Purely Organic Room-Temperature Phosphorescence Endowing Fast Intersystem Crossing from Through-Space Spin–Orbit Coupling
Ontology highlight
ABSTRACT:
SUBMITTER: Yu J
PROVIDER: S-EPMC8549040 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:The development of efficient organic light-emitting diodes (OLED) and organic photovoltaic cells requires control over the dynamics of spin sensitive excitations. Embedding heavy metal atoms in ?-conjugated polymer chains enhances the spin-orbit coupling (SOC), and thus facilitates intersystem crossing (ISC) from the singlet to triplet manifolds. Here we use various nonlinear optical spectroscopies such as two-photon absorption and electroabsorption in conjunction with electronic structure calculations, for studying the energies, emission bands and ultrafast dynamics of spin photoexcitations in two newly synthesized ?-conjugated polymers that contain intrachain platinum (Pt) atoms separated by one (Pt-1) or three (Pt-3) organic spacer units. The controllable SOC in these polymers leads to a record ISC time of <~1?ps in Pt-1 and ~6?ps in Pt-3. The tunable ultrafast ISC rate modulates the intensity ratio of the phosphorescence and fluorescence emission bands, with potential applications for white OLEDs.
| S-EPMC3772376 | biostudies-literature
Project description:Currently, organic phosphorescent particles are heavily used in sensing and imaging. Up to now, most of these particles contain poisonous and/or expensive metal complexes. Environmentally friendly systems are therefore highly desired. A purely amorphous system consisting of poly(methyl methacrylate) particles with incorporated N,N,N',N'-tetrakis(4-carboxyphenyl)benzidine emitter molecules is presented in this work. Single particles with sizes between 400 and 840 nm show-depending on the environment-bright fluorescence and phosphorescence. The latter is observed when oxygen is not in the proximity of the emitting dye molecules. These particles can scavenge singlet oxygen, which is produced during the photoexcitation process, by incorporating it into the polymer matrix. This renders their use to be unharmful for the surrounding matter with possible application in marking schemes for living bodies.
| S-EPMC8158833 | biostudies-literature
Project description:The persistent room-temperature phosphorescence (RTP) of purely organic materials in the solid state has recently attracted much research interest and found promising, rapid and visual applications by the naked eye, after the removal of the excitation source. However, almost all reported organic persistent RTP processes are induced by using a UV-light irradiation source. In this report, persistent RTP with an emission lifetime as long as 0.15 s which can be induced not only by photoirradiation but also by mechanical action is presented, which merges mechano-induced luminescence and persistent RTP together. It is found that such persistent RTP is produced through intermolecular electronic coupling (IEC) of units with different excited state configurations. Interestingly, there are two different crystals with and without mechano-induced persistent RTP which can be grown from this organic material, as such a new type of mechano-luminescence (ML) is strongly dependent on their intermolecular interactions. Furthermore, the intensity of such mechano-induced persistent RTP can be increased by lowing the temperature as well, similar to that of photo-induced persistent RTP. Notably, these two crystals exhibit a ML enhancement and ML "turn on", respectively, with decreasing temperature. Therefore, such mechano-induced persistent RTP provides an example of new types of organic luminescent materials, which is a missing jigsaw piece of organic luminescence and important for both fundamental research and practical applications of both persistent RTP and ML of organic materials.
| S-EPMC5939606 | biostudies-literature
Project description:Purely organic room temperature phosphorescence (RTP) has attracted wide attention recently due to its various application potentials. However, ultralong RTP (URTP) with high efficiency is still rarely achieved. Herein, by dissolving 1,8-naphthalic anhydride in certain organic solid hosts, URTP with a lifetime of over 600?ms and overall quantum yield of over 20% is realized. Meanwhile, the URTP can also be achieved by mechanical excitation when the host is mechanoluminescent. Femtosecond transient absorption studies reveal that intersystem crossing of the host is accelerated substantially in the presence of a trace amount of 1,8-naphthalic anhydride. Accordingly, we propose that a cluster exciton spanning the host and guest forms as a transient state before the guest acts as an energy trap for the RTP state. The cluster exciton model proposed here is expected to help expand the varieties of purely organic URTP materials based on an advanced understanding of guest/host combinations.
| S-EPMC6856348 | biostudies-literature
Project description:The host-guest doping system has aroused great attention due to its promising advantage in stimulating bright and persistent room-temperature phosphorescence (RTP). Currently, exploration of the explicit structure-property relationship of bicomponent systems has encountered obstacles. In this work, two sets of heterocyclic isomers showing promising RTP emissions in the solid state were designed and synthesized. By encapsulating these phosphors into a robust phosphorus-containing host, several host-guest cocrystalline systems were further developed, achieving highly efficient RTP performance with a phosphorescence quantum efficiency (ϕ P) of ∼26% and lifetime (τ P) of ∼32 ms. Detailed photophysical characterization and molecular dynamics (MD) simulation were conducted to reveal the structure-property relationships in such bicomponent systems. It was verified that other than restricting the molecular configuration, the host matrix could also dilute the guest to avoid concentration quenching and provide an external heavy atom effect for the population of triplet excitons, thus boosting the RTP performance of the guest.
| S-EPMC8528018 | biostudies-literature
Project description:We prepared conceptually novel, fully rigid, spiro compact electron donor (Rhodamine B, lactam form, RB)/acceptor (naphthalimide; NI) orthogonal dyad to attain the long-lived triplet charge-transfer (3 CT) state, based on the electron spin control using spin-orbit charge transfer intersystem crossing (SOCT-ISC). Transient absorption (TA) spectra indicate the first charge separation (CS) takes place within 2.5 ps, subsequent SOCT-ISC takes 8 ns to produce the 3 NI* state. Then the slow secondary CS (125 ns) gives the long-lived 3 CT state (0.94 μs in deaerated n-hexane) with high energy level (ca. 2.12 eV). The cascade photophysical processes of the dyad upon photoexcitation are summarized as 1 NI*→1 CT→3 NI*→3 CT. With time-resolved electron paramagnetic resonance (TREPR) spectra, an EEEAAA electron-spin polarization pattern was observed for the naphthalimide-localized triplet state. Our spiro compact dyad structure and the electron spin-control approach is different to previous methods for which invoking transition-metal coordination or chromophores with intrinsic ISC ability is mandatory.
| S-EPMC7496792 | biostudies-literature
Project description:Orthogonal phenoxazine-styryl BODIPY compact electron donor/acceptor dyads were prepared as heavy atom-free triplet photosensitizers (PSs) with strong red light absorption (ϵ=1.33×105 M-1 cm-1 at 630 nm), whereas the previously reported triplet photosensitizers based on the spin-orbit charge transfer intersystem crossing (SOCT-ISC) mechanism show absorption in a shorter wavelength range (<500 nm). More importantly, a long-lived triplet state (τT =333 μs) was observed for the new dyads. In comparison, the triplet state lifetime of the same chromophore accessed with the conventional heavy atom effect (HAE) is much shorter (τT =1.8 μs). Long triplet state lifetime is beneficial to enhance electron or energy transfer, the primary photophysical processes in the application of triplet PSs. Our approach is based on SOCT-ISC, without invoking of the HAE, which may shorten the triplet state lifetime. We used bisstyrylBodipy both as the electron acceptor and the visible light-harvesting chromophore, which shows red-light absorption. Femtosecond transient absorption spectra indicated the charge separation (109 ps) and SOCT-ISC (charge recombination, CR; 2.3 ns) for BDP-1. ISC efficiency of BDP-1 was determined as ΦT =25 % (in toluene). The dyad BDP-3 was used as triplet PS for triplet-triplet annihilation upconversion (upconversion quantum yield ΦUC =1.5 %; anti-Stokes shift is 5900 cm-1 ).
| S-EPMC7383670 | biostudies-literature
Project description:Organic luminogens with persistent room temperature phosphorescence (RTP) have attracted great attention for their wide applications in optoelectronic devices and bioimaging. However, these materials are still very scarce, partially due to the unclear mechanism and lack of designing guidelines. Herein we develop seven 10-phenyl-10H-phenothiazine-5,5-dioxide-based derivatives, reveal their different RTP properties and underlying mechanism, and exploit their potential imaging applications. Coupled with the preliminary theoretical calculations, it is found that strong π-π interactions in solid state can promote the persistent RTP. Particularly, CS-CF3 shows the unique photo-induced phosphorescence in response to the changes in molecular packing, further confirming the key influence of the molecular packing on the RTP property. Furthermore, CS-F with its long RTP lifetime could be utilized for real-time excitation-free phosphorescent imaging in living mice. Thus, our study paves the way for the development of persistent RTP materials, in both the practical applications and the inherent mechanism.
| S-EPMC5826932 | biostudies-literature
Project description:Organic luminogens with room temperature phosphorescence (RTP) have been paid great attention and developed rapidly for their wide application values. Until now, the internal mechanism and source of phosphorescence are still obscure, especially for the relationship between molecular dimer and RTP emission. Hence, we designed and synthesized eight phenothiazine 5,5-dioxide derivatives to directly reveal how the monomer and dimer in packing affect the RTP behavior. Dimers with strong π-π stacking (θ < 20.66°; d < 3.86 Å) lead to pure triplet excimer emission, while those with weak π-π stacking (27.02°< θ < 40.64°; 3.84 Å < d < 4.41 Å) contribute to dual RTP emissions of both monomer and triplet excimer. The valuable information of this work would promote the further development of this research field, as well as others in aggregate.
| S-EPMC9114335 | biostudies-literature
Project description:We present a detailed investigation into the excited state properties of a planar D3h symmetric azatriangulenetrione, HTANGO, which has received significant interest due to its high solid-state phosphorescence quantum yield and therefore potential as an organic room temperature phosphorescent (ORTP) dye. Using a model linear vibronic coupling Hamiltonian in combination with quantum dynamics simulations, we observe that intersystem crossing (ISC) in HTANGO occurs with a rate of ∼1010 s-1, comparable to benzophenone, an archetypal molecule for fast ISC in heavy metal free molecules. Our simulations demonstrate that the mechanism for fast ISC is associated with the high density of excited triplet states which lie in close proximity to the lowest singlet states, offering multiple channels into the triplet manifold facilitating rapid population transfer. Finally, to rationalize the solid-state emission properties, we use quantum chemistry to investigate the excited state surfaces of the HTANGO dimer, highlighting the influence and importance of the rotational alignment between the two HTANGO molecules in the solid state and how this contributes to high phosphorescence quantum yield.
| S-EPMC10867843 | biostudies-literature