N, N-Dimethyl-Substituted Boron Ketoiminates for Multicolor Fluorescent Initiators and Polymers

In this contribution, an efficient synthesis strategy of multicolor fluorescent N,N-dimethyl-substituted boron ketoiminates (NBKI) was presented. The introduction of dimethylamino group as donor and NOBF₂ moiety as acceptor with variously tunable substituents led to the formation of D (donor)-π-A (acceptor) system in NBKI molecules, which exhibited a high fluorescence efficiency and a significant red shift of absorption/emission in solution. NBKI molecules were applied in the synthesis of multicolor fluorescent ATRP initiators (i-NBKI 1-4) and RAFT initiator (i-NBKI 5), as well as multicolor fluorescent PS, PMMA, PDBA, or PEG-based homopolymers/copolymers. It was demonstrated that PEG-based polymers showed effective fluorescence emission, good water solubility, and great potential in biological applications. This work bridges the gap in current organoboron compounds and multicolor fluorescent polymerization initiators and related fluorescent polymers/copolymers by utilizing D-π-A design. It may shed light on the downstream applications in next-generation multicolor fluorescent probes/devices.