Optical detection of Al3+ and Fe3+ via multiple readout using a Ru(II)-terpyridyl platform: Insights from experimental and theoretical studies

Abstract

Ru(II)-terpyridyl complex (1) has shown the ability to recognize trivalent Al³⁺ and Fe³⁺ ions. This complex addressed practical challenges by offering a straightforward synthetic route, rapid detection process, reusability, high specificity, and multiple ways to interpret the results for accurate analysis. Probe 1 exhibited a “turn-on” response while detecting Al³⁺ and Fe³⁺ through an optical readout method. Additionally, the structural and spectral changes observed during the ion-binding events strongly correlated with the theoretical calculations, confirming the mechanistic understanding of the binding modes for Al³⁺ and Fe³⁺. The detection limits (LoD) of probe 1 for Al³⁺ and Fe³⁺ were depicted to be 0.514 μM and 4.5 μM, respectively. Notably, the LoD for Al³⁺ falls below the permissible Al³⁺ level in drinking water as set by the World Health Organization (WHO). The binding constants of 1 with Al³⁺ and Fe³⁺ have been depicted as 26.6 × 10⁴ M⁻¹ and 2.35 × 10⁵ M⁻¹, respectively. Inspired from its high selectivity and quick response, a two-input logic gate and keypad lock system have also been developed.