Bis(difluoroborylamidinates) with Flexible Alkylene Bridges as Aggregation-Induced Emitters

4,4-Difluoro-4-bora-3a,4a-diaza-s-indacenes (BODIPYs) represent one of the most prominent classes of dyes because of their small Stokes shifts, high fluorescence quantum yields, and remarkable chemical and photochemical stability. Closely related aza-BODIPYs offer an additional N-donor atom in the bora-heterocycle that is susceptible to Lewis acids, which is particularly useful for chemical sensor applications. Amidinate ligands with various predominantly aromatic substituents allow the incorporation of an unsymmetrical scaffold for the triaza-BF2 heterocycle which is also substantially bulky and therefore beneficial to promote aggregation-induced emission (AIE) as well as increased Stokes shifts. Our concept is based on a series of new polydentate bis(amidine) ligands LH2 with overall six N-donor atoms and flexible alkylene linkers that serve as ligands for emissive bis(difluoroborylamidinates) [L(BF2)2] that show AIE behavior