Postsynthetic Integration of Silver Atoms into Spin Crossover Hofmann-Type Clathrates

Spin crossover (SCO) materials hold exceptional potential for applications in sensors, memory and photonic devices, and actuators, but their practical use remains constrained by a scarcity of compounds exhibiting transition temperatures above room temperature. Herein, we report a postsynthetic strategy to incorporate silver atoms within the pores of a Hofmann-type clathrate {Fe(pyrazine)[Ni(CN)₄]} framework. This in situ silver integration induces an 80 K shift in the spin transition temperature, accompanied by a 45 K wide hysteresis loop. Structural analyses using high-resolution TEM, PXRD, 3D electron diffraction, and spectroscopic techniques reveal that silver insertion proceeds via a redox-driven Ni(II) to Ni(III) transformation, leading to partial decoordination of the framework and the formation of silver atoms.