Crystal structure, assembly process, and single-molecule magnet behavior of a triangular prismatic {Co9} cluster

Abstract

Using the polydentate ligand of H₄L with the Co^II ion, a triangular prism-type nine-nucleus cluster [Co₉(L)₃(CH₂OCH₂OH)₆]·3.5H₂O ({Co9}-Eg, H₄L = 6,6'-(1H,1'H-[3,3'-bi(1,2,4-triazole)]-5,5'-diyl)dipicolinic acid) was constructed. Ion fragmentation during the formation of the {Co9}-Eg cluster was tracked using time-dependent electrospray ionization mass spectrometry. In addition, we proposed two possible formation processes (i) H₄L → CoL → Co₂L → Co₆L₃ → Co₇L₃ → Co₉L₃ and (ii) H₄L → CoL → Co₂L → Co₃L → Co₅L₂ → Co₇L₃ → Co₉L₃. Magnetic studies show that {Co9}-Eg exhibits slow relaxation under a static zero field at low temperature, which is the main characteristic of single molecule magnets (SMMs).