Acid-Induced Multicolor Fluorescence of Pyridazine Derivative

Smart luminescent materials that are responsive to external stimuli have received considerable attention. Here, we report a new D-A type 1,2-pyridiazine derivative (3,4,5,6-tetrakis(4-methoxyphenyl)pyridazine (TPP)) exhibiting turn-on fluorescence upon acid exposure both in solution and in the solid state. The protonation of the 1,2-pyridiazine ring caused a variation in the emission colors of the acidification species from blue (406 nm) to orange-red (630 nm) with a huge Δλ_em (224 nm). As a result, a synthetic rainbow of emission in solution could be achieved from one single molecule, and white photoluminescence was readily tuned by controlled protonation. A trifluoroacetic acid (TFA)-sensor film made from TPP was demonstrated as a TFA-sensitive surface with high sensitivity and reversibility. On the basis of these findings, we constructed a solid-state TPP film with a photoacid generator and demonstrated data encryption and decryption via a cascade protonation reaction that was well controlled by UV light.