Reaction-based energy level modulation of a cyclometalated iridium complex for electrochemiluminescent detection of formaldehyde

Formaldehyde is a toxic compound present in both the environment and living systems, and its detection is important due to its association with various pathological process. In this study, we report a new electrochemiluminescence (ECL) probe based on a cyclometalated iridium complex (IrHAA) for the selective detection of formaldehyde. The homoallylamine moiety in IrHAA reacts with formaldehyde, undergoing a 2-aza-Cope-rearrangement reaction to form a formyl group. Significant changes in the electronic properties and molecular orbital energies of the iridium complex through the functional group transformation result in enhanced ECL and radiometric phosphorescence changes, enabling the quantitative and selective detection of formaldehyde. The energetic requirements for ECL sensing were investigated, highlighting the importance of the excited state energy for achieving efficient ECL. The sensing mechanism was elucidated using NMR spectroscopy and MALDI-TOF analysis. An ECL formaldehyde probe was developed by modulating the LUMO energy level of the probe before and after the reaction with formaldehyde.

Automated summary

This study reports a new electrochemiluminescence (ECL) probe based on a cyclometalated iridium complex for the selective detection of formaldehyde. By undergoing a functional group transformation, the iridium complex exhibits significant changes in electronic properties and molecular orbital energies, leading to enhanced ECL and radiometric phosphorescence changes. The energetic requirements for ECL sensing were investigated, and the sensing mechanism was elucidated using spectroscopic analysis.