Phosphorescence Enhancement Triggered by Π Stacking in Solid-State [Cu(N−N)(P−P)]BF4 Complexes

Abstract

In this article, we report a phosphorescence enhancement phenomenon of [Cu(N−N)(P−P)]BF₄ complexes in the solid state. The phosphorescence enhancement phenomenon is composed of three features: (1) an obvious emission blue shift, (2) a greatly enhanced photoluminescence quantum yield, and (3) a longer excited-state lifetime. Systematic analyses prove that the main cause of this phenomenon is nonradiative process suppression triggered by the π stacking between [Cu(N−N)(P−P)]BF₄ molecules. The phorsphorescence enhancement widely exists in [Cu(N−N)(P−P)]BF₄ complexes because of the π surfaces in their diimine ligands.