The solvent effect on the structural and magnetic features of bidentate ligand-capped {CoII9[WV(CN)8]6} single-molecule magnets

Abstract

Cyanido-bridged {Co^II₉[W^V(CN)₈]₆} Single-Molecule Magnets grow spontaneously from the methanolic solution of Co²⁺ and [W^V(CN)₈]³⁻ ions. Here, these molecules were combined with the 2,2′-bipyridine N-oxide (2,2′-bpmo) ligand resulting in three novel crystalline phases: {Co^II[Co^II(2,2′-bpmo)(MeOH)]₆[Co^II(2,2′-bpmo)(MeCN)]₂[W^V(CN)₈]₆}·8H₂O·2MeCN·2MeOH (1) and {Co^II[Co^II(2,2′-bpmo)(MeOH)]₈[W^V(CN)₈]₆}·H₂O·8.5MeCN·11.5MeOH (2) which grow from the MeOH–MeCN solution, and {Co^II[Co^II(2,2′-bpmo)(EtOH)]₈[W^V(CN)₈]₆}·3H₂O·5.5MeCN·5EtOH (3) which crystallizes from the EtOH–MeCN mixture. They are constructed by {Co^II₉W^V₆} clusters of a six-capped body-centered cube topology, coordinating 2,2′-bpmo ligands at the external Co^II sites. 1–3 exhibit different composition and geometrical arrangement in their outer fac-[Co^II(μ-NC)₃(2,2′-bpmo)(solvent)]⁻ moieties, and different solvent organization in the intercluster space. This results in a well pronounced geometrical isomerism of cluster cores being further related to the diverse non-covalent interaction schemes governing the supramolecular arrangement of the molecules. 1, 2, and 3 reveal ferromagnetic coupling within Co–NC–W linkages leading to a high-spin ground state of 15/2, and slow magnetic relaxation at low temperatures. The single-molecule magnet characteristics are only slightly modulated by the solvent-dependent variation of the structural features.