A new family of {CoLn} metallacrowns with a butterfly-shaped structure

A series of cobalt-lanthanide metallacrowns (MCs) {Co III 4 Ln 8 } (Ln = Dy 3+ 1 , Ho 3+ 2 and Tm 3+ 3 ) based on pyrazinehydroxamic acid (H 2 pyzha) and pyrazinic acid (Hpyzic) ligands have been synthesized. These isomorphous 3d-4f MCs contain two novel [12-MC-4] with -[Co-N-O-Ln]- connectivity to capture one Ln 3+ ion in the core of each MC. Two [12-MC-4] units are connected with the central Ln 3+ ions forming a butterfly-shaped structure. The existence of this structure leads to a new coordination mode of H 2 pyzha which has never previously been reported. The magnetic properties of these MCs have been studied and the {Co III 4 Dy 8 } ( 1 ) was found to exhibit the single-molecule magnet (SMM) behavior. A series of cobalt-lanthanide metallacrowns (MCs) {Co III 4 Ln 8 } (Ln = Dy 3+ 1 , Ho 3+ 2 and Tm 3+ 3 ) based on pyrazinehydroxamic acid (H 2 pyzha) and pyrazinic acid (Hpyzic) ligands have been synthesized.