Cyclometalated Iridium(III) Complex with Substituted Benzimidazole: pH Directed Organelle‐specific Localization within Lysosome

Abstract

We report the synthesis and pH dependent emission spectral behaviour of four emissive iridium(III) complexes (Ir1 – Ir4) with two isomeric pairs of bis‐trifluoromethyl appended benzimidazole ligands. The imidazolyl hydrogen(N‐H) has been replaced by phenyl groups (N‐Ph) in two ligands to understand the impact of hydrogen bonding on the photophysical properties of the complexes and it indeed plays interesting role in the charge‐transfer dynamics. The pH dependent electronic spectral change is observed for two of the complexes. The enhancement of emission intensity is observed at different wavelength for pH < 7 and pH > 7 for Ir1 and Ir3. The emission sensing of biogenic amines with pka values ranging from 5.80 – 9.74 is reported along with cellular imaging. The complex Ir1 specifically localizes within lysosome (pH = 4.5 – 5) and thus image this organelle with great precision. The detail electronic spectra and electrochemical behaviour were reported here along with TDDFT results.