Bistable Switching of π-Conjugation in a Dithienylethene-Bridged Luminescent Trityl Diradicaloid.

Robust external manipulation of spin communication in molecular frameworks is desirable for potential applications in quantum information science. Herein, we incorporate two types of dithienylethene (DTE) units into tris(2,4,6-trichlorophenyl)methyl (TTM)-based diradicaloids and report on the successful bistable switching of the optical and magnetic properties of the molecule. Visible-light irradiation of the open form generates up to 97% of the closed form, in which conjugation between the two radical centers leads to absorption over the entire visible range of the spectrum as well as a twofold increase of the singlet-triplet gap. These results establish TTM/DTE hybrids as persistent and multi-level responsive diradicaloids.