Turning On MLCT Phosphorescence of Iridium(III)-Borane Conjugates upon Fluoride Binding

Abstract

The heteroleptic complexes (C boolean AND N)(2)Ir-III (C boolean AND N: ppy, 2; btp, 3), bearing a 4-(dimesitylbory)benzoate (Bbz) auxiliary ligand, and their fluoride adducts were prepared and characterized. While the PL spectra of 2 and 3 exhibit very weak emission in solution, the addition of fluoride turned on (C boolean AND N)(2)Ir-centered phosphorescence (lambda(em) 527 nm for 2 and 617 nm for 3). Experimental and DFT calculations suggest that the weak emission is ascribable to a photoinduced electron transfer from the MLCT state of the (C boolean AND N)(2)Ir moiety to the Bbz ligand and is switched on by fluoride binding to the boron center of the Bbz ligand.