Remarkable Effects of Terminal Groups and Solvents on Helical Folding of o-Phenylene Oligomers
Remarkable Effects of Terminal Groups and Solvents on Helical Folding of o-Phenylene Oligomers
复制标题
DOI：
10.1021/ja303117z
复制
发表时间：
2012-07-11
影响因子：
15
通讯作者：
Aida, Takuzo
中科院分区：
文献类型：
--
作者：
Ando, Shinji;Ohta, Eisuke;Aida, Takuzo
虽然邻亚苯基低聚物（OPnR）制成的二甲氧基亚苯基单元被认为是固有的动态由于π-电子排斥，我们表明，它们折叠成一个规则的螺旋几何形状在CH 3CN当它们携带端基，如CH 3，CH 2 OH，Br，CO2 Bn，和NO2。我们通过手性HPLC对长链低聚物（例如16-和24-聚体）进行光学拆分，评价了它们的螺旋反转动力学。OP 24 Br在298 K下在CH 3OH/水（7/3 v/v）中的光学活性半衰期为5.5 h，完全外消旋化需要34 h。OPnR的完全折叠的螺旋构象，不像他们的不完全折叠的，是没有扩展的π共轭，并显示具有可逆的多步氧化波的循环伏安图。
Although o-phenylene oligomers (OPnR) made of dimethoxyphenylene units are thought to be intrinsically dynamic due to pi-electronic repulsion, we show that they fold into a regular helical geometry in CH3CN when they carry terminal groups such as CH3, CH2OH, Br, CO2Bn, and NO2. We evaluated their helical inversion kinetics via optical resolution of long-chain oligomers (e.g. 16- and 24-mers) by chiral HPLC. OP24Br at 298 K shows a half-life for the optical activity of 5.5 h in CH3OH/water (7/3 v/v) and requires 34 h for complete racemization. The perfectly folded helical conformers of OPnR, unlike their imperfectly folded ones, are devoid of extended pi-conjugation and show a cyclic voltammogram featuring reversible multistep oxidation waves.