Circularly Polarized Luminescence Research Articles

2,3 : 6,7‐Naphthalenediimide‐Based Chiral Triangular Macrocycle: Self‐Assembled Helix, Outer π‐Surface Directed Co‐Assembly and Circularly Polarized Luminescence

AbstractHere, we report the synthesis and self‐assembly of a novel chiral 2,3 : 6,7‐naphthalenediimide‐based triangular macrocycle (NDI‐Δ) and its chiroptical properties. The enantiomeric NDI‐Δ is synthesized by condensation of (RR) or (SS)‐trans‐1,2‐cyclohexanediamine and 2,3,6,7‐naphthalenetetracarboxylic 2,3 : 6,7‐dianhydride, in which the chirality of the macrocycles is controlled by the diamine. With the rigid outer π‐surface, the macrocycle exhibits unique chiroptical properties and self‐assembly modes. The NDI‐Δ shows circularly polarized luminescence (CPL) in solution and can self‐assemble into helical structures with the inversion of CPL signal and the enhancement of |glum|. Moreover, the NDI‐Δ has a tailored electron‐deficient outer π‐surface, which can co‐assemble with an electron‐rich anthracene (AN) to form an intermolecular charge transfer (CT) complex, generating a yellow‐green CT‐CPL. Crystal structure analysis confirms that AN is mounted on the outer surface of NDI‐Δ through π‐π stacking and C−H π interactions. This work provides a critical example for the self‐assembly of macrocycles into helical structures and outer π‐surface directed CT complexes formation, opening up a new clue for designing chiral macrocycle‐based chiroptical materials.

2,3 : 6,7-Naphthalenediimide-Based Chiral Triangular Macrocycle: Self-Assembled Helix, Outer π-Surface Directed Co-Assembly and Circularly Polarized Luminescence.

Here, we report the synthesis and self-assembly of a novel chiral 2,3 : 6,7-naphthalenediimide-based triangular macrocycle (NDI-Δ) and its chiroptical properties. The enantiomeric NDI-Δ is synthesized by condensation of (RR) or (SS)-trans-1,2-cyclohexanediamine and 2,3,6,7-naphthalenetetracarboxylic 2,3 : 6,7-dianhydride, in which the chirality of the macrocycles is controlled by the diamine. With the rigid outer π-surface, the macrocycle exhibits unique chiroptical properties and self-assembly modes. The NDI-Δ shows circularly polarized luminescence (CPL) in solution and can self-assemble into helical structures with the inversion of CPL signal and the enhancement of |glum|. Moreover, the NDI-Δ has a tailored electron-deficient outer π-surface, which can co-assemble with an electron-rich anthracene (AN) to form an intermolecular charge transfer (CT) complex, generating a yellow-green CT-CPL. Crystal structure analysis confirms that AN is mounted on the outer surface of NDI-Δ through π-π stacking and C-H π interactions. This work provides a critical example for the self-assembly of macrocycles into helical structures and outer π-surface directed CT complexes formation, opening up a new clue for designing chiral macrocycle-based chiroptical materials.

Structures and Properties of Axially Chiral (2E,4E,6Z,8Z)-Nona-2,4,6,8-Tetraenoate Derivatives Highly Substituted by Aryl groups.

Unprecedented (2E,4E,6Z,8Z)-nona-2,4,6,8-tetraenoate derivatives highly substituted by aryl groups have been synthesized by the reaction of rhodium complexes having aryl-substituted hexa-1,3,5-trienyl ligands with acrylates. These compounds have potential axial chirality, and their enantiomers are isolable by the chiral HPLC technique. Although the racemization barrier of isolated enantiomers was not high, it was found that a cyclic dimer synthesized by head-to-tail transesterification of a modified analog has quite a stable axial chirality even at a high temperature. From a structural analogy with tetraphenylethene, those compounds are emissive in the solid state, and the chiral cyclic dimer exhibits solid-state circularly polarized luminescence (CPL) activity.

Phosphorescent Liquid Crystalline Polymer-based Circularly Polarized Luminescence Optical Waveguides for Enhanced Photonic Signal Processing and Information Encryption.

Efficient circularly polarized luminescence (CPL) optical waveguides have significant potential for advancing photonic and optoelectronic devices. However, the development of CPL optical waveguides materials (OWMs) with low optical loss coefficient remains a considerable challenge. To overcome this, we design and synthesize CPL OWMs based on room-temperature phosphorescent liquid crystalline polymers (LCPs). Experimental results demonstrate that these LCPs exhibit a nematic liquid crystal phase and a phosphorescence lifetime of approximately 0.145 ms. By introducing a chiral dopant, we induce a chiral arrangement in the LCPs, followed by crosslinking via photo-cycloaddition and removal of the chiral dopants through solvent soaking. The resulting polymers exhibit stable solvent resistance and highly efficient circularly polarized phosphorescence (CPP) properties, with dissymmetric factors (gRTP) in the range of 0.16 to 0.17. Notably, the CPP-active OWMs exhibit efficient circularly polarized photonic signal waveguiding, with an optical loss coefficient of approximately 0.175 dB/mm. Ultimately, these CPP-active OWMs are sucessfully applied in information encryption, decryption, and optical switching, paving the way for advanced photonic and optoelectronic devices.

Phosphorescent Liquid Crystalline Polymer‐based Circularly Polarized Luminescence Optical Waveguides for Enhanced Photonic Signal Processing and Information Encryption

Efficient circularly polarized luminescence (CPL) optical waveguides have significant potential for advancing photonic and optoelectronic devices. However, the development of CPL optical waveguides materials (OWMs) with low optical loss coefficient remains a considerable challenge. To overcome this, we design and synthesize CPL OWMs based on room‐temperature phosphorescent liquid crystalline polymers (LCPs). Experimental results demonstrate that these LCPs exhibit a nematic liquid crystal phase and a phosphorescence lifetime of approximately 0.145 ms. By introducing a chiral dopant, we induce a chiral arrangement in the LCPs, followed by crosslinking via photo‐cycloaddition and removal of the chiral dopants through solvent soaking. The resulting polymers exhibit stable solvent resistance and highly efficient circularly polarized phosphorescence (CPP) properties, with dissymmetric factors (gRTP) in the range of 0.16 to 0.17. Notably, the CPP‐active OWMs exhibit efficient circularly polarized photonic signal waveguiding, with an optical loss coefficient of approximately 0.175 dB/mm. Ultimately, these CPP‐active OWMs are sucessfully applied in information encryption, decryption, and optical switching, paving the way for advanced photonic and optoelectronic devices.

Circularly Polarized Room-Temperature Phosphorescence from Dye-Doped Cholesteric Liquid Crystalline Polymer Networks.

Circularly polarized luminescence (CPL) materials have drawn increasing attention for their potential applications in optical displays and chemo/biosensing. Nevertheless, the construction of circularly polarized room-temperature phosphorescence (CPRTP) materials is still a significant challenge. In this work, four liquid crystalline polymer network films with RTP properties have been fabricated via photopolymerization of cholesteric liquid-crystalline mixtures containing different amounts of commercially available dyes. The films show a yellow-green structural color, enhanced RTP, blue CPL, and green CPRTP with phosphorescence dissymmetry factors up to -0.90, quantum yields up to 14.8%, and emission lifetimes up to 607 ms. Furthermore, the prepared film pattern presents different colors in reflective, fluorescent, and phosphorescent modes. This work not only provides a deep understanding of RTP and CPRTP, but also presents a facile strategy to fabricate film patterns for decoration and anticounterfeiting applications.

Amino-Acid-Induced Circularly Polarized Luminescence of Octahedral Lanthanide Cage.

Chiral metal organic cage compounds with excellent circularly polarized luminescent performance have broad application prospects in many fields. Herein, two lanthanide complexes with luminescent properties in the form of racemic hexagonal octahedral cages were synthesized using a tri (β-diketone) ligand. Eu6(C21H6F15O6)8(H2O)6 exhibited red light emission with high quantum yields of 61%. Then, we successfully synthesized lanthanide compounds with circularly polarized luminescent activity by chiral induction of the racemic mixture with arginine. The luminescence asymmetry factor was 0.53, and the circularly polarized luminescent merit figure reached 0.323. High-performance circularly polarized luminescent of racemic cage like compound systems have achieved using cheap and readily available chiral amino acid molecules through chiral induction.

Amino‐Acid‐Induced Circularly Polarized Luminescence of Octahedral Lanthanide Cage

Amino‐Acid‐Induced Circularly Polarized Luminescence of Octahedral Lanthanide Cage

Technical Routes to Achieve High Circular Polarized Luminescence in Chiral Perovskites: A Mini‐Review

AbstractChiral hybrid organic‐inorganic perovskites (HOIPs) have emerged as promising materials for optoelectronic and spintronic applications, leveraging unique properties such as circularly polarized luminescence (CPL), circularly polarized nonlinear optical (NLO) emission, and chiral‐induced spin selectivity (CISS). However, challenges remain in stabilizing these materials under environmental stresses and precisely controlling chirality for scalable use. This review summarizes five main strategies to induce chirality in HOIPs, i.e., direct incorporation of chiral cations, surface modification with chiral ligands, ion doping, template‐induced chirality, and chiral metasurfaces. Each approach offers distinct advantages for optimizing CPL efficiency and device stability, paving the way for next‐generation applications in CPL detectors, information encryption, spintronic devices, etc.

Shape-Persistent Tetraphenylethylene Macrocycle: Highly Efficient Synthesis and Circularly Polarized Luminescence

Circularly polarized luminescence (CPL) is an emerging field with significant applications in molecular electronics, optical materials, and chiroptical sensing. Achieving efficient CPL emission in organic systems remains a major challenge, particularly in the development of materials with high fluorescence quantum yields (ΦF) and large luminescence dissymmetry factors (glum). Herein, we report the efficient synthesis of shape-persistent tetraphenylethylene macrocycles and investigate its potential as a CPL material. Chiral side chains were introduced to induce chiroptical properties. The macrocycles and their properties were characterized using NMR, MALDI-TOF MS, FT-IR, TGA, DSC, UV-Vis spectroscopy, SEM, fluorescence spectroscopy, ECD, and CPL. A significant fluorescence enhancement was observed upon aggregation, demonstrating a typical aggregation-induced emission (AIE) behavior. Moreover, one of the macrocycles in the solid state displayed distinct CPL emission with a high glum of 2 × 10−2 and a ΦF value reaching 60%, and exhibited aggregation-induced circularly polarized luminescence (AICPL). These findings highlight the advantage of using a macrocycle with a noncollapsible backbone for the design of organic systems with CPL property, offering promising applications in chiroptical materials.

Near-Infrared Magnetic Circularly Polarized Luminescence and Slow Magnetic Relaxation in a Tetrazinyl-Bridged Erbium Metallocene.

The magnetic and magneto-optical properties of a tetrazinyl radical-bridged ErIII metallocene, [(Cp*2ErIII)2(bpytz•-)][BPh4] (1; Cp* = pentamethylcyclopentadienyl, bpytz = 3,6-bis(3,5-dimethyl-pyrazolyl)-1,2,4,5-tetrazine), are reported. As confirmed by these studies strong Ln-rad coupling is achieved, with 1 exhibiting slow magnetic relaxation under a 1000 Oe dc field. The optical and magneto-optical profile of 1 is completed by both near-infrared (NIR) luminescence and magnetic circularly polarized luminescence (MCPL), representing the first example of NIR MCPL with ErIII.

A Helically-Twisted Stereodynamic Probe for Chiroptical Sensing of Chiral Amines through Point-to-Helical Chirality Transmission.

Chiral amines and amino alcohols form an important category of molecules employed in the designing of new drugs and catalyst. Herein, we present a helically-twisted stereodynamic dialdehyde probe 1 for the determining of absolute configuration, and enantiomeric excess of chiral amine and amino alcohols. Probe 1 is based on the pyridine-2,6-dicarboxamide (PDC) core and undergoes rapid interconversion between the P- and M- conformers. However, upon imine formation with chiral amines, probe 1 gets locked it in a single conformer majorly. This induces a strong CD signal in addition to changes in the UV-vis and fluorescence signals. The CD spectral change allowed for quantitative enantiomeric excess determination of chiral amines. Circular polarized luminescence (CPL) spectra having the glum of 1×10-3 was obtained upon imine formation between probe 1 and diamine 2. Single crystal X-ray diffraction studies (SCXRD) confirmed the twisted conformation in 1@(R)-4 and 1@(S)-4, stabilized by intramolecular hydrogen bonding between bound imine nitrogen and proximate amide group.

Construction of a circularly polarized luminescence sensor based on self-assembly of carbon dots and G-quartet chiral nanofibers.

Circularly polarized luminescence (CPL) is a fascinating luminescence phenomenon that has garnered significant research attention for chiroptical applications. In this study, we developed a highly sensitive chiroptical sensor by co-assembling G-quartet nanofibers and nonchiral nitrogen sulfur-doped carbon dots (N-S-CDs) for dual ion detection. The N-S-CDs were synthesized using the one-step microwave method, and a helical G-quartet-based nanofiber structure (g-fiber) was simultaneously formed from guanosine 5'-monophosphate (GMP) in the presence of Sr2+. An adjustable helical G-quartet-based nanofiber provided an optimal chiral environment for CPL emission, with a dissymmetry factor (glum) reaching ±0.02. Notably, the left-handed (L-) and right-handed (R-) helical chirality of the complex was determined by switching between kinetic trap states and thermodynamic equilibrium during the reaction process. An optimized CPL sensor was developed based on chiral CDs/g-fiber composite materials, utilizing sensitive CPL as the signal output of dual detection for Hg2+ and I-. Similar limits of detection (LODs) were achieved for both L-/R-nanocomposites, with the best results being 83.5 nM for Hg2+ and 142.8 nM for I-. These values are comparable with or even better than those obtained with other optical analytical methods. Since CPL biosensors are relatively rare to date, our work presents a new horizon for the application of chiral CPL composites in biological assays.

From synthesis to chiroptical activities: advancements in circularly polarized luminescent inorganic quantum dots.

Circularly polarized luminescence (CPL) in inorganic quantum dots (QDs) represents a burgeoning and dynamic research domain, offering immense potential across a spectrum of applications, including three-dimensional displays, optical data storage, asymmetric catalysis, and chiral sensing. However, the persistent trade-off between fluorescence brightness and the emission dissymmetry factor highlights the nascent stage of current research. This review delves into the synthesis methodologies of CPL QDs, providing an exhaustive analysis of existing approaches and the resulting material properties. It elucidates the critical factors influencing CPL characteristics, such as ligand types, interaction modes, and QD architectures. Furthermore, it synthesizes the theoretical frameworks underlying chirality and CPL generation, ranging from time-dependent density functional theory (TDDFT) to ab initio molecular dynamics (AIMD), thereby deepening the understanding of CPL mechanisms within QDs. The review culminates with a comprehensive exploration of potential applications, alongside a forward-looking perspective on the future trajectory of CPL QD research.

Multicolor and sign-invertible circularly polarized luminescence from nonchiral charge-transfer complexes assembled with N-terminal aromatic amino acids.

Circularly polarized luminescence (CPL) materials with precisely controlled emission colors and handedness are highly desirable for their promising applications in advanced optical technologies, but it is rather challenging to obtain them primarily due to the lack of convenient, powerful, and universal preparation strategies. Herein, we report a simple yet versatile solution route for constructing multicolor CPL materials with controllable handedness from nonchiral luminescent charge-transfer (CT) complexes through co-assembly with chiral N-terminal aromatic amino acids. The resulting ternary co-assemblies exhibit obvious CPL signals from 489 to 601 nm, covering from blue via green and yellow to orange-red. Notably, the CPL sign can be readily inverted by changing the substituents at the α-position of amino acids or the molecular structure of achiral electron donors due to effects on the hydrogen bonds, CT interactions, and stacking patterns. This work provides a new insight into developing CPL materials with tunable color and inverted handedness.

Structural relaxation chirality transfer enhanced circularly polarized luminescence in heteronuclear CeIII-MnII complexes.

Circularly polarized luminescence (CPL) materials have developed rapidly in recent years due to their wide application prospects in fields like 3D displays and anti-counterfeiting. Utilizing energy transfer processes to transfer chirality has been proven as an efficient way to obtain CPL materials. However, the physics behind energy-transfer induced CPL is still not clear. Herein, in a well-designed heteronuclear CeIII-MnII complex system [(Ce((R/S)-L)Br(μ-Br))2]MnBr4 [(R/S)-L = (2R,3R)- or (2S,3S)-2,3-dimethyl-1,4,7,10,13,16-hexaoxacyclooctadecane] with intra energy transfer from CeIII to MnII, the luminescence dissymmetry factor of MnII obtained by excitation of CeIII is around 10 times higher than that obtained by direct excitation of MnII, while the CeIII center itself shows an almost negligible CPL. To address this unusual phenomenon, we proposed a new mechanism named structural relaxation chirality transfer (SRCT) where structural relaxation of the excited chiral donor amplified chirality transfer to the acceptor by intramolecular interactions. As an assistant proof, a mixture of CeIII-ZnII and LaIII-MnII complexes with inter energy transfer showed no CPL amplification. These results will inspire more breakthroughs in the physics nature and development of energy-transfer induced CPL.

Peptide-induced chirality transfer and circularly polarized luminescence in achiral BODIPY emitters via halogen bonding.

This study explores peptide-mediated chiral induction and circularly polarized luminescence (CPL) in achiral BODIPY dyes, leading to a high glum value of up to -1.2 × 10-2 through orthogonal halogen bonding and hydrogen bonding. It unravels the impact of these combined directional interactions on the formation of heterostructures and their thermal stability.

White circularly polarized luminescence from a dual-component emitter induced by FRET between tetraphenylene and PDI derivatives.

A chiral agent, TPE-ASP, incorporating aspartic acid as the chiral source and tetraphenylene derivatives as chromophores, was designed and synthesized. The chiral agent was self-assembled into regular spherical nanoparticles with a maximum luminescence asymmetry factor of |2.41 × 10-2| at 460 nm which is attributed to TPE-ASP. These nanoparticles can be co-assembled with a perylenediimide (PDI) derivative through electrostatic interactions, enabling the successful construction of a chiral light-harvesting system (C-LHS). The maximum Förster resonance energy transfer (FRET) efficiency (ΦET) of 94.7% was achieved at the optimal molar ratio of TPE-ASP to PDI. Fortunately, multicolour circularly polarized luminescence (CPL), spanning from blue to red, was successfully achieved with a two-component co-assembly system, and bright white CPL with CIE coordinates of (0.33, 0.32) was also obtained. Meanwhile, the average glum is |7.1 × 10-3| in the wavelength range of 400-700 nm. This discovery demonstrates the potential for spectral regulation through the two-component co-assembly strategy. It is significant for developing CPL devices with white light emission via the FRET process and also expands the functional range of chiral light-harvesting systems.

Controlling Sign and Magnitude of Circularly Polarized Luminescence of Axially Chiral Schiff-Base Boron Difluoride Complexes Bearing Polyethylene Glycol Chains.

The synthesis, structure, and circularly polarized luminescence (CPL) properties of axially chiral boron difluoride complexes are described. A series of optically pure bis (boron difluoride) complexes were prepared in 5 steps from commercially available (S)- or (R)-BINOL as starting materials. The complexes were found to exhibit similar yellow photoluminescence in solution, regardless of the type of substituents on the nitrogen atoms. Notably, for the complex with polyethylene glycol chains, homogeneous and transparent films were formed by the drop-cast method, showing intense CPL with a different sign from that of the solution state. Density functional theory (DFT) calculations were performed to understand their photophysical behavior including configuration-dependent CPL properties.

Inversion of circularly polarized luminescence by electric current flow during transition.

The development of chiral compounds exhibiting circularly polarized luminescence (CPL) has advanced remarkably in recent years. Designing CPL-active compounds requires an understanding of the electric transition dipole moment (μ) and the magnetic transition dipole moment (m) in the excited state. However, while the direction and magnitude of μ can, to some extent, be visually inferred from chemical structures, m remains elusive, posing challenges for direct predictions based on structural information. This study utilized binaphthol, a prominent chiral scaffold, and achieved CPL-sign inversion by strategically varying the substitution positions of phenylethynyl (PE) groups on the binaphthyl backbone, while maintaining consistent axial chirality. Theoretical investigation revealed that the substitution position of PE groups significantly affects the orientation of m in the excited state, leading to CPL-sign inversion. Furthermore, we propose that this CPL-sign inversion results from a reversal in the rotation of instantaneous current flow during the S1 → S0 transition, which in turn alters the orientation of m. The current flow can be predicted from the chemical structure, allowing anticipation of the properties of m and, consequently, the characteristics of CPL. This insight provides a new perspective in designing CPL-active compounds, particularly for C2-symmetric molecules where the S1 → S0 transition predominantly involves LUMO → HOMO transitions. If μ represents the directionality of electron movement during transitions, i.e., the "difference" in electron locations before and after transitions, then m could be represented as the "path" of electron movement based on the current flow during the transition.