Sign inversion of magnetic circularly polarized luminescence in Iridium() complexes bearing achiral ligands

Optically inactive, paramagnetic Ir( iii )(ppy) 3 and Ir( iii )(ppy) 2 (acac) (ppy: 2-phenylpyridinate and acac: acetylacetonate) showed nearly mirror-symmetric magnetic circularly polarised luminescence (MCPL) spectra in dilute dichloromethane and dimethyl sulfoxide under N-up and S-up geometries in a 1.6-T magnetic field. However, the MCPL signs of Ir( iii )(ppy) 3 and Ir( iii )(ppy) 2 (acac) under the same N-up (or S-up) Faraday geometry were opposite to each other when one ppy was replaced with an acac. This ligand exchange approach provides facile control of the MCPL sign, irrespective of the Faraday geometry. MCPL signs of Ir( iii ) luminophores can be controlled by the magnetic field's direction and the type of achiral ligands.