Synthesis of Catenanes from a BMP32C10-Based Cryptand Tuned by the Linkage Length of Paraquat Salts

Abstract

A series of catenanes have been synthesized through olefin metathesis from a BMP32C10-based cryptand and paraquat guests attached with two terminal alkenes. Distribution of the catenane products can be significantly affected by the linkage length on the paraquat guests. In the presence of BMP32C10-based cryptand, the paraquat salt with a long linkage facilitates intramolecular olefin metathesis to release a [2]catenane as the sole catenation product, while the use of a paraquat salt with a shorter linkage leads to the simultaneous generation of [2]-, [3]-, and [4]-catenanes.

Construction of Supramolecular Polymers with Different Topologies by Orthogonal Self-Assembly of Cryptand–Paraquat Recognition and Metal Coordination

“…A Job plot [68] ( Figure S10) based on UV-vis absorbance data of the charge transfer band at λ = 400 nm demonstrated that their complex was of 1:1 stoichiometry in solution. The 1 H NMR spectrum of a mixed solution of 4 (5.00 mM) and 6 (5.00 mM) in CD3COCD3 showed that the complexation is a fast exchange system (Figure 1b), just like other reported cryptand-paraquat systems [54][55][56][57][58]. The opposite chemical shift changes of their protons, including upfield shifts of H6a, H6b, H6c, H4e, H4f, and H4g and downfield shifts of H4a and H4b, provided evidence about the electron density changes of these aromatic rings (Figure 1).…”

“…Compared to the corresponding crown ethers, cryptands are better hosts for paraquat derivatives due to the introduction of additional binding sites, which provide them not only better preorganization of complex conformations but also higher association constants. Normally, the association constants (Ka) of cryptands to the same guests can be 10 3 −10 4 times higher than those of their analogous crown ethers [54][55][56][57][58]. On the other hand, as one of the most common but important non-covalent interactions, metal coordination is often described as a strong, highly directional, and versatile supramolecular force, which can produce self-assemblies with various coordination geometries [59][60][61][62][63].…”