Adaptive maleimide-fused macrocyclic clamps: Synthesis, structures, and complexations with polycyclic aromatic hydrocarbons

The photoactive macrocyclic molecules attract attention because of their important roles in supramolecular chemistry as well as photoelectronic applications. Herein, two D-A conjugated macrocycles containing two maleimide nodes have been successfully obtained via an one-pot cascade reaction of Perkin and imidization condensations. Owing to the incorporation of two bulky 1,4-dimethoxybenzene moieties at the narrow maleimide corners, the obtained conjugated macrocycles have been equipped with two adaptive clamps, which can adjust to the guest sizes to capture the guest molecules. Interestingly, the co-crystallization with larger-sized polycyclic aromatic hydrocarbons (PAHs) leads to the 1:1 host-guest complexes, while with smaller-sized solvents results in the 1:2 complexes. Furthermore, the rotatable 1,4-dimethoxybenzene moieties endowed such macrocyclic fluorophores with pronounced solvatochromic and aggregation-induced emission enhancement (AIEE) phenomena.