Synergistic Photoconductivity and Ultralow Thermal Conductivity upon Stabilizing Iron(III)-tris(2,2?-bipyridine) in a Two-Dimensional Haloargentate Network

Abstract

Crystalline organic–inorganic halometallate hybrids have emerged as promising materials for optoelectronic applications due to their structural diversity and tunable properties. We report a three-dimensional (3D) hybrid organic–inorganic crystal?[Fe(bpy)<inf>3</inf>]<inf>2</inf>Ag<inf>6</inf>Br<inf>11</inf>·NO<inf>3</inf>(bpy = 2,2? bipyridine)?consisting of two-dimensional (2D) Ag(I)-based (Ag<inf>6</inf>Br<inf>11</inf>)<inf>n</inf>5n–anionic sheets, zero-dimensional (0D) [Fe(bpy)<inf>3</inf>]3+complexes (acting as the structure-directing agent), and interlayer disordered NO<inf>3</inf>–anions. Specifically, the thermodynamically unstable cation [Fe(bpy)<inf>3</inf>]3+is stabilized under ambient conditions by the two-dimensional (2D) inorganic anionic scaffold. The crystal exhibits strong ligand-supported argentophilic interactions (Ag···Ag bond distance of 2.98 Å), forming an extended (Ag<inf>6</inf>Br<inf>11</inf>)<inf>n</inf>5n–network, and displays broad UV–visible absorption with a band gap of 1.90 eV. Remarkably, this organic–inorganic hybrid shows a ?103-fold increase in photocurrent under 532 nm light illumination. Density functional theory calculations provided the mechanistic insights, and such a remarkable photoconductivity is attributed to an efficient charge delocalization and inorganic-to-organic charge transfer. Additionally, the crystal exhibits an ultralow thermal conductivity over a broad temperature range (?0.3 W/m·K; 300–400 K), making it an excellent candidate for heat management applications. © 2025 American Chemical Society