A binuclear zinc complex (Zn₂L) as ratiometric probe for the pyrophosphate (PPi) sensing

Phosphate anion (PPi) as hydrolysis products of adenosine triphosphate (ATP), is related to various biochemical reactions, particularly energy storage and transfer, nucleotide metabolism, and cellular signaling. In this paper, a binuclear zinc complex (Zn₂L) was prepared for the PPi sensing in Tris-HCl solution. The results showed a clear fluorescence change from blue to green (425 nm → 500 nm) with the addition of PPi to the probe. The probe Zn₂L demonstrated a remarkable selectivity for PPi in comparison to common anions, with an estimated limit of detection (LOD) of 0.29 μM within a working range of 0-9 μM. UV titration experiments showed two binding steps from 1 : 1 to 1 : 2 complex (Zn₂L-PPi). Density-functional theory (DFT) studies were further conducted to find an energy gap that decreases with complex (probe + 2PPi) formation, resulting in a redshift of the absorption spectrum (360 nm → 430 nm). In addition, the Zn₂L probe was also used for PPi sensing in a urine sample, in which relative standard deviation values (1.19-2.17%) and recoveries (95.00-103.00%) were obtained.