AIE Triggers the Circularly Polarized Luminescence of Atomically Precise Enantiomeric Copper(I) Alkynyl Clusters

Abstract

Atomically precise enantiomeric metal clusters are scarce, and copper(I) alkynyl clusters with intense circularly polarized luminescence (CPL) responses have not been reported. A pair of chiral alkynyl ligands, (R/S)-2-diphenyl-2-hydroxylmethylpyrrolidine-1-propyne (abbreviated as R/S-DPM) we successfully prepared and single crystals were characterized of optically pure enantiomeric pair of atomically-precise copper(I) clusters, [Cu₁₄ (R/S-DPM)₈ ](PF₆ )₆ (denoted as R/S-Cu₁₄ ), which feature bright red luminescence and CPL with a high luminescence anisotropy factor (g_lum ). A dilute solution containing R/S-Cu₁₄ was nonluminescent and CPL inactive at room temperature. Crystallization- and aggregation-induced emission (CIE and AIE, respectively) contribute to the triggering of the CPL of R/S-Cu₁₄ in the crystalline and aggregated states. Their AIE behavior and good biocompatibility indicated applications of these copper(I) clusters in cell imaging in HeLa and NG108-15 cells.