Four Discrete Silver Iodobismuthates/Bromobismuthates with Metal Complexes: Syntheses, Structures, Photocurrent Responses, and Theoretical Studies.

Abstract

Using in situ formed metal complexes of [Fe(bipy)3]2+ or [Ni(bipy)3]2+ (bipy = 2,2'-bipyridine) as templates, four new Ag-Bi-X (X = I and Br) compounds are first isolated in the metal-complex-decorated heterometallic halobismuthate family, namely [M(bipy)3]AgBiI6 (M = Fe (1), Ni (2)), [Fe(bipy)3]AgBiBr6 (3), and [Ni(bipy)3]AgBiBr6 (4). Compounds 1-4 feature discrete [AgBiX6]n2n- anions, exhibiting three polymorphisms that may be ascribed to the different stackings and the flexible condensations of [BiX6] octahedrons and [AgX4] tetrahedra/[AgX3] triangles. UV-vis diffuse reflectance analyses reveal that they are narrow band gap semiconductor materials (ca. 1.82-2.13 eV). Intriguingly, the title compounds display excellent photoelectrical switching properties, with photocurrent density following the order 3 > 4 > 2 > 1. In addition, the comparative studies of intermolecular interactions, theoretical band structures, density of states, and effective masses of three polymorphisms have also been investigated.