| Abstract |
Solvothermal reaction of zinc(II) and cadmium(II) salts with 5-propionamidoisophthalic acid (H(2)L1) and 5-benzamidoisophthalic acid (H(2)L2) in the presence or absence of an auxiliary ligand gives rise to a series of 1D, 2D and 3D Zn(II) or Cd(II) self-assembled metal-organic frameworks as revealed by X-ray diffraction structural analyses: [Zn(mu-L1-mu-1 kappa OO :2 kappa O )(formamide)(2)](n) (1), [\Zn-2(mu-L1-1 kappa O:2 kappa O )(2)(4,4 -bipyridine)(2)(H2O)\center dot 2(DMF)center dot 5(H2O)](n) (2), [Cd(mu-L1-mu-1 kappa(OO)-O-2 :2 kappa O O-2 )(DMF)](n) (3), [\Zn(mu-L2-1 kappa O:2 kappa O )(4,4 -bipyridine)(H2O)\center dot(H2O)](n) (4) and [\Cd(mu-L2-mu-1 kappa(OO)-O-2 :2 kappa O O-2 )(formamide)(4,4 -bipyridine)\center dot(formamide)](n) (5), which are also characterized by elemental analysis, IR spectroscopy and thermogravimetric analysis. The different architectures found in 1-5 result from the coordination modes of the carboxylate groups, which can assume nonbridging monodentate (in 1, 2 and 4), bridging bidentate (also in 1), bridging chelate (in 3 and 5) and chelate bidentate (also in 5) coordination. While 1 and 5 possess one dimensional double chain type structures, 3 has a 1D cyclic type structure and 2 and 4 have 2D or 3D wave-like structures, respectively. Topological analysis has shown that 1 and 5 have a 3-connected uninodal net with a topological type SP1-periodic net, 2 has a 2,4-connected binodal net, 3 has a 4-connected uninodal net structure and 4 has a more complex 2,2,2,4-connected tetranodal net. Frameworks 1-5 act as heterogeneous catalysts for the transesterification reaction of different carboxylate esters, with 4 showing the highest activity. These heterogeneous catalysts can be recycled without losing activity. |
