Low Band Gap Coplanar Conjugated Molecules Featuring Dynamic Intramolecular Lewis Acid–Base Coordination

Ladder-type conjugated molecules with a low band gap and low LUMO level were synthesized through an N-directed borylation reaction of pyrazine-derived donor–acceptor–donor precursors. The intramolecular boron–nitrogen coordination bonds played a key role in rendering the rigid and coplanar conformation of these molecules and their corresponding electronic structures. Experimental investigation and theoretical simulation revealed the dynamic nature of such coordination, which allowed for active manipulation of the optical properties of these molecules by using competing Lewis basic solvents.