Metallates hexacyanometallate

L.M. Siperko and T. Kuwana, Electrochemical and spectroscopic studies of metal hexacyanometalate films. I. Cupric hexacyanoferrate. J. Electrochem. Soc. 130, 396-402 (1983). 

The Structure of Polycyanometalates metal hexacyanometalates. The chemical formulae indicate the... 

The most important feature of all polymeric metal hexacyanometalates is that they possess channels and holes, the size of which is mostly determined by the... 

Since many metal hexacyanometalates have very similar structures, the formation of solid solutions is possible. The positions and can be occupied not only by one kind of ion, but by a variety of similar ions, allowing the existence of substitutional solid solutions with a random distribution of the different ions on their specific positions. Table 2 gives an overview of the types of solid solutions that can be formed and some examples. 

The differences in formal potentials of different metal hexacyanometalates is the basis of tuning the redox properties of PCMs by synthesis of mixed solutions, as far as that is possible due to the ion radii. Examples for a continuous tuning of the hexacyanoferrate redox potential are mixed nickel/iron hexacyanoferrates [30], mixed copper/iron hexacyanoferrates [56], and mixed cadmium/iron hexacyanoferrates [33]. 

Prussian blue — iron(III) hexacyanoferrate(II) is the archetype of sparingly soluble mixed valence polymeric metal hexacyanometalates with the formula Me Me(N) [Me c (CN)6] with (i), (N), and (C) indicating the position in the crystal lattice, where (i) means interstitial sites, (N) means metal coordinated to the nitrogen of the cyanides, and (C) means metal ions coordinated to the carbon of the cyanides. It is one of the oldest synthetically produced coordination compounds and was widely used as pigment in paints because of the intensive blue color. The compound has been studied extensively by electrochemical and other methods. The importance of Prussian blue in electrochemistry is related to the fact that it has two redox-active metal centers and that it has an open structure that allows small cations to... 

Tab. 1 Space groups of some metal hexacyanometalates. The chemical formulae indicate the coordination of the metal ions bv usine the notation Me dMe - fCNlfill (cf. Fig. 1)...

Polynuclear transition metal hexacyanometallates, e.g., PB (iron(III) hexacyanoferrate(II)), are a class of insoluble mixed-valence compounds that have the general formula M j.[M"(CN)g] where M and M" are... 

Sawai, K. and N. Suzuki (2004). Heat-treated transition metal hexacyanometallates as electrocatalysts for oxygen reduction insensitive to methanol. J. Electwchem. Soc. 151, A682-A688. 

Apart from in the materials discussed so far, electrochromism is known to occur in mai binary and ternary mixed oxides and in oxyfluorides. There are also some simple oxides that have been reported to display electrochromism, although this phenomenon has not yet been explored in detail oxides based on Cu, Sr-Ti, Rtt, and Pr belong to this latter class.Finally, among the nonoxides pronounced anodic electrochromism is known in transition metal hexacyanometallates, especially Pmssian Blue (PB). ... 

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