Two-Dimensional Coordination Polymers with Spin Crossover Functionality

Abstract

In the solid state, the propagation of spin crossover (SCO) information is governed by a complex interplay between inner and outer coordination sphere effects. In this way, lattice cooperativity can be enhanced through solid state packing interactions (i.e. hydrogen-bonding and π-stacking) and via coordinatively linking spin switching sites (i.e. coordination polymers). SCO framework materials have successfully provided an avenue for enhanced cooperativity and additional function as host–guest sensors via their potential porosity. In this review, we explore two-dimensional SCO coordination polymers: (1) spin crossover frameworks (SCOFs) consisting of (4,4) grids and (2) Hofmann-type materials where layers are separated by organic ligands. These families have each allowed the elucidation of important structure–function properties and provided a novel platform for molecular sensing applications. Towards advancing the field of infinite polymeric SCO materials, two-dimensional materials can offer flexible porosity, potentially leading to novel spin state-switching functionality.