Harvesting Fluorescence from Efficient Tk 鈫?Sj (j, k > 1) Reverse Intersystem Crossing for 蟺蟺* Emissive Transition-Metal Complexes

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• 作者：Yuh-Chia Chang ; Kuo-Chun Tang ; Hsiao-An Pan ; Igor O. Koshevoy ; Antti J. Karttunen ; Pi-Tai Chou
• 刊名：Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：October 10, 2013
• 年：2013
• 卷：117
• 期：40
• 页码：20494-20499
• 全文大小：321K
• 年卷期：v.117,no.40(October 10, 2013)
• ISSN：1932-7455

文摘

Using a bimetallic Au(I) complex bearing alkynyl-(phenylene)₃-diphosphine ligand (A-3), we demonstrate that the fluorescence can be exquisitely harvested upon T₁ 鈫?T_k (k > 1) excitation followed by T_k 鈫?S_j (j, k > 1) intersystem crossing (ISC) back to the S₁ state. Upon S₀ 鈫?S₁ 355 nm excitation, the S₁ 鈫?T₁ intersystem crossing rate has been determined to be 8.9 脳 10⁸ s^鈥?. Subsequently, in a two-step laser pump鈥損robe experiment, following a 355 nm laser excitation, the 532 nm T₁ 鈫?T_k probing gives the prominent blue 375 nm fluorescence, and this time-dependent pump鈥損robe signal correlates well with the lifetime of the T₁ state. Careful examination reveals the efficiency of T_k 鈫?S_j (j, k > 1) reverse intersystem crossing to be 5.2%. The result is rationalized by a mechanism incorporating substantial involvement of metal-to-ligand charge transfer (MLCT) in the T_k (S_j) states, enhancing the rate of T_k 鈫?S_j ISC, which is competitive with the rate of T_k 鈫?T₁ internal conversion. This mechanism is also proven to be operative in the A-3 solid film and should be universally applicable to the transition-metal complexes possessing a dominant 蟺蟺* configuration in the lowest-lying states. From an energy point of view, the UV fluorescence (375 nm) generated by green (532 nm) excitation can be recognized as a signal up-conversion process.