Liu Zong-Ying, Hu Jiun-Wei, Huang Chun-Hao, Huang Teng-Hsing, Chen Deng-Gao, Ho Ssu-Yu, Chen Kew-Yu, Li Elise Y, Chou Pi-Tai
Department of Chemistry , National Taiwan University , Taipei , 10617 Taiwan , Republic of China.
Department of Chemical Engineering , Feng Chia University , Taichung , 40724 Taiwan , Republic of China.
J Am Chem Soc. 2019 Jun 26;141(25):9885-9894. doi: 10.1021/jacs.9b02765. Epub 2019 Jun 17.
We report O-H----S hydrogen-bond (H-bond) formation and its excited-state intramolecular H-bond on/off reaction unveiled by room-temperature phosphorescence (RTP). In this seminal work, this phenomenon is demonstrated with 7-hydroxy-2,2-dimethyl-2,3-dihydro-1 H-indene-1-thione (DM-7HIT), which possesses a strong polar (hydroxy)-dispersive (thione) type H-bond. Upon excitation, DM-7HIT exhibits anomalous dual RTP with maxima at 550 and 685 nm. This study found that the lowest lying excited state (S) of DM-7HIT is a sulfur nonbonding (n) to π* transition, which undergoes O-H bond flipping from S(nπ*) to the non-H-bonded S'(nπ*) state, followed by intersystem crossing and internal conversion to populate the T'(nπ*) state. Fast H-bond on/off switching then takes place between T'(nπ*) and T(nπ*), forming a pre-equilibrium that affords both the T'(nπ*, 685 nm) and T(nπ*, 550 nm) RTP. The generality of the sulfur H-bond on/off switching mechanism, dubbed a molecule wiper, was rigorously evaluated with a variety of other H-bonded thiones, and these results open a new chapter in the chemistry of hydrogen bonds.
我们报道了通过室温磷光（RTP）揭示的O-H----S氢键（H键）形成及其激发态分子内H键的开/关反应。在这项开创性工作中，用7-羟基-2,2-二甲基-2,3-二氢-1H-茚-1-硫酮（DM-7HIT）证明了这一现象，它具有强极性（羟基）-色散（硫酮）型H键。激发后，DM-7HIT表现出异常的双重RTP，最大发射波长分别为550和685nm。该研究发现，DM-7HIT的最低激发态（S）是硫的孤对电子（n）到π跃迁，经历O-H键从S（nπ）翻转到非H键合的S'（nπ*）态，随后发生系间窜越和内转换以填充T'（nπ*）态。然后在T'（nπ*）和T（nπ*）之间快速进行H键的开/关切换，形成一个预平衡，产生T'（nπ*，685nm）和T（nπ*，550nm）的RTP。用多种其他H键合硫酮对被称为分子擦拭器的硫H键开/关切换机制的普遍性进行了严格评估，这些结果开启了氢键化学的新篇章。
