Tuning the Phosphorescence and Solid State Luminescence of Triarylborane-Functionalized Acetylacetonato Platinum Complexes

A new series of luminescent cyclometalated platinum complexes with triarylborane-functionalized acetylacetonate ligands is reported. The complexes exhibit solid state luminescence and phosphorescence under ambient conditions. The luminescence color can be tuned from green to red by varying the cyclometalating ligand [2-phenylpyridine (for 1 and 2), 2-thiophenylpyridine (for 3 and 4), 2-thianapthenylpyridine (for 5 and 6)]. The luminescence originates from mixed 3MLCT/3IL [MLCT, metal to ligand charge transfer; IL, intraligand] states of square planar platinum and borane moieties. The π spacer (phenyl or duryl) which connects the boryl and platinum entities has a significant role in determining the photoluminescence efficiency. The bulky duryl spacer in 2, 4, and 6 significantly reduces π–π stacking of the square planar platinum moiety in the solid state and provides a rigid backbone, thereby increasing their quantum yield significantly. The role of Lewis-acidic borane on the photoluminescence features is evaluated by fluoride binding experiments.