Metal-to-ligand and ligand-to-metal charge transfer in thin films of Prussian blue analogues investigated by X-ray absorption spectroscopy

Abstract

A series of thin films of Prussian blue analogues is investigated by X-ray absorption spectroscopy (XAS) at the Fe, Co and Mn L 2,3 -edges. The ligand field multiplet theory enables us to examine accurately the electronic structure of these materials. Experimental XAS spectra of CoFe Prussian blue analogues are successfully reproduced using a ground state configuration including metal-toligand (MLCT) and ligand-to-metal charge transfer (LMCT) at the Co and Fe L 2,3 -edges. In particular, a huge improvement is achieved for satellite peaks at the Co(III) L 2,3 -edges compared to previous calculations in the literature based on LMCT effects only. On the other hand, XAS spectra of MnFe analogues synthesized for the first time, can be reproduced conveniently by taking into account either MLCT or LMCT depending on the conditions of the sample preparation. For each thin film, the proportion of the different oxidation states of Co, Fe and Mn is evaluated. Unexpectedly, this analysis reveals the presence of a significant amount of a reduced phase, which turns out to be strongly dependent on the sample synthesis and storage conditions.

Retracted Article: On the enzymatic activity of catalase: an iron L-edge X-ray absorption study of the active centre

“…In fact, only 3% of the d 4 L À MLCT configuration should be introduced in the ground state (Table 1) to reduce the intensity of the pre-edge peak at the L 3 -edge, obtained by means of a calculation including only LMCT. Such sensitivity due to the addition of MLCT has already been observed in a solid state molecular material at the Co L 2,3 -edges, 27 but this is the first time that it has been observed at the Fe L 2,3 -edges of a haem protein in a physiological solution. In addition, this reveals that XAS is able to probe very efficiently the electronic structure and shed light on even weak charge-transfer effects in metal-based molecular complexes.…”

Reversible mechanism for spin crossover in transition-metal cyanides

“…1,2 The calculated Co crystal field splitting (∆ Co o =0.97 eV) also agrees with x-ray absorption spectra (1.1 eV). 16,31,32 There is a further splitting between the majority and minority spin channels due to intra-atomic exchange interaction. If this exchange splitting ∆ x is higher than ∆ o , the majority spin channel is occupied first, followed by minority spin channel.…”

“…eV). 16,31,32 For the ferromagnetic (FM) high spin state, the band gap energy of 1.25 eV in the minority spin channel represents the Co II →Fe III CT excitation (Fig. 2).…”

Soft x-ray absorption spectroscopy study of the electronic structures of the MnFe Prussian blue analogs (RbxBay)Mn[3−(Lee1, Seong2, Kim3 et al. 2017Phys. Rev. B9010View full textAdd to dashboardCite

“…Then, as in CoFe PBAs, the valence transition between the Mn 2+ (S = 5/2)−Fe 3+ (S = 1/2) pairs at HT and the Mn 3+ (S = 2)-Fe 2+ (S = 0) pairs at LT has been suggested for MnFe PBAs [6,10,16,17]. However, these models are controversial [3,9,[12][13][14][15][16][17], and the experimental evidence for them is lacking. Therefore, in order to understand the origin of the switching phenomena in PBAs, it is crucial to determine the valence and spin states of M and M ions experimentally.…”

“…The switching phenomena, observed in a CoFe PBA [3], were often ascribed due to a charge transfer between the Co 2+ (S = 3/2)-Fe 3+ (S = 1/2) pairs and the Co 3+ (S = 0)-Fe 2+ (S = 0) pairs through the cyanide C ≡ N bridge. In this interpretation, the low-spin (LS) Co 3+ (t [3,[12][13][14][15]. In certain Rb x Mn z [Fe(CN) 6 ] · mH 2 O PBAs, a temperature (T ) -induced phase transition with a large thermal hysteresis was observed [10,16,17].…”