ChemPhotoChem最新文献

The Front Cover illustrates the photophysical relaxation mechanisms of archetypal aromatic/antiaromatic molecules, starting from low-energy excited states, and their rationalisation in terms of electronic descriptors that allow quantifying the extent to which the formation of biradicaloid structures affects the crossing of the potential energy surfaces. More information can be found in the Research Article by Jesús Jara-Cortés et al. (DOI 10.1002/cptc.202300291).

Hot exciton emitters based on 9,10-substituted anthracenes are a well-investigated class of molecules featuring thermally activated delayed fluorescence (TADF). TADF converts triplet excitons into singlet excitons and improves the internal quantum efficiency of electroluminescent devices to performance beyond the limit of spin-statistics of conventional emitters. In this paper, we compare different 1,8-functionalized donor/acceptor-substituted anthracenes and compare these to established 9,10-functionalized hot exciton emitters. Interestingly, our new 1,8-substituted anthracenes make use of a beneficial hot exciplex pathway, resulting in improved emission characteristics and higher photoluminescence quantum yield.

The electronic structure and photophysical properties of several acrylaldehyde-bridged deazaflavin derivatives (cFLs) were investigated theoretically. The impact of acrylaldehyde bridging on photophysical properties of deazaflavin (cFL) is strongly site-dependent. Specifically, the change of adiabatic energy of electronic transitions(ΔE_ad) and vibronic coupling promote fluorescent emission to be comparable to internal conversion of cFL and cFL4 (both C5−C6 and C9−N10 bridged, but C9−N10 bridged by propene), turning them eligible as fluorescent sensors. As El-Sayed's rule is satisfied in cFL1(C5−C6 bridged), cFL2(C9−N10 bridged) and cFL3(both C5−C6 and C9−N10 bridged), intersystem crossing from first singlet excited state to triplet excited states (T_n) become dominant and the evolution of excited cFLs from T₁ appears vital. The rate constants of photophysical processes indicate these cFLs are of dominantly high steady state T₁ concentration and are potential triplet sensitizers. We expect the findings would pave the way for rational design of novel cFLs with extraordinary photophysical properties.

Luminescent metal halides, as a type of luminescent semiconductor material, offer advantages that fulfill the requirements of emerging light source devices, such as high luminescence efficiency, good thermal stability, and tunable colorful emission. Blue light being one of the three primary colors plays a crucial role in the field of lighting and colorful displays. However, the progress in device performance of blue-light materials lags behind that of green and red-light materials. Currently, there have been numerous reports on metal halide perovskite blue-light materials, but a comprehensive review on the development and performance control of blue-light metal halides is yet to be found. This paper provides a comprehensive summary of the design strategies and luminescence mechanisms of blue-light perovskites with various luminescence centers, as well as their application progress in the fields of light-emitting diodes (LEDs), X-ray scintillators, information anti-counterfeiting and encryption. It also explores possible directions for subsequent performance improvement. This work aims to offer valuable insights and recommendations for the future development of blue-light metal halides, with significant implications for the fabrication of novel blue light devices and advancements in detection technology.

Norbornadiene/Quadricyclane (NBD/QC) is a prototypical bridged bicyclic diene (BBD)-based photoswitch that has been well-studied for molecular solar thermal energy storage (MOST). Inspired by the recent synthetically accessed BBDs, herein several photoswitches are rationally designed with modulated ring strain energies (RSE) in photoisomers to incorporate high energy storage density (ESD) and storage time in a single couple. The storage energy ($$) calculated at DLPNO-CCSD(T)/Def2TZVP level is correlated with difference in RSE of two isomers (ΔRSE) whereas thermal back reaction (TBR) barrier calculated at (8,8)-CASPT2/6-311++G** shows correlation with RSE in metastable photoproduct. On the basis of these structure-property-RSE relationships, we recognized that two photoisomers need not to be highly strained. Instead, the RSE in the photoproduct and diene should be minimized while maintaining a large enthalpy difference between them to increase ESD and extend energy storage times in a single photoswitch. TBR barrier is governed by RSE in photoproduct and increasing strain in photoproduct may improve the $$ but at the cost of the TBR barrier. Herein, the structural skeletons are explored that holds promise to remarkably improve thermochemical properties relative to the unsubstituted BBD-based photoswitches reported so far. The BBD molecules with short saturated bridge length but elongated unsaturated bridges could bestow desirable thermochemical parameters and can be regarded as excellent candidates for MOST application. The work lays a theoretical foundation that guides to improve thermochemical properties via strain engineering of BBD-based photoswitches and opens a new avenue for designing principles and future experimental investigations of MOST systems.

Organic materials possessing multiple functional properties such as aggregation induced emission, mechanochromism and acidochromism are rare. In this paper we demonstrate the design of polyfunctional materials using the aggregation quenching chromophore, pyrene. The pyrene derivatives possessing 2,3,3-triphenylacrylonitrile as aggregation induced emission chromophore and phenanthroimidazole or N-phenylcarbazole as auxiliary electron-rich chromophore are designed, synthesized by Suzuki coupling reactions and characterized as aggregation induced emissive mechanochromic materials. Though all the dyes exhibit aggregation induced emission, the dyes containing para-linked 2,3,3-triphenylacrylonitrile and auxiliary chromophore such as phenanthroimidazole or N-phenylcarbazole display mechanochromism. Additionally, the phenanthroimidazole containing dyes show acidochromism attributable to the protonation of phenanthroimidazole moiety.

Two regioisomeric extended tetrathiafulvalenes (TTFs) incorporating diindeno-fused corannulene spacers were synthesized from suitable dione precursors using Horner-Wadsworth-Emmons olefination reactions. Both compounds are strong chromophores with a longest-wavelength absorption that exhibited some degree of charge-transfer character as inferred from solvatochromic behaviors and frontier orbital calculations. The compounds underwent two reversible one-electron oxidations and a quasi-reversible third oxidation during cyclic voltammetry conditions. The mono- and dications had characteristic NIR absorptions and both were EPR active. The dications with potential diradicaloid characters underwent reactions when generated in bulk.

Miniaturization of organic afterglow materials has shown promising application in biomedical and other areas. Current technologies, such as nanoprecipitation, mechanical treatment, and emulsion polymerization, lack the capability of facile control on the morphology and dimension of the miniaturized organic afterglow materials. Here we report the fabrication of organic afterglow nanostructures via block copolymer self-assembly at room temperature. The fabrication is based on two-component design strategy where hydrophobic luminescent emitters with small rate constants of phosphorescence decay or reverse intersystem crossing are designed as the first component. Amphiphilic block copolymers that can form spherical core-shell micelles and worm-like micelles with glassy hydrophobic cores are used as the second component. Upon addition of water into a dimethylformamide solution that contains the two components, the amphiphilic block copolymers self-assemble into well-defined nanostructures and accommodate the hydrophobic luminescent emitters in nanostructure's hydrophobic cores. After switching to pure water by dialysis, room-temperature afterglow nanostructures have been obtained because of the excellent protection of organic triplets by the glassy hydrophobic cores. The afterglow nanostructures exhibit intriguing afterglow mechanism modulated by the types of luminescent emitters, controlled dimensions and morphologies by the structural parameters of the block copolymers.

The reactivity of Cannabigerol (CBG, 1) in organic solvents under photochemical and acid catalyzed conditions has been investigated in detail. The obtained results pointed out the presence of different reaction paths in the photochemical and the acid-catalyzed conditions, with a remarkable selectivity toward the formation of a 2,2-disubstituted-chromane derivative in the first case.

Metal mixed-halide perovskite has demonstrated considerable potential in the development of solution-treated blue light-emitting diodes (LEDs) with high external quantum efficiency, excellent color purity, and tunable wavelength. However, the severe phase segregation of mixed-halide perovskite under bias voltage would lead to the spectral instability of LEDs. Therefore, suppressing phase segregation of Br/Cl perovskite towards spectrally stable blue perovskite LEDs (PeLEDs) is a big challenge. In this work, we systematically explore the influence of perovskite component, preparation conditions, and device structures on the spectral stability of PeLEDs. We have observed that the stable spectra increased the proportion of Cs in the A-site cations, passivator, and the annealing temperature of perovskite films. Finally, we achieve a spectra-stable and high-performance blue PeLED under optimized conditions. Our findings provide important guidance for preparing spectrally stable PeLEDs.