Implementation of Chirality into High-Spin Ferromagnetic Co9IIW6V and Ni9IIW6V Cyanido-Bridged Clusters

The synthesized chiral (R)- and (S)-2-(1-hydroxyethyl)pyridine ligands (R/S-mpm) were introduced to self-assembled Co-II-[W-V(CN)(8)] and Ni-II-[W-V(CN)(8)] magnetic systems giving a remarkable series of four enantiopure cyanido-bridged clusters, {M-II[M-II(R/S-mpm)(MeOH)](8)[W-V(CN)(8)](6)}center dot 14MeOH (M = Co, 1-R and 1-S; M = Ni, 2-R and 2-S). They consist of 15, metal centers, 9 Co-II or Ni-II ions, and 6 [W-V(CN)(8)](3-) ions, embedded in a 6-capped body-centered cube topology. Bidentate enantiopure mpm ligands coordinated to eight external Co-II or Ni-II sites induce their chiral character, which results in the Strong natural optical activity in the broad UV-vis range of 200-700 nm. All (1-R/S) and (2-R/S) clusters reveal cyanido-mediated ferromagnetic exchange interaction giving high-spin ground states of 15/2 (1-R/S) and 12 (2-R/S). For (2-R/S) forms of {Ni9W6}, the exchange constant J = +16.1 cm(-1) was obtained using exact diagonalization of the exchange Hamiltonian. Because of the significant magnetic anisotropy, (1-R/S) forms of {Co9W6} duster reveal the low temperature onset of the slow magnetic relaxation characteristic of single-molecule magnets (SMMs). Thus, they can be considered as a rare example of chiral SMM molecules.