of buckybowls are reversed after bowl inversion. So far, this unique phenomenon has been studied in solution and on surface, but not in solid state due to spatial constraint. Now a series of exo‐type supramolecular assemblies of trithiasumanene and nanographene are investigated. Tuning the electron density of the nanogaphene component was found to directly affect the binding constant of the complex. Reversible bowl inversion in the solid state was then successfully achieved by subjecting the trithiasumanene–nanographene assembly with the weakest binding strength to repeated heating–cooling cycles, which was unambiguously observed by single crystal X‐ray diffraction.

Nature Communications, Published online: 18 July 2019; doi:10.1038/s41467-019-11141-9

A lightbulb moment for W^VI complexes: Incorporation of arylamino substituents into the ligand scaffold leads to the realization of the first W^VI Schiff base complex with TADF properties, which shows Φ _em of 56 % in solution and 84 % in thin film at room temperature. High‐efficiency solution‐processed W‐OLEDs were fabricated, exhibiting a maximum EQE and luminance of up to 15.6 % and 16890 cd m⁻², respectively.

Abstract

Metal‐TADF (thermally activated delayed fluorescence) emitters hold promise in the development of next generation light‐emitting materials for display and lighting applications, examples of which are, however, largely confined to Cu^I and recently Au^I, Ag^I, and Au^III emitters. Herein is described the design strategy for an unprecedented type of metal‐TADF emitter based on inexpensive tungsten metal chelated with Schiff base ligand that exhibit high emission quantum yields of up to 56 % in solutions and 84 % in thin‐film (5 wt % in 1,3‐bis(N‐carbazolyl)benzene, mCP) at room temperature. Femtosecond time‐resolved emission (fs‐TRE) spectroscopy and DFT calculations were undertaken to decipher the TADF properties. Solution‐processed OLEDs fabricated with the W‐TADF emitter demonstrated external quantum efficiency (EQE) and luminance of up to 15.6 % and 16890 cd m⁻², respectively.

The generation of topologically complex nanocarbons can spur developments in science and technology. However, conventional synthetic routes to interlocked molecules require heteroatoms. We report the synthesis of catenanes and a molecular trefoil knot consisting solely of para-connected benzene rings. Characteristic fluorescence of a heterocatenane associated with fast energy transfer between two rings was observed, and the topological chirality of the all-benzene knot was confirmed by enantiomer separation and circular dichroism spectroscopy. The seemingly rigid all-benzene knot has rapid vortex-like motion in solution even at –95°C, resulting in averaged nuclear magnetic resonance signals for all hydrogen atoms. This interesting dynamic behavior of the knot was theoretically predicted and could stimulate deeper understanding and applications of these previously untapped classes of topological molecular nanocarbons.

Anion H‐bonding and ion‐pairing are combined with anion–π recognition to produce triazole quartets with T₄ columnar channel architectures, as shown by M. Barboiu and co‐workers in their Communication on https://doi.org/10.1002/anie.201904808page 12037 ff.

Two types: Experimental proof is given for the ability of volatile anesthetic halothane to form halogen bonds and hydrogen bonds with nonbonding‐electron‐pair‐containing atoms and anions in the solid state and in solution. This provides new insight into the understanding of halothane–membrane interactions as well as other features of the agent, such as its eudismic ratio.

Abstract

Although instrumental for optimizing their pharmacological activity, a molecular understanding of the preferential interactions given by volatile anesthetics is quite poor. This paper confirms the ability of halothane to work as a hydrogen‐bond (HB) donor and gives the first experimental proof that halothane also works as a halogen‐bond (HaB) donor in the solid state and in solution. A halothane/hexamethylphosphortriamide co‐crystal is described and its single‐crystal X‐ray structure shows short HaBs between bromine, or chlorine, and the phosphoryl oxygen. New UV/Vis absorption bands appear upon addition of diazabicyclooctane and tetra(n‐butyl)ammonium iodide to halothane solutions, indicating that nitrogen atoms and anions may mediate the HaB‐driven binding processes involving halothane as well. The ability of halothane to work as a bidentate/tridentate tecton by acting as a HaB and HB donor gives an atomic rationale for the eudismic ratio shown by this agent.

A tale of two esters: Abundant carboxylic acids can be converted into dialkyl and aryl alkyl ketones through a decarboxylative, non‐symmetric coupling. The keys to this approach are the use of a nickel catalyst with an electron‐poor bipyridine or terpyridine ligand, a THF/DMA mixed solvent system, and ZnCl₂ to enhance the reactivity of the NHP ester.

Abstract

Synthesis of the C−C bonds of ketones relies upon one high‐availability reagent (carboxylic acids) and one low‐availability reagent (organometallic reagents or alkyl iodides). We demonstrate here a ketone synthesis that couples two different carboxylic acid esters, N‐hydroxyphthalimide esters and S‐2‐pyridyl thioesters, to form aryl alkyl and dialkyl ketones in high yields. The keys to this approach are the use of a nickel catalyst with an electron‐poor bipyridine or terpyridine ligand, a THF/DMA mixed solvent system, and ZnCl₂ to enhance the reactivity of the NHP ester. The resulting reaction can be used to form ketones that have previously been difficult to access, such as hindered tertiary/tertiary ketones with strained rings and ketones with α‐heteroatoms. The conditions can be employed in the coupling of complex fragments, including a 20‐mer peptide fragment analog of Exendin(9–39) on solid support.

Pair at work: Optically driven charge transfer in nondissociated donor–acceptor ion pairs induces a counterion migration, reminiscent of a molecular machine. This motion leads to relocation of the cation and anion, and results in unusual dual fluorescence through the previously unrecognized properties of ionic D‐π‐A systems in nonpolar media.

Abstract

The D‐π‐A type phosphonium salts in which electron acceptor (A=‐⁺PR₃) and donor (D=‐NPh₂) groups are linked by polarizable π‐conjugated spacers show intense fluorescence that is classically ascribed to excited‐state intramolecular charge transfer (ICT). Unexpectedly, salts with π=‐(C₆H₄) _n ‐ and ‐(C₁₀H₆C₆H₄)‐ exhibit an unusual dual emission (F₁ and F₂ bands) in weakly polar or nonpolar solvents. Time‐resolved fluorescence studies show a successive temporal evolution from the F₁ to F₂ emission, which can be rationalized by an ICT‐driven counterion migration. Upon optically induced ICT, the counterions move from ‐⁺PR₃ to ‐NPh₂ and back in the ground state, thus achieving an ion‐transfer cycle. Increasing the solvent polarity makes the solvent stabilization dominant, and virtually stops the ion migration. Providing that either D or A has ionic character (by static ion‐pair stabilization), the ICT‐induced counterion migration should not be uncommon in weakly polar to nonpolar media, thereby providing a facile avenue for mimicking a photoinduced molecular machine‐like motion.

The covalent appendage of electron deficient perfluoroaryl substituents to a bis‐iodotriazole pyridinium group produces a powerful halogen bond donor for anion recognition. Using this motif, halogen bonding anion templation is demonstrated as a highly efficient method for constructing a rotaxane in near quantitative yield, capable of strong halide binding in 50 % water‐containing aqueous media.

Abstract

The covalent attachment of electron deficient perfluoroaryl substituents to a bis‐iodotriazole pyridinium group produces a remarkably potent halogen bonding donor motif for anion recognition in aqueous media. Such a motif also establishes halogen bonding anion templation as a highly efficient method for constructing a mechanically interlocked molecule in unprecedented near quantitative yield. The resulting bis‐perfluoroaryl substituted iodotriazole pyridinium axle containing halogen bonding [2]rotaxane host exhibits exceptionally strong halide binding affinities in competitive 50 % water containing aqueous media, by a factor of at least three orders of magnitude greater in comparison to a hydrogen bonding rotaxane host analogue. These observations further champion and advance halogen bonding as a powerful tool for recognizing anions in aqueous media.

A polyrotaxane‐linked poly(acrylic acid) (PRPAA) binder is incorporated to a carbon nanotube (CNT) network that serves as a lithium‐uptake scaffold in lithium‐metal batteries. The ring‐sliding motion of polyrotaxane endows PRPAA with extraordinary elasticity, which enables the CNT network to endure stress during repeated lithium uptake–release cycles. By utilizing this elastic binder, the CNT network exhibits enhanced cycling stability.

Abstract

Despite their unparalleled theoretical capacity, lithium‐metal anodes suffer from well‐known indiscriminate dendrite growth and parasitic surface reactions. Conductive scaffolds with lithium uptake capacity are recently highlighted as promising lithium hosts, and carbon nanotubes (CNTs) are an ideal candidate for this purpose because of their capability of percolating a conductive network. However, CNT networks are prone to rupture easily due to a large tensile stress generated during lithium uptake–release cycles. Herein, CNT networks integrated with a polyrotaxane‐incorporated poly(acrylic acid) (PRPAA) binder via supramolecular interactions are reported, in which the ring‐sliding motion of the polyrotaxanes endows extraordinary stretchability and elasticity to the entire binder network. In comparison to a control sample with inelastic binder (i.e., poly(vinyl alcohol)), the CNT network with PRPAA binder can endure a large stress during repeated lithium uptake–release cycles, thereby enhancing the mechanical integrity of the corresponding electrode over battery cycling. As a result, the PRPAA‐incorporated CNT network exhibits substantially improved cyclability in lithium–copper asymmetric cells and full cells paired with olivine‐LiFePO₄, indicating that high elasticity enabled by mechanically interlocked molecules such as polyrotaxanes can be a useful concept in advancing lithium‐metal batteries.

Buckyball in cage catalyst: A redox‐switchable self‐assembled Zn^II ₄L₆ cage was synthesized that contains naphthalenediimide (NDI) motifs. The redox activity of this cage allows it to act as a catalyst for the oxidative coupling of different tetraaryl borates to give biaryls. The catalytic activity of the cage was enhanced following its binding of C₆₀, which implies a mechanism that does not involve encapsulation of the substrate.

Abstract

A redox‐switchable self‐assembled Zn^II ₄L₆ cage was synthesized that contains naphthalenediimide (NDI) motifs. Its reduction lent these NDI panels persistent radical anion character. The redox activity of this cage allows it to act as a catalyst for the oxidative coupling of different tetraaryl borates to give biaryls. The catalytic activity of the cage was enhanced following its binding of C₆₀, which implies a mechanism that does not involve encapsulation of the substrate.

Sophisticated porphyrin nanocages, which can be utilized as a functional platform to develop single molecular nanoparticles, were synthesized. The unique topological structure of the nanocages results in their excellent performance as cancer nanotheranostics, as demonstrated through applications in PET imaging and photodynamic therapy.

Abstract

Single molecular nanoparticles (SMNPs) integrating imaging and therapeutic capabilities exhibit unparalleled advantages in cancer theranostics, ranging from excellent biocompatibility, high stability, prolonged blood lifetime to abundant tumor accumulation. Herein, we synthesize a sophisticated porphyrin nanocage that is further functionalized with twelve polyethylene glycol arms to prepare SMNPs (porSMNPs). The porphyrin nanocage embedded in porSMNPs can be utilized as a theranostic platform. PET imaging allows dynamic observation of the bio‐distribution of porSMNPs, confirming their excellent circulation time and preferential accumulation at the tumor site, which is attributed to the enhanced permeability and retention effect. Moreover, the cage structure significantly promotes the photosensitizing effect of porSMNs by inhibiting the π–π stacking interactions of the photosensitizers, ablating of the tumors without relapse by taking advantage of photodynamic therapy.