On stabilizing spin crossover complex [Fe(tBu₂qsal)₂] on suitable supports: insights from ab initio studies

Selecting suitable supports that can preserve intrinsic properties of spin cross over (SCO) complexes is an essential step for enabling their applications. Here, for the SCO complex [Fe(tBu₂qsal)₂], on the basis of density functional theory calculations, we conclude that while the Au(111) surface may not be a suitable support for the molecule, it may be so for their  monolayer (ML). Our rationale is based on charge transfer characteristics from the highest occupied molecular orbital of the molecule to the substrate which is noticeable for a single molecule but minimal for a monolayer on Au(111), leaving the electronic structure of the molecules unaltered. We also find a small magnetic exchange coupling (~0.01 meV) between the molecules in the ML indicating a weak magnetic coupling. These results suggest Au(111) as a plausible support for a monolayer of [Fe(tBu₂qsal)­₂], suitable for electronic and spin transport applications. As for [Fe(tBu₂qsal)­₂] SCO molecules themselves, we find h-BN to be a viable support for them, as there is hardly any charge transfer between the molecule and h-BN, unlike the case of graphene which displays stronger interaction with the molecule resulting in larger charge transfer from the molecule to graphene.