Synthesis, Structure, and Magnetic Properties of Two {Co16IICo4III} Supertetrahedral T4 Clusters Formed from the In Situ Dissociation of a Tertiary N-Containing Ligand

Two mixed-vale nt cobalt clusters {[(CoII)16(CoIII)4(mu 6-O)4(mu 3-OH)12(OCH3)12(H2O)8(BMBC)4]center dot ( N O 3 ) 8 } (1) and { [ ( C o I I ) 1 6 ( C oI I I ) 4 (mu 3- OH)20(OCH2CH3)4(HOCH2CH3)8(BMBC)4]center dot(NO3)8} (2) were synthesized and constructed by a semiflexible dicarboxylic ligand 4 ',4 '-[ammoniobis(methylene)]-bis[(1,1 '-biphenyl)-2-carboxylate] (BMBC-) with Co(NO3)2 center dot 6H2O under solvothermal systems. Interestingly, the ligand BMBC- is afforded from the in situ dissociation reaction of tertiary N-containing organic carboxylic acid ligands. The complexes present a beautiful supertetrahedral T4 cluster formed by an interior Co4IIIO4 cubane and four exterior Co4IIO4 cubanes bridged via mu 6-O2 and mu 3-OH- ions and stabilized by four BMBC- organic ligands. The complexes were confirmed by single-crystal X-ray diffraction (XRD), elemental analysis, infrared spectroscopy, and thermogravimetric analysis. Furthermore, the magnetic analyses reveal that the [Co20] cluster exhibits an antiferromagnetic behavior.