科研之友
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摘要
The reaction of metal ions, flexible aliphatic dicarboxylates and rigid bidentate linear ligands under mild conditions in water afford four novel metal - organic coordination polymers, [Cd(mu-mal)(mu-pyz)(0.5)(H2O)](n) 1 (mal = malonate dianion, pyz = pyrazine), [Cd-2(mu-suc)(2)(mu-pyz)(H2O)(2)](n) 2 (suc = succinate dianion), and {[M(mu-bipy)(H2O)(4)][suc] . 4H(2)O}(n) (M = Co, 3, M = Zn, 4, bipy = 4,4'-bipyridine). The molecular structures of 1 - 4 have been established by single-crystal X-ray crystallography. 1 is a 3D network being composed of layers of octahedrally coordinated Cd atoms bridged by malonate anions in syn-anti configurations within the layers and pyz molecules between layers. Unlike that in 1, each Cd atom in 2 displays uncommon pentagonal-bipyramidal geometry to form 2D infinite grid sheets with square grid dimensions of ca. 7.936 x 7.936 Angstrom. Both 3 and 4 exhibit 1D linear - M - bipy - M - bipy - chain polymers, and these chains were packed as ... ABCABC ... layered structures. The bridging succinate ligands in 2 adopt the syn-anti mode with a torsion angle of 60.8(7)degrees, while the solvated succinate ligands in 3 and 4 adopt the anti - anti mode with a torsion angle of 180.0degrees. To our knowledge, compound 2 represents the first example of flexible self-assembled succinate - pyrazine mixed bridging ligand coordination network. 3 and 4 are the first two cases of succinate - bipy polymers with non-coordinated succinate. The magnetic behavior for 3 was studied in the temperature range of 5 - 300 K. The result indicates the occurrence of a weak antiferromagnetic coupling between the cobalt(II) ions.
