A complete review of all known octacyanide-based clusters with an extensive discussion of their structures, magnetic properties and multifunctionality.

tribute of molecule-based compounds called photomagnets and is inaccessible for conventional magnetic solids. The design and synthesis of such compounds, however, is a formidable challenge and only a few examples are known, all with rather low magnetic ordering temperatures well below the boiling point of liquid nitrogen. Herein, a cyanide-bridged coordination polymer {[Mn II (imidazole)]2[W IV (CN)8]}n exhibiting the highest light-induced magnetic ordering temperature ever observed and a magnetic hysteresis loop up to 90 K is reported. The photomagnetic effect results from the blue light excitation (450 nm) of the constituent octacyanotungstate(IV) moiety which then couples magnetically with manganese(II) resulting in light-induced ferrimagnetic ordering. The reported coordination framework shows also outstanding water sorption properties that are strongly correlated with the photomagnetic functionality. The photo-switching observed in the anhydrous state is completely quenched by the reversible capture of water with the fully hydrated phase becoming practically non-photomagnetic.

An alternating bimetallic {(H3O)[Ni(III)(cyclam)][Fe(II)(CN)6]·5H2O}n chain undergoes reversible dehydration at 40 °C accompanied by electron transfer which leads to Ni(II)-Fe(III) in about 50% of metal centres. The hydrated dark blue form is a paramagnet while the dehydrated yellowish-green form shows ferromagnetic coupling between neighbouring Ni(II) and Fe(III).

The synthesized chiral (R)- and (S)-2-(1-hydroxyethyl)­pyridine ligands (R/S-mpm) were introduced to self-assembled CoII-[WV(CN)8] and NiII-[WV(CN)8] magnetic systems giving a remarkable series of four enantiopure cyanido-bridged clusters, {MII[MII(R/S-mpm)­(MeOH)]8­[WV(CN)8]6}­·14MeOH (M = Co, 1-R and 1-S; M = Ni, 2-R and 2-S). They consist of 15 metal centers, 9 CoII or NiII ions, and 6 [WV(CN)8]3– ions, embedded in a 6-capped body-centered cube topology. Bidentate enantiopure mpm ligands coordinated to eight external CoII or NiII sites induce their chiral character, which results in the strong natural optical activity in the broad UV–vis range of 200–700 nm. All (1-R/S) and (2-R/S) clusters reveal cyanido-mediated ferromagnetic exchange interaction giving high-spin ground states of 15/2 (1-R/S) and 12 (2-R/S). For (2-R/S) forms of {Ni9W6}, the exchange constant J = +16.1 cm–1 was obtained using exact diagonalization of the exchange Hamiltonian. Because of the significant magnetic anisotropy, (1-R/S) forms of {Co9W6} cluster reveal the low temperature onset of the slow magnetic relaxation characteristic of single-molecule magnets (SMMs). Thus, they can be considered as a rare example of chiral SMM molecules.

A new form of 2D honeycomb-like network is characterised by flat layers and undergoes single-crystal-to-single-crystal transformation to corrugated hexadecahydrate.

Hexacyanidometallates of transition metal ions govern the topology and the photoluminescence of bimetallic d–f hybrid coordination networks incorporating uranyl cations.

Functional materials incorporating cyanido-bridged DyIIICoIII molecules combine visible photoluminescence and slow magnetic relaxation, both switchable by the level of humidity within the reversible room temperature dehydration process.

Reaction between [Ni(cyclam)](2+) and [W(CN)(8)](4-) leads to the formation of a 3D diamond-like network [Ni(cyclam)](2)[W(CN)(8)]·3.5H(2)O (1). The structure is characterised by a network of intersecting channels of 3-4 Å in diameter, filled with crystallisation water, most of which is released upon drying in air, causing the crystals to collapse. Analogous compound [Ni(cyclam)](2)[Nb(CN)(8)]·3.5H(2)O (2), based on paramagnetic Nb(IV), could only be obtained as a powder, due to the decomposition of the [Nb(CN)(8)](4-) complex under slow diffusion conditions. It shows long-range magnetic ordering with T(C) = 11.8 K and magnetic hysteresis at 2 K. These properties are lost upon drying in air. After rehydration differently shaped hysteresis appears, which together with AC susceptibility measurements suggests the formation of a multiphase system. Subsequent dehydration-rehydration experiments show partial reversibility.