Assembly of metal coordination framework, [MII(C5O5)(dpe)], with a 2D bi-layer architecture: Thermal stability and magnetic properties (M=Mn, Fe, Cd and Co; dpe=1,2-bis(4-pyridyl)ethane)
摘要:
A series of coordination polymers, [M(C5O5)(dpe)] (M = Mn 1, Fe 2, Cd 3 and Co 4; dpe = 1,2-bis(4-pyridyl)ethane) with a 2D metal-organic framework (MOF) has been synthesized and characterized by single-crystal X-ray diffraction studies. Structural determination reveals that compounds 1-4 are isostructural and possess a 2D brick-wall-like layered framework with a rectangle grid as the basic building unit through the connectivity of metal ions with mu(3), mu(3)-croconates and anti-dpe ligands. Two 2D layers are then cross-linkaged by gauche-dpe ligands to complete a 2D bi-layered MOF and then extended to a 3D supramolecular architecture through pi-pi and C-H center dot center dot center dot O interactions between the croconate and pyridyl rings of dpe, which exhibit high thermo-stability and keep their crystalline forms up to 350 degrees C. The magnetic exchange coupling between the metal centers for compounds 1, 2 and 4 was analyzed and based on the Curie-Weiss expression and a binuclear magnetic model. The negative values of the Weiss constant and the magnetic exchange coupling constant indicate the antiferromagnetic nature between the metal ions via the bridges of bis-bidentate adjacent mu(3)-croconate ligands. (c) 2007 Elsevier B.V. All rights reserved.