Temperature-Dependent Conformational Change of meso-Hexakis(pentafluorophenyl) [28]Hexaphyrins(1.1.1.1.1.1) into Mbius Structures
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- 作者：Kil Suk Kim ; Zin Seok Yoon ; Annie Butler Ricks ; Jae-Yoon Shin ; Shigeki Mori ; Jeyaraman Sankar ; Shohei Saito ; Young Mee Jung ; Michael R. Wasielewski ; Atsuhiro Osuka ; Dongho Kim
- 刊名：Journal of Physical Chemistry A
- 出版年：2009
- 出版时间：April 23, 2009
- 年：2009
- 卷：113
- 期：16
- 页码：4498-4506
- 全文大小：320K
- 年卷期：v.113,no.16(April 23, 2009)
- ISSN：1520-5215
文摘
At room temperature, meso-hexaaryl-substituted [28]hexaphyrins(1.1.1.1.1.1) in solution exist largely as an equilibrium between planar antiaromatic and distorted Mbius aromatic conformers. As the temperature decreases, the molecular structure changes into the distorted Mbius topology that commonly occurs in [28]hexaphyrins, which gives rise to longer excited singlet and triplet state lifetimes than planar antiaromatic [28]hexaphyrins. Temperature-dependent two-photon absorption measurements of [28]hexaphyrin indicate that the degree of aromaticity of Mbius [28]hexaphyrin is large, comparable to that of Hckel aromatic planar [26]hexaphyrin. Through our spectroscopic investigations, we have demonstrated that a subtle balance between the strains induced by the size of the [28]hexaphyrin macrocyclic ring and the energy stabilization contributed by π-electron delocalization in the formation of distorted Mbius [28]hexaphyrin leads to the molecular structure change into the Mbius topology as the temperature decreases.