Polyoxometalate-Assisted Assembly of Pearl-Chain-Like Cyanide-Bridged Single-Chain Magnets.

The introduction of Keggin-type POMs of [PMoO] or [SiWO] as counteranions into the Fe-M cyanometalate system afforded three chain complexes: [(Tp*)Fe(CN)Ni(DMF)]{[(Tp*)Fe(CN)Ni(DMF)(HO)]Ni(DMF)}[PMoO]·14DMF (, Tp*= hydridotris(3,5-dimethylpyrazol-1-yl)borate) and {[(Tp*)Fe(CN)M(DMF)(HO)]M(DMF)}[SiWO]·3DMF (, M = Ni; , M = Co). Complex contains both discrete cationic [FeNi] squares and less-studied {FeNi} pearl chains, namely 3,2-chains, while and consist of pure 3,2-chains due to the replacement of [PMoO] with [SiWO] bearing one more negative charge. Magnetic studies revealed that all of the complexes exhibit single-chain-magnet (SCM) behaviors with the effective thermal barriers of Δ/ = 61.6 K (infinite regime) and Δ/ = 36.5 K (finite regime) for , Δ/ = 46.9 K for (finite), and Δ/ = 30.6 K for (finite). The POM moieties may play a pivotal role for the realization of this promising archetype of favoring SCM property: (1) the highly negatively charged POMs may facilitate the formation of the uncommon highly positive "pearl chain"; (2) the nanosized POMs necessarily led to the good isolation of the chains in the title complexes, and (3) the employment of POMs with different charges may regulate the resultant complexes in both structure and magnetism.