Expanding the Molecular Switches Toolbox: Photoreloadable Dithienylethene Mechanophores

Molecular switches are often thought of as nanoscopic equivalents to the electrical buttons and knobs ubiquitous in everyday life. However, mechanical force is rarely used to reversibly trigger rearrangements at the atomic scale, due to the difficulty in selectively breaking certain bonds, while keeping others intact. Here, we introduce two new mechanophores based on dithienylethene (DTE), which can be toggled between two states by ultraviolet light and sonication. Attaching various lengths of poly(ϵ-caprolactone) either to the 2,2' or the 5,5' positions of the DTE core allowed us to study the kinetics of its mechanochemical cycloreversion. We employed computational methods to understand the root causes of the observed mechano-regiochemical differences. Lastly, we show that our best performing DTE-polymer conjugate can undergo numerous switching cycles by the alternating action of electromagnetic radiation and mechanical force.