Synthesis of aromatic substituted B ← N embedded units with good stability and strong electron-affinity

[Display omitted] •Two fused ladder-type units containing B ← N bonds with good stability were synthesized.•The single crystal structures and optoelectronic properties were studied along with theoretical simulations.•Fluorescence quenching phenomenon was found between the PBDB-T and these B ← N embedded units. Two chemically stable B ← N embedded units were synthesized, namely, BNIDT-Ph and BNIDT-Th, with aromatic phenyl (Ph) or thiophene (Th) groups, respectively, attached to the four coordination boron (B) atom. Single crystal data revealed that BNIDT-Ph and BNIDT-Th show obvious π-π interactions (3.83 vs. 3.79 Å) and B ← N dipole-dipole interactions (6.51 vs. 6.67 Å). BNIDT-Ph and BNIDT-Th exhibit strong electronic affinities of 3.70 and 3.81 eV, respectively. Fluorescence quenching was found between PBDB-T and the B ← N embedded molecules in solution, indicating exciton dissociation. These B ← N embedded molecules are potentially useful to further construct novel n-type semiconductors.