Dithienoazaborine derivatives with selective π-conjugated extensionvialate-stage functionalization

The selective late-stage functionalization of BN-containing polycyclic aromatic hydrocarbons (BN-PAHs) is very challenging. Herein, dithienoazaborines (BNDT,3aand3b) were synthesized as model compounds, and two kinds of selective functionalizedBNDTprecursors,4aand4bwere synthesized due to the strong polar effect of the BN bond, leading to a series ofBNDTderivatives for the following coupling reactions. Based on this, two kinds ofBNDT-based small molecules and oligomers with BN bonds on the conjugated main chain and side chain were synthesized accordingly. TheBNDTderivatives (5b/6b/7b) with a BN bond on the conjugated side chain showed lower LUMO energy levels and narrower band gaps than those with a BN bond on the conjugated main chain (5a/6a/7a). Different modifications and polymerization have effects on the photophysical properties and all derivatives are highly selective to fluoride ions. This work realized a new strategy for selective late-stage functionalization of BN-PAHs with selective π-conjugated extension, laying a solid foundation for the subsequent BN chemistry and application of functionalized BN-PAHs.