Investigation of spin-crossover complexes for surface deposition

Divya Kumar, Miguel Gakiya-Teruya, Michael Shatruk

Florida State University

Spin crossover (SCO) is a reversible change in the electronic spin state of d⁴-d⁷ transition metal ions upon action by an external stimulus, such as temperature, pressure, or light. Arguably, SCO has been the most extensively studied example of magnetic, structural, and optical bistability in molecule-based materials.¹ Although the SCO phenomenon has been widely studied and well understood in the bulk form and in solution, recent interest in the use of such materials in electronic devices necessitates translating SCO complexes to thin-film architectures.^2,3 We are exploring ways to reduce SCO materials to thin films via gas-phase transport (sublimation) or direct mechanical exfoliation of molecular layers from bulk crystals. In this contribution, we demonstrate (1) the use of asymmetric tridentate Schiff-base ligands with different substituents to increase the volatility of Fe(II) SCO complexes for non-covalent deposition, and (2) to study the effect of oxidation of Fe(II) into Fe(III) on the spin state of the complex. The variable-temperature structural and magnetic properties of several such complexes will be discussed. We show that the oxidation of the metal center from the Fe(II) to Fe(III) state generally increases the ligand field strength and promotes spin crossover.

References:

Gakiya-Teruya, M.; Shatruk, M.; et al. Asymmetric design of spin-crossover complexes to increase the volatility for surface deposition. J. Am. Chem. Soc. 2021, 143, 14563.Gruber, M.; Berndt, R. Spin-crossover complexes in direct contact with surfaces. Magnetochemistry 2020, 6, 35.Kumar, K. S.; Ruben, M. Sublimable spin‐crossover complexes: from spin‐state switching to molecular devices. Angew. Chem. Int. E. 2021, 60, 7502.