Limonene induced chiroptical generation and inversion during aggregation of achiral polyfluorene analogs: structure-dependence and mechanism
Limonene induced chiroptical generation and inversion during aggregation of achiral polyfluorene analogs: structure-dependence and mechanism
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DOI：
10.1039/c4py00865k
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发表时间：
2014-09
影响因子：
4.6
通讯作者：
Laibing Wang;Nozomu Suzuki;Jiangfei Liu;T. Matsuda;N. Rahim;Wei Zhang-;M. Fujiki;Zhengbiao Zhang;Nianchen Zhou;Xiu-lin Zhu
中科院分区：
文献类型：
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作者：
Laibing Wang;Nozomu Suzuki;Jiangfei Liu;T. Matsuda;N. Rahim;Wei Zhang-;M. Fujiki;Zhengbiao Zhang;Nianchen Zhou;Xiu-lin Zhu
从生物试剂到固态π共轭聚合物的手性转移是产生、切换和放大手性的有吸引力的方法，特别是当考虑几种有效的器件应用时。然而，溶剂诱导的手性转移机制的聚合物结构的依赖性还没有得到很好的理解。为了阐明聚合物聚集体的结构-手性性质关系，合成了聚（9，9-二正辛基芴基-2，7-二基）（PF 8）、聚（9，9-二正辛基硅杂芴基-2，7-二基）（PSi 8）、聚（9-（1-辛基壬基）-9H-咔唑-2，7-二基）（PCz 8）、P（F8-alt-Si 8）、P（F8-alt-Cz 8）和P（Si 8-alt-Cz 8）。在CHCl_3-柠檬烯-CH_3OH三元溶剂中，柠檬烯手性被有效地转移到PF_8、PSi_8和P（F_8-alt-PSi_8）聚集体中，但对P（F_8-alt-PCz_8）和P（Si_8-alt-PCz_8）聚集体没有观察到光学活性。在含Cz 8的聚合物中不存在手性光学活性的原因可能是那些聚合物与柠檬烯相比具有更强的极性，因此与含Cz 8的聚合物之间的相互作用相比，柠檬烯和聚合物链之间的相互作用太弱。令人惊讶的是，在PF 8和PSi 8聚集体之间的CD光谱中发现了手旋光反转，更令人惊讶的是，在PSi 8聚集体的CD和CPL光谱之间观察到了手旋光反转。独特的手旋光反转归因于Si 8中的9-Si和F8单元中的9-C之间以及Si 8中的Cipso（1）和F8单元中的Cipso（1）之间的相反Mulliken电荷。另一个可能的原因，这种意想不到的手性反转行为是相反的方向的偶极矩在三个稳定的旋转异构体的赤道柠檬烯旋转异构体。
Chirality transfer from biological agents to π-conjugated polymers in the solid state is an attractive method to generate, switch, and amplify chirality, especially when one considers several potent device applications. However, the polymer-structure dependence on the solvent-induced chirality transfer mechanism is not well understood. To elucidate the structural–chiroptical property relationship of the polymer aggregates, poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PF8), poly(9,9-di-n-octylsila-fluorenyl-2,7-diyl) (PSi8), poly(9-(1-octylnonyl)-9H-carbazole-2,7-diyl) (PCz8), P(F8-alt-Si8), P(F8-alt-Cz8), and P(Si8-alt-Cz8) were synthesized. The limonene chirality was efficiently transferred to PF8, PSi8 and P(F8-alt-PSi8) aggregates in CHCl3–limonene–CH3OH tersolvent, but the optical activity was not observable for PCz8, P(F8-alt-PCz8), and P(Si8-alt-PCz8). The reason for the absence of chiroptical activity in Cz8-containing polymers could be that those polymers have stronger polarity compared to limonenes, and thus the interaction between limonene and polymer chains was too weak compared to the interaction among Cz8-containing polymers. Surprisingly, chiroptical inversion in CD spectra between PF8 and PSi8 aggregates was found. More surprisingly, chiroptical inversion between CD and CPL spectra of PSi8 aggregates was observed. The unique chiroptical inversion was attributable to the opposite Mulliken charges between 9-Si in Si8 and 9-C in F8 unit and between Cipso(1) in Si8 and Cipso(1) in F8 unit. Another possible reason for this unexpected chiroptical inversion behaviour is the opposite direction of dipole moments in three stable rotational isomers of the equatorial limonene rotamer.