Bulk and Surface Switching in Mn−Fe-Based Prussian Blue Analogues

Abstract

Many Prussian Blue Analogues are known to show a thermally induced phase transition close to room temperature and a reversible, photo-induced phase transition at low temperatures. This work reports on magnetic measurements, X-ray photoemission and Raman spectroscopy on a particular class of these molecular heterobimetallic systems, specifically on Rb0.97Mn[Fe(CN)6]0.98·1.03H2O, Rb0.81Mn[Fe(CN)6]0.95·1.24H2O and Rb0.70Cu0.22Mn0.78[Fe(CN)6]0.86·2.05H2O, to investigate these transition phenomena both in the bulk of the material and at the sample surface. Results indicate a high degree of charge transfer in the bulk, while a substantially reduced conversion is found at the sample surface, even in case of a near perfect (Rb:Mn:Fe=1:1:1) stoichiometry. Thus, the intrinsic incompleteness of the charge transfer transition in these materials is found to be primarily due to surface reconstruction. Substitution of a large fraction of charge transfer active Mn ions by charge transfer inactive Cu ions leads to a proportional conversion reduction with respect to the maximum conversion that is still stoichiometrically possible and shows the charge transfer capability of metal centers to be quite robust upon inclusion of a neighboring impurity. Additionally, a 532 nm photoinduced metastable state, reminiscent of the high temperature Fe III Mn II ground state, is found at temperatures 50-100 K. The efficiency of photo-excitation to the metastable state is found to be maximized 90 K. The photo-induced state is observed to relax to the low temperature Fe II Mn III ground state at a temperature of approximately 123 K.

On the Scope of XPS as Sensor in Coordination Chemistry of Transition Metal Hexacyanometallates

“…Such structural features modulate the charge density on the metal linked at the N end, which is sensed through the core electrons binding energy. With few exceptions,, the main reports on the applications of XPS in that sense dated from several decades ago, when some of the mentioned structural features were unknown or received little attention. In addition, in the last two decades, the possibility to have XPS data recorded under high‐resolution condition has received large improvement, mainly due to the availability of more versatile instruments and advanced models and software for data processing.…”

New Rhodium‐rich Germanides RERh6Ge4 (RE = Y, La, Pr, Nd, Sm–Lu)

“…The peaks at 2088 and 2149 cm −1 are assigned to symmetry‐spit normal modes of Fe II ‐CN‐Fe III , which are observed for PB, but not for MWCNT‐PB in 31b. 32 The FTIR and Raman spectra both show the absence of the ν(CN) band of PB in MWCNTs‐PB in , which again validates the successful removal of outer‐surface PB.…”

Growth Dynamics of Photoinduced Phase Domain in Cyano-Complex Studied by Boundary Sensitive Raman Spectroscopy

“…and Fe 3+ -CN-M 3+ (M = transition metal) have been reported to typically correspond to the ranges of 2065-2110, 2090-2140, 2146-2185 and 2180-2210 cm −1 in the Raman and infrared spectrum, respectively [10,11]. Therefore, the peaks at 2170 and 2234 cm −1 in Fig.…”

“…2b can be assigned to LTP, since a previous report by Cobo et al [12] clearly assigned two sharp peaks at 2096 and 2114 cm −1 to LTP. Furthermore, Vertelman et al [10] and Lummen et al [11] have observed several broadened peaks at 2086-2130 cm −1 in the Raman spectra and assigned them to LTP. Based on these studies, we attributed the peaks at 2096 and 2137 cm −1 in Fig.…”