A molecular crystal with an unprecedentedly long-lived photoexcited state
A molecular crystal with an unprecedentedly long-lived photoexcited state
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具有前所未有的长寿命光激发态的分子晶体
DOI：
10.1039/c9dt02377a
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发表时间：
2019
影响因子：
4
通讯作者：
Sawa Hiroshi
中科院分区：
文献类型：
--
作者：
Naito Toshio;Watanabe Naoki;Sakamoto Yuuka;Miyaji Yuuko;Shirahata Takashi;Misaki Yohji;Kitou Shunsuke;Sawa Hiroshi
新合成的配合物BPY[Au（dmit）2]2（BPY = N，N′-亚乙基-2，2 ′-联吡啶，dmit = 1，3-二硫杂环戊烯-2-正-4，5-二硫纶）中的Au（III）配合阴离子在紫外光照射下在固态下可逆地表现出分子畸变.光激发态在298 K下维持一周，在此期间分子松弛到其原始结构，能量逐渐释放为热量，而不分解或发光。大多数Au原子采用正方形平面（SP）配位几何构型，但一些阴离子具有不寻常的非平面（NP）配位几何构型，这在Au位点处产生无序。系统的总（吉布斯）能取决于NP几何构型的Au原子的比例，其通过X射线衍射法由占有率（Occ（%））直接确定。由于相变，Occ在280 K的临界温度（TC）下发生显著变化，而没有其他结构变化;然而，它在每个相中几乎保持恒定。此外，由于BPY和Au（dmit）2之间的UV促进的电荷转移跃迁，可以通过UV照射（λ 250-450 nm）来控制Occ。紫外激发态具有前所未有的长弛豫时间（t1/2 > 36 h，298 K），这归因于电荷，自旋和分子结构的自由度之间的密切联系。
The Au(III)-complex anions in a newly synthesised compound BPY[Au(dmit)2]2 (BPY = N,N′-ethylene-2,2′-bipyridinium, dmit = 1,3-dithiole-2-thione-4,5-dithiolate) reversibly exhibit a molecular distortion in the solid state under UV-radiation. The photoexcited state is maintained for a week at 298 K, during which time molecules relax to their original structures and energy is gradually released as heat without decomposition or light emission. Most Au atoms adopt square planar (SP) coordination geometries, but some anions have unusual non-planar (NP) coordination geometries that produce disorder at the Au sites. The total (Gibbs) energy of the system depends on the proportion of Au atoms of NP geometry, which is directly determined from the occupancy (Occ (%)) by X-ray diffractometry. Due to phase transition, Occ substantially changes at a critical temperature (TC) of ∼280 K without other structural changes; however it remains almost constant in each phase. In addition, due to UV-promoted charge-transfer transitions between BPY and Au(dmit)2, Occ can be controlled by UV irradiation (∼250–450 nm). The UV-excited states have unprecedentedly long relaxation times (t1/2 > 36 h at 298 K), which is attributed to the close connection between the degrees of freedom on charge, spin, and molecular structures.