Abstract
Two novel thiacalix[4]arene-based high-nuclearity cobalt clusters, [Na2Co24(BTC(4)A)(6)(PO4)(6)(HCOO())6(DMC)(2)(DMF)(2)(dma)4(]).5DMF.9CH(3)OH (denoted as Na-2@Co-24, 1) and [KCo24(BTC(4)A)(6)(PO4)(6)(Cl)(2)(HCOO)4(DMF)(8)][KCo24(BTC(4)A)(6)(PO4)(6)(Cl)(2)(HCOO)(6)(DMF)(4)(CH3OH)(2)].8DMF.23CH(3)OH (denoted as K@Co-24, 2) (H4BTC(4)A = p-tert-butylthiacalix[4]arene, DMC = N,N'-dimethylcarbamic acid anion, dma = dimethylamine), have been solvothermally prepared and structurally characterized. Compounds 1 and 2 are each capped by six Co4-BTC4A molecular building blocks (MBBs) and six phosphate linkers and other different auxiliary anions, possessing an eicositetranuclear Co-24 core templated by alkali-metal cations. In essence, compound 1 is templated by two Na+ cations with an attractive interaction in the center of the core, while 2 is templated by one K+ with a larger radius. Such differences convert an oval-shaped Co-24 disklike core in 1 to a circular core in 2. Interestingly, 2 contains both anionic and cationic KCo24 cores, representing the largest cobalt aggregate salt reported, to the best of our knowledge. In addition, magnetic measurements of 1 and 2 were investigated, revealing the existence of antiferromagnetic interactions between the magnetic Co-II centers.