Host-Guest Chemistry and Light Driven Molecular Lock of Ru(bpy)3-Viologen with Cucurbit[7-8]urils

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• 作者：Shiguo Sun ; Rong Zhang ; Samir Andersson ; Jingxi Pan ; Dapeng Zou ; Bj&ouml ; rn Å ; kermark ; Licheng Sun
• 刊名：Journal of Physical Chemistry B
• 出版年：2007
• 出版时间：November 29, 2007
• 年：2007
• 卷：111
• 期：47
• 页码：13357 - 13363
• 全文大小：223K
• 年卷期：v.111,no.47(November 29, 2007)
• ISSN：1520-5207

文摘

Host-guest chemistry and photoinduced electron-transfer processes have been studied in the systems containingRu(bpy)₃ complex covalently linked to viologen as a guest molecule and cucurbit[n]urils (n = 7, 8) as hostmolecules in aqueous solution. The Ru(bpy)₃-viologen complex, [Ru(2,2'-bipyridine)₂(4-(4-(1'-methyl-4,4'-bipyridinediium-1-yl)butyl)-4'-methyl-2,2'-bipyridine)]Cl₄ (denoted as Ru²⁺-MV²⁺, 1) was shown to formstable 1:1 inclusion complexes with cucurbit[7]uril (CB[7]) and cucurbit[8]uril (CB[8]). The binding modesare slightly different with CB[7] and CB[8]. CB[7] preferentially binds to part of the viologen residue in 1together with the butyl chain, whereas CB[8] preferentially encloses the whole viologen residue. Photoinducedintramolecular electron transfer from the excited-state of the Ru moiety to MV²⁺ which is inserted into thecavity of the CBs occurred. Long-lived charge-separated states Ru³⁺-MV⁺ were generated with the lifetimesof 280 ns with CB[7] and 2060 ns with CB[8]. This shows that CBs can slow down the charge recombinationwithin supramolecular systems, and the difference in lifetimes seems to be due to the difference in bindingmodes. In the presence of a sacrificial electron donor triethanolamine, light-driven formation of a dimer ofMV⁺ inside the CB[8] cavity was observed. This "locked" molecular dimer can be "unlocked" by molecularoxygen to give back the original form of the molecular dyad 1 with the MV²⁺ moiety inserted in the cavityof CB[8]. The processes could be repeated several times and showed nice reversibility.