Chiral recognition among helical molecules is of essential importance in many chemical and biochemical processes. The complexity necessitates investigating manageable model systems for unveiling the ...fundamental principles of chiral recognition at the molecular level. Here, we reported chiral recognition in the self-assembly of enantiopure and racemic hexahelicene on a Au(111) surface. Combing scanning tunneling microscopy (STM) and atomic force microscopy (AFM) measurements, the asymmetric heterochiral trimers were observed as a new type of building block in racemic helicene self-assembly on Au(111). The intermolecular recognition of the heterochiral trimer was investigated upon manual separation so that the absolute configuration of each helicene molecule was unambiguously determined one by one, thus confirming that the trimer was "2+1" in handedness. These heterochiral trimers showed strong stability upon different coverages, which was also supported by theoretical calculations. Our results provide valuable insights for understanding the intermolecular recognition of helical molecules.
The rapid development of continuous flow processes is driving innovations in various chemical syntheses and industrial productions. Immobilizing catalysts in flow reactors allows transformations with ...high‐efficiency and excludes the subsequent separation procedures. This concept outlines the approaches to incorporate catalysts within flow reactors, with particular focus on the application of additional supports including inorganic materials like silica, zeolite and reduced graphene oxide, polymeric materials like polymer packings, monoliths, cross‐linked gels and polymer brushes, and other materials for specific conditions like transparent glass fibers and glass beads. Furthermore, advanced methods to develop ordered micro‐/nanoarrays from internal walls of flow channels for immobilization of catalysts as well as application of innovative vortex fluidic devices are discussed to inspire new designs of supports for novel fluidic reactors with broad applications.
Supports for immobilization of catalysts in flow reactors are outlined, with emphases on sustainable binding with channel walls and catalysts, boosted catalysts loading and ability to maintain fine flow properties. Particularly, the synergy of supports and catalysts are discerned, as well as the specific designs. In addition, fabrication of array‐like catalytic supports and application of advanced fluidic devices are included.
Antipodal twisted helical ribbons with lamellar bilayer structure were obtained by self‐assembly of chiral amphiphilic molecules in water and water/ethanol. The handedness inversion of the molecular ...arrangement in these antipodal helical ribbons was investigated by using chiroptical spectroscopy and molecular probes in their antipodal mesoporous silica assemblies synthesized through pairing interaction between the head group of the chiral amphiphilic molecules and a co‐structure‐directing agent. The supramolecular chirality is imprinted in the pore surface through the organic group of the co‐structure‐directing agent. The mirror‐image diffuse‐reflectance circular dichroism spectra of the conjugated discotic probing molecule introduced into their supramolecular chiral imprinted mesoporous silica demonstrated the origin of inverse chirality from the antipodal helical stacking of the molecules.
Twisted helical ribbons with lamellar bilayer structures were obtained by self‐assembly of chiral amphiphilic molecules in water (left‐handed) and water/ethanol (right‐handed). The handedness inversion of these chiral amphiphilic molecular assemblies was investigated by supramolecular chiral imprinting in mesoporous silica replicas (see figure).
We report a facile and tailored method to prepare globally twisted chiral molecular cages through tunable coordination of bis-bipyridine-terminated helicene ligands to a series of transition metals ...including Fe(II), Co(II), Ni(II) and Zn(II). This system shows an efficient remote transfer of stereogenecity from the helicene core to the bipyridine-metal coordination sites and subsequently the entire cages. While the Fe(II), Co(II) and Ni(II)-derived M2L3 (M for metal and L for ligand) cages exhibit quasi-reversible redox features, the Zn(II) analogues reveal prominent yellow circularly polarized luminescence. Interestingly, with the addition of Na2SO4, the Zn2L3 cages reassemble into sextuple-stranded Zn6L6(SO4)4 cages in which three Zn2L2 units are bound together by four sulfates and further coalesced by offset inter-ligand π-π interactions.
Coordination of bis-dipyridine-terminated helicene ligands with a variety of transition metals leads to the formation of various triple-stranded binuclear chiral cages and the addition of sulfate further promotes the transformation to sextuple-stranded hexanuclear chiral cages. Display omitted
A large number of current chemotherapeutic agents prevent the growth of tumors by inhibiting DNA synthesis of cancer cells. It has been found recently that many planar polycyclic aromatic ...hydrocarbons (PAHs) derivatives, previously known as carcinogenic, display anticancer activity through DNA cross‐linking. However, the practical use of these PAHs is substantially limited by their low therapeutic efficiency and selectivity toward most tumors. Herein, the anticancer property of a nonplanar PAH named 4helicenium, which exhibits highly selective cytotoxicity toward liver, lung cancer, and leukemia cells compared with normal cells, is reported. Moreover, 4helicenium effectively inhibits tumor growth in liver cancer‐bearing mice and shows little side effects in normal mice. RNA sequencing and confirmatory results demonstrate that 4helicenium induces more DNA damage in tumor cells than in normal cells, resulting in tumor cell cycle arrest and apoptosis increment. This study reveals an unexpected role and molecular mechanism for PAHs in selectively killing tumor cells and provides an effective strategy for precision cancer therapies.
Nonplanar polycyclic aromatic hydrocarbons (PAH) 4helicenium selectively kills cancer cells and efficiently inhibits tumor growth, and has no obvious side effect on normal cells. This study provides a distinctive pathway for the use of nonplanar PAHs for the treatment of tumors.
Although the solution self-assembly of block copolymers has enabled the fabrication of a broad range of complex, functional nanostructures, their precise manipulation and patterning remain a key ...challenge. Here we demonstrate that spherical and linear supermicelles, supramolecular structures held together by non-covalent solvophobic and coordination interactions and formed by the hierarchical self-assembly of block copolymer micelle and block comicelle precursors, can be manipulated, transformed and patterned with mediation by dynamic holographic assembly (optical tweezers). This allows the creation of new and stable soft-matter superstructures far from equilibrium. For example, individual spherical supermicelles can be optically held in close proximity and photocrosslinked through controlled coronal chemistry to generate linear oligomeric arrays. The use of optical tweezers also enables the directed deposition and immobilization of supermicelles on surfaces, allowing the precise creation of arrays of soft-matter nano-objects with potentially diverse functionality and a range of applications.
Frontispiece: Continuous flow systems are of growing interests in diverse fields attributing to their prominent ability to uniform the system and facilitate the operation process. Immobilizing ...catalysts in flow reactors allows high‐efficiency transformations and excludes the subsequent separation procedures. In this Concept article, G. Lin and H. Qiu outline the approaches to incorporate catalysts within various flow reactors, with particular focus on the employment of additional supports with a diverse array of constitutions and structures. Notably, the synergy between the supports and catalysts are discerned, as well as the specific designs. For more information, see the Review by Lin and Qiu (DOI: 10.1002/chem.202200069)
The synthesis mechanism of anionic surfactant-templated mesoporous silica (AMS) is described. A family of highly ordered mesoporous silica structures have been synthesized via an approach based on ...the self-assembly of anionic surfactants and inorganic precursors by using aminopropylsiloxane or quaternized aminopropylsiloxane as the co-structure-directing agent (CSDA), which is a different route from previous pathways. Mesophases with differing surface curvatures, varying from cage type (tetragonal P42/mnm; cubic Pm3̄n with modulations; cubic Fd3̄m) to cylindrical (two-dimensional hexagonal p6mm), bicontinuous (cubic Ia3̄d and Pn3̄m), and lamellar have been obtained by controlling the charge density of the micelle surfaces by varying the degree of ionization of the carboxylate surfactants. Changing the degree of ionization of the surfactant results in changes of the surfactant packing parameter g, which leads to different mesostructures. Furthermore, variation of the charge density of positively charged amino groups of the CSDA also gives rise to different values of g. Mesoporous silicas, functionalized with amino and quaternary ammonium groups and with the various structures given above, have been obtained by extraction of the surfactant. This report leads to a deeper understanding of the interactions between the surfactant anions and the CSDA and provides a feasible and facile approach to the mesophase design of AMS materials.
A series of achiral cationic and anionic amphiphiles employed as templates for mesoporous silica, all showed an excellent ability to form highly ordered helical mesoporous silica (HMS) crystals. It ...was supposed that the helical mesostructure may originate from the helical propeller-like micelle formed by the achiral amphiphilic molecules due to their instantaneous asymmetric shape survived in the micelle. The existence of the mirror-imaged conformations of equal proportion may result in the racemic nature of the achiral amphiphile-templated HMSs. The helicity of the HMS greatly depends on the templating molecules which may be modulated by the twisting power of the helical propeller-like packing of the amphiphiles in the micelle. The dependence of the pitch length on different factors was explained by mechanical analysis indicating that the pitch length should be in direct proportion to the rod diameter but inversely proportional to the moment of micelle (M 0). Additionally, chiral amphiphiles with opposite charge were used as chiral dopants to control the enantiopurity of the achiral amphiphile-templated HMSs. The absolute enantiomeric excess (ee) of the HMSs increased with increasing amounts of dopant.
PDF
