Volume 27, Issue 2 p. 712-723
Full Paper

Deposition of the Spin Crossover FeII–Pyrazolylborate Complex on Au(111) Surface at the Molecular Level

Dr. Nicolás Montenegro-Pohlhammer

Dr. Nicolás Montenegro-Pohlhammer

Departamento de Química Física, Universidad de Sevilla, c/ Profesor García González, s/n., 41012 Sevilla, Spain

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Dr. Rocío Sánchez-de-Armas

Dr. Rocío Sánchez-de-Armas

Departamento de Química Física, Universidad de Sevilla, c/ Profesor García González, s/n., 41012 Sevilla, Spain

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Dr. Carmen J. Calzado

Corresponding Author

Dr. Carmen J. Calzado

Departamento de Química Física, Universidad de Sevilla, c/ Profesor García González, s/n., 41012 Sevilla, Spain

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First published: 02 September 2020
Citations: 11

Graphical Abstract

The deposition of FeII((3,5-(CH3)2Pz)3BH)2 on Au(111) surface is explored through rPBE periodic calculations. The LS (low spin) → HS (high spin) transition energy is enhanced by the surface. The adsorption is spin-dependent, and favors the LS state. The different strength of the Fe ligand field at low and high temperature is at the origin of the differential adsorption of the LS and HS molecules, the spin-dependent conductance, and the differences found in the STM images, correctly reproduced from the density of states (DOS) provided by rPBE calculations.

Abstract

The interaction at the molecular level of the spin-crossover (SCO) FeII((3,5-(CH3)2Pz)3BH)2 complex with the Au(111) surface is analyzed by means of rPBE periodic calculations. Our results show that the adsorption on the metallic surface enhances the transition energy, increasing the relative stability of the low spin (LS) state. The interaction indeed is spin-dependent, stronger for the low spin than the high spin (HS) state. The different strength of the Fe ligand field at low and high temperature manifests on the nature, spatial extension and relative energy of the states close to the Fermi level, with a larger metal–ligand hybridization in the LS state. This feature is of relevance for the differential adsorption of the LS and HS molecules, the spin-dependent conductance, and for the differences found in the corresponding STM images, correctly reproduced from the density of states provided by the rPBE calculations. It is expected that this spin dependence will be a general feature of the SCO molecule–substrate interaction, since it is rooted in the different ligand field of Fe site at low and high temperatures, a common hallmark of the FeII SCO complexes. Finally, the states involved in the LIESST phenomenon has been identified through NEVPT2 calculations on a model reaction path. A tentative pathway for the photoinduced LS→HS transition is proposed, that does not involve the intermediate triplet states, and nicely reproduces both the blue laser wavelength required for the activation, and the wavelength of the reverse HS → LS transition.

Conflict of interest

The authors declare no conflict of interest.