This review highlights recent advances in identifying and characterizing structurally well-resolved conformational isomers in expanded porphyrinoids. Molecular topological variations between these conformers often lead to distinct electronic properties, influencing aromaticity and photophysical behavior. These versatile macrocycles thus offer in-depth insight into structure–property relationships, advancing fundamental and applied research.

Abstract

Conformational isomerism plays a fundamental role in determining molecular properties and has aroused considerable interest across fields of chemistry, biochemistry, and material science. In this context, expanded porphyrinoids represent the most appropriate molecular platforms to study the intricate structure-properties relationships, since their intrinsic conformational flexibility enables the occurrence of multiple conformers within a single molecular entity. Leveraging these advantages, many efforts have been devoted to identifying distinct conformational isomers and elucidating their attendant electronic features, so that in-depth insights into conformational modulation, aromaticity, and photophysical behavior can be provided. In this review, we summarize recent advances in the study of structurally well-resolved conformational isomers of expanded porphyrinoids, along with their basic photophysical properties. It is our hope that this review will serve not only to codify our current understanding of conformational effect in these systems, but also inspire new thoughts for the rational design and synthesis of conformational isomers.