Prussian Blue family

The redox chemistry of the Prussian blue family (Table 7) has attracted considerable attention. The generation of thin films of Prussian blue has led to studies of its mediation in electron transfer reactions and of the electrochemical processes involved in its deposition and redox reactions. This work has been spurred by its electrochromic properties which have been used in prototype electronic display devices based, for example, on Prussian blue modified Sn02 electrodes. A recent review deals with the electrochemistry of electrodes modified by depositing thin films of PB and related compounds on them. Interestingly, true Prussian blue is somewhat difficult to process and modern iron blue pigments such as Milori blue are derived from the oxidation of rlin white Fe(NH4)2[Fe(CN)e] to give iron(III) ammonium ferrocyanides. 

The prime example of this is the many magnets based on the Prussian Blue family (Figure 2.7) [63,65-68]. It is also believed that the other example of a room temperature molecule based magnet , V(tetracyanoethylene)-x(CH2Cl2), has a structure formed by a three dimensional irregular net (this compound is not crystalline) [69]. 

Another series of important compounds that arc based on pcu nets arc the Prussian blue family, [IVI(CN)f,M J, many of them with magnetic properties [4446J. Note however that in Prussian Blue itself one out of every four hexacyanide-units is missing from the structure. 

An additional family of organometallic materials is the cyanometallates, which are Prussian blue analogues. These are microporous materials, similar to zeolites, with relatively large adsorption space and small access windows [237-241], These Prussian blue analogues develop zeolite-like structures based upon a simple cubic (T[M(CN)6]) framework, in which octahedral [M(CN)6]" complexes are linked via octahedrally coordinated, nitrogen-bound Tm+ ions [237], In the prototypic compound, that is, Prussian blue, specifically (Fe4[Fe(CN)6]3 14H20), charge balance with the Fe3+ ions conducts to vacancies at one-quarter of the [Fe(CN)6]4 complexes [242],... 

The most intensely colored inorganic substances contain elements of the same atom in two different valence states. Two examples are Prussian Blue KFenFeni(CN)6 (Chap. 24), and the family of tungsten bronzes which may be considered to contain tungsten in both the +5 and +6 states (Chap. 21). 

Whereas within the family of the cubic Prussian blue analogs a large number of lattice constants have been determined, little attention has been devoted so far to polymeric cyanides not belonging to the cubic system. It must be emphasized, however, that polynuclear cyanides having unit cell symmetries other than cubic are by no means rare exceptions. Hexacyanometalates(III) of Zn2+ and Cd2+ are obtained not only in a cubic modification but also as samples with complicated and not yet resolved X-ray patterns of definitely lower symmetry than cubic (55). The exact conditions for obtaining either modification are not yet known in detail. The hexacyanoferrates(II), -ruthenates(II), and -osmates(II) of Mn2+ and several modifications of the corresponding Co 2+ salts show very complicated X-ray powder patterns which cannot be indexed in the cubic system (55). Preliminary spectroscopic studies show the presence of nearly octahedral M C6-units in these compounds, too. 

Prussian blue analogues that represent a large family of compounds based on a cubic M [M(CN)6] framework could be prepared by following the general reaction scheme ... 

The Cyanotype process is the most successful of a family of imaging methods based on the photochemistry of iron compounds. The basic system involves the photochemical formation of the pigment Prussian Blue or iron(III) hexacyanoferrate. 

Figure 2.7 Bimetallic Prussian Blue-like a-polonium or pcu nets (compare Figure 2.2) based on hcxacyanomctallatc building blocks form an important family of moicculc-bascd magnets.

PCPs have infinite networks with backbones constructed by metal ions as connectors and ligands as linkers, and form a family of inorganic and organic hybrid polymers. The structural integrity of the building units, which can be maintained throughout the reactions, allows for their use as modules in the assembly of extended structures. Werner complexes, /3-M(4-melhylpyridyl)4(NCS)2 (M = Ni(II) or Co(II)) [48], Prussian blue compounds [49-51], and Hofmann clathrates and their... 

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