<i>N</i> -Heteroaromatic Fused BODIPY Dimers: Ring-Size Effects from Five- to Six-Membered Rings

Three BODIPY dimers fused with five- and six-membered <i>N</i>-heterocycles were synthesized via an S_NAr and C-H activation strategy. <i>N</i>-Heterocycle size enables precise modulation of electronic delocalization and excited-state character. The six-membered fused <b>PP-di</b> exhibits panchromatic absorption, a narrowed HOMO-LUMO gap, and enhanced intramolecular charge-transfer behavior, whereas the five-membered analogues <b>Cl-PL-di</b> and <b>PL-di</b> display predominantly localized-excited states.