Cis-Cisoid Helical Structures of Poly(3,5-disubstituted phenylacetylene)s Stabilized by Intramolecular n -> pi Interactions
Cis-Cisoid Helical Structures of Poly(3,5-disubstituted phenylacetylene)s Stabilized by Intramolecular n -> pi Interactions
复制标题
通过分子内 n -> pi 相互作用稳定聚（3,5-二取代苯乙炔）的顺-顺螺旋结构
DOI：
10.1021/acs.macromol.8b00078
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发表时间：
2018
期刊：
影响因子：
5.5
通讯作者：
Wan Xinhua
中科院分区：
文献类型：
--
作者：
Wang Sheng;Shi Ge;Guan Xiaoyan;Zhang Jie;Wan Xinhua
一对对映体顺式聚（苯乙炔）（PPA）在侧苯环的中间位被非手性甲氧羰基和手性1-甲基丙氧羰基取代（即，sP-Me-C4/rP-Me-C4）以及仅带有甲氧羰基（即，m-aP-Me）或1-甲基丙氧基羰基（即，在[Rh（nbd）Cl]2（nbd =降冰片二烯）的催化下，合成了间位取代的Meta取代基.采用~ 1H NMR、FTIR、拉曼、UV-vis、CD、DSC、STM、DLS/SLS和计算机计算等技术表征了这些聚合物在溶液和固体状态下的螺旋结构。顺-顺式螺旋被认为是通过在相邻羰基之间的多烯主链上存在六个沿着n → π* 相互作用带而稳定的。这种相互作用对溶剂的介电常数和极性不敏感，但对溶剂的氢键贡献能力和温度敏感。在氢键接受溶剂中，顺-顺式螺旋结构是热稳定的，而在氢键给予溶剂中，升高温度可以触发顺-顺式-反式螺旋转变。溶剂分子和羰基之间的氢键越强，维持顺式-顺式螺旋所需的温度就越低。此外，通过分子内n → π* 相互作用稳定的顺-顺螺旋比通过分子内氢键稳定的顺-顺螺旋对溶剂极性的耐受性更好，且恢复速度更快。无论是甲氧羰基还是1-甲基丙氧羰基被去除，都只观察到反式-反式螺旋，这意味着n → π* 相互作用的弱性质和精细的大分子设计的需要。这项工作提供了一个不寻常的战略，buildcis-cisoidPPA。
A pair of enantiomericcis-poly(phenylacetylene)s (PPAs) substituted at themeta-positions of pendant phenyl rings by an achiral methoxycarbonyl group and a chiral 1-methylpropyloxycarbonyl group (i.e.,sP-Me-C4/rP-Me-C4) as well as twocis-PPAs bearing either just a methoxycarbonyl (i.e.,m-aP-Me) or a 1-methylpropyloxycarbonyl (i.e.,m-sP-C4) meta substituent were synthesized under the catalysis of [Rh(nbd)Cl]2(nbd = norbornadiene). Various techniques including1H NMR, FTIR, Raman, UV–vis, CD, DSC, STM, DLS/SLS, and computer calculation were applied to characterize the helical structures of these polymers in both solution and solid states.sP-Me-C4/rP-Me-C4adopted contractedcis-cisoidhelical conformations in THF, toluene, CH2Cl2, and ClCH2CH2Cl butcis-transoidones in CHCl3and Cl2CHCHCl2. Thecis-cisoidhelices were considered to be stabilized by the existence of six n → π* interaction bands along the polyene backbones between vicinal carbonyl groups. Such interactions were insensitive to the dielectric constant and polarity of solvent but sensitive to the hydrogen bond donating ability of solvent and temperature. In hydrogen bond accepting solvent, thecis-cisoidhelical structures were thermal stable, whereas thecis-cisoidtocis-transoidhelix transition could be triggered by raising temperature in the hydrogen bond donating solvent. The stronger the hydrogen bondings between solvent molecules and carbonyl groups, the lower the temperature required to maintaincis-cisoidhelix. Moreover, thecis-cisoidhelices stabilized by intramolecular n → π* interactions had better tolerance to the polarity of solvent and faster recovery than those stabilized by intramolecular hydrogen bonds. No matter whether methoxycarbonyl or 1-methylpropyloxycarbonyl group was removed, only acis-transoidhelix was observed, implying the weak nature of n → π* interaction and the need for a delicate macromolecular design. This work provided an unusual strategy to buildcis-cisoidPPAs.