Intense Red-Blue Luminescence Based on Superfine Control of Metal-Metal Interactions for Self-Assembled Platinum(II) Complexes

Abstract

A series of assembled Pt^II complexes comprising N-heterocyclic carbene and cyanide ligands was constructed using different substituent groups, [Pt(CN)₂ (R-impy)] (R-impyH⁺ =1-alkyl-3-(2-pyridyl)-1H-imidazolium, R=Me (Pt-Me), Et (Pt-Et), ⁱ Pr (Pt-ⁱ Pr), and ^t Bu (Pt-^t Bu)). All the complexes exhibited highly efficient photoluminescence with an emission quantum yield of 0.51-0.81 in the solid state at room temperature, originating from the triplet metal-metal-to-ligand charge transfer (³ MMLCT) state. Their emission colors cover the entire visible region from red for Pt-Me to blue for Pt-^t Bu. Importantly, Pt-^t Bu is the first example that exhibits blue ³ MMLCT emission. The ³ MMLCT emission was proved and characterized based on the temperature dependences of the crystal structures and emission properties. The wide-range color tuning of luminescence using the ³ MMLCT emission presents a new strategy of superfine control of the emission color.

Keywords: assembly-induced luminescence; metal-metal interactions; photoluminescence; platinum complex; self-assembled systems.