查看更多>>摘要：Circular polarized light is utilized in communication and display technologies and a major challenge is to develop systems that can be switched between left and right circular polarized luminescence with high degrees of polarization and enable multiple addressable stable states. Luminescent dyes in Liquid Crystal (LC) cholesteric phases are attractive systems to generate, amplify and modulate circularly polarized luminescence (CPL). In the present study, we employ light-driven molecular motors as photo-controlled chiral dopants in LCs to switch the handedness of the LC and the circular polarization of luminescence from an achiral dye embedded in the mesogenic material. Tuning of the color of the CPL and the retention time of the photo-programmed helicity is demonstrated making use of a variety of motors and dyes. The flexibility offered by the design based on inherently chiral unidirectional rotary motors provides full control over CPL non-invasively by light, opening possibilities for pixilated displays with externally addressable polarization.
查看更多>>摘要：Chiral quinacridines react up to four times, step-by-step, with a-diazomalonates under Ru~(II) and Rh~(II) catalysis. By selecting the catalyst, [CpRu(CH3CN)3][PF6] (Cp = cyclopentadienyl) or Rh2-(oct)4, chemo and regioselective insertions of derived metal carbenes are achieved in favor of mono-or bis-functionalized malonate derivatives, respectively, (r.r. > 49:1, up to 77% yield, 12 examples). This multi-introduction of malonate groups is particularly useful to tune optical and chemical properties such as absorption, emission or Br0nsted acidity but also cellular bioimag-ing. Density-functional theory further elucidates the origin of the carbene insertion selectivity and also showcases the importance of conformations in the optical response.
查看更多>>摘要：An efficient "one-pot" strategy for the structure-controlled synthesis of hyperbranched polymers (HBPs) based on a "latent" inimer (LI-Br), containing a furan-protected maleimide monomer and a haloalkane initiator, is presented. At high temperatures, the "latent" inimer is converted to a "real" inimer after releasing maleimide (MI) via a retro-Diels-Alder (r-DA) reaction and then copolymerized with methyl methacrylate by self-condensing vinyl copolymeriza-tion. Due to the dynamic characteristic of the r-DA reaction, the release of naked MI and the subsequent copolymerization can be regulated by the temperature or stereochemistry of Diels-AIder (DA) adducts. Thus, the "one-pot" structure-controlled synthesis of HBPs with various degrees of branching was achieved. By further implementation of a programmable temperature change, some valuable hyperbranched topologies such as star-shaped and long-chain hyperbranched polymers can be constructed avoiding sophisticated synthetic routes.
查看更多>>摘要：Postsynthetic modification (PSM) has been widely used in porous crystalline materials to gain better performance in adsorptive separation of gases or hydrocarbons. We here report that guest adsorption selectivity in a kind of nonporous crystalline materials, namely nonporous adaptive crystals (NACs), can be readily and precisely tuned via a facile substituent-size-dependent solid-vapor PSM method. Before PSM, NACs of pillar-[4]arene[l]quinone EtP4Ql show negligible selectivity for C5 hydrocarbons. PSM with a larger substituent, cyclopentylamine, onto EtP4Ql NACs does not improve the selectivity, while EtP4Ql NACs after PSM with a slightly smaller substituent, cyclobutylamine, is endowed with very high preference of n-pentane over cyclopentane. Comprehensive structural analyses confirm that the intermolecular interactions among the host compounds and host-guest interactions between the adsorbent and the adsorbate are the two major factors in determining the guest selectivity.
查看更多>>摘要：Challenges remain in establishing a universal method to precisely tune electrochemical properties of conducting polymers for multifunctional neurosensing with high selectivity and sensitivity. Here, we demonstrate a facile and general approach to achieving synergistic charge percolation in conducting polymers (i.e., poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate), PEDOT:PSS) by incorporating conductive catalysts (i.e., carbon nanotubes, CNTs) and post-processing. The approach shows synergistic effects: (i) CNTs and post-processing together promote PEDOT ordered interconnection for highly efficient charge percolation that accelerates electrochemical kinetics; (ii) CNTs catalyze the electrooxidation of vitamin C for selective electrochemical sensing; (iii) CNTs enhance the charge storage/injection capacity of PEDOT:PSS. The prepared CNT-PEDOT:PSS fiber mechanically matches with neural tissues and is proved to be a biocompatible versatile microsensor capable of high-performance neurosensing in vivo.
查看更多>>摘要：Achieving wide-range tunable emission colors, especially in the solid state of single-fluorophore materials, remains a significant challenge. Herein, we report a molecular design strategy that affords wide-range excitation-dependent emissions spanning over = 230 nm in crystalline states. Under the donor-n-acceptor configuration, we judiciously choose a rotatable acceptor fragment, o-carborane, to enrich conformational diversities in the crystalline state and generate conformation-dependent multicolor emissions. We further show that this molecular platform is generalizable in creating crystalline materials with multicolor emissions. Based on these materials, a high-capacity information storage device and a finite-state machine were fabricated to showcase multicolor displays and information storage.
查看更多>>摘要：The desire to construct complex molecular systems is driven by the need for technological (r)evolution and our intrinsic curiosity to comprehend the origin of life. Supramolecular chemists tackle this challenge by combining covalent and noncovalent reactions leading to multicomponent systems with emerging complexity. However, this synthetic strategy often coincides with difficult preparation protocols and a narrow window of suitable conditions. Here, we report on unsuspected observations of our group that highlight the impact of subtle "irregularities" on supramolecular systems. Based on the effects of pathway complexity, minute amounts of water in organic solvents or small impurities in the supramolecular building block, we discuss potential pitfalls in the study of complex systems. This article is intended to draw attention to often overlooked details and to initiate an open discussion on the importance of reporting experimental details to increase reproducibility in supramolecular chemistry.
查看更多>>摘要：Acinetobacter baumannii is a opportunistic bacterial pathogen responsible for serious nosocomial infections that is becoming increasingly resistant against antibiotics. Capsular polysaccharides (CPS) that cover A. baumannii are a major virulence factor that play an important role in pathogenesis, are used to assign serotypes and provide the basis for vaccine development. Synthetic oligosaccharides resembling the CPS of A. baumannii 17978 were printed onto microarray slides and used to screen sera from patients infected with A. baumannii as well as a monoclonal mouse antibody (mAb C8). A synthetic oligosaccharide emerged from glycan array screening as lead for the development of a vaccine against A. baumannii 17978. Tetrasaccharide 20 is a key epitope for recognition by an antibody and is a vaccine lead.
查看更多>>摘要：Materials which selectively transport molecules offer powerful opportunities for concentrating and separating chemical agents. Here, utilizing static and dynamic chemical gradients, transport of molecules within swollen crosslinked polymers is demonstrated. Using an =200 urn static hydroxyl to hexyl gradient, the neutral ambipolar nerve agent surrogate diethyl (cyanomethyl)phosphonate (DECP) is directionally transported and concentrated 60-fold within 4 hours. To accelerate transport kinetics, a dynamic gradient (a "travelling wave") is utilized. Here, the non-polar dye pyrene was transported. The dynamic gradient is generated by an ion exchange process triggered by the localized introduction of an aqueous NaCl solution, which converts the gel from hydrophobic to hydrophilic. As the hydrophilic region expands, associated water enters the gel, and pyrene is pushed ahead of the expansion front. The dynamic gradient provides about 10-fold faster transport kinetics than the static gradient.
查看更多>>摘要：Oxidation of C—B bonds is extensively used in organic synthesis, materials science, and chemically biology. However, these oxidations are usually limited to the oxidation of C(sp3)-B and C(sp2)-B bonds. The C(sp)—B bond oxidation is rarely developed. Herein we present a novel strategy for the preparation of y-lactones via the oxidation of enynyl boronates. This process successively involves the C(sp)—B bond oxidation, the epoxidation of C—C double bond and the lactonization. This protocol provided various y-lactones and unsaturated butenolides efficiently that are prevalent in numerous nature products and bioactive molecules. Most importantly, asymmetric oxidative lactonization of enynyl boronates was also achieved, providing chiral y-lactones in high enantioselectivities and diastereoselec-tivities. The versatile transformations and ubiquity of y-lactones shed light on the importance of this strategy in the construction and late-stage functionalization of complex molecules.
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