Vapor-triggered Green-to-Yellow Luminescence Conversion due to the Variation of Ligand Orientations in Tetranuclear Copper(I) Complex.

The reaction of 3,6-di-butyl-1,8-bis(diphenylphosphino)-9-methyl-9H-carbazole (L) with CuBr resulted in the isolation of tetranuclear copper(I) complex CuBrL as two colorless crystal morphs, i.e., green-emitting and yellow-emitting . As demonstrated by X-ray crystallography, the CuBr moiety in both and adopts the same chair conformations. When L is bonded perpendicularly to the Cu plane, with green emission is obtained, while it gives a yellow emission of once the L is parallelly bonded to Cu plane. Theoretical computational studies suggest that the variation in ligand orientation results in a different degree of structural distortion in triplet state and thus different luminescent energy. Particularly, undergoes dramatic structural distortion from the ground (S) to triplet excied state (T). Interestingly, can be converted into upon exposed to saturated hexane vapor, which would return to upon exposure to acetonitrile vapor. As demonstrated experimentally and theoretically, the reversible luminescence transformation between and is ascribed to the variation of ligand L orientations.