Magnetic interactions controlled by light in the family of Fe(ii)–M(iv) (M = Mo, W, Nb) hybrid organic–inorganic frameworks

Abstract

Three new hybrid organic–inorganic frameworks employing octacyanidometallates and 4,4′-bypiridine dioxide (4,4′-bpdo) as bridging molecules were prepared and characterized. The three-dimensional coordination frameworks {[Fe^II(μ-4,4′-bpdo)(H₂O)₂]₂[M^IV(CN)₈]·9H₂O}_n (Fe₂Mo, Fe₂W and Fe₂Nb; M = Mo, W and Nb) are composed of cyanido-bridged chains, which are interconnected by the organic linkers. Magnetic measurements for Fe₂Nb show a two-step transition to the antiferromagnetic state, which results from the cooperation of antiferromagnetic intra- and inter-chain interactions. Fe₂Mo and Fe₂W, on the other hand, behave as paramagnets at 2 K because of the diamagnetic character of the corresponding octacyanidometallate(IV) building units. However, after 450 nm light irradiation they show transition to the metastable high spin Mo^IV or W^IV states, respectively, with distinct ferromagnetic intrachain spin interactions, as opposed to the antiferromagnetic ones observed in the Fe₂Nb framework.