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)3]2Ag6Br11·NO3 (bpy = 2,2′ bipyridine)─consisting of two-dimensional (2D) Ag(I)-based (Ag6Br11)n5n– anionic sheets, zero-dimensional (0D) [Fe(bpy)3]3+ complexes (acting as the structure-directing agent), and interlayer disordered NO3– anions. Specifically, the thermodynamically unstable cation [Fe(bpy)3]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 (Ag6Br11)n5n– 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.