A near-infrared phosphorescent probe for F− based on a cationic iridium(III) complex with triarylboron moieties

Abstract

In this work, a near-infrared (NIR) phosphorescent probe for F− based on a cationic Ir(III) complex [Ir(Bpq)2(quqo)]PF6 (1) with dimesitylboryl (Mes2B) groups on the cyclometalated C∧N ligands (Bpq) and 2-(quinolin-2-yl)quinoxaline (quqo) as N∧N ligand was designed and synthesized. The excited state properties of 1 were investigated in detail using molecular orbital calculations and experimental methods. Upon excitation, complex 1 shows NIR phosphorescent emission around 680 nm. Interestingly, the complex can be excited with long wavelength around 610 nm. Such long-wavelength excitation can reduce the background emission interference and improve the signal-to-noise ratio. Furthermore, the selective binding between boron atom and F− can give rise to the quenching of emission and realize the near-infrared phosphorescent sensing for F−. We wish that the results reported herein will be helpful for the further design of excellent near-infrared phosphorescent probes based on heavy-metal complexes.