Organo Chalcogenone-Triggered Luminescent Copper(I) Clusters for Light Emitting Applications

A novel organo sulfur and selenium-controlled emission behavior in discrete copper(I) clusters has been demonstrated for the first time. The pentanuclear [Cu₅Br₅(L)₂] (1), trinuclear [Cu₃Br₃(L)₂] (2), dinuclear [Cu₂I₂(L)₂] (3), and tetranuclear [Cu₄I₄(L)₂CH₃CN] (4) copper(I) discrete clusters have been synthesized from the reaction between L [L = 1-isopropyl-3-(pyridin-2-yl)-imidazol-2-thione] or L [L = 1-isopropyl-3-(pyridin-2-yl)-imidazol-2-selone] chelating ligands and corresponding copper(I) halide salts. These new clusters have been characterized by FT-IR, UV-visible, thermogravimetric analysis, and fluorescence spectroscopy techniques. Single-crystal X-ray diffraction studies reveal that 1-4 consists of abundant d interactions. The structural and bonding features of clusters have been investigated using density functional theory calculations. Notably, the L-ligated 2 and 4 are poorly emissive, while L-ligated 1 and 3 showed strong emission in the orange and green regions, respectively. The time-dependent density functional theory natural transition orbital calculations of 1 and 3 reveal the nature of the transitions contributed by ³MLCT/³LLCT/³ILCT. Photoluminescence quantum yields of 1 and 3 are 19 and 11%, with average lifetimes of 21.55 and 6.57 μs, respectively. 1 and 3 were coated on prototype LED bulbs for light-emitting performance.