The synthesis and spectroscopic properties of macrocyclic polyethers containing two different aromatic moieties and their [2] catenanes incorporating cyclobis(paraquat-p-phenylene)

Abstract

The synthesis of six derivatives of bis-p-phenylene-34-crown-10 (BPP34C10) in which one or both of the p-phenylene rings are replaced by other η-electron-rich aromatic ring systems, and their subsequent use as templates for the self-assembly of the tetracationic cyclophane cyclobis(paraquat-p-phenylene) and thus the construction of [2]catenanes, are described. The p-phenylene rings in BPP34C10 have been replaced variously by p-xylyl units, 1,5-, 1,6-, 2,6- and 2,7-naphtho units, and naphthalene-2,6-dimethylyl ring system in the six new crown ether derivatives. Five of the [2]catenanes have the potential to exist in solution as equilibrating mixtures of two translational isomers, the proportions of which have been determined in solution by dynamic 1H NMR spectroscopy. The absorption spectra and luminescence properties (fluorescence, phosphorescence, and excitation spectra, excitation state lifetimes, and fluorescence quantum yields) of the BPP34C10 derivatives (in which one of the p-phenylene rings has been replaced by either a p-xylyl unit or a naphthalene-2,6-dimethylyl unit or where both of the p-phenylene rings have been replaced, one by a p-xylyl unit and the other by a 1,5-naphtho unit) and their derived [2]catenanes, with cyclobis(paraquat-p-phenylene) as the interlocking cyclophane component, have been investigated. Comparison with the properties of simple model compounds shows the presence of intra- and intermolecular electronic interactions between the component units of the crown ethers and catenanes. The main consequences of these interactions in the crown ethers are small perturbations in the absorption spectra of the two chromophobic units, and strong changes in the luminescence properties due to the occurrence of intercomponent energy-transfer processes and charge-transfer (CT) interactions. In the [2]catenanes, perturbations in the absorption spectra of the component units of the crown ether and tetracationic cyclophane, accompanied by the appearance of CT absorption bands in the visible region, and complete luminescence quenching caused by the presence of low-energy CT levels are observed.