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.