Deciphering Spin-Governed Dual Emissions in TTM Diradicaloids: Unraveling the Interplay of Singlet and Triplet Fluorescence Pathways

作者：Zekun Tong, Shuo Zhang, Weiwei Niu, Tao Yu, Xinfang Zhang, Penglei Yao, Jinfeng Wang, Yibo Han, Guangwu Li, Shaoqiang Dong · 发表于：Journal of the American Chemical Society · 年份：2025 · DOI：10.1021/jacs.5c10608 · 被引用次数：18 · 研究领域：Molecular Junctions and Nanostructures、Magnetism in coordination complexes、2D Materials and Applications

The photophysical mechanisms governing luminescent diradicals, particularly the interplay between their singlet and triplet emissions, remain incompletely understood. Herein, we report three luminescent radicals, monoradical MTA and diradical DTA and DTA( t -Bu) 2, based on a tris(2,4,6-trichlorophenyl)methyl (TTM) scaffold. Experimental results and DFT calculations demonstrated the dual emission mechanism of two diradicaloids with distinct S 1 → S 0 (first excited singlet state to singlet ground state) and T 1 → T 0 (first excited triplet state to triplet ground state) fluorescent radiative pathways, while monoradical MTA shows only doublet emission with a D 1 → D 0 (first excited doublet state to doublet ground state) fluorescent radiative pathway. Varying-temperature electron spin resonance measurements revealed the singlet ground state and thermal accessible triplet ground state of DTA and DTA( t -Bu) 2, with Δ E S–T values of −0.33 and −0.35 kcal/mol, respectively. Boltzmann population analysis based on the Δ E S–T values reveals the coexistence of singlet and triplet states at 298 K, with the S 0 state predominating at 63.6% for DTA and 64.4% for DTA( t -Bu) 2, while the corresponding T 0 state populations are 36.4% and 35.6%, respectively. Moreover, two diradicaloids exhibit maximum magnetoluminescence phenomena near 100 K, reflecting the synergistic interplay of thermal energy and magnetic-field-induced S 0 → T 0 spin conversion. Notably, temperature-dependent photolu...