Synthesis of Dithienylcycloalkene Molecular Switches Enabled by a Bench-Stable Ti-Complex

Herein, we report a set of cycloalkene-bridged dithienylethene (DTE) molecular switches with ring sizes ranging from 4- to 7-membered rings. These analogs were accessed via McMurry carbonyl coupling using a bench-stable Ti(IV)-complex reagent instead of the generally applied fuming, liquid TiCl₄, making the synthesis more practical and reproducible. The efficiency of the reaction was dependent on the ring size, providing the lowest yield for the largest, 7-membered ring. Structures having 3-membered cyclopropene bridges were prepared using an alternative strategy. Remarkably, the comparison of the photoswitching properties of the series showed that molecules bearing a strained cyclobutene bridge outperform the other switches in terms of reversibility and fatigue resistance.