Assemblies of two mixed-ligand coordination polymers with two-dimensional metal-organic frameworks constructed from M(II) ions with croconate and 1,2-bis-(4-pyridyl)ethylene (M = Cd and Zn)

摘要

Two metal-croconate (C5O52-) complexes, {[Cd-2(bpe)(C5O5)(2)(H2O)]center dot 2H(2)O}(n) (1) and {[Zn-2(bpe)(2)(C5O5)2]}center dot H2O}(n) (2) (bpe = 1,2-bis(4-pyridyl)ethylene)) with two-dimensional (2-D) metal-organic frameworks (MOFs), have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction studies. Structural determination reveals that compound 1 possesses a 2-D layered MOF with two rectangular boxes as the basic building units through the connectivity of Cd-II with mu(3)-croconates,mu(5)-croconates, and bpe ligands. In compound 2, a 2-D brick-wall-like layered framework is formed by using a rectangular grid as the basic building unit through the connectivity of Zn-II with hybrid mu(3)-croconates, mu(4)-croconates, and bpe ligands. Two layers are then cross-linked by the other bpe ligands to complete a 2-D bilayered MOF. Both of the 2-D MOFs are extended to three-dimensional supramolecular architectures through pi-pi and C-H center dot center dot center dot O interactions between the croconate and the pyridyl rings of bpe, which exhibit high thermal stability and retain their crystalline forms up to 350 degrees C.