Synthesis of a Doubly Strapped Light-Harvesting Porphyrin Bearing Energy Donor Molecules Hanging on to the Straps: An Attempt toward Macroscopic Control over Molecular Conformation that Affects the Efficiency of Fluorescence Resonance Energy Transfer
作者:Soichiro Ogi、Kazunori Sugiyasu、Masayuki Takeuchi
DOI:10.1246/bcsj.20100232
日期:2011.1.15
We report here the synthesis of a light-harvesting molecule 1, in which 5,5′-diphenyl-2,2′-bithiophene units (energy donors) and a doubly strapped porphyrin (energy acceptor) are three-dimensionally connected through four alkyl chains to form a “universal joint”-like architecture. From the results of the optical properties of 1 in solution, fluorescence resonance energy transfer (FRET) takes place from the donor to the acceptor in 1 with the FRET efficiency of 99.7%. We prepared 1/polydimethylsiloxane (PDMS) elastomeric films in which 1 is connected to a polysiloxane network through covalent bonds. When we stretched the 1/PDMS film (elongation: up to 60%), the FRET efficiency decreased by 13.1%. The theoretical analysis suggests that the FRET efficiency of 1 (E) is virtually uninfluenced by any changes in the distance between the donor and acceptor (r). Therefore, the observed change in FRET efficiency should have been derived from the orientation factor (κ2), which describes the relative orientation of the emission transition dipole of the donor and the absorption transition dipole of the acceptor. The anisotropic absorption spectral measurements support the notion that the transition dipoles of the fluorophores became orthogonally aligned upon stretching, as expected from the molecular design.
我们在此报告了一种光收集分子1的合成,其中5,5'-二苯基-2,2'-双噻吩单元(能量供体)与双支撑的卟啉(能量受体)通过四条烷基链三维连接形成了类似“万向节”的结构。从1在溶液中的光学性质结果来看,能量共振转移(FRET)从供体传递到受体,FRET效率高达99.7%。我们制备了1/聚二甲基硅氧烷(PDMS)弹性薄膜,其中1通过共价键连接到聚硅氧烷网络。当我们拉伸1/PDMS薄膜(延伸率:最高可达60%)时,FRET效率降低了13.1%。理论分析表明,1的FRET效率(E)几乎不受供体和受体之间距离(r)变化的影响。因此,观察到的FRET效率变化应源于取向因子(κ²),该因子描述了供体的发射跃迁偶极与受体的吸收跃迁偶极之间的相对取向。各向异性吸收光谱测量支持这样的观点,即发光体的跃迁偶极在拉伸过程中变得正交排列,这与分子设计的预期一致。