Self-assembly of two high-nuclearity manganese calixarene-phosphonate clusters: diamond-like Mn16 and drum-like Mn14

Abstract

Two novel high-nuclearity manganese clusters, [Mn₁₄(BSC4A)₃(tBuPO₃)₆(μ₄-OH)₃Cl(H₂O)(CH₃OH)]·1.5CH₃OH (1) and [Mn₁₆(BSC4A)₃(PhPO₃)₇(HPO₄)(μ₄-OH)₃Cl(H₂O)(CH₃OH)₄]·4.5CH₃OH (2) (H₄BSC4A = p-tert-butylsulfonylcalix[4]arene; tBuPO₃H₂ = tert-butylphosphonic acid; PhPO₃H₂ = phenylphosphonic acid) have been solvothermally obtained and structurally characterized. Crystal structural analyses reveal that the phosphonate ligands have a large influence on the structures of the polynuclear manganese clusters: complex 1 possesses a drum-like Mn^II₁₄ core, which is constructed from three Mn₄–BSC4A molecular building blocks (MBBs) and six tBuPO₃²⁻ ligands and capped by two Mn^II ions; while complex 2 has a diamond-like Mn^II₁₆ core, which also consists of three Mn₄–BSC4A MBBs, but connected by seven PhPO₃²⁻ linkers and a tetrahedral Mn₄ cluster housing a phosphate anion generated in situ. To the best of our knowledge, complex 2 gives the first calixarene-based cluster linked by both organic phosphonate and inorganic phosphate ligands, and also presents the highest nuclearity manganese complex with the H₄BSC4A ligand to date. Magnetic measurements suggest the presence of antiferromagnetic interactions between the adjacent Mn^II spin carriers for both complexes.