Systematic derivatives of 1‐(dicyanomethylene)indan and their photophysical properties as potential viscosity sensors

This study focuses on derivatizing 1‐(dicyanomethylene)indan as a viscosity sensor. The indan was extended with various functionalized naphthaldehydes under a push–pull design strategy. Among synthesized derivatives, salt‐capped derivatives exhibited an excellent linearity between fluorescent intensity and viscosity (R2 = 0.99), and further investigation underscores the reversible nature of fluorescence intensity changes at two temperatures as an important trait of viscosity sensors. This research demonstrates creating a viscosity sensor from 1‐(dicyanomethylene)indan as a new skeleton. Salt‐capped derivatives show notable linearity (R2 = 0.99) between fluorescence intensity and viscosity, with reversible changes at two temperatures, a crucial trait.