Vemuri Gopi Nath, Chu Meng, Dong Han, Spinello Brian J, Hartley C Scott
Department of Chemistry & Biochemistry, Miami University, Oxford, OH 45056, USA.
Org Biomol Chem. 2017 Jan 25;15(4):845-851. doi: 10.1039/c6ob02512a.
ortho-Phenylene oligomers fold into compact helical conformations in solution, and have therefore recently emerged as a class of foldamers. Previous work has shown that their folding is controlled by arene-arene stacking interactions parallel to the helical axis. Such interactions might reasonably be expected to be sensitive to solvent, but little is known of solvent effects in this system. Here, we report on the behavior of a representative set of o-phenylene oligomers in solvents ranging from non-polar (benzene) to polar and protic (methanol and water). The oligomers have been synthesized using post-oligomerization functionalization by click chemistry. Their folding is good in all solvents studied, but becomes measurably worse as the dielectric constant of the solvent increases. Thus, in contrast to the behavior of many other classes of aromatic foldamers, the folding propensity of o-phenylenes does not appear to be strongly affected by the solvophobic effect. Instead, the greater polarity of "frayed end" states governs their behavior.
邻亚苯基低聚物在溶液中折叠成紧密的螺旋构象，因此最近已成为一类折叠体。先前的研究表明，它们的折叠受平行于螺旋轴的芳烃-芳烃堆积相互作用控制。可以合理地预期这种相互作用对溶剂敏感，但对该体系中的溶剂效应知之甚少。在此，我们报告了一组具有代表性的邻亚苯基低聚物在从非极性（苯）到极性和质子性（甲醇和水）的溶剂中的行为。这些低聚物是通过点击化学的后低聚功能化合成的。它们在所有研究的溶剂中都能很好地折叠，但随着溶剂介电常数的增加，折叠明显变差。因此，与许多其他类别的芳香族折叠体的行为相反，邻亚苯基的折叠倾向似乎不受疏溶剂效应的强烈影响。相反，“松散末端”状态的更大极性决定了它们的行为。
