Molecular rotors as luminescence sensors of local viscosity and viscous flow in solutions and organized systems

The results of studies of various classes of molecular rotors are generalized. The compounds in question are fluorophores whose molecules can pass to a twisted state upon charge transfer on excitation, this state being characterized by non-radiative deactivation. The structures of the main classes of molecular rotors and principles of their functioning are analyzed. In the discussion of applications of molecular rotors, the attention is focused on their use as sensors of polymerization, aggregation and conformational changes in protein molecules, as local viscosity probes in biological systems and flow sensors and also for viscosity measurements in liquids. The bibliography includes 104 references.