One-Step Construction of Fluorenone-Based Donor-Acceptor-Type Conjugated Polymers via Direct Arylation Polymerization for Cell-Imaging Applications.

Direct arylation polymerization (DARP) is a novel approach to obtain conjugated polymers (CPs) through the straightforward C-H activation of monomer building blocks. In this work, a convenient DARP method with high efficiency and excellent regioselectivity is developed to synthesize a series of donor-acceptor (D-A)-type CPs composed of electron-acceptor moiety fluorenones (FOs) and various electron-donor moieties. CPs with different band gaps are obtained in good yields and display large Stokes shifts up to 295 nm. Two ionic CPs, PFOP-NEt3(+) and PFOP-COO(-), were prepared in a polar solvent system to improve the water solubility and biocompatibility using the proposed DARP method. Detailed photophysical studies of these two CPs suggest that both solvation and hydrogen bonds play important roles in determining the polymers' spectroscopic properties. Further studies of the cationic polymer PFOP-NEt3(+) in cell imaging demonstrate its potential application in labeling cell membranes and lysosomes given its low cytotoxicity, excellent photostability, and specific subcellular localization.