Novel fast photochromic phenothiazine-imidazolyl radical complex (PTIC) derivatives were developed, which form the charge transfer (CT) states and the neutral openshell transient species in a stepwise manner upon light irradiation. The lifetimes of the CT states were extended from picoseconds to hundreds of picoseconds by the substitution of a triphenylamine group on the phenothiazine moiety. The CT forms have different optical properties and chemical reactivities from those of the neutral open-shell transient species. Therefore, the developments of fast T-type photochromic molecules that generate long-lived CT forms are important for expanding potential applications of fast photoswitching materials.

A carbazole-incorporated photochromic radical complex is synthesized.