The incorporation of proton ionizable moieties, such as 1H-1,2,4-triazole rings, within cyclophanes and π-donor/π-acceptor catenanes is explored as a tool of inducing chemical switchability through either the inherent prototropic tautomerism or chemical deprotonation. Bearing this in mind, in this paper we describe the template-directed synthesis of two tetracationic cyclophanes incorporating two bipyridinium units linked by either one 3,5-bis(methylene)-1H-1,2,4-triazole unit and a p-xylyl unit or two 3,5-bis(methylene)-1H-1,2,4-triazole units, as well as the template-directed synthesis of two catenanes wherein these π-acceptor cyclophanes are interlocked with (bis-p-phenylene-34-crown-10), as the π-electron rich polyether macrocycle. We also report on the full characterization of the cyclophanes and the catenanes by electrospray mass spectrometry (ESMS) and fast atom bombardment mass spectrometry (FABMS), X-ray crystallography of the catenanes and dynamic 1 H NMR spectroscopy. We reveal that the catenane incorporating one triazole ring in the tetracationic cyclophane exists, in the solid-state, as hydrogen bond cross-linked enantiomeric pair stacks, whereas the catenane incorporating two triazole rings in the tetracationic cyclophane does not form polar stacks, unlike most of the catenanes of this class. Finally, we studied the chemical stability of these π-donor/π-acceptor motifs to explore their chemical switchability, to show the triazolate-bipyridinium pair is a challenging one in this sense.
ASJC Scopus subject areas
- Materials Chemistry