Amplified Circularly Polarized Luminescence Behavior in Chiral Co-assembled Liquid Crystal Polymer Films via the Strategic Manipulation of Chiral Inducers.

One of the most important factors for the future application of circularly polarized luminescence (CPL) materials is their high dissymmetry factors (gem), and more and more studies are working tirelessly to focus on increasing the gem value. Herein, we chose an achiral liquid crystal polymer (LC-P) and two chiral binaphthyl-based inducers (R/S-3 and R/S-6) with different substitution positions (3,3' positions for R/S-3 and 6,6' positions for R/S-6) to construct chiral co-assemblies and explored their induced amplification CPL behaviors. Interestingly, after the thermal annealing treatment, this kind of chiral co-assembly (R/S-3)0.05-(LC-P)0.95 can emit a superior CPL signal (|gem| = 0.31 and λem = 424 nm), which achieves about 13-fold signal amplification in the spin-coated film, compared to (R/S-6)0.1-(LC-P)0.9 (|gem| = 0.023 and λem = 424 nm). This is because (R/S-3)0.05-(LC-P)0.95 could further co-assemble to form a more ordered arrangement LC state and generate regular helix nanofibers than that of (R/S-6)0.1-(LC-P)0.9. This work provides an efficient method for synthesizing high-quality CPL-active materials through the strategic manipulation of the structure of chiral binaphthyl-based inducers in chiral co-assembled LCP systems.

Tunable circularly polarized luminescence behaviors caused by the structural symmetry of achiral pyrene-based emitters in chiral co-assembled systems.

The regulation of circularly polarized luminescence (CPL) behavior is of great significance for practical applications. Herein, we deliberately designed three achiral pyrene derivatives (Py-1, Py-2, and Py-3) with different butoxy-phenyl substituents and the chiral binaphthyl-based inducer (R/S-B) with anchored dihedral angle to construct chiral co-assemblies, and explored their induced CPL behaviors. Interestingly, the resulting co-assemblies demonstrate tunable CPL emission behaviors caused by the structural symmetry effect of achiral pyrene-based emitters during the chiral co-assembly process. And in spin-coated films, the dissymmetry factor (gem) values were 9.1 × 10-3 for (R/S-B)1-(Py-1)10, 5.6 × 10-2 for (R/S-B)1-(Py-2)7, and 8.6 × 10-4 for (R/S-B)1-(Py-3)1, respectively. The strongest CPL emission (|gem| = 5.6 × 10-2, λem = 423 nm, QY = 34.8 %) was detected on (R/S-B)1-(Py-2)7 due to the formation of regular and ordered helical nanofibers through the strong π-π stacking interaction between the R/S-B and the achiral Py-2 emitter. The strategy presented here provides a creative approach for progressively regulating CPL emission behaviors in the chiral co-assembly process.

One-Pot Synthesis, Circularly Polarized Luminescence, and Controlled Self-Assembly of Janus-Type Miktoarm Star Copolymers.

With the aim of broadening the scope of Janus-type polymers with new functionalities, Janus-type miktoarm star copolymers comprising helical poly(phenyl isocyanide) (PPI) and a vinyl polymer were designed and synthesized via a combination of Pd(II)-initiated isocyanide polymerization and atom transfer radical polymerization (ATRP). A functional ß-cyclodextrin bearing 7 Pd(II) complexes at one side and 14 bromine groups at the other side ((Pd(II))7-CD-(Br)14) was prepared and used as an initiator for the one-pot polymerization of phenyl isocyanide and the ATRP of vinyl monomers in a living and controlled manner. A variety of Janus-type copolymers with different structures and tunable compositions were facilely obtained by using this method. Thus, Janus-type copolymers composed of helical PPIs and tetraphenylethylene-modified vinyl polymers exhibited a significant circularly polarized luminescence performance in both soluble and aggregated states. Meanwhile, Janus-type copolymers containing PPIs and hydrophilic vinyl polymers presented amphiphilicity and self-assembled into diverse morphologies.

Rh(III)-Catalyzed N-Amino-Directed C-H Coupling with 3-Methyleneoxetan-2-ones for 1,2-Dihydroquinoline-3-carboxylic Acid Synthesis.

Dynamic polarity analysis is proposed herein as a general tool for investigating static polarity and transient polarity and revealing expanded reactivity patterns. Through this analysis formalism, polarity matching has been established for Rh(III)-catalyzed N-amino-directed C-H coupling with 3-methyleneoxetan-2-ones, providing efficient access to 1,2-dihydroquinoline-3-carboxylic acids. The identified reaction, by virtue of the internal oxidative mechanism, showcases mild reaction conditions (room temperature), a short reaction time (2 h), and a generally high product yield.

Rh(III)-catalyzed synthesis of amino-side-chained poly(phenylene vinylene) via C-H bond olefination.

A Rh(III)-catalyzed hydrazine-directed C-H olefination approach was developed for synthesizing amino-side-chained poly(phenylene vinylene) (PPV). The creation of such a divergent portfolio of PPV candidates enabled the discovery of a mega Stokes shift, high fluorescence quantum yield, and solid-state fluorescence, highlighting the great prospects of our synthetic protocol as an innovative tool.

Cobalt-Catalyzed, Directed Intermolecular C-H Bond Functionalization for Multiheteroatom Heterocycle Synthesis: The Case of Benzotriazine.

Transition-metal-catalyzed, directed intermolecular C-H bond functionalization is synthetically useful but heavily underexplored in multiheteroatom heterocycle synthesis. Herein we report a cobalt catalytic method for the formation of a three-nitrogen-bearing benzotriazine scaffold via the coupling of arylhydrazine and oxadiazolone. This synthetic protocol features a low-cost base metal catalyst, a maximum number of heteroatoms built into a heterocycle, a distinct synthetic logic for benzotriazines, a superior step economy, and a broad substrate scope.

Selective Synthesis of Single-Handed Helical Polymers from Achiral Monomer and a Mechanism Study on Helix-Sense-Selective Polymerization.

Inspired by the exquisite helices in Nature, fabrication of helical materials with controlled handedness has attracted considerable attention. Herein, we report on precis synthesis of single left- and right-handed helical polyisocyanides through living polymerization of achiral monomers using chiral palladium catalysts under helix-sense-selective manner. Mechanism study revealed that the yielded helices with opposite handedness showed different activity of the living chain end. The helix with unfavored handedness was self-terminated, while the one with favored handedness showed high activity and could undergo chain propagation to form a high molecular weight polymer with maintained single-handed helicity.

Facile Synthesis of Optically Active and Thermoresponsive Star Block Copolymers Carrying Helical Polyisocyanide Arms and Their Thermo-Triggered Chiral Resolution Ability.

A left-handed helical poly(phenyl isocyanide) bearing a norbornene unit and a Pd(II) complex on each terminus was prepared. The norbornene terminus was core cross-linked with a bisnorbornene linker via ring-opening metathesis polymerization (ROMP), yielding a star polymer carrying left-handed helical arms decorated with Pd(II) units at the exterior. The optical activities of the helical arms were maintained after the cross-linking reaction. The Pd(II) units on the surface of the star polymer were chain extended with a new phenyl isocyanide bearing three hydrophilic triethylene glycol monomethyl chains, which afforded an amphiphilic star block copolymer carrying helical arms. Such a star block copolymer showed excellent thermoresponsiveness with the lower critical solution temperature (LCST) around 55 °C. This optically active and thermoresponsive star polymer can enantioselectively capture the S-enantiomer of racemic methyl benzyl alcohol solution at a temperature lower than the LCST and precipitated when the temperature was higher than the LCST, leaving the R-enantiomer in the solution. The enantiomeric excess (ee) of the isolated enantiomer is up to 75%.