Acharya Nirmalya, Dey Suvendu, Deka Raktim, Ray Debdas
Advanced Photofunctional Materials Laboratory, Department of Chemistry, Shiv Nadar University, Delhi NCR, NH-91, Gautam Buddha Nagar, Tehsil Dadri, Uttar Pradesh 201314, India.
ACS Omega. 2022 Jan 21;7(4):3722-3730. doi: 10.1021/acsomega.1c06390. eCollection 2022 Feb 1.
Dual-room-temperature phosphorescence (DRTP) from organic molecules is of utmost importance in chemical physics. The Dexter-type triplet-to-triplet energy transfer mechanism can therefore be used to achieve DRTP at ambient conditions. Here, we report two donor-acceptor (D-A)-based guests (, ) in which the donor (D) and acceptor (A) parts are held in angular orientation around the C-N single bond. Spectroscopic analysis along with computational calculations revealed that both guests are incapable of emitting either thermally activated delayed fluorescence (TADF) or RTP at ambient conditions due to large singlet-triplet gaps, which are presented to show host (benzophenone, BP)-sensitized DRTP multiple intermolecular triplet-to-triplet energy transfer (TTET) channels that originate from the triplet state (T ) of BP to the triplet states (T , T ) of the D and A parts (TTET-I:T → T ; TTET-II:T → T ). In addition, an intramolecular TTET channel that occurs from the T to T states of the D and A parts of is also activated due to the low triplet (T )-triplet (T ) gap at ambient conditions. The efficiency of TTET processes was found to be 100%. The phosphorescence quantum yields (ϕ) and lifetimes (τ) were shown to be 13-20% and 0.48-0.55 s, respectively. Given the high lifetime of the DRTP feature of both host-guest systems (1000:1 molar ratio), a data security application is achieved. This design principle provides the first solid proof that DRTP radiative decay of the dark triplet states of the D and A parts of D-A-based non-TADF systems is possible, revealing a method to increase the efficiency and lifetime of DRTP.
有机分子的双室温磷光（DRTP）在化学物理中至关重要。因此，德克斯特型三重态到三重态能量转移机制可用于在环境条件下实现DRTP。在此，我们报道了两种基于供体-受体（D-A）的客体（，），其中供体（D）和受体（A）部分围绕C-N单键呈角向排列。光谱分析以及计算结果表明，由于单重态-三重态能隙较大，两种客体在环境条件下均无法发射热激活延迟荧光（TADF）或室温磷光（RTP），呈现出主体（二苯甲酮，BP）敏化的DRTP，存在多个分子间三重态到三重态能量转移（TTET）通道，这些通道源自BP的三重态（T）到D和A部分的三重态（T，T）（TTET-I：T→T；TTET-II：T→T）。此外，由于环境条件下单重态（T）-三重态（T）能隙较低，还激活了一种分子内TTET通道，该通道发生在的D和A部分的T到T态之间。发现TTET过程的效率为100%。磷光量子产率（ϕ）和寿命（τ）分别显示为13 - 20%和0.48 - 0.55秒。鉴于两种主客体体系（摩尔比为1000:1）的DRTP特征具有较长的寿命，实现了数据安全应用。这一设计原理首次确凿证明基于D-A的非TADF体系的D和A部分的暗三重态的DRTP辐射衰变是可能的，揭示了一种提高DRTP效率和寿命的方法。
