One "click" access to self-complementary molecular modules for halogen bonding

Novel D-π-A push-pull chromophores were synthesized in good yields by CuAAc coupling of 4-X-2,3,5,6-tetrafluorophenyl-1-azides (X = H, Br, I) with 4-ethynyl-dimethylaniline. Thanks to the self-complementary binding sites at the molecular ends, the iodo derivative self-organizes in the solid state forming head-to-tail halogen-bonded one-dimensional unlimited chains. The second-order NLO properties of the iodo compound have been investigated by the solution-phase electric field induced second-harmonic generation method (EFISH).