Unveiling stereoselective ladders via photo-oligomerization of a diazaanthracene macrocycle

Abstract

We present an efficient light-driven oligomerization of a flat aromatic tetra-amide macrocycle containing photoresponsive 1,8-diazaanthracenes. Oligomers with molecular weights exceeding 10 kDa were straightforwardly obtained, isolated using gel permeation chromatography (GPC), and characterized by NMR and mass spectrometry up to an octamer. We finely tuned the side chain size to exclusively favor the exo-[4 + 4] photoadduct over the endo-[4 + 4] photoadduct, thus controlling the stereoselectivity of the photoreaction to produce a single isomer, which yielded ladder-like architectures. The octamer is a ∼10 nm long ladder with a step size of 4.6 Å. The oligomers retained sufficient photoreactivity to undergo further oligomerization, either between themselves or upon adding fresh monomers, to generate longer oligomers. These oligomers are fully degradable as thermal reversibility allows for monomer recovery.