Ion-Pairing Assemblies of Anion-Responsive π-Electronic Systems That Have Noncovalently Assisted Expanded Planar Region.

Arylethynyl-substituted dipyrrolyldiketone BF 2 complexes as anion-responsive π-electronic molecules exhibited characteristic electronic properties derived from conformation changes upon anion binding, which caused an increase in UV/vis absorption and associated two-photon absorption. The anion complexes showed expanded planar regions assisted by intramolecular interactions, resulting in charge-by-charge ion-pairing assemblies in the solid state.