Coordination-induced self-assembly of metallosalens enables sustainable monitoring of phytic acid in agricultural foods

Phytic acid (PA), a naturally occurring phosphorylated anti-nutrient present in various food sources, exhibits both health benefits and adverse effects. Due to its strong metal-chelating ability, excessive intake can negatively impact human health, while its persistence in agricultural runoff also contributes to environmental pollution. Therefore, sensitive and reliable detection of PA is crucial for promoting both human well-being and sustainable development. In this study, we have developed and synthesized a series of metallosalen complexes containing zinc, copper, and iron centers. The zinc-based complexes exhibited high selectivity toward PA, showing a distinct fluorescence turn-off response accompanied by a visible color change from deep yellow to faint. Mechanistic investigations revealed that the observed quenching originated from PA-induced aggregation of the complexes <i>via</i> coordination through phosphate groups and electrostatic interactions. Notably, the dimeric zinc complex demonstrated a significantly stronger quenching effect compared to monomeric zinc complex, with a detection limit as low as 2.10 µM. In contrast, replacing zinc with iron resulted in a turn-off to turn-on response, attributed to demetallation of the iron complex upon PA addition, while the copper-based complex showed negligible interaction. Furthermore, the zinc complex with superior sensitivity was successfully applied for the quantification of PA in vegetable extracts such as carrot, soybean, and sesame seed, achieving excellent recovery rates between 97.2% and 115.2% with relative standard deviations (RSD) of 2-3.7%. Finally, a cellulose-based paper strip embedded with this zinc complex was fabricated for rapid, on-site PA detection.