Pyrazolo[4,3-h]quinoline Ligand-Based Iridium(III) Complexes for Electrochemiluminescence

Electrochemiluminescence (ECL) based on [Ru(bpy)₃ ]²⁺ systems is widely utilized for immunoassays. In order to extend the promising potential of ECL-based applications, Ir^III complexes have recently attracted attention as probes because of their excellent luminescent properties and tunable emission wavelength. Here we describe a series of Ir complexes using a large π-conjugated ligand and different ancillary chelates. The complexes synthesized have been chemically and spectroscopically characterized and used for ECL measurements with annihilation and co-reactant methods. One of the Ir^III complexes investigated exhibits the brightest, ever reported, ECL efficiency in acetonitrile employing the benzoyl peroxide (BPO) co-reactant method.