Cyanido-Bridged Clusters with Remote N‑Oxide Groups for Branched Multimetallic Systems

The combination of [W^V(CN)₈]^3– anions with 3d metal cations M^II in MeOH leads to the formation of pentadecanuclear spherical cyanido-bridged clusters {M­[M­(solv)₃]₈[M′(CN)₈]₆}, <b>M</b>_<b>9</b><b>M′</b>_<b>6</b>. By decorating their surface with organic ligands or/and by installation of different ions in their coordination skeleton, one could tune high spin in the ground state, slow relaxation of magnetization, or structural/spin phase transition. In this work we present the extended molecular high spin (<i>S</i>_GS = ¹⁵/₂, <i>g</i>_eff = 3.4) clusters or chains of clusters {Co₉W₆(<i>N</i>,<i>O</i>-L)_<i>x</i>} (<i>N</i>,<i>O</i>-L – pyrazine mono-N-oxide, <i>pzmo</i>; 4,4-bipyridine mono-N-oxide – 4,4′-<i>bpmo</i>) equipped with the structurally ordered remote (2–2.5 nm) N-oxide functions, as a result of deliberate combination of solvated Co₉W₆ supercomplexes with asymmetric <i>N</i>,<i>O</i>-donor linkers L. The systematic occurrence of such motifs in the series <b>1</b>–<b>3</b> is a result of preference for the Co–N_L coordination over the Co–O_L coordination, controlled also by strongly competing supramolecular interactions including simple hydrogen bonding {_LNO···H-donor} as well as cooperative π-costacked hydrogen bonding in double cyclic synthons {Co–O–H_MeOH···O–N_bpmoN−}₂. The observed coordination backbones are discussed in terms of the potential to bind the specific external molecular units and create the new type of branched molecular organization. The magnetic properties are confronted with structural differences along <b>1</b>–<b>3</b>, considering coordination polyhedra, Co–N bond lengths, Co–N–C angles, and hydrogen bonds. The diversity of slow magnetic relaxation images for the known Co₉W₆ based phases are discussed in terms of local deformation of Co coordination polyhedra and global deformation of cyanide bridged backbones