Circularly polarized light emission from encapsulated aggregation-induced emission achiral luminogen within the supramolecular helical nanofilament networks

Circularly polarized light emission (CPLE) materials have attracted considerable attention owing to their broad range of potential applications, including spintronics. In this study, we introduce an innovative approach to impart CPLE activity to achiral aggregation-induced emission luminogens (AIEgens) by leveraging the nanoscale spontaneous phase separation between rod-like AIEgens and helical filaments formed by bent-core molecules. This phase separation was confirmed by transmittance analysis, X-ray diffraction, and other techniques as supported by transmission electron microscopy. Intrinsically, CPLE-inactive AIEgens aggregate in nanosized spaces, isolated from the helical filament network, and become CPLE-active via chirality transfer from the helical filaments. Thus, CPLE emission was achieved from the AIEgens encapsulated within the supramolecular helical nanofilament networks. The CPLE properties were significantly influenced by the size of the nanospace occupied by the AIEgens between the helical filament networks, as evaluated using scanning electron microscopy. This nanospace created a chiral environment, allowing the chirality of the helical filaments to transfer to the AIEgens during aggregation, rendering them CPLE-active. This study presents a universal strategy for fabricating CPLE materials without the need for complex chemical synthesis or the molecular design of luminogens.

Bright circularly polarized photoluminescence in chiral layered hybrid lead-halide perovskites

Hybrid perovskite semiconductor materials are predicted to lock chirality into place and encode asymmetry into their electronic states, while softness of their crystal lattice accommodates lattice strain to maintain high crystal quality with low defect densities, necessary for high luminescence yields. We report photoluminescence quantum efficiencies as high as 39% and degrees of circularly polarized photoluminescence of up to 52%, at room temperature, in the chiral layered hybrid lead-halide perovskites (R/S/Rac)-3BrMBA2PbI4 [3BrMBA = 1-(3-bromphenyl)-ethylamine]. Using transient chiroptical spectroscopy, we explain the excellent photoluminescence yields from suppression of nonradiative loss channels and high rates of radiative recombination. We further find that photoexcitations show polarization lifetimes that exceed the time scales of radiative decays, which rationalize the high degrees of polarized luminescence. Our findings pave the way toward high-performance solution-processed photonic systems for chiroptical applications and chiral-spintronic logic at room temperature.

Inter- and intramolecular excimer circularly polarised luminescence of planar chiral paracyclophane-pyrene luminophores

Two types of planar chiral [2,2]paracyclophane-pyrene luminophores (1 and 2) with different binding positions of the fluorescent pyrene units were synthesised. (R)/(S)-1 with 1-pyrene units exhibited green intermolecular excimer circularly polarised luminescence (CPL) at 530 nm in the KBr-pellet, but exhibited no CPL signal in dilute CHCl3 solution. In contrast, (R)/(S)-2 with 2-pyrene units exhibited a blue intramolecular excimer CPL at 450 nm in CHCl3 solution. This is the first example of using the binding position of pyrene and the external environment to tune the type (inter- or intramolecular) and chiroptical sign of excimer CPL.

Circularly Polarized Luminescence from Chiral Tetranuclear Copper(I) Iodide Clusters

Circularly polarized luminescent (CPL) materials are promising in applications such as 3D displays and quantum communication. Hybrid organic-inorganic copper(I) iodides have been rapidly developed due to their intense photoluminescence and structural diversity; nevertheless, the reported Cu-I clusters rarely show CPL activities. In this study, we introduced chiral organic molecules R/S-methylbenzylammonium (R/S-MBA) into Cu-I inorganic skeletons to achieve chiral tetranuclear (R/S-MBA)₄Cu₄I₄ clusters with intense orange luminescence and CPL activity at room temperature. These enantiomeric (R/S-MBA)₄Cu₄I₄ clusters show oppositely signed circular dichroism (CD) signals, which agree well with their simulated electronic CD spectra. The crystallization-induced helical arrangement of (R/S-MBA)₄Cu₄I₄ clusters and their largely distorted polynuclear configuration demonstrate a new platform for the study of chiral-related properties.

Solid-state AIEnh-circularly polarised luminescence of chiral perylene diimide fluorophores

Chiral N,N′-bis(1-phenylethyl)perylene-3,4,9,10-tetracarboxylic acid diimide (BPP) exhibits solid-state aggregation-induced enhanced circularly polarized luminescence (AIEnh-CPL) in KBr, PMMA, and myo-IPU matrices..

Solvent-sensitive signs and magnitudes of circularly polarised luminescence and circular dichroism spectra: probing two phenanthrenes as emitters endowed with BINOL derivatives

A C₂-symmeric binaphthyl framework bearing phenanthrene as the emitter exhibited circularly polarised luminescence (CPL) in dilute solutions.

A New Polymer-Based Fluorescent Chemosensor Incorporating Propane-1,3-Dione and 2,5-Diethynylbenzene Moieties for Detection of Copper(II) and Iron(III)

A novel conjugated polymer (PDBDBM) was developed by the polymerization of 1,4-dioctyloxy-2,5-diethynylbenzene with 1,3-bis(4-bromophenyl)propane-1,3-dione based on Pd-catalyzed Sonogashira-coupling reaction. The obtained polymer PDBDBM exhibited bright green photoluminescence under UV irradiation. According to the metal ion titration experiments, PDBDBM showed high sensitivity and selectivity for detection of Cu2+ and Fe3+ over other metal ions. The fluorescent detection limits of PDBDBM were calculated to be 5 nM for Cu2+ and 0.4 μM for Fe3+ and the Stern⁻Volmer quenching constant for Cu2+ and Fe3+ were found to be 1.28 × 10⁸ M-1 and 2.40 × 10⁴ M-1, respectively. These results indicated that the polymer can be used as a potential probe for Cu2+ and Fe3+ detection.

Circularly polarised luminescence of pyrenyl di- and tri-peptides with mixed d- and l-amino acid residues

Multiple pyrenes as pendants of enantioimpure di-/tripeptides showed pyrene-origin CPL and CD signals, which were associated with conflicting CPL-/CD-signs.

Circularly-Polarized Luminescence (CPL) from Chiral AIE Molecules and Macrostructures

Circularly-polarized luminescence (CPL) has received new attention on the rise of applications to generate devices and biologically active probes. These applications require fluorophores that are not only chiral but also provide strong fluorescence intensity in aggregated state. Thus, a new research branch has opened up a few years ago, which allows CPL-active fluorophores to be emissive in aggregated-state. As a result, reports on the combination of the CPL property with the aggregation-induced emission (AIE) phenomenon have emerged. Herein the early design principles that have been reported until now to generate CPL-active AIE-active fluorophores (AIEgens) are summarized. In this regard the alignment of monomeric emitters in a chiral fashion, either in supramolecules, polymers or liquid crystals has been proven to be a successful approach. Additionally, first reports have appeared that demonstrate how to tackle the daunting task to furnish individual CPL-active AIEgens.

Synthesis, characterization and properties of furan-containing difluoroboron complexes

New β-diketonate difluoroboron complexes (F1–F4) containing a furan ring have been developed, and their luminescence properties have been investigated systematically.

Cryptochiral binaphthyl–bipyrene luminophores linked with alkylene esters: intense circularly polarised luminescence, but ultraweak circular dichroism

A C₂-symmetric binaphthyl-based luminophore with two luminescent pyrenes was designed to express cryptochirality, as proven by the ultraweak circular dichroisms in the ground state.

Synthesis and fluorescence study of conjugated polymers based on 2,4,6-triphenylpyridine moieties

Three novel 2,4,6-triphenylpyridine-based conjugated polymers showed strong fluorescence emission with large Stokes' shifts, tunable band gaps and high quantum yields.

Sign inversion of circularly polarized luminescence by geometry manipulation of four naphthalene units introduced into a tartaric acid scaffold

Tethering four 1- versus 2-naphthyls to the same chiral scaffold derived from tartaric acid led to oppositely signed circularly polarized luminescence (CPL) and circular dichroism (CD) in solution, which not only reveals the decisive role of the spatial arrangement of chromophores/fluorophores in determining the chiroptical behaviors but also provides us with a versatile tool for switching the signs of CPL and CD without using the antipodal scaffold.

A study on tunable AIE (AIEE) of boron ketoiminate-based conjugated polymers for live cell imaging

In this study, four boron ketoiminate-based conjugated polymers P1–P4 are designed and synthesized via Suzuki polymerization.

Photon magic: chiroptical polarisation, depolarisation, inversion, retention and switching of non-photochromic light-emitting polymers in optofluidic medium

A circularly polarised photon hand, l- and r-, was not a deterministic factor for the induced chiroptical sign of π-conjugated polymer aggregates. This anomaly originates from circular dichroism inversion characteristics between shorter and longer π–π* bands.

Solid-state circularly polarised luminescence of atropisomeric fluorophores embedded in achiral myo-inositol-containing polyurethanes

Two chiral binaphthyl fluorophores in two myo-inositol based polyurethane matrices with high grass transition temperatures emitted circularly polarised luminescence with a high circular anisotropy factor.

Circularly polarized luminescence of biaryl atropisomers: subtle but significant structural dependency

The signs of circularly polarised luminescence and circular dichroism of chiral biaryl organic fluorophores in CHCl₃⁻ and PMMA film were successfully controlled by the internal axial chirality and the axial bonding position of biaryl units.

Circularly polarised luminescence and circular dichroism of l- and d-oligopeptides with multiple pyrenes

Among l- and d-oligopeptides with multiple pyrenes as pendants, the dipeptides with two and three pyrenes showed blue-coloured circularly polarised luminescence as high as |g_em| ≈ (0.86−1.1) × 10⁻² at around 450 nm, reflecting from exciton couplets of twisted pyrenes.

Dual-Emissive Difluoroboron Naphthyl-Phenyl β-Diketonate Polylactide Materials: Effects of Heavy Atom Placement and Polymer Molecular Weight

Luminescent materials are important for imaging and sensing. Aromatic difluoroboron β-diketonate complexes (BF₂bdks) are classic fluorescent molecules that have been explored as photochemical reagents, two-photon dyes, and oxygen sensors. A series of BF₂bdks with naphthyl and phenyl groups was synthesized, and photophysical properties were investigated in both methylene chloride and poly(lactic acid) (PLA). Polymer molecular weight and dye attachment site along with bromide heavy atom placement were varied to tune optical properties of dye–PLA materials. Systems without heavy atoms have long phosphorescence lifetimes, which is useful for lifetime-based oxygen sensing. Bromine substitution on the naphthyl ring resulted in intense, clearly distinguishable fluorescence and phosphorescence peaks important for ratiometric oxygen sensing and imaging.

Nonclassical dual control of circularly polarized luminescence modes of binaphthyl–pyrene organic fluorophores in fluidic and glassy media

The fluorescent modes and signs of the circularly polarized luminescence of an axially chiral binaphthyl–pyrene organic fluorophore were successfully controlled by changing from a fluidic chloroform solution to a glassy poly(methyl methacrylate) solid film.