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Controlling triplet states is crucial to improve the efficiency and lifetime of organic room temperature phosphorescence (ORTP). Although the intrinsic factors from intramolecular radiative and non-radiative decay have been intensively investigated, the extrinsic factors that affect triplet exciton quenching are rarely reported. Diffusion to the defect sites inside the crystal or at the crystal surface may bring about quenching of triplet exciton. Here, the phosphorescence lifetime is found to have a negative correlation with the triplet exciton diffusion coefficient based on the density functional theory (DFT)/time-dependent density functional theory (TD-DFT) calculations on a series of ORTP materials. For systems with a weak charge transfer (CT) characteristic, close π–π stacking will lead to strong triplet coupling and fast triplet exciton diffusion in most cases, which is detrimental to the phosphorescence lifetime. Notably, for intramolcular donor–acceptor (D–A) type systems with a CT characteristic, intermolecular D–A stacking results in ultra-small triplet coupling, thus contributing to slow triplet diffusion and long phosphorescence lifetime. These findings shed some light on molecular design toward high-efficiency long persistent ORTP. [ABSTRACT FROM AUTHOR]

The large‐scale fabrication of long‐lived and sustainable room‐temperature phosphorescence (RTP) materials with color‐tunable afterglow is of considerable practical importance in diverse optoelectronic applications but remains challenging. Herein, based on a process for the mass production of cellulose acetoacetate filaments, large‐scale RTP filaments are synthesized by introducing amino‐bearing luminophores via a mild enamine reaction. Attributed to efficient intersystem crossing facilitated by acetoacetyl and benzoyloxy groups alongside a rigid environment provided by multiple hydrogen bonding, the resulting filaments exhibit impressive RTP with a lifetime of 772 ms and a phosphorescence quantum yield of 45.06%. Furthermore, the afterglow color of RTP filaments is rationally modulated from blue to greenish‐yellow to rosy‐red through triplet‐to‐singlet Förster resonance energy transfer. Meanwhile, the formation of diverse clusters with comparable but different lifetimes leads to interesting excitation‐dependent afterglows. This work not only provides an effective strategy to construct long‐lived, color‐tunable, sustainable afterglows but also establishes large‐scale and continuous preparation routes for functional cellulose filaments. [ABSTRACT FROM AUTHOR]

Comprehensive Summary Chiral phosphorescent materials have received extensive research owing to the unique properties of optical activity in recent years. Many phosphorescent carbon dots (CDs) materials have been reported, but the research on chiral phosphorescence is still in the exploratory stage. This work designs multi‐color room temperature phosphorescent (RTP) CDs with chiral signals, which are fully mixed with aromatic aldehyde precursors and chiral amino compounds precursors in a boric acid (BA) matrix and can be easily prepared by solvent‐free thermal method. The prepared (R)‐GCDs, (R)‐YCDs and (R)‐RCDs achieved phosphorescence emission at 545 nm, 582 nm, and 654 nm, respectively, and exhibited corresponding circular dichroism (CD) signals at 341 nm, 394 nm, 384 nm, and 380 nm, 448 nm, and 435 nm, respectively. The longest phosphorescence lifetime is up to 946 ms. Specifically, YCDs exhibit time‐dependent phosphorescence under UV excitation, and the afterglow time under white light excitation can reach 40 s. This article provides a new approach to the study of chiral phosphorescence. [ABSTRACT FROM AUTHOR]

This article discusses the use of photoswitchable compounds, specifically azoheteroarenes, which can be switched between two isomers by light. The author presents their research on arylazopyrazoles, a type of azoheteroarene, and describes their discovery of compounds with high thermal stability and tunable properties. The article highlights the potential applications of these compounds in various fields, particularly in photopharmacology, where light-addressable drugs could be developed. Overall, the research suggests that azoheteroaryl photoswitches have significant potential for optically addressable applications. [Extracted from the article]

A novel lysosome-targeted photosensitizer/photoredox catalyst based on cyclometalated Ir(III) complex IrL has been designed and synthesized, which exhibited excellent phosphorescence properties and the ability to generate single oxygen (1O2) and photocatalytically oxidize 1,4-dihydronicotinamide adenine dinucleotide (NADH) under light irradiation. Most importantly, the aforementioned activities are significantly enhanced due to protonation under acidic conditions, which makes them highly attractive in light-activated tumor therapy, especially for acidic lysosomes and tumor microenvironments. The photocytotoxicity of IrL and the mechanism of cell death have been investigated. Additionally, the tumor-killing ability of IrL under light irradiation was evaluated using a 4T1 tumor-bearing mouse model. This work provides a strategy for the development of lysosome-targeted photosensitizers/photoredox catalysts to overcome hypoxic tumors. [ABSTRACT FROM AUTHOR]

The development of polymer‐based luminescent materials with efficient photoactivated ultralong organic phosphorescence (UOP) is of great importance but very challenging. Herein, a new class of organic phosphorescent luminogens is constructed by attaching phenyl rings and/or ethyl benzoates to the nitrogen atoms of a planar aromatic heterocycle pyrrolodiindole (PDI). The compounds show a significant elevation in phosphorescence emission capability after incorporating the ester group(s). However, they cannot produce room‐temperature phosphorescence in the crystalline state. These observations are identified to be associated with the formation of dimers and excimers and the motions of substituents within the molecules. In this context, the PDI derivatives are doped into epoxy polymers with compact and permanent 3D covalent networks. The resulting polymer films show reversible photoactivated UOP under ambient conditions, with quantum yields and lifetimes of up to 24.4% and 2.03 s, respectively, thereby enabling high‐quality and erasable light printing and multi‐level anti‐counterfeiting applications. In addition, they also exhibit excellent water and chemical resistance. This work is conducive to understanding the generation and decay mechanisms of the triplet excitons of organic luminophores with planar aromatic heterocycles in the crystalline state and provides a direction for the development of high‐performance photoactivated UOP materials. [ABSTRACT FROM AUTHOR]

Organic near‐infrared (NIR) room temperature phosphorescence (RTP) materials become a hot topic in bioimaging and biosensing for the large penetration depth and high signal‐to‐background ratio (SBR). However, it is challenging to achieve persistent NIR phosphorescence for severe nonradiative transitions by energy‐gap law. Herein, a universal system with persistent NIR RTP is built by visible (host) and NIR phosphorescence (guest) materials, which can efficiently suppress the nonradiative transitions by rigid environment of crystalline host materials with good matching, and further promote phosphorescence emission by the additional phosphorescence resonance energy transfer (≈100%) between them. The persistent NIR phosphorescence with ten‐folds enhancement of RTP lifetimes, compared to those of guest luminogens, can be achieved by modulation of aggregated structures of host–guest systems. This work provides a convenient way to largely prolong the phosphorescence lifetimes of various NIR luminogens, promoting their application in afterglow imaging with deeper penetration and higher SBRs. [ABSTRACT FROM AUTHOR]

Purely organic molecules with room‐temperature phosphorescence (RTP) are potential luminescent materials with high exciton utilization for organic light‐emitting diodes (OLEDs), but those exhibiting superb electroluminescence (EL) performances are rarely explored, mainly due to their long phosphorescence lifetimes. Herein, a robust purely organic RTP molecule, 3,6‐bis(5‐phenylindolo[3,2‐a]carbazol‐12(5H)‐yl)‐xanthen‐9‐one (3,2‐PIC‐XT), is developed. The neat film of 3,2‐PIC‐XT shows strong green RTP with a very short lifetime (2.9 μs) and a high photoluminescence quantum yield (72 %), and behaviors balanced bipolar charge transport. The RTP nature of 3,2‐PIC‐XT is validated by steady‐state and transient absorption and emission spectroscopies, and the working mechanism is deciphered by theoretical simulation. Non‐doped multilayer OLEDs using thin neat films of 3,2‐PIC‐XT furnish an outstanding external quantum efficiency (EQE) of 24.91 % with an extremely low roll‐off (1.6 %) at 1000 cd m−2. High‐performance non‐doped top‐emitting and tandem OLEDs are also achieved, providing remarkable EQEs of 24.53 % and 42.50 %, respectively. Delightfully, non‐doped simplified OLEDs employing thick neat films of 3,2‐PIC‐XT are also realized, furnishing an excellent EQE of 17.79 % and greatly enhanced operational lifetime. The temperature‐dependent and transient EL spectroscopies demonstrate the electrophosphorescence attribute of 3,2‐PIC‐XT. These non‐doped OLEDs are the best devices based on purely organic RTP materials reported so far. [ABSTRACT FROM AUTHOR]

Aggregation is a conventional method to enhance the quantum yields (QYs) of pure organic luminophores due to the restriction of intramolecular motions (RIM). However, how to realize RIM in metal–organic frameworks (MOFs) is still unclear and challenging. In this work, the ligand meta‐anchoring strategy is first proposed and proved to be an effective and systematic approach to restrict the intramolecular motions of MOFs for the QY improvement. By simply shifting the substituent position in the ligand from para to meta, the QY of the resulting MOF is significantly enhanced by eleven‐fold. The value is even higher than that of ligand aggregates, demonstrating the strong RIM effect of this ligand meta‐anchoring strategy. The introduction of co‐ligand induces the appearance of visible yellow room temperature phosphorescence with a lifetime of 222 ms due to the QY enhancement and the charge transfer between the donor and accepter units. The present work thus broadens the understanding of the RIM mechanism from a new perspective, develops a novel method to realize RIM and expands the applicable objects from pure organic materials to organic–inorganic hybrid materials. [ABSTRACT FROM AUTHOR]

Aliphatic quaternary ammonium salts (QASs) with intrinsic photoluminescence (PL) have drawn increasing attention due to the importance of exploring the mechanism of ionic emissive clusters, whereas it remains challenging to clarify structure–property relationships. Here, the effective modulation of photophysical properties of gemini aliphatic QASs (n‐BTADB) is managed by altering the alkyl chain length. Boosted quantum yields (up to 24.6%), prolonged phosphorescence lifetimes (up to 515.2 ms), and varied PL colors are achieved by manipulating the aggregation states of the compounds. Interlaced herringbone packing patterns and strong ionic interactions facilitate the intersystem crossing process and stabilize the triplets. The confluence of varied hydrophobic interactions and chain flexibility results in the fluctuation of phosphorescence lifetimes as the alkyl chain lengthens. Furthermore, the single‐component white‐light emission is obtained in 12‐HBTADB crystals by introducing electron‐rich hydroxyls. These results shed new light on the structure–property relationships of ionic emissive clusters and the rational design of nonconventional ionic luminophores. [ABSTRACT FROM AUTHOR]

This work presents a comprehensive study of the UV–Visible and fluorescence properties, as well as the redox behavior of the [AuIII(Salen)]Cl complex in acetonitrile. The [AuIII(Salen)]+ complex exhibited intriguing fluorescence and phosphorescence characteristics on an indium tin oxide (ITO)-coated glass plate when excited at wavelength λexc ~ 260 nm, with fluorescence emission observed at λems ~ 437 nm and phosphorescence at λems ~ 520 nm. The origin of fluorescence emission was attributed to the intra-ligand charge transfer effect, commonly known as the "Push–Pull" effect. The electrochemical behavior of [AuIII(Salen)]+ on a glassy carbon electrode (GCE) revealed a remarkable one-step three-electron reduction process, leading to the reduction of [AuIII(Salen)]+ to Au(0). Furthermore, the reduction of [AuI(Salen)]− to Au(0) resulted in the removal of gold metal from the SalenH2 ligand. The electrochemical results suggested a mixed diffusion-adsorption redox process occurring at the GCE surface, indicating the involvement of both diffusion and adsorption during redox reactions. The cyclic voltammogram demonstrated the non-reversibility of the electrochemical redox reactions. Overall, the redox behavior of the [AuIII(Salen)]Cl complex proved to be intriguing, opening up avenues for further exploration and potential applications of this complex in various fields. [ABSTRACT FROM AUTHOR]

Easy non-radiative decay property of long-lived triplet excitons in aqueous solution obstructs their applications in aquatic surroundings. Recently reported phosphorescence phenomena in aqueous solution have excited researchers enormously but achieving full-color water-soluble phosphorescent carbon nanodots (CNDs) is still a challenging issue. Herein, full-color phosphorescence of water-soluble CNDs has been demonstrated by triggering their triplet excitons through nanospace domain confinement, and Förster energy resonance transfer is used for further tuning phosphorescence range. The phosphorescence spans across most of the visible spectrum, ranging from 400 to 700 nm. In an aqueous solution, the CNDs exhibits blue, green, and red phosphorescence, lasting for approximately 6, 10, and 7 s, respectively. Correspondingly, the phosphorescence quantum yields are 11.85%, 8.6% and 3.56%, making them readily discernible to the naked eyes and laying a solid foundation for practical application. Furthermore, phosphorescence flexible optical display and bioimaging have been demonstrated by using the multicolor CNDs-based nanomaterials, showing distinct superiority for accuracy and complete display and imaging in complex emission background. [ABSTRACT FROM AUTHOR]

In this paper, we outline a physically motivated framework for describing spin-selective recombination processes in chiral systems, from which we derive spin-selective reaction operators for recombination reactions of donor–bridge–acceptor molecules, where the electron transfer is mediated by chirality and spin–orbit coupling. In general, the recombination process is selective only for spin-coherence between singlet and triplet states, and it is not, in general, selective for spin polarization. We find that spin polarization selectivity only arises in hopping-mediated electron transfer. We describe how this effective spin-polarization selectivity is a consequence of spin-polarization generated transiently in the intermediate state. The recombination process also augments the coherent spin dynamics of the charge separated state, which is found to have a significant effect on the recombination dynamics and to destroy any long-lived spin polarization. Although we only consider a simple donor–bridge–acceptor system, the framework we present here can be straightforwardly extended to describe spin-selective recombination processes in more complex systems. [ABSTRACT FROM AUTHOR]

Text: The novel photocatalyst OrPhC 2 Cu was developed by creatively converting the adsorbed oxygen on the surface of PhC 2 Cu into a functional Cu–O bond. It proves to be effective in promoting Cr(VI) photoreduction, as well as the photodegradation of pharmaceuticals and personal care products (PPCPs) and dyes. This effectiveness is attributed to its enhanced visible-light response, as well as the promotion of exciton dissociation and charge transfer. [Display omitted] The widespread contamination of hexavalent chromium (Cr(VI)), pharmaceuticals and personal care products (PPCPs), and dyes is a growing concern. necessitating the development of convenient and effective technologies for their removal. Copper(I) phenylacetylide (PhC 2 Cu) has emerged as a promising photocatalyst for environmental remediation. In this study, we introduced a functional Cu–O bond into PhC 2 Cu (referred to as OrPhC 2 Cu) by creatively converting the adsorbed oxygen on the surface of PhC 2 Cu into a Cu–O bond to enhance the efficiency of Cr(VI) photoreduction, PPCPs photodegradation, and dyes photodegradation through a facile vacuum activating method. The incorporation of the Cu–O bond optimized the electron structure of OrPhC 2 Cu, facilitating exciton dissociation and charge transfer. The exciton dissociation behavior and charge transfer mechanism were systematically investigated for the first time in the OrPhC 2 Cu system by photoelectrochemical tests, fluorescence and phosphorescence (PH) techniques, and density functional theory (DFT) calculations. Remarkably, the enhanced visible-light response of OrPhC 2 Cu improved photon utilization and significantly promoted the generation of reactive species (RSs), leading to the highly efficient Cr(VI) photoreduction (98.52% within 25 min) and sulfamethazine photodegradation (94.65% within 60 min), with 3.91 and 5.23 times higher activity compared to PhC 2 Cu. Additionally, the photocatalytic efficiency of OrPhC 2 Cu in degrading anionic dyes surpassed that of cationic dyes. The performance of the OrPhC 2 Cu system in treating electroplating effluent or natural water bodies suggests its potential for practical applications. [ABSTRACT FROM AUTHOR]

Over the last two decades, the low-valent compounds of group-14 elements have received significant attention in several fields of chemistry owing to their unique electronic properties. The low-valent group-14 species include tetrylenes, tetryliumylidene, tetrylones, dimetallenes and dimetallynes. These low-valent group-14 species have shown applications in various areas such as organic transformations (hydroboration, cyanosilylation, N-functionalisation of amines, and hydroamination), small molecule activation (e.g. P4, As4, CO2, CO, H2, alkene, and alkyne) and materials. This review presents an in-depth discussion on low-valent group-14 species-catalyzed reactions, including polymerization of rac-lactide, L -lactide, DL -lactide, and caprolactone, followed by their photophysical properties (phosphorescence and fluorescence), thin film deposition (atomic layer deposition and vapor phase deposition), and medicinal applications. This review concisely summarizes current developments of low-valent heavier group-14 compounds, covering synthetic methodologies, structural aspects, and their applications in various fields of chemistry. Finally, their opportunities and challenges are examined and emphasized. [ABSTRACT FROM AUTHOR]

Supramolecular organic framework (SOF) has recently garnered significant research interest in the field of luminescent materials. However, SOF with room‐temperature phosphorescence emission in solution is very rare due to the quenching of dissolved oxygen and free molecular motions, which would lead to nonradiative deactivation of triplet exciton in liquid state. In this work, a 3D cationic phosphorescent SOF is synthesized through host‐guest interaction between CB[8] and a tetrahedral monomer TBBP, which can rapidly adsorb anionic guests in solution. When anionic dyes are introduced, triplet to singlet Förster resonance energy transfer (TS‐FRET) in solution can be achieved, and delayed fluorescence with large Stokes shift can be realized. Additionally, when anionic drugs are introduced, the phosphorescence of TBBP‐CB[8] can be quenched due to charge transfer, enabling the detection of drugs through phosphorescence signals. Taking advantage of the fast adsorption property of 3D SOF, an INHIBIT logic gate with three inputs and two outputs is constructed. These findings provide a novel method to prepare phosphorescent functional materials and a new pathway to construct TS‐FRET system in solution. [ABSTRACT FROM AUTHOR]

This paper reports the discovery of a magnetophotoluminescence response in metallofullerene Y3N@C80 triggered by the triplet excited state. In experiments, Y3N@C80 exhibits magnetic field‐dependent (0→±42 T) phosphorescence emission at 4.2 K. Crucially, with increasing magnetic field, the phosphorescence peaks shift to longer wavelengths owing to the Zeeman effect. Further, a nanoring of [9]CPPH is employed to modulate the magnetophotoluminescence response of Y3N@C80 through host−guest interaction. The circularly polarized phosphorescence spectra of Y3N@C80 and Y3N@C80⊂[9]CPPH are investigated to further reveal their magnetophotoluminescence properties using the technique of field‐induced circular polarization (FICPO). These results show that metallofullerene Y3N@C80 with magnetophotoluminescence response has potential applications in spin‐related optical devices and quantum technology. [ABSTRACT FROM AUTHOR]

The document is the contents list for an issue of the journal Chemical Communications. It includes a range of articles on various topics, such as nanopesticides, molecular dynamics simulations, radical qubits, enzymatic activity, and electrochemical reactions. The journal is published by The Royal Society of Chemistry and aims to connect the world with the chemical sciences. The document provides a snapshot of the articles included in the issue, allowing library patrons to quickly identify relevant research topics. [Extracted from the article]

Ice has been suggested to have played a significant role in the origin of life partly owing to its ability to concentrate organic molecules and promote reaction efficiency. However, the techniques for studying organic molecules in ice are absorption‐based, which limits the sensitivity of measurements. Here we introduce an emission‐based method to study organic molecules in water ice: the phosphorescence displays high sensitivity depending on the hydration state of an organic salt probe, acridinium iodide (ADI). The designed ADI aqueous system exhibits phosphorescence that can be severely perturbed when the temperature is higher than 110 K at a concentration of the order of 10−5 M, indicating changes in hydration for ADI. Using the ADI phosphorescent probe, it is found that the microstructures of water ice, i.e., crystalline vs. glassy, can be strongly dictated by a trace amount (as low as 10−5 M) of water‐soluble organic molecules. Consistent with cryoSEM images and temperature‐dependent Raman spectral data, the ADI is dehydrated in more crystalline ice and hydrated in more glassy ice. The current investigation serves as a starting point for using more sensitive spectroscopic techniques for studying water‐organics interactions at a much lower concentration and wider temperature range. [ABSTRACT FROM AUTHOR]

Long‐lived room temperature phosphorescence (RTP) materials have many potential applications in areas such as luminescent lighting, biological imaging, and information security owing to their unique optical properties. However, traditional RTP materials are challenged by the fact that their phosphorescence can be easily quenched by dissolved oxygen and solvent‐assisted relaxation, making it difficult for them to emit phosphorescence in aqueous solutions, particularly in extreme pH environments. In this study, a multicolor RTP carbon dot‐based composite material (u‐CDs) is developed with urea and 3‐aminophenylboronic acid as raw materials. This material exhibits ultra‐long phosphorescence emission lifetime and high pH stability by constructing a rigid hydrogen bond network structure in an aqueous environment. The u‐CDs have an optimal emission of 448 nm, a quantum yield of 21.6%, a phosphorescence lifetime of 2.35 s, and an afterglow time of more than 50 s. With such unique properties, u‐CDs have great potential for applications in anti‐counterfeiting, information encryption, and 3D printing. [ABSTRACT FROM AUTHOR]

Photoactivated dynamic ultralong room‐temperature phosphorescent (PAD‐URTP) materials with changing emission colors are attractive and meaningful but are rarely reported. Herein, a one‐pot heat treatment strategy for embedding 1‐hydroxy‐2‐naphthoic acid (1H2NA) and 2‐hydroxy‐1‐naphthoic acid (2H1NA) into boric acid (BA) matrix (named 1H2NA@BA and 2H1NA@BA) to construct PAD‐URTP materials is developed, which exhibits rapid and reversible photoactivated phosphorescence, as well as photo‐stimulated dynamic change of luminescence color. The luminescent color of 1H2NA@BA could continuously change from blue‐purple to bright cyan‐white upon prolonged 365 nm UV light irradiation, which is attributed to the combined effect of static blue fluorescence and dynamic photoactivated green phosphorescence. Significantly, it could emit over 10 s green afterglow after switching off the UV irradiation. The combination of experiment and theoretical calculation results reveal that their PAD‐URTP behavior is attributed to the energy accumulation of triplet states under UV light irradiation. Finally, a series of information encryption and a complete story of "a mouse and cake" are successfully fabricated by using 1H2NA@BA with other luminescence materials. Thus, this study demonstrates fast PAD‐URTP materials with dynamic color‐changing luminescence and opens up new possibilities as the photo‐responsive luminescent material for further mechanistic understanding and future application. [ABSTRACT FROM AUTHOR]

The synthesis of group 4 metal 1‐metallacyclobuta‐2,3‐dienes as organometallic analogues of elusive 1,2‐cyclobutadiene has so far been limited to SiMe3 substituted examples. We present the synthesis of two Ph substituted dilithiated ligand precursors for the preparation of four new 1‐metallacyclobuta‐2,3‐dienes [rac‐(ebthi)M] (M=Ti, Zr; ebthi=1,2‐ethylene‐1,10‐bis(η5‐tetrahydroindenyl)). The organolithium compounds [Li2(RC3Ph)] (1 b: R=Ph, 1 c: R=SiMe3) as well as the metallacycles of the general formula [rac‐(ebthi)M(R1C3R2)] (2 b: M=Ti, R1=R2=Ph, 2 c: M=Ti, R1=Ph, R2=SiMe3; 3 b: M=Zr, R1=R2=Ph; 3 c: M=Zr, R1=Ph, R2=SiMe3) were fully characterised. Single crystal X‐ray diffraction and quantum chemical bond analysis of the Ti and Zr complexes reveal ligand influence on the biradicaloid character of the titanocene complexes. X‐band EPR spectroscopy of structurally similar Ti complexes [rac‐(ebthi)Ti(Me3SiC3SiMe3)] (2 a), 2 b, and 2 c was carried out to evaluate the accessibility of an EPR active triplet state. Cyclic voltammetry shows that introduction of Ph groups renders the complexes easier to reduce. 13C CPMAS NMR analysis provides insights into the cause of the low field shift of the resonances of metal‐bonded carbon atoms and provides evidence of the absence of the β−C−Ti interaction. [ABSTRACT FROM AUTHOR]

Luminescent materials with narrowband emission show great potential for diverse applications in optoelectronics. Purely organic phosphors with room-temperature phosphorescence (RTP) have made significant success in rationally manipulating quantum efficiency, lifetimes, and colour gamut in the past years, but there is limited attention on the purity of the RTP colours. Herein we report a series of closed-loop molecules with narrowband phosphorescence by multiple resonance effect, which significantly improves the colour purity of RTP. Phosphors show narrowband phosphorescence with full width at half maxima (FWHM) of 30 nm after doping into a rigid benzophenone matrix under ambient conditions, of which the RTP efficiency reaches 51.8%. At 77 K, the FWHM of phosphorescence is only 11 nm. Meanwhile, the colour of narrowband RTP can be tuned from sky blue to green with the modification of methyl groups. Additionally, the potential applications in X-ray imaging and display are demonstrated. This work not only outlines a design principle for developing narrowband RTP materials but also makes a major step forward extending the potential applications of narrowband luminescent materials in optoelectronics. Luminescent materials with narrowband emissions are vital for optoelectronic applications. Here, the authors achieve room temperature phosphorescence with a FWHM of 30 nm through the multiple resonance effect and showcase its practical application in X-ray imaging. [ABSTRACT FROM AUTHOR]

In this work, two new biscyclometalated Ir(III) complexes with diimine ligands were synthesized. The compounds were characterized by 1D and 2D NMR spectroscopy and HR ESI mass spectrometry. All complexes exhibit efficient phosphorescence with pronounced sensitivity to the presence of oxygen. The photophysical properties of the obtained compounds, including absorption, emission spectra, lifetimes and quantum yields of phosphorescence were measured in various aqueous and model biological media with variations in pH, temperature and at various O2 concentrations. The complexes exhibit a very good sensory response to the changes in oxygen concentration, resulting in an increase in quantum yields and lifetimes by 2.8–5.5 times upon oxygen removal from aerated aqueous solutions. Biological tests with CHO‐K1 cell line have shown that these compounds display low toxicity, rapid internalization into cells and localization predominantly in lysosomes. For the most promising complex the phosphorescence lifetime imaging experiments were conducted, revealing that this sensor markedly changes the phosphorescence lifetime values in cells from 1.8 to 4.1 μs upon transition from normoxia to simulated hypoxia. The obtained results indicate that this type of iridium chromophores can be effectively used for assessing the oxygen status of living objects by using time‐resolved luminescent microscopy. [ABSTRACT FROM AUTHOR]

Recently, stimulus‐responsive organic materials with room‐temperature phosphorescence (RTP) properties have attracted significant attention owing to their potential applications in chemical sensing, anticounterfeiting, and displays. However, molecular design currently lacks systematicity and effectiveness. Herein, we report a capture‐release strategy for the construction of reversible RTP via B/N Lewis pairs. Specifically, the RTP of the Lewis acid of 7‐bromo‐5,9‐dioxa‐13b‐boranaphtho[3,2,1‐de]anthracene (BrBA) can be deactivated through capturing by the Lewis base, N,N‐diphenyl‐4‐(pyridin‐4‐yl)aniline (TPAPy), and reactivated by dissociation of B−N bonds to release BrBA. Reversible RTP is attributed to the exceptional self‐assembly capability of BrBA, whereas the tunable RTP colors are derived from distinct Förster resonance energy transfer (FRET) processes. The potential applications of RTP materials in information storage and anti‐counterfeiting were also experimentally validated. The capture‐release approach proposed in this study offers an effective strategy for designing stimulus‐responsive materials. [ABSTRACT FROM AUTHOR]

Organic room temperature phosphorescent (ORTP) materials with stimuli-responsive, multicomponent emissive behaviour are extremely desirable for various applications. The derivative of cyclic triimidazole (TT) functionalized with an ethynyl group, TT-CCH, is isolated and investigated. The compound possesses crystallization-enhanced emission (CEE) comprising dual fluorescence and dual phosphorescence of both molecular and supramolecular origin with aggregation-induced components highly sensitive to grinding. The mechanisms involved in the emissions have been disclosed thanks to combined structural, spectroscopic and computational investigations. In particular, strong CH⋯N hydrogen bonds are deemed responsible, for the first time in the TT family, together with frequently observed π⋯π stacking interactions, for the aggregated fluorescence and phosphorescence. [ABSTRACT FROM AUTHOR]

The thermally activated delayed fluorescence (TADF) or phosphorescence‐sensitized organic light‐emitting diodes (OLEDs) based on multi‐resonance TADF (MR‐TADF) emitters are greatly studied to develop an effective narrowband emitting system for wide color gamut display applications. However, developing pure green OLEDs to meet BT2020 and NTSC requirements is challenging. In this study, we investigated the TADF and phosphorescence‐sensitized OLEDs based on two green MR‐TADF final emitters, namely, BpIC‐DPA and BpIC‐Cz. The unique molecular structure of these emitters resulted in a pure green emission with narrow full width at half‐maximum (FWHM) and high PLQY in both solution and solid state. Notably, under optimal conditions, the BpIC‐Cz‐based OLEDs demonstrated a maximum external quantum efficiency (EQEmax) of 25.7% with alleviated efficiency roll‐off characteristics even at high luminescence (EQE5000 nits = 22.6%). The corresponding CIE coordinates are almost at the level of BT2020 and NTSC green‐color industrial standards. Additionally, the BpIC‐Cz‐based device displayed remarkable stability as seen by a noticeably longer device lifetime (LT90) of 25.3 h at a high initial luminance of 5000 nits. [ABSTRACT FROM AUTHOR]

Based on the explosive nature and harmful effects of nitro-based explosive materials on living beings and the environment, it is extremely important to develop luminescence-based probe molecules for their detection with excellent selectivity and sensitivity. Two AIPE (aggregation-induced phosphorescence emission)-active iridium(III) complexes (M1 and M2) were developed for the sensitive detection of TNT in both contact and non-contact modes. The aggregate solutions of both complexes (M1 and M2 in THF/H2O, 1/9 by volume) detected TNT at the pico-molar (pM) level. These complexes showed greatly enhanced emission intensity while embedded in a PMMA(polymethyl methacrylate) matrix film. The amplified quantum efficiency, improved phosphorescence lifetime, and enhanced porous network of M2-PMMA composite helps to improve the sesitivity of TNT vapor detection. Interestingly, the sensitivity of the detection of TNT by the M2 complex was significantly improved (5-fold) in a PMMA-incorporated complex (CP) with an observed limit of detection (LOD) of 12.8 ppb. From the BET analysis of CP, it was observed that the mesoporous network of CP has an average pore diameter of 8.52 nm and a surface area of 2.03 m2 g−1. The porous network of CP assists in trapping TNT vapor in a polymeric network containing an electron-rich probe (iridium(III) complex, M2), which helps to effectively trap TNT, thus enhancing electronic communication. As a result, significant emission quenching was observed. [ABSTRACT FROM AUTHOR]

This document summarizes the research conducted by Dr. Yang Qin and his team on the design and synthesis of Pt(II)-bisacetylide-containing molecules for use in organic solar cells (OSCs). The researchers propose a new structural design called "roller wheels" that enhances π-π interactions and potentially improves device performance. They successfully synthesize three different "roller wheel" compounds and demonstrate their potential for use in OSCs. The researchers also optimize the construction of bulk heterojunction devices using different solution concentrations, spin-casting conditions, annealing temperature, and duration. They achieve power conversion efficiencies of 5.9% and 3.9% with two of the compounds. The document provides a summary of the researchers' findings and the potential applications of their work. [Extracted from the article]

The kinetics of spin-selective reactions involving triplet molecules, such as triplet–triplet annihilation or electron transfer to dioxygen molecules in the ground triplet spin state, are strongly dependent on the dipole–dipole interaction (DDI) of electron spins in spin-1 particles. The effect of this interaction on the intersystem crossing in the reaction encounter complex of the paramagnetic particles was previously considered for some particular cases using oversimplified approaches. In this study, we consider a rigorous kinetic model of the irreversible reaction between the spin-1/2 and spin-1 particles in an encounter complex with the reactive doublet state. This model explicitly includes both isotropic exchange coupling of the reactants and spin dependence of the reaction rate in the form of the Haberkorn reaction term. For the time-independent DDI, an analytical expression for the reaction kinetics was derived. The effect of DDI fluctuations was analyzed using numerical simulations. It was found that increasing both the exchange coupling and the reaction rate constants can significantly slow down the quartet–doublet spin transitions and, as a consequence, the observed spin-selective reaction rate. Additionally, the presence of the irreversible reaction in the doublet states affects a coherent evolution in the non-reactive quartet subsystem. [ABSTRACT FROM AUTHOR]

In this work, we investigated bonding features of 15 ruthenium(II) nitrile complexes of the type [Ru(tpy)(L)-(CH3CN)]n+, containing the tridentate tpy ligand (tpy = 2,2′:6′,2″-terpyridine) and various bidentate ancillary ligands L; 12 compounds originally synthesized by Loftus et al. [J. Phys. Chem. C 123, 10291–10299 (2019)] and three new complexes. We utilized local vibrational force constants derived from the local mode theory as a quantitative measure of bond strength complemented with the topological analysis of the electron density and the natural bond orbital analysis. Loftus et al. suggested that nitrile dissociation occurs after light induced singlet–triplet transition of the original complexes and they used as a measure of nitrile release efficiency quantum yields for ligand exchange in water. They observed larger quantum yields for complexes with smaller singlet–triplet energy gaps. The major goal of this work was to assess how the Ru–NC and Ru–L bond strengths in these 15 compounds relate to and explain the experimental data of Loftus et al., particularly focusing on the question whether there is a direct correlation between Ru–NC bond strength and measured quantum yield. Our study provides the interesting result that the compounds with the highest quantum yields also have the strongest Ru–NC bonds suggesting that breaking the Ru–NC bond is not the driving force for the delivery process rather than the change of the metal framework as revealed by first results of a unified reaction valley approach investigation of the mechanism. Compounds with the highest quantum yield show larger electronic structure changes upon singlet–triplet excitation, i.e., larger changes in bond strength, covalency, and difference between the singlet and triplet HOMOs, with exception of the compound 12. In summary, this work provides new insights into the interplay of local properties and experimental quantum yields forming in synergy a useful tool for fine tuning of existing and future design of new nitrile releasing ruthenium compounds. We hope that this work will bring theoretical and experimental studies closer together and serves as an incubator for future collaboration between computational chemists and their experimental colleagues. [ABSTRACT FROM AUTHOR]

In this work, we perform variational calculations of two-electron reduced density matrices corresponding to open-shell N-electron systems within the framework of the doubly occupied configuration interaction treatment, traditionally limited to studies of closed-shell systems. This has allowed us to provide a satisfactory description of molecular systems in triplet states following two methods. One of them adds hydrogen atoms at an infinite distance of the triplet system studied, constituting a singlet supersystem. The energies and reduced density matrices of the triplet system are obtained by removing the contributions of the added atoms from the singlet supersystem results. The second procedure involves variational determination of the two-electron reduced density matrices corresponding to the triplet systems by means of adequate couplings of basis-set functions. Both models have been studied by imposing N-representability conditions on the reduced density matrix calculations. Results obtained from these methods for molecular systems in triplet ground states are reported and compared with those provided by benchmark methods. [ABSTRACT FROM AUTHOR]

The specific states of aggregation of metal atoms in sub‐nanometer‐sized gold clusters are related to the different quantum confinement volumes of electrons, leading to novel optical and electronic properties. These volumes can be tuned by changing the relative positions of the gold atoms to generate isomers. Studying the isomeric gold core and the electron coupling between the basic units is fundamentally important for nanoelectronic devices and luminescence; however, appropriate cases are lacking. In this study, the structure of the first staggered di‐superatomic Au25‐S was solved using single‐crystal X‐ray diffraction. The optical properties of Au25‐S were studied by comparing with eclipsed Au25‐E. From Au25‐E to Au25‐S, changes in the electronic structures occurred, resulting in significantly different optical absorptions originating from the coupling between the two Au13 modules. Au25‐S shows a longer electron decay lifetime of 307.7 ps before populating the lowest triplet emissive state, compared to 1.29 ps for Au25‐E. The experimental and theoretical results show that variations in the geometric isomerism lead to distinct photophysical processes owing to isomerism‐dependent electronic coupling. This study offers new insights into the connection between the geometric isomerism of nanosized building blocks and the optical properties of their assemblies, opening new possibilities for constructing function‐specific nanomaterials. [ABSTRACT FROM AUTHOR]

Information leakage and counterfeiting are serious worldwide issues that tremendously impact legitimate businesses and human life. Inspired by the Noctiluca scintillans, a new fluorescence‐afterglow dual‐modal information encryption enabled by precisely coordination‐modulated ultralong organic phosphorescence (UOP) is presented. Strikingly, the optical properties including fluorescence, lifetime and intensity of UOP can be precisely modulated on‐demand through energy transfer by lanthanide (LnIII) coordination, which enables information camouflage by similar LnIII luminescence to provide misleading information along with data decryption in the form of mutual afterglow. Moreover, the important data can be encrypted in a spatial‐time‐resolved way by programmatically coding information with afterglow gradients, yielding greatly improved security for verifying the authenticity. This study provides a new avenue to precisely modulate the optical properties of UOP materials and broadens the scope of optical materials for innovative information encryption and anticounterfeiting applications. [ABSTRACT FROM AUTHOR]

In this work, full‐color and stable white organic afterglow materials with outstanding water, organic solvents, and temperature resistances have been developed for the first time by embedding the selected polycyclic aromatic hydrocarbons into melamine‐formaldehyde polymer via solution polymerization. The afterglow quantum yields and lifetimes of the resulting polymer films were up to 22.7 % and 4.83 s, respectively, under ambient conditions. For the coronene‐doped sample, its afterglow color could be linearly tuned between yellow and blue by adjusting the temperature, and it could still emit an intense blue afterglow with a lifetime of 0.68 s at 440 K. Moreover, the films showed a bright and stable white afterglow at 370 K with a lifetime of 2.80 s and maintained an excellent afterglow performance after soaking in water and organic solvents for more than 150 days. In addition, the application potential of the polymer films in information encryption and anti‐counterfeiting was also demonstrated. [ABSTRACT FROM AUTHOR]

Molecular emitters with multi‐emissive properties are in high demand in numerous fields, while these properties basically depend on specific molecular conformation and packing. For amorphous systems, special molecular arrangement is unnecessary, but it remains challenging to achieve such luminescent behaviors. Herein, we present a general strategy that takes advantage of molecular rigidity and S1‐T1 energy gap balance for emitter design, which enables fluorescence–phosphorescence dual‐emission properties in various solid forms, whether crystalline or amorphous. Subsequently, the amorphism of the emitters based polymethyl methacrylate films endowed an in situ regulation of the dual‐emissive characteristics. With the ratiometric regulation of phosphorescence by external stimuli and stable fluorescence as internal reference, highly controllable luminescent color tuning (yellow to blue including white emission) was achieved. There properties together with a persistent luminous behavior is of benefit for an irreplaceable set of optical information combination, featuring an ultrahigh‐security anti‐counterfeiting ability. Our research introduces a concept of eliminating the crystal‐form and molecular‐conformational dependence of complex luminescent properties through emitter molecular design. This has profound implications for the development of functional materials. [ABSTRACT FROM AUTHOR]

Colloidal carbon dots (C‐dots) are considered as promising heavy‐metal‐free materials to achieve room‐temperature phosphorescence (RTP) properties for promising applications, such as photoelectronic devices, information encryption, and bio‐imaging. However, most of the current obtained RTP C‐dots have a short lifetime with a relatively low quantum yield (QY). In this work, the C‐dots large‐scale synthesized via a vacuum heating approach have multiple RTP emissions (blue, green, and yellow), a long RTP lifetime of as high as 1.92 s, and a high QY of 34.4% by selecting different types of precursors, which is superior to most of reported RTP C‐dots. The multiple atoms doping and strong bonding between neighbored C‐dots promoted by vacuum heating contributes to the excellent RTP properties. As a proof‐of‐concept, the as‐obtained RTP C‐dots are used as optical ink for flexible security codes, exhibiting a bright shape with a lifetime of 1.37 s. This work offers an efficient approach for producing large‐scale high‐quality RTP C‐dots, which can be applied to anti‐counterfeiting and information encryption systems. [ABSTRACT FROM AUTHOR]

The effects of halide ligands on the photoluminescence (PL) and photoredox properties were examined on [IrAu12(dppe)5X2]+ (1X; X=Cl, Br, I; dppe=1,2‐bis(diphenylphosphino)ethane). The PL quantum yield was enhanced in the order of 1Cl (67 %)<1Br (75 %)<1I (77 %). The lifetime of the photoexcited state was shortened in the order of 1Cl>1Br>1I due to the acceleration of radiative relaxation by the heavy atom effect in 1I. Despite the shortest PL lifetime, cluster 1I exhibited the highest conversion in the photocatalytic [2+2] cycloaddition of bisenone. The PL from 1Cl and 1Br was quenched by adding Lewis acid Li+, required for activation of bisenone, whereas that from 1I remained unaffected. Theoretical calculations showed that the Au−Cl and Au−Br bonds of 1Cl and 1Br were weakened by interaction with Li+, while the Au−I bond of 1I was not. Clusters 1Cl and 1Br underwent halide exchange with isocyanide in the presence of Li+, whereas 1I did not. These results suggested that the photoredox activity of 1Cl and 1Br was suppressed by the Li+‐induced nonradiative quenching of the photoexcited state. This study highlights the unexpected importance of halide ligands in the design of efficient cluster photocatalysts. [ABSTRACT FROM AUTHOR]

In current approaches for circularly polarized phosphorescent materials, the crystallization of chiral phosphors suffers from poor processability, while integrating them into an amorphous polymer matrix results in unsatisfactory chiroptical signals due to the absence of chirality communication. Here, we have developed an innovative strategy through chiral supramolecular polymerization of benzil phosphors facilitated by intermolecular hydrogen bonds. The inherent film‐forming capabilities of non‐covalent supramolecular polymers obviate the need for an external polymer matrix. The pronounced helical asymmetry of benzil phosphors resulting from chiral supramolecular polymerization leads to enhanced circularly polarized phosphorescence compared to their non‐hydrogen‐bonded counterparts. The circularly polarized phosphorescent signals can be further modulated by varying the location of stereogenic centers or introducing halogen bonding to benzils. Incorporation of platinum(II) phosphor into the benzil supramolecular polymers induces both chirality and triplet‐to‐triplet energy transfer, leading to a change in circularly polarized phosphorescent color from yellow to red. In summary, chiral supramolecular polymerization of phosphors represents a novel and effective approach to circularly polarized phosphorescent materials. [ABSTRACT FROM AUTHOR]

Triplet dynamics in singlet fission depend strongly on the strength of the electronic coupling. Covalent systems in solution offer precise control over such couplings. Nonetheless, efficient free triplet generation remains elusive in most systems, as the intermediate triplet pair 1(T1T1) is prone to triplet‐triplet annihilation due to its spatial confinement. In the solid state, entropically driven triplet diffusion assists in the spatial separation of triplets, resulting in higher yields of free triplets. Control over electronic coupling in the solid state is, however, challenging given its sensitivity to molecular packing. We have thus developed a hexameric system (HexPnc) to enable solid‐state‐like triplet diffusion at the molecular scale. This system is realized by covalently tethering three pentacene dimers to a central subphthalocyanine scaffold. Transient absorption spectroscopy, complemented by theoretical structural optimizations and steady‐state spectroscopy, reveals that triplet diffusion is indeed facilitated due to intramolecular cluster formation. The yield of free triplets in HexPnc is increased by a factor of up to 14 compared to the corresponding dimeric reference (DiPnc). Thus, HexPnc establishes crucial design aspects for achieving efficient triplet dissociation in strongly coupled systems by providing avenues for diffusive separation of 1(T1T1), while, concomitantly, retaining strong interchromophore coupling which preserves rapid formation of 1(T1T1). [ABSTRACT FROM AUTHOR]

We previously reported a cyclic Zn(II) porphyrin trimer in which three Zn porphyrins are alternately bridged by three 2,2′‐bipyridine (bpy) moieties, enabling the encapsulation of metal complexes within the nanopore formed by the Zn porphyrins. In this study, we introduced a [Re(CO)3Br] fragment into one of the bpy moieties of the cyclic trimer to form the catalytic Re(4,4'‐R2‐bpy)(CO)3Br center (R=methyl ester). The ester groups (R) play an important role in the synthesis of the cyclic structure. However, it was observed that these ester groups significantly deactivated the photocatalytic CO2 reduction reaction. Therefore, we converted the ester groups with a suitable reducing reagent into hydroxymethyl groups, followed by acetylation to form acetoxymethyl groups. This modification remarkably enhanced the photocatalytic activity of the cyclic trimer=Re complex system for CO2 reduction. Moreover, in the modified system, the presence of the Re complex induced room‐temperature phosphorescence of the Zn porphyrin. The phosphorescence was significantly quenched by 1,3‐dimethyl‐2‐phenyl‐2,3‐dihydro‐1H‐benzo[d]imidazole, indicating that efficient electron transfer mediated by the excited triplet state of the Zn porphyrin occurs during the photocatalytic CO2 reduction. [ABSTRACT FROM AUTHOR]

The photoluminescence spectra of the dominant H3 and H4 centers in a natural diamond sample, which is preliminarily characterized by optical and infrared spectrophotometry, are excited by femtosecond laser pulses with a wavelength of 470 nm and varying intensity. Saturation of the photoluminescence intensity of the H3 and H4 centers normalized by the intensity of laser radiation is observed and attributed to the saturation of the resonance transition responsible for the excitation. This makes it possible for the first time to estimate the absorption cross sections of H3 and H4 centers, which can be compared with values known from the literature and those determined from photoluminescence kinetics. The total concentration of H3 and H4 centers can then be found. Taking into account the known absorption coefficient of the sample at a wavelength of 470 nm and the previously established ratio of the contributions from H3 and H4 centers, their concentrations have been estimated separately for the first time. [ABSTRACT FROM AUTHOR]

The development of metal halides that enable multiple information storage and cryptographic security is highly desirable but remains a challenge. Here, a pair of 0D Zn(II) metal halide enantiomers ZnCl2·R/S‐2‐MP with excitation wavelength‐dependent emission and room temperature phosphorescence properties are reported. Organic ligands via N─H···Cl hydrogen bonding induce structural chirality. In order to stabilize the triplet state exciton and achieve excellent photophysical properties, the organic ligands combine with halogens to promote emission. The differences between the photophysical properties of ZnCl2·R‐2‐MP and ZnCl2·S‐2‐MP are analyzed in depth. Furthermore, combined with femtosecond transient absorption (fs‐TA) results, the long phosphorescence lifetimes may originate from the triplet state emission due to the synergistic effect between the organic components and the inorganic metal halides. The design strategy of advanced multiple anticounterfeiting technology is further extended. [ABSTRACT FROM AUTHOR]

Living system involves a plenty of delicate processes where a tiny structural variation of biological substance may lead to drastic change of the fate of the living system. Inspired by this, in artificial photofunctional systems, if tiny structural variation changes the fate of excited states, a new class of advanced material would emerge for optical analysis, sensing, and next‐generation display is reasoned. However, such delicate processes remain rarely explored in photofunctional systems, especially in room temperature organic afterglow systems. Here the attachment/detachment of methoxy group can switch off/on twisted intramolecular charge transfer property in difluoroboron β‐diketonate systems is reported. In addition, structural isomerization triggers afterglow transformation from room temperature phosphorescence to thermally activated delayed fluorescence. These observations are helpful for better photophysical understanding on luminescence systems and advanced material design. [ABSTRACT FROM AUTHOR]

Room temperature phosphorescent carbon dots (RTP CDs) have received increasing attention in recent years due to their outstanding optical properties and potential applications. It is worth noting that RTP CDs in aqueous solution have inspired special interests because of their low toxicity, long lifetime, and ability to avoid autofluorescence and background fluorescence, exhibiting wide application prospects in time‐resolved biological imaging and sensing. However, achieving phosphorescent CDs in aqueous solutions remains a considerable challenge because water molecules and oxygen can cause the deactivation of triplet‐state excitons, resulting in phosphorescence quenching. Several strategies have been proposed to counter the problem including encapsulated CDs in a rigid matrix, hydrogen bonding, and covalent bonding fixation. Consequently, a more significant number of RTP CDs materials with excellent optical stability, long lifetime, and multicolor are successfully obtained. Herein, the recent development of RTP CDs materials in aqueous solution as well as the corresponding fabricated strategies and luminescence mechanism is detailly summarized and reviewed. Furthermore, various applications of water‐phase RTP CDs materials in information security, sensing, bioimaging, light‐emitting diodes, and fingerprinting are also discussed. Finally, an outlook on the development of CDs materials and applications is proposed. [ABSTRACT FROM AUTHOR]

The mechanism of aggregation-induced emission (AIE) for the bis(1-(2,4-difluorophenyl)-1H-pyrazole)(2-(20-hydroxyphenyl)-2-oxazoline)iridium(III) complex, denoted as Ir(dfppz)2(oz), was investigated with use DFT and the TD-DFT level of theory. The mechanism of radiationless deactivation of the triplet state was elucidated. Such a mechanism requires an additional, photophysical triplet channel of the internal conversion (IC) type, which is activated as a result of intramolecular motion deforming the structure of the oz ligand and distorting the iridium coordination sphere. Formally, the rotational movement of the oxazoline relative to the C–C bond in the oz ligand is the main active coordinate that leads to the opening of the triplet channel. The rotation of the oxazoline group and the elongation of the Ir-Nox bond cause a transition between the luminescent, low-lying triplet state with a d / π → π * characteristic ( T 1 (eq) ), and the radiationless d → d triplet state ( T 1 (Ir) ). This transition is made possible by the low energy barrier, which, based on calculations, was estimated at approximately 8.5 kcal/mol. Dimerization, or generally aggregation of the complex molecules, blocks the intramolecular movement in the ligand and is responsible for a strong increase in the energy barrier for the T 1 (eq) ⇝ T 1 (Ir) conversion of triplet states. Thus, the aggregation phenomenon blocks the nonradiative deactivation channel of the excited states and, consequently, contributes to directing the photophysical process toward phosphorescence. The mechanism involved in locking the nonradiative triplet path can be called restricted access to singlet–triplet crossing (RASTC). [ABSTRACT FROM AUTHOR]

Supramolecular systems demonstrating resonance energy transfer have recently became a topical area on the borderline of supramolecular chemistry, photochemistry, photophysics and biology. The modularity of supramolecular interactions is a prerequisite for fine tuning of optical properties, which is difficult to achieve by other means. As a component of such systems, cucurbit[n]uril (CB[n]) macrocycles can play a wide spectrum of roles from anchoring of FRET pairs and modulation of the optical output to providing biocompatibility of FRET stains for cell imaging. The aim of this Review is to outline the development of the CB[n]‐based systems with fluorescence (FRET) and phosphorescence (TS‐FRET) energy transfer and to highlight achievements, challenges and perspectives of this fascinating combination of a classical photophysical process and a classical supramolecular host. Particular attention in this Review is given to the current and potential applications of the reviewed systems. [ABSTRACT FROM AUTHOR]

Based on the (differential) Encounter theory developed in the literature, which describes the change in the internal quantum states of particles encountered in liquid dilute solutions due to stochastic (diffusion) molecular motion, closed kinetic equations for the temporal change in the concentration of free radicals recombining at encounters were obtained. The recombination rates from singlet and triplet states are often different, the recombination products from these states may also be different, i.e., the recombination process is spin-selective. The radical spins experience any quantum spin interactions including Zeeman interaction with external magnetic fields and hyperfine couplings with magnetic nuclei and the processes of longitudinal and transverse spin relaxation. In general, recombination can occur both from singlet and triplet states. The rates of such recombination are not limited by the traditional contact model, implying that recombination occurs only at the radicals contact, and, like any spin interactions, are not assumed to be spherically symmetric. Under these general conditions, an unambiguous relationship has been established between the bulk recombination rate constant and the recombination yields of the corresponding geminate reaction from the singlet and triplet states. In the particular case of the same spatial dependence of the rates of singlet and triplet recombination, the rate constant can be expressed only through the singlet recombination yield for a singlet precursor or through the triplet recombination yield for a triplet precursor, despite the fact that recombination occurs from both spin states. The particular case of spherically symmetric recombination probability of the freely diffusing radical pairs in liquid solution, which is the most common one in the literature, is also considered. [ABSTRACT FROM AUTHOR]

This work was aimed at the complex analysis of the metabolic and oxygen statuses of tumors in vivo after photodynamic therapy (PDT). Studies were conducted on mouse tumor model using two types of photosensitizers—chlorin e6-based drug Photoditazine predominantly targeted to the vasculature and genetically encoded photosensitizer KillerRed targeted to the chromatin. Metabolism of tumor cells was assessed by the fluorescence lifetime of the metabolic redox-cofactor NAD(P)H, using fluorescence lifetime imaging. Oxygen content was assessed using phosphorescence lifetime macro-imaging with an oxygen-sensitive probe. For visualization of the perfused microvasculature, an optical coherence tomography-based angiography was used. It was found that PDT induces different alterations in cellular metabolism, depending on the degree of oxygen depletion. Moderate decrease in oxygen in the case of KillerRed was accompanied by an increase in the fraction of free NAD(P)H, an indicator of glycolytic switch, early after the treatment. Severe hypoxia after PDT with Photoditazine resulted from a vascular shutdown yielded in a persistent increase in protein-bound (mitochondrial) fraction of NAD(P)H. These findings improve our understanding of physiological mechanisms of PDT in cellular and vascular modes and can be useful to develop new approaches to monitoring its efficacy. [ABSTRACT FROM AUTHOR]

A series of luminescent Cu4I4 clusters with stair-step, cubane, and octahedral geometries supported by a novel type of cyclic As,N-ligand, pyridyl-containing 10-phenoxarsines, were synthesized and characterized by NMR spectroscopy, mass spectrometry, elemental analysis, and single-crystal X-ray diffraction analysis. An unusual arrangement of As,N-bidentate and μ2-iodo ligands was found in the octahedral cluster. The structural diversity of the Cu(I) complexes is reflected in their photophysical properties: the phosphorescence spectra of the compounds display emission in a broad spectral range of 495–597 nm. The complex with the Cu4I4L2 stoichiometry bearing a stair-step Cu4I4 core demonstrates temperature-dependent dual emission. The luminescence properties of all complexes were rationalized by DFT calculations. [ABSTRACT FROM AUTHOR]