Tunable full-color dual-state (solution and solid) emission of push-pull molecules containing the 1-pyrindane moiety

A facile method for the synthesis of arylidene derivatives of pyrindane - (E)-7-arylmethylene-2-chloro-6,7-dihydro-5H-cyclopenta[b]pyridine-3,4-dicarbonitriles - was developed. Tunable full-color emission was achieved for the synthesized push-pull molecules, solely by changing donor groups while keeping both the conjugated system and acceptor part of the molecule unchanged. This represents a rare approach for the design of such fluorophores. Arylidene derivatives of pyrindane were found to be efficient fluorescent dyes showing a moderate to high emission quantum yield. The push-pull molecules were also characterized by a dual-state emission (in solution and in the solid state). Emission maxima ranged from 469 to 721 nm in solution depending on the solvent and type of donor substituent, and from 493 to 767 nm in the solid state. For the arylidene derivative of pyrindane with a dimethylamino group, it was shown that fluorescence can be changed by the action of an acid both in solution and in the solid state.