A series of new rotaxanes with axles different in length was prepared. Following the synthetic protocol utilizing a known anion template effect (Scheme 1), surprisingly low yields in the order of 2 - 5% were obtained (Scheme 3), which furthermore significantly depended on the nature of the stopper (Fig. 1). Variations in the synthetic procedures and computational results from Monte Carlo simulations allowed us to analyze the origin of these findings: The rotaxane wheel 3 acts as a noncovalently bound 'protecting group' for the stopper nucleophile. The protection of the nucleophilic phenolate O-atom depends much on the steric demands of the stoppers (see 2 vs. 10) which induce different conformations of the wheel. Based on this model. an improved synthetic scheme is suggested.
US9310681B2
申请人:——
公开号:US9310681B2
公开(公告)日:2016-04-12
Bolaamphiphilic liquid crystals based on bis-imidazolium cations
作者:Alexandre Al Abbas、Benoît Heinrich、Matthieu L'Her、Emilie Couzigné、Richard Welter、Laurent Douce
DOI:10.1039/c6nj03590f
日期:——
investigate the nature anion influence on its interactions with the cation, crystalstructures from single crystal X-ray diffraction have been obtained for both [Ag(CN)2]− and [Ni(CN)4]2− derivatives. These studies showed that the square planar Ni anion disrupts the lateral cohesion of the ionic layers. This may explain the loss of liquid crystal behavior in this case and Pt salt.
A set of 27- to 39-membered pyridine macrocycles 2 and 3 has been synthesized by Williamson ethersynthesis or ring-closingmetathesis. The pyridines are 2,6-disubstituted to allow endo interactions. In addition to the length, also the nature of the aliphatic chain was varied: saturated (2) and unsaturated (3).