Elucidating Fundamental Structure-Property Relationships of Naphthopyran Mechanophores

Naphthopyran mechanophores have been identified as a privileged class of molecules due to their synthetic accessibility and structural modularity. In response to mechanical force, naphthopyran mechanophores undergo a ring-opening reaction to generate highly colored merocyanine dyes. Force is transduced to naphthopyran small molecules by covalently attached polymer chains, and naphthopyrans that are incorporated into polymeric materials visually report on macroscopic stress and/or strain. The properties of merocyanine dyes produced under mechanical force have been effectively tuned through straightforward structural modifications on various naphthopyran scaffolds. Additionally, the sensitivity of naphthopyran mechanophores toward mechanochemical ring-opening has been modified through targeted molecular design. The studies discussed herein provide insight into the fundamental relationship between the structure of naphthopyran mechanophores and their mechanochromic properties.