Electron transfer and spin transition in metal-hexacyanoferrates driven by anatase TiO2: electronic and structural order effects

Michela Ciabocco (1) , Mario Berrettoni (1) , Marco Giorgetti (1) , Sougrati Moulay-Tahar (2, 3) , Nicolas Louvain (3, 2) , Lorenzo Stievano (3, 2)

1 UNIBO - Alma Mater Studiorum Università di Bologna = University of Bologna
2 RS2E - Réseau sur le stockage électrochimique de l'énergie
3 ICGM - Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier

57 Fe Mössbauer spectroscopy was used to highlight a charge transfer mechanism in cobalt hexacyanoferrate (CoHCF) when synthetized in the presence of anatase TiO2. The electron transfer in TiO2–CoHCF composites along the Co–NC–Fe–CN–Co chain is confirmed by the unequivocal evolution of the typical quadrupole doublet of Fe(II) and Fe(III) in pristine CoHCF into the single line spectrum of the Fe(II) species when CoHCF is nanodispersed on TiO2 anatase. Parallel galvanostatic measurements also confirm the electron transfer mechanism induced by TiO2. To the best of our knowledge, this is one of the first examples of the triggering of spin-crossover phenomena in metal-hexacyanoferrate based-molecular solids by an external stimulus other than photoexcitation and most of all one of the first studies in which a completely pure low-spin Fe(II) is obtained starting from a mix of low-spin Fe(II) and Fe(III).

Domaines: Matériaux

Michela Ciabocco, Mario Berrettoni, Marco Giorgetti, Sougrati Moulay-Tahar, Nicolas Louvain, et al.. Electron transfer and spin transition in metal-hexacyanoferrates driven by anatase TiO2: electronic and structural order effects. New Journal of Chemistry, 2016, 40 (12), pp.10406-10411. ⟨10.1039/C6NJ02650H⟩. ⟨hal-01404501⟩