Design and synthesis of light-harvesting rotor based on 1,8-naphthalimide units

[Display omitted] •Multicomponent molecular device based on 1,8-naphthalimide fluorophores is synthesized.•Energy supplier, molecular rotor and switch are integrated in light-harvesting antenna.•The system shows high efficient FRET (99 %).•Fluorescence changes of the antenna are caused by a TICT driven molecular motion.•Preventing the TICT motion in viscous or acid media increases the fluorescence output. A novel pH and viscosity fluorescence sensing multicomponent molecular device based on 1,8-naphthalimide fluorophores is synthesized and investigated. The system is designed as a light-harvesting antenna where energy supplier, molecular rotor and molecular “on-off” switcher are integrated. The peripheral 1,8-naphthalimide energy suppliers transfer rapidly the trapped energy to the core molecular rotor through high efficient FRET (99 %). The 4-piperazinyl-1,8-naphthalimide core excitation results in a TICT driven molecular motion. Due to the non-emissive de-excitation nature of the TICT core fluorophore, system shows low yellow-green fluorescence that is a “power-on”/“rotor-on” state. The protonation of the methylpiperazine amine destabilized TICT process thus indicating a “power-on”/“rotor-off” system state.