Novel bisthienylethene containing ferrocenyl-substituted naphthalimide: a photo- and redox multi-addressable molecular switch

A new photochromic bisthienylethene system (BTE-NAFc) is reported in which the ferrocene unit (Fc) is incorporated into a naphthalimide chromophore as the central ethene bridging unit. The incorporated Fc unit in the photochromic system of BTE-NAFc has several effects on optical properties, such as fluorescence-modulation through photoinduced electron transfer (PET), a decrease in the photochromic cyclization quantum yield, and a selective two-step oxidation process. The ability to drive ring-opening and ring-closing reactions with a secondary redox-modulation provides increased functionality to the photochromic system. Based on these meaningful photo- and redox-modulation properties, five unprecedented multi-addressable states (BTE-NAFc, BTE-NAFc(+), c-BTE-NAFc, c-BTE-NAFc(+), and BTE(+)-NAFc(+)) and gated photochromism are successfully obtained within the unimolecular BTE platform, thus providing deeper insight into photochromic systems as multifunctional outputs.