Molecular tweezers with a rotationally restricted linker and freely rotating porphyrin moieties
Abstract
The effect of the degree of conformational rigidity and/or flexibility on preorganisation in artificial molecular
receptors continues to be actively explored by supramolecular chemists. This work describes a bisporphyrin
architecture, linked via a rigid polycyclic backbone, in which a sterically bulky 2,3,5,6-tetramethylphenyl
diimide core restricts rotation to afford two non-interconvertible tweezer conformations;
syn- and anti-. After separation, the host–guest chemistry of each conformation was studied independently.
The difference in host geometry allows only the syn-conformation to form a strong 1 : 1 bis-porphyrin
complex with the diamino ligand 1,4-diazabicyclo[2.2.2]octane (DABCO) (K11 = 1.25 × 108 M−1),
with the anti-conformation adopting a 2 : 2 sandwich complex with DABCO (K22 = 5.57 × 1017 M−3).
Description
Open Access article. This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 unported licence.
This journal is © The Royal Society of Chemistry 2018.