Synthesis and Photophysics of Coaxial Threaded Molecular Wires: Polyrotaxanes with Triarylamine Jackets
Synthesis and Photophysics of Coaxial Threaded Molecular Wires: Polyrotaxanes with Triarylamine Jackets
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DOI：
10.1021/jp500624q
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发表时间：
2014-02-27
影响因子：
3.7
通讯作者：
Anderson, Harry L.
中科院分区：
文献类型：
--
作者：
Sforazzini, Giuseppe;Kahnt, Axel;Anderson, Harry L.
通过β-环糊精大环连接的多茂-联苯(PFBP)共轭聚合物合成了包覆有空穴传输基团的水溶性聚轮烷。低聚糖的羟基被有效地用三苯胺(TPA)官能化，使得每个多轮烷分子都带有大约200个TPA单元的外壳，形成了超分子同轴结构。这种体系结构使用了一系列技术来表征，包括小角X射线散射。TPA单元对光的吸收导致激发能量转移(EET)和光致电子转移(ET)到内部共轭聚合物核心。用稳态和时间分辨荧光光谱、飞秒瞬时吸收光谱和分子模拟研究了这些能量和电荷转移过程。时间分辨测量揭示了TPA涂层的异质性：靠近中心聚合物核的TPA单元倾向于进行EET，而远离核心的多轮烷外表面的TPA单元则进行EET。通过EET间接激发的主干部分往往离TPA单元更远，因此不太容易受到电子转移猝灭的影响。通过考虑TPA-PFBP距离的异质性，使用分布式单极子方法有效地模拟了从TPA单元到PFBP核心的EET比率。这项工作代表了一种建立和研究>；100共价连接发色团的定义良好的阵列的新策略。
Conjugated polyrotaxanes jacketed with hole-transport groups have been synthesized from water-soluble polyrotaxanes consisting of a polyfluorene-alt-biphenylene (PFBP) conjugated polymer threaded through beta-cyclodextrin macrocycles. The hydroxyl groups of the oligosaccharides were efficiently functionalized with triphenylamine (TPA) so that every polyrotaxane molecule carries a coat of about 200 TPA units, forming a supramolecular coaxial structure. This architecture was characterized using a range of techniques, including small-angle X-ray scattering. Absorption of light by the TPA units results in excitation energy transfer (EET) and photoinduced electron transfer (ET) to the inner conjugated polymer core. These energy- and charge-transfer processes were explored by steady-state and time-resolved fluorescence spectroscopy, femtosecond transient absorption spectroscopy, and molecular modeling. The time-resolved measurements yielded insights into the heterogeneity of the TPA coat: those TPA units which are close to the central polymer core tend to undergo ET, whereas those on the outer surface of the polyrotaxane, far from the core, undergo EET. Sections of the backbone that are excited indirectly via EET tend to be more remote from the TPA units and thus are less susceptible to electron-transfer quenching. The rate of EET from the TPA units to the PFBP core was effectively modeled by taking account of the heterogeneity in the TPA-PFBP distance, using a distributed monopole approach. This work represents a new strategy for building and studying well-defined arrays of >100 covalently linked chromophores.