Fluorescent Polymers via Coordination of bis-Terpyridine Ligands with Transition Metals and Their pH Response Properties

Stimulus-responsive luminescent materials are pivotal in the field of sensing. Fluorescent transition metal complexes with a charge transfer excited state, especially terpyridine-coordinated polymers, are of particular interest due to their tunable emission. In this paper, a novel bis-terpyridine ligand was synthesized and assembled into a coordination polymer, which showed intense visible light absorption and fluorescence emission in the solid state that could be regulated by an acidic or basic pH. After being protonated by acid, the fluorescence of the polymer <b>P2</b> was quenched. The emission of the polymer split from 635 nm to two peaks of 674 and 440 nm, and then stabilized at 728 nm for 7 days, which showed a significant red-shift and good protonation stability. The fluorescence emission wavelength of the protonated polymers recovered after alkalization, and the fluorescence intensity of the polymer was greatly improved after alkalization, showing interesting acid-base-response luminescence characteristics. The sensitive response of the synthesized coordination polymers to acids and bases will contribute to expanding the application of linear coordination polymers in sensing and other fields.