Carboxyl group bearing iridium(III) solvent complex as photoluminescence and electrochemiluminescence probe for the detection of histidine

Histidine (His), as the essential amino acid in human body, plays crucial roles in many biological activities. Here, a new carboxyl group bearing iridium(III) solvent complex [Ir(pbz)2(DMSO)Cl] (pbz = 3-(2-pyridyl)benzoic acid, Ir1-DMSO) was synthesized as photoluminescence (PL) and electrochemiluminescence (ECL) probe for the detection of His. Ir1-DMSO exhibits weak PL and ECL emissions. In the presence of His, the coordination interaction of the Ir1-DMSO with His led to the enhancement of PL and ECL emissions. Two “signal on” PL and ECL methods were developed for the selective and sensitive detection of His. The detection limit of His is calculated to be 100 nM and 7 nM via PL and ECL methods, respectively. The coordination interaction between Ir1-DMSO and His was investigated. 1:1 of binding stoichiometry and (2.31 ± 1.43) × 109 M−1 of binding constant were obtained for the interaction of Ir1-DMSO and His. This work demonstrates that carboxyl group bearing Ir1-DMSO is an alternative “signal on” PL and ECL probe for the detection of histidine with high sensitivity, good selectivity and larger binding ability, which can be extended in the assay of His-related molecules.