Modulation of Deep-Red to Near-Infrared Room-Temperature Charge-Transfer Phosphorescence of Crystalline "Pyrene Box" Cages by Coupled Ion/Guest Structural Self-Assembly

Full-color processible afterglow organic small molecular glass

Organic afterglow materials, known for their unique luminescent properties and diverse applications, have garnered significant attention in recent years. However, developing long-lasting, high-efficiency, full-color afterglow systems and exploring simple materials processing strategies for new applications are still challenging in this field. Herein, we rationally design a processable molecular glass and employ it as a host in a host-guest strategy to address these challenges. By strategically modifying the host via othyl-methylation, we successfully create a molecular glass and capture its temperature-dependent, processable viscous supercooled liquid state. High-efficiency full color from violet to near-infrared afterglow systems with ultralong lifetimes are developed by doping varied structural dopants. The underlying glass-forming and afterglow mechanisms are also clearly elucidated and verified. Moreover, the excellent glass-forming ability of the host and its viscous supercooled liquid enabled the glass system for large-area fabrication, shaping of objects with diverse 3D structures, and creation of flexible, meter-long afterglow fibers. This work offers significant potential for practical applications in advanced textiles, displays, and other fields.

Tunable luminescence of hyperbranched polysiloxanes by nonsaturation-induced electrostatic potential polarization for activatable fluorescent theranostics

Developing high-efficiency luminescent polysiloxanes with activatable fluorescent theranostics is highly desirable in biomedicine. In this work, we compared hyperbranched polysiloxanes (HBPSis) with diverse nonsaturation and built an intelligent chemodynamic therapy (CDT) system with activatable fluorescence imaging. Experimental characterization and theoretical calculations reveal that increased nonsaturation offers numerous delocalized π electrons to modulate the polarization of electrostatic potential, which further drives the clusterization of carbonyl groups. Consequently, through-space interactions are enhanced, leading to a red-shifted emission and improved quantum yield. Furthermore, an intelligent CDT system, HBPSi-Fe3+@AT, is fabricated. Both the CDT process and fluorescence imaging can be activated in the presence of overexpressed glutathione. This work provides fresh insight into nonsaturation-induced electrostatic potential polarization and presents an activatable CDT system for versatile fluorescence imaging-guided theranostics.

Stimulus-Responsive Emission via Dynamic Triplet Energy Transfer in Organic Room-Temperature Phosphorescence Glass

Dynamic organic room-temperature phosphorescence (RTP) glasses with color tunability offer significant potential for practical applications due to their high transparency and excellent machinability. In this study, organic glasses with efficient and dynamic RTP properties are used as triplet donors, combined with commercially available chromophores as singlet/triplet acceptors, to successfully fabricate a series of host-guest doping glasses with color-tunable organic afterglow and dynamic responses to external stimuli. The energy transfer mechanisms, including triplet-to-singlet phosphorescence resonance energy transfer and Dexter-type triplet-to-triplet energy transfer, are confirmed using state-of-the-art femtosecond time-resolved transient absorption spectroscopy. These organic glasses demonstrate excellent transparency, good machinability, and dynamic responsiveness to external stimuli. The study highlights their potential applications in large-area afterglow glass fabrication, dynamic data encryption, and flexible afterglow displays. This work not only provides a simple design principle for developing novel organic glass materials with color tunability and dynamic responses but also promotes the potential applications of organic RTP materials in dynamic information encryption and flexible optoelectronics.

High-Performance Organic Ultralong Room Temperature Phosphorescence Based on Biomass Macrocycle

The pursuit of sustainable, high-performance organic ultralong room temperature phosphorescence (OURTP) materials with stimulus-responsive properties presents a significant and enticing yet formidable challenge. Herein, an efficient strategy to confining boric acid-based compounds into biomass macrocycle γ-cyclodextrin through multiple interactions is developed, enabling the construction of high-performance and multicolor OURTP doped systems. The synergistic effects of strong hydrogen bonding, C─O─B covalent cross-linking, and host-guest encapsulation significantly suppress non-radiative transition, culminating in an extraordinary lifetime and excellent phosphorescence quantum yield of 4.65 s and 32.8%, respectively, which are far superior to reported biomass RTP materials. Additionally, merging biomass macrocycle with phosphors contributes to multiple stimulus responses, overcoming the inherent limitations of degradation and recycling of organic RTP compounds, and dynamically modulating RTP signals through multiple-stimulus responses, achieving the integration of multifunctional dynamic data processing techniques. This work will provide a direction for new environmentally friendly and potentially commercially available stimulus-responsive OURTP materials.

Cocrystallization-Induced Red Ultralong Organic Phosphorescence

Organic cocrystals formed through multicomponent self-assembly have attracted significant interest owing to their clear structure and tunable optical properties. However, most cocrystal systems suffer from inefficient long-wavelength emission and low phosphorescence efficiency due to strong non-radiative processes governed by the energy gap law. Herein, an efficient long-lived red afterglow is achieved using a pyrene (Py) cocrystal system incorporating a second component (NPYC4) with thermally activated delayed fluorescence (TADF) and ultralong organic phosphorescence (UOP) properties. The cocrystal (NPYC4-Py) not only inherits the excellent luminescence of its monomeric counterparts, but also exhibits unique dual-mode characteristics, including persistent TADF and UOP emission with a high quantum yield of 58 % and a lifetime of 362 ms. The precise cocrystal stacking distinctly reveals that intermolecular interactions lock the cocrystal formation and weaken the intermolecular π-π interactions between NPYC4 and Py, thereby stabilizing the excited triplet excitons. Furthermore, the favorable energy level of NPYC4 acts as a bridge, reducing the energy gap between the S1 and T1 states for Py, therefore activating its red phosphorescence from Py. This research provides direct insights into achieving efficient red UOP through co-crystallization.

Achieving Controllable Thermochromic Fluorescence via Synergistic Intramolecular Charge Transfer and Molecular Packing

Thermochromic fluorescent materials (TFMs) have attracted significant attention due to their unique fluorescent colorimetric response to temperature. However, existing TFMs still suffer from weak stimulus responsiveness, broad temperature response ranges, uncontrollable emission color changes, and low quantum yields. In this study, we address these issues by designing and synthesizing three diketone-boron complexes with distinct emission wavelengths (NWPU-(2-4)). Utilizing a molecular engineering strategy to manipulate intramolecular charge transfer transitions and molecular packing modes, our synthesized complexes exhibit efficient fluorescence emission in both solution and solid states. Moreover, their emission wavelengths are highly sensitive to environmental polarity. By incorporating these compounds into thermosensitive matrices of long-chain alkanes, we produced TFMs with varied fluorescence emission peak variation ranges. Notably, the TFM based on NWPU-4, owing to its strong charge transfer transitions and dense J-aggregate packing configuration, not only exhibits intense fluorescence emission spanning the deep red to near-infrared spectrum but also displays a remarkable 90 nm broad range of thermochromic properties. Ultimately, it was successfully applied to programmable, thermally controlled, multi-level information encryption.

Triarylmethanol Derivatives with Ultralong Organic Room-Temperature Phosphorescence

Triphenylmethyl-based compounds such as rhodamines and fluoresceine representing an old and well-known class of triphenylmethane dyes, are widely used in fluorescent labeling of bioimaging. Inspired by ultralong room temperature phosphorescence of triphenylphosphine derivatives, herein we report a methoxy substituted triarylmethanol ((4-methoxyphenyl)diphenylmethanol, LJW-1) exhibits ultralong room temperature phosphorescence (RTP) under ambient condition with afterglows of about 7 seconds. Its multiple C-H ⋅ ⋅ ⋅ π intermolecular interactions, C-H ⋅ ⋅ ⋅ O intermolecular interactions, hydrogen bond and π-π interactions are beneficial for forming rigid environment in the aggregated state which is evidently an important factor in the appearance of excellent RTP. Different substituents on triarylmethanol result in compounds with different lifetimes varying from 7 μs to 818 ms. The substituent effects on the phosphorescence of triarylmethanol derivatives provide an efficient method for the design of organic RTP materials and may be enlightening the phosphorescence research of triarylmethanol derivatives.

Recent Advances of Organic Cocrystals in Emerging Cutting-Edge Properties and Applications

Organic cocrystals, representing one type of new functional materials, have gathered significant interest in various engineering areas. Owing to their diverse stacking modes, rich intermolecular interactions and abundant functional components, the physicochemical properties of organic cocrystals can be tailored to meet different requirements and exhibit novel characteristics. The past few years have witnessed the rapid development of organic cocrystals in both fundamental characteristics and various applications. Beyond the typical properties like ambipolarity, emission tuning ability, ferroelectricity, etc. that are previously well demonstrated, many novel, impressive and cutting-edge properties and applications of cocrystals are also emerged and advanced recently. Especially during the nearest five years, photothermal conversion, room-temperature phosphorescence, thermally activated delay fluorescence, circularly polarized luminescence, organic solid-state lasers, near-infrared sensing, photocatalysis, batteries, and stimuli responses have been reported. In this review, these new properties are carefully summarized. Besides, some neoteric architecture and methodologies, such as host-guest structures and machine learning-based screening, are introduced. Finally, the potential future developments and expectations for organic cocrystals are discussed for further investigations on multiple functions and applications.

Stimulating Chiral Selective Expression of Room Temperature Phosphorescence for Chirality Recognition

Chiral recognition is crucial for applications in chiral purity assessment and biomedical fields. However, achieving chiral recognition through visible room temperature phosphorescence remains challenging. Here, two chiral molecules, designated as host and guest are synthesized, which possess similar structural configurations. A viable strategy involving a chiral configuration-dependent energy transfer process to enable selective phosphorescence expression is proposed, thereby enabling chiral recognition in a host-guest doping system. The chiral and structural similarity between host and guest facilitates efficient Dexter energy transfer due to the reduced spatial distance between the molecules. This mechanism significantly enhances the intensity of red phosphorescence from the guest molecule, characterized by an emission peak at 612 nm and a prolonged lifetime of 32.7 ms. This work elucidates the mechanism of chiral-dependent energy transfer, demonstrating its potential for selectively expressing phosphorescence in chiral recognition.

The Delayed Box: Biphenyl Bisimide Cyclophane, a Supramolecular Nano-environment for the Efficient Generation of Delayed Fluorescence

Activating delayed fluorescence emission in a dilute solution via a non-covalent approach is a formidable challenge. In this report, we propose a strategy for efficient delayed fluorescence generation in dilute solution using a non-covalent approach via supramolecularly engineered cyclophane-based nanoenvironments that provide sufficient binding strength to π-conjugated guests and that can stabilize triplet excitons by reducing vibrational dissipation and lowering the singlet-triplet energy gap for efficient delayed fluorescence emission. Toward this goal, a novel biphenyl bisimide-derived cyclophane is introduced as an electron-deficient and efficient triplet-generating host. Upon encapsulation of various carbazole-derived guests inside the nanocavity of this cyclophane, emissive charge transfer (CT) states close to the triplet energy level of the biphenyl bisimide are generated. The experimental results of host-guest studies manifest high association constants up to 104 M-1 as the prerequisite for inclusion complex formation, the generation of emissive CT states, and triplet-state stabilization in a diluted solution state. By means of different carbazole guest molecules, we could realize tunable delayed fluorescence emission in this carbazole-encapsulated biphenyl bisimide cyclophane in methylcyclohexane/carbon tetrachloride solutions with a quantum yield (QY) of up to 15.6%. Crystal structure analyses and solid-state photophysical studies validate the conclusions from our solution studies and provide insights into the delayed fluorescence emission mechanism.

Hybridization of short-range and long-range charge transfer boosts room-temperature phosphorescence performance

At present, mainstream room-temperature phosphorescence (RTP) emission relies on organic materials with long-range charge-transfer effects; therefore, exploring new forms of charge transfer to generate RTP is worth studying. In this work, indole-carbazole was used as the core to ensure the narrowband fluorescence emission of the material based on its characteristic short-range charge-transfer effect. In addition, halogenated carbazoles were introduced into the periphery to construct long-range charge transfer, resulting in VTCzNL-Cl and VTCzNL-Br. By encapsulating these phosphors into a robust host (TPP), two host-guest crystalline systems were further developed, achieving efficient RTP performance with phosphorescence quantum yields of 26% and phosphorescence lifetimes of 3.2 and 39.2 ms, respectively.

Regulation of Photophysical Behaviors in Hyperbranched Aggregation-Induced Emission Polymers for Reactive Oxygen Species Scavenging

Developing nonconjugated materials with large Stokes shifts is highly desired. In this work, three kinds of hyperbranched aggregation-induced emission (AIE) polymers with tunable n/π electronic effects were synthesized. HBPSi-CBD contains alkenyl groups in the backbone and possesses a promoted n-π* transition and red-shifted emission wavelength with a large Stokes shift of 186 nm. Experiments and theoretical simulations confirmed that the planar π electrons in the backbone are responsible for the red-shifted emission due to the strong through-space n···π interactions and restricted backbone motions. Additionally, the designed HBPSi-CBD could be utilized as an ROS scavenger after coupling with l-methionine. The HBPSi-Met exhibits remarkable ROS scavenging properties with a scavenging capacity of 77%. This work not only gains further insight into the structure-property relationship of nonconjugated hyperbranched AIE polymers but also provides a promising ROS-scavenging biomaterial for the treatment of ROS-related diseases.