Excited-state lifetime modulation in triphenylene-based conjugated polymers.
Excited-state lifetime modulation in triphenylene-based conjugated polymers.
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DOI：
10.1021/ja016662l
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发表时间：
2001-11
影响因子：
15
通讯作者：
A. Rose;C. Lugmair;T. Swager
中科院分区：
文献类型：
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作者：
A. Rose;C. Lugmair;T. Swager
共轭聚合物是将电子激发1-4传输到具有最大有效共轭长度的链段的非凡管道。为了在感觉方案5中提供最高的放大，我们对增强能量迁移感兴趣。这种改进将允许激发具有更大的扩散长度和遇到被分析物占据的受体的更高概率。共轭体系5-7相对于具有侧基发色团的体系8，9的高能量转移效率表明，除了控制弱相互作用发色团的偶极-偶极（Förster型）过程之外，这些体系中的传输还可以通过强电子耦合链内（Dextertype）过程来增强。为了确定这些类型的过程的相对优势，我们合成和研究了聚合物，通过新颖的设计，具有较长的激发态寿命。寿命的增加意味着跃迁偶极的减少，因此应该降低Förster速率，而Dexter机制的传输应该得到增强。我们在此报告，孤立的聚（亚芳基乙炔）在溶液中，德克斯特运输占主导地位。聚（亚苯基乙炔）（PPE）由于其刚性几何形状和长距离有效传递能量的能力而引起了相当大的兴趣。为了改变这些系统的寿命，我们选择将具有众所周知的对称禁戒S 0-S1跃迁的苯并菲发色团掺入聚合物主链中。显然，苯并菲波函数12将受到扰动，导致其光学性质的严格对称性将被打破;然而，我们认为这种强芳香结构应该保留其一些个体身份，并且聚（苯并菲乙炔）（TPE）将具有延长的激发态寿命。除了它们所需的电子性质之外，苯并菲材料还具有形成π-堆叠的离散液晶相的趋势，这有助于电荷和能量传输。13,14
Conjugated polymers are an extraordinary conduit for the transport of electronic excitations 1-4 to segments with the greatest effective conjugation length. To provide the highest amplification in sensory schemes 5 we are interested in enhancing energy migration. Such improvements will allow the excitation a greater diffusion length and a higher probability of encountering a receptor occupied by an analyte. The high efficiency of energy transfer in conjugated systems 5-7 relative to systems with pendant chromophores 8,9 suggests that transport in these systems may be enhanced by the strongly electronic coupled intrachain (Dextertype) processes in addition to the dipole -dipole (Förster-type) processes that govern weakly interacting chromophores. To determine the relative dominance of these types of processes we have synthesized and studied polymers that by novel design have longer excited-state lifetimes. Increases in lifetime imply a reduction in transition dipole and should therefore decrease the Förster rate, whereas transport by the Dexter mechanism should be enhanced. We report herein that for isolated poly(arylene ethynylenes) in solution that Dexter transport is dominant. Poly(phenylene ethynylenes) (PPEs) have seen considerable interest due to their rigid geometry and ability to effectively transfer energy over long distances. 10 To modify the lifetimes of these systems we have chosen to incorporate into the polymer backbone triphenylene chromophores with a well-known 11 symmetrically forbidden S0-S1 transition. Clearly, the triphenylene wavefunction12 will be perturbed, and the stringent symmetry responsible for its optical properties will be broken; however, we considered that this strongly aromatic structure should retain some of its individual identity and that poly(triphenylene ethynylenes) (TPPEs) would have extended excited-state lifetimes. In addition to their desired electronic properties triphenylene materials also have a tendency to form π-stacked discotic liquid crystalline phases that facilitate charge and energy transport. 13,14