Isolation and crystal structure of a dithiophene dication: controlling covalent connection and disconnection with temperature and phase†
Abstract
A dithienylethene (1o) undergoes a two-electron chemical oxidation to a singlet diradical as an open-isomer (1o2+) in solution, which cyclizes to a closed-form (1c2+) upon cooling. The latter crystallizes out and its structure is analyzed by single crystal X-ray diffraction. Equilibrium between 1o2+ and 1c2+ in solution is observed by NMR and UV spectroscopy at various temperatures and is further supported by reduction reactions with Zn powder.