Two Thermochromic Layered Iodoargentate Hybrids Directed by 4- and 3‑Cyanopyridinium Cations

Abstract

Two layered iodoargentates, [HCP]­[Ag₂I₃] (HCP⁺ = NH-4-cyanopyridinium) (<b>1</b>) and [MCP]­[Ag₄I₅] (MCP⁺ = <i>N</i>-methyl-3-cyanopyridinium) (<b>2</b>) have been solvothermally synthesized. For <b>1</b>, the inorganic layer is built up by 4-connected Ag₄I₈ unit with cubane-type Ag₄I₄ core via sharing peripheral μ₂-I in <i>ab</i> plane, while the HCP⁺ cations are located at the apertures and interlayer space. For <b>2</b>, the inorganic layer is constructed from [Ag₆I₆]_<i>n</i> and [AgI₃]_<i>n</i>^2<i>n</i>– chains via alternative corner- and edge-sharing modes along the <i>b</i>-axis, while the MCP⁺ cations lie between neighboring layers. Compounds <b>1</b> and <b>2</b> exhibit reducing band gaps relative to the bulk β-AgI and remarkable thermochromism, which are ascribed to the intermolecular charge transfer (CT) and affected by electron affinity of pyridinium cations