Hierarchical Spin-Crossover Cooperativity in Hybrid 1D Chains of FeII-1,2,4-Triazole Trimers Linked by [Au(CN)2]- Bridges

Foremost, practical applications of spin-crossover (SCO) materials require control of the nature of the spin-state coupling. In existing SCO materials, there is a single, well-defined dimensionality relevant to the switching behavior. A new material, consisting of 1,2,4-triazole-based trimers coordinated into 1D chains by [Au(CN)(2)](-) and spaced by anions and exchangeable guests, underwent SCO defined by elastic coupling across multiple dimensional hierarchies. Detailed structural, vibrational, and theoretical studies conclusively confirmed that intra-trimer coupling was an order of magnitude greater than the intramolecular coupling, which was an order of magnitude greater than intermolecular coupling. As such, a clear hierarchy on the nature of elastic coupling in SCO materials was ascertained for the first time, which is a necessary step for the technological development of molecular switching materials.

Automated summary

A new study revealed that the elastic coupling in the new SCO material occurs across multiple dimensional hierarchies, with intra-trimer coupling being significantly greater than intramolecular and intermolecular coupling. This clear hierarchy in the nature of elastic coupling in SCO materials is essential for the technological development of molecular switching materials.