Mixed Amide Paracyclophane Assemblies Emulating Supramolecular Copolymers

[2.2]Paracyclophanes ([2.2]pCps), with their intimately spaced arene decks, have been used to study intermolecular charge-transfer effects in chromophores and for applications in photoredox chemistry and organic electronics. In 2016, we reported the synthesis and characterization of the first [2.2]pCp-tetracarboxamide ([2.2]pCpTA), envisaged as a covalently fixed supramolecular dimer of 2,5-dimethylterephthalamides. Demonstrated here is the idea that mixed-amide [n.n]pCpMTAs can be used to emulate stereoelectronic effects in alternating supramolecular copolymers. As exemplars, we report mixed-deck pseudo-ortho and pseudo-meta [2.2]pCpMTA monomers, each furnished with pairs of C- and N-centered amides arrayed in distinct substitution patterns. Programmable transannular H-bonding pairs dictate both small-molecule conformations and specific amide sequencing in emergent supramolecular assemblies. Variable-concentration and variable-temperature spectroscopy, X-ray crystallography, and density functional theory (DFT) data have been obtained that relate H-bonding geometry, elongation constant (K_e), assembly mechanism, and dipolar effects to the realization of unique structural control in amide-based supramolecular polymers. Characterization of the [2.2]pCpMTA monomers and their self-assembly behavior more broadly shows how stereoelectronic engineering either encourages or dissuades supramolecular polymerization, insight that can be applied beyond cyclophane-based architectures.