Inverted and Amplified CP-EL Behavior Promoted by AIE-Active Chiral Co-Assembled Helical Nanofibers

It is well-known that high-performance circularly polarized organic light-emitting diodes (CP-OLEDs) remain a formidable challenge to the future application of circularly polarized luminescent (CPL)-active materials. Herein, the design of a pair of AIE-active chiral enantiomers (L/D-HP) is described to construct chiral co-assemblies with an achiral naphthalimide dye (NTi). The resulting co-assemblies emit an inverted CPL signal compared with that from the L/D-HP enantiomers. After thermal annealing at 120 °C, the inverted CPL signal of this kind of L/D-HP-NTi with a 1:1 molar ratio shows regular and ordered helical nanofibers arranged through intermolecularly ordered layered packing and is accompanied with a further amplified effect (|g_em | = 0.032, λ_em  = 535 nm). Significantly, non-doped CP-OLEDs based on a device emitting layer (EML) of L/D-HP-NTi exhibits a low turn-on voltage (V_on ) of 4.7 V, a high maximum brightness (L_max ) of 2001 cd m^-2 , and moderate maximum external quantum efficiency (EQE_max ) of 2.3%, as well as excellent circularly polarized electroluminescence (CP-EL) (|g_EL | = 0.023, λ_em  = 533 nm).

Host-Guest Complexation-Induced Aggregation Based on Pyrene-Modified Cyclodextrins for Improved Electronic Circular Dichroism and Circularly Polarized Luminescence

Several γ-cyclodextrin (CD) derivatives mono- or di-substituted by pyrenes at the primary rim of the CD were demonstrated to aggregate into nano-strips in aqueous solutions, with the pyrene moieties interpenetrating into γ-CD cavities. The hydrophobic complexation-induced aggregation provides a rigid chiral environment for the pyrenes and leads to significant electronic circular dichroism (ECD) and circularly polarized luminescence (CPL) activities, giving unprecedently high g_abs and g_lum values up to 4.3×10^-2 and 5.3×10^-2 , respectively. The aggregates lead to excimer emission with high quantum yields and show B_CPL and Bⁱ _CPL up to 338. 6 M^-1  cm^-1 and 169.3 M^-1  cm^-1 , respectively.

Chiral Arylene Diimide Phosphors: Circularly Polarized Ambient Phosphorescence from Bischromophoric Pyromellitic Diimides

Chiral organic phosphors with circularly polarized room-temperature phosphorescence (CPP) provide new prospects to the realm of circularly polarized luminescence (CPL) materials, owing to the long-lived triplet states and persistent emission. Although several molecular designs show efficient room-temperature phosphorescence (RTP), realization of ambient organic CPP remains a formidable challenge. Herein, we introduce a chiral bischromophoric phosphor design to realize ambient CPP emission by appending molecular phosphors to a chiral diaminocyclohexane core. Thus, solution-processable polymer films of the trans-1,2-diaminocyclohexane (DAC) chiral cores with heavy-atom substituted pyromellitic diimide phosphors, exhibits one of the most efficient exclusive CPP emissions with high phosphorescence quantum yield (≈18 % in air and ≈46 % under vacuum) and significant luminescence dissymmetry factor (|g_lum |≈4.0×10^-3 ).

Modulating the Excited State Chirality of Dynamic Chemical Reactions in Chiral Micelles

Chirality generation and transfer is not only of critical importance in resolving the origin of biological homochirality, but also is of great significance for exploring the chirality-related functionalities in nanomaterials and supramolecular systems. Although modulating the ground state chirality in chiral nanomaterials has been widely demonstrated, it remains a big challenge to steer the excited state chirality (circularly polarized luminescence, CPL). Herein, we present a kind of chiral spherical micelles constructed by chiral cationic gemini surfactants, whose surfaces and cavities could co-assemble with hydrophilic and hydrophobic emitters concurrently. Subsequently, the hydrophilic and hydrophobic emitters could be endowed with CPL activity in the aqueous phase. Additionally, the cavities of such micelles can be regarded as the powerful chiral confined space, which could effectively modulate the excited state chirality of dynamic chemical reactions, enabling color-adjustable CPL emission.

X⋅⋅⋅X Halogen Bond-Induced Supramolecular Helices

The halogen bond is the attractive interaction between the electrophilic region of a halogen atom and the nucleophilic region of another molecular entity, emerging as a favorable manner to manipulate supramolecular chirality in self-assemblies. Engineering halogen bonded helical structures remains a challenge due to its sensitivity to solvent polarity and competitive forces like hydrogen bonds. Herein, we report a X⋅⋅⋅X (X=Cl, Br, I) type weak halogen bond that induces the formation and evolution of supramolecular helical structures both in solid and solution state. The π-conjugated phenylalanine derivatives with F, Cl, Br and I substitution self-assembled into 2₁ helical packing driven by hydrogen bond and halogen bond, respectively. The specific molecular geometries of π-conjugated amino acids gave rise to multiple noncovalent forces to stabilize the X⋅⋅⋅X halogen bond with small bond energies ranging from -0.69 to -1.49 kcal mol^-1 . Halogen bond induced an opposite helicity compared to the fluorinated species, accompanied by the inversed circularly polarized luminescence.