Hydrogen-Bonded Dicubane Co^II₇ Single-Molecule-Magnet Coordinated by in Situ Solvothermally Generated 1,2-Bis(8-hydroxyquinolin-2-yl)ethane-1,2-diol Arranged in a Trefoil

Abstract

A novel single vertex-shared dicubane-based cobalt(II) compound, [CoII7(bhqe)3(OH)2(H2O)6]·2C2H5OH·H2O (1), was obtained through the solvothermal generation of 1,2-bis(8-hydroxyquinolin-2-yl)ethane-1,2-diol, H4bhqe, from 2-(hydroxymethyl)quinolin-8-ol, H2hmq, by in situ C−C coupling reaction in ethanol containing Co(NO3)2·6H2O and triethylamine. The crystal structure consists of dicubane Co7 cores with six ligands wrapped around it in a trefoil through strong intramolecular π−π interactions and features an unusual one-dimensional hydrogen-bonded (OHwater···Obhqe) supramolecular organization (along the c-axis). The key factor of the cluster is that every pair of cobalt atoms are bridged by a single oxygen atoms making an average angle of approximately 95° and is expected theoretically and experimentally to generate ferromagnetic coupling. The temperature dependence magnetization exhibits a blocking temperature at approximately 3 K which is confirmed by observation of large frequency dependence of the ac-susceptibilities in zero dc-field, and detailed analysis of the dynamics properties allows an unambiguous demonstration of the single-molecule magnet (SMM) behavior in 1, though some interesting complexities in the slow magnetization relaxation processes may be influenced by the crystal system, the large anisotropy of cobalt(II) and the supramolecular interactions.