A π‑Conjugated System with Flexibility and Rigidity That Shows Environment-Dependent RGB Luminescence

We have designed and synthesized
a π-conjugated system that
consists of a flexible and nonplanar π joint and two emissive
rigid and planar wings. This molecular system exhibits respectively
red, green, and blue (RGB) emission from a single-component luminophore
in different environments, namely in polymer matrix, in solution,
and in crystals. The flexible unit gives rise to a dynamic conformational
change in the excited state from a nonplanar V-shaped structure to
a planar structure, leading to a dual fluorescence of blue and green
colors. The rigid and planar moieties favor the formation of a two-fold
π-stacked array of the V-shaped molecules in the crystalline
state, which produces a red excimer-like emission. These RGB emissions
are attained without changing the excitation energy.