| Summary: | © the Partner Organisations. Nanoscopic macrocycles could have unusual magnetic, optical, and electronic properties when compared to their linear counterparts. Conjugated π-systems in unsaturated macrocycles are particularly interesting as they have no end groups that limit electronic delocalization in equivalent linear oligomers. The rigid four-membered ring structure in 3,4-bis(methylene)cyclobutene with vicinal connections provides a vertex with an angle slightly less than 90°, which promotes macrocycle formation. We report herein a facile high-yielding synthesis of a series of 3,4-bis(methylene)cyclobutene-base π-conjugation macrocycles. The structure-property studies reveal that the smaller macrocycles are rigid crystalline frameworks and display symmetrical conformations in solution. The electrochemical, photophysical and magnetic properties of these macrocycles were also studied with a framework of characterization methods, revealing their size- and linkage-dependent properties. Density functional theory (DFT) calculations and molecular dynamics (MD) simulations at the molecular level suggest that several possible configurations are possible for macrocycles with larger ring sizes.
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