Cascade C-H-Activated Polyannulations toward Ring-Fused Heteroaromatic Polymers for Intracellular pH Mapping and Cancer Cell Killing

The development of straightforward and efficient synthetic methods toward ring-fused heteroaromatic polymers with attractive functionalities has great significance in both chemistry and materials science. Herein, we develop a facile cascade C-Hactivated polyannulation route that can in situ generate multiple ring-fused aza-heteroaromatic polymers from readily available monomers in an atom-economical manner. A series of complex polybenzimidazole derivatives with high absolute molecular weights of up to 24 000 are efficiently produced in high yields within 2 h. Benefiting from their unique imidazole-containing ringfused structures with multiple aryl pendants, the obtained polymers show excellent thermal and morphological stability, good solution processability, high refractive index, small chromic dispersion, as well as remarkable acid-base-responsive fluorescence. Taking advantage of the ratiometric fluorescence response of the triphenylamine-substituted heteroaromatic polymer to pH variations, we successfully apply it as a sensitive fluorescence probe for the mapping and quantitative analysis of intracellular pH in live cells. Furthermore, through the simple N-methylation reaction of the ring-fused polybenzimidazoles, diverse azonia-containing polyelectrolytes are readily produced, which can efficiently kill cancer cells via the synergistic effects of dark toxicity and phototoxicity.

Automated summary

The development of straightforward and efficient synthetic methods toward ring-fused heteroaromatic polymers with attractive functionalities has great significance in both chemistry and materials science. In this study, a facile cascade C-H-activated polyannulation route was developed to in situ generate ring-fused aza-heteroaromatic polymers with multiple aryl pendants. The obtained polymers showed excellent thermal and morphological stability, good solution processability, high refractive index, small chromic dispersion, as well as remarkable acid-base-responsive fluorescence. The triphenylamine-substituted heteroaromatic polymer was successfully applied as a sensitive fluorescence probe for intracellular pH mapping and quantitative analysis. Additionally, diverse azonia-containing polyelectrolytes were produced through the N-methylation reaction of the ring-fused polybenzimidazoles, exhibiting efficient cancer cell-killing effects.