Synthesis and optical properties of new tricyano-p-quinodimethane dyes: molecular and polymeric systems

The reaction of N,N-bis(2-hydroxyethyl)aniline 1 with tetracyano-p-quinodimethane (TCNQ) 2 yields the photochromic red chromophore 3 [λmax (acetone/dichloromethane) 497 nm] which upon UV irradiation is converted into the blue zwitterionic form 3′ (λmax 680 nm) by a novel intramolecular charge transfer process involving a d-quinoid-aryl-A→d+-aryl-quinoid-A− conversion. The analogous process occurs in the polyimide derived system 8. Different products are isolated from reactions of 1 with the stronger electron acceptors TCNQBr2 and TCNQF4.