Synthesis, Crystal Structures, and Magnetic Properties of Cyanide-Bridged WVMnIII Anionic Coordination Polymers Containing Divalent Cationic Moieties: Slow Magnetic Relaxations and Spin Crossover Phenomenon

Two trimetallic coordination complexes were prepared by self-assembly of [W­(CN)8]3– and the Mn­(III) Schiff base followed by the addition of a Zn­(II) or Fe­(II) cationic unit. The octacyanotungstate connects neighboring Mn­(III) centers to form a one-dimensional chain. The anionic chain requires cationic units of Zn­(II) or Fe­(II) to maintain charge balance in the structure. The Zn-containing complex shows ferrimagnetic behavior originating from the antiparallel alignment of W­(V) and Mn­(III) spins within the chain, which leads to slow magnetic relaxation at low temperatures. For the Fe­(II)-containing compound, Fe­(II) moieties are integrated into the ferrimagnetic chains, altering their spin states depending on the temperature. It appears that the coexistence of high- and low-spin states in the low temperature regime is responsible for the slower and faster relaxations of the magnetization.