Four novel Zn(II)/Cd(II) metal-organic frameworks constructed from 4 '-(4-pyridyl)-4,2 ':6 ',4 ''-terpyridine: hydrothermal synthesis, crystal structures, and luminescent properties

Four novel polymeric frameworks, [Zn(pytpy)Cl-2](n) (1), [Zn-2(pytpy)(2)(ox)(2)](n)center dot n(H2O) (2), [Cd(pytpy)(mal)](n)center dot n(H2O) (3) and [Zn-2(pytpy)(btc)(OH)](n) (4), (pytpy =4'-(4-pyridyl)-4,2':6',4 ''-terpyridine, H(2)ox oxalic acid, H(2)mal = malic acid and H(3)btc = 1,3,5-benzenetricarboxylic acid) have been hydrothermally synthesized and structurally characterized. Compound 1 shows infinite helical chains, which are extended into a 3D supramolecular network by intermolecular hydrogen bonds. In the structure of 2, there is coexistence of left-and right-handed helical chains arranged alternately to generate a 2D layer. In 3, an in-situ reaction occurred, maleic acid was converted to malate by the hydroxylation of the ethylene group to prepare the microporous architecture. Compound 4 is a twofold interpenetrating 3D ploymeric network with an intriguing topological structure. The luminescence properties of 1-4 have been investigated with fluorescence emission spectra and the UV-vis diffuse reflectance spectra in the solid state. Additionally, these four compounds possess great thermal stabilities, especially for 2, the framework is stable up to 400 degrees C.