RETRACTED: Structure Types and Magnetic Behavior of Cobalt Nanoclusters (Retracted article. See vol. 61, pg. 2378, 2022)

Caprylic hydrazide ligands are ideal ligands for the synthesis of novel polynuclear metal complexes, because they contain many N,O coordination atoms with a strong coordination ability, abundant hydrogen-bond donors, acceptors, and large conjugation systems. Here, we successfully obtained one dodecanuclear cobalt nanocluster [(Co8Co4III)-Co-II(L1)(4)(Py)(12)(CH3OH)(4)(CH3COO)(4)]center dot(CH3OH)(13) (1) and one octadecanuclear cobalt nanocluster [Co-18(II)(L2)(6)(Py)(48)]center dot(DMF)(5)center dot(CH3OH)(8) (2) by using H(6)L1 and H(6)L2 ligands, respectively (Py = pyridine; DMF = dimethylformamide). The cyclic cobalt nanocluster 1 can be regarded as two pentanuclear cobalt units (Co-5(N-N)(4)) connected by two cobalt ions, and it is a mixed-valent Co nanocluster. Every H(6)L1 ligand contains 10 coordination atoms, each of which coordinates with the Co ions. And every two H(6)L1 ligands form a structure similar to a handshake. The abnormal cylindrical cobalt nanocluster 2 can be regarded six trinuclear cobalt units Co-3(N-N)(2) connected by one L2(6-) ligand, and every L2(6-) ligand splits the structure on both sides, with a twisted cyclohexane in the middle. AC magnetic susceptibilities show that nanocluster 1 exhibits no frequency-dependent behavior, but nanocluster 2 shows an obviously single-molecule magnetic behavior, and the relaxation process of the energy barrier is 20.4 K.