Systematic study of phenyl substitutions in a terpyridine Zn²⁺ complex for pyrophosphate sensing in water

Terpyridine Zn²⁺ complex-based pyrophosphate (PPi) fluorescent probes have shown promise, however, a systematic study on the optimal structure of terpyridine for PPi sensing is still lacking. In this study a series of six-coordinated terpyridine Zn²⁺ complexes were designed and synthesized. The impact of the position and the number of electron-donating groups on the aromatic ring of terpyridine, as well as changes in hydrophobicity, on the ability to selectively recognize PPi was explored. Six terpyridine Zn²⁺ complexes with meta-methoxy groups on the phenyl ring can detect PPi in aqueous solution through an AIE-mediated mechanism, exhibiting excellent selectivity for PPi over other nucleoside triphosphates (NTPs). More importantly, the introduction of an additional propoxy group at the para-position enhances the anti-interference capability and fluorescence response speed of the terpyridine Zn²⁺ complex towards PPi. Furthermore, four selected probes have also demonstrated the capability to monitor inorganic pyrophosphatase (IPP)-mediated PPi hydrolysis.