A thermoresponsive fluorescent rotor based on a hinged naphthalimide for a viscometer and a viscosity-related thermometer - 光功能分子传感研究组

A new fluorescent smart unit (BNAP) based on bisnaphthalimide was designed and synthesized, of which two naphthalimide segments were conjugated through a twisted single bond at the 4-site. With the dual naphthalimide planes, BNAP can act as a double-channel rotor, which can output the shorter emission in twisted state and the longer emission in planar state. Because of the restriction of intramolecular rotation (RIR) effect, BNAP showed strong emission character in high viscosity circumstance. The longer and moderated emission in aggregates is attributed to the synergetic effects of RIR and intramolecular planarization. As a molecular rotor with dramatic changes in both emission wavelength and intensity, BNAP could be developed for rapid detection of viscosity. The probe generates a logarithmic response to viscosity of glycerol/water system with different ratio. Furthermore, the probe exhibits high sensitivity to the viscosity-related temperature variations. This property is very important because temperature always change surrounding viscosity in many biological systems and mechanical systems.