Synthesis, Structures, and Properties of New Discrete Hetero-tetranuclear Metallocycle Complexes Based on Macrocyclic Oxamide Metalloligands

Two new discrete hetero-tetranuclear metallocycle complexes based on metalloligands, {[Zn2(NiL1)2(H2O)6]center dot 4H2O}n (1) and {[Ca2(NiL2)2(CH3OH)0.5(H2O)7]center dot CH3OH center dot 2H2O}n (2) were synthesized under self-assembly conditions and structurally determined. X-ray diffraction analyses revealed that the two compounds involve the discrete metallocyclic units, which serve as building blocks to further expand to three-dimensional supramolecular frameworks through second interactions such as hydrogen bonds and center dot center dot center dot stacking interactions. The central ZnII and CaII ions of the compounds 1 and 2 are bridged by macrocyclic oxamido metalloligands fusing the metallocycle with head-to-tail arrangement. The metallocycles have Zn center dot center dot center dot Zn distances of 9.48 angstrom in 1 and Ca center dot center dot center dot Ca distances of 9.90 angstrom in 2. Further, compounds 1 and 2 were investigated by thermogravimetric analysis.