Anion-Directed Regulation of Structures and Luminescence of Heterometallic Clusters

Anions have been used to regulate the structures and luminescence of heterometallic clusters. Introducing ClO4- into orange-emissive, butterfly-like [(C)(Au-PPhpy(2))(6)Ag-4](BF4)(6) (1, PPhpy(2) = bis(2-pyridyl)-phenylphosphine) leads to the formation of red-emissive [(C)(Au-PPhpy(2))(6)Ag-5(ClO4)(3)](ClO4)(4) (2) with a novel trigonal bipyramidal structure; employing PhCO2- gives yellow-emissive, hexagram-like [(C)(Au-PPhpy(2))(6)Ag-6(PhCO2)(3)](BF4)(5) (3). Notably, 1 exhibits weak luminescence in CH2Cl2/CH3OH =1:1 (v :v) with a quantum yield (QY) of 0.05, whereas it was dramatically increased to 0.49 and 0.83 for 2 and 3, respectively. Theoretical calculation confirms that the involvement of anions in the electronic structures is responsible for the shifts of emission. The high QYs of 2 and 3 are attributed to the protection provided by ligands and anions. This work demonstrates that anions may serve as an extra designable factor beyond just counterions for functional metal clusters.

Automated summary

Anions have been used to regulate the structures and luminescence of heterometallic clusters. Different anions can change the emission color and structure of metal clusters. The involvement of anions leads to a shift of emission peak, and the high quantum yields of the clusters are attributed to the protection provided by ligands and anions.