Solvothermal reactions of MnCl2with pyridylbenzoic acids gave three-dimensional metal-carboxylate frameworks(MCFs),named MCF-34,MCF-43,and MCF-44,based on one-dimensional Mn-carboxylate chains.The crystal structure,stability,porosity,and framework flexibility of the new compound MCF-44 were studied in detail and compared with its analogs.Depending on their shapes and the bridging angles of the ligands,these compounds possess different network connectivities and porosities.Considering the pyridylbenzote ligands and Mn(II)ions as,respectively,3-and 6-connected nodes,they resemble either the anatase(ant)or rutile(rtl)polymorph of TiO2.Variable-temperature single-crystal X-ray diffraction studies revealed large thermal expansion coefficients for these compounds,which are probably related to the relatively flexible edge-sharing polyhedral structure of their Mn-carboxylate chains.Interestingly,the new compound MCF-44,with its highly porous rtl structure exhibits the largest thermal expansion coefficienct among the coordination polymers reported so far.
Four 3d-4f heterometallic complexes, [CuⅡ LnⅢ (bpt) 2 (NO 3 ) 3 (MeOH)] (Ln = Gd, 1; Dy, 2; bptH = 3,5-bis(pyrid-2-yl)-1,2,4- triazole), [CuⅡ 2 LnⅢ 2 (μ-OH) 2 (bpt) 4 Cl 4 (H 2 O) 2 ]·6H 2 O (Ln = Gd, 3; Dy, 4), have been synthesized under solvothermal conditions. X-ray structural analyses reveal that 1 and 2 are isostructural while 3 and 4 are isostructural. In each complex, the copper and gadolinium or dysprosium ions are linked by two triazolate bridges and form a CuⅡ -LnⅢ dinuclear unit. The intramolecular Cu-Ln distances are 4.542, 4.525, 4.545 and 4.538 for 1, 2, 3 and 4, respectively. Two dinuclear CuLn units are bridged by two OH- groups into the zig-zag tetranuclear {CuⅡ 2 LnⅢ 2 } structures with the Ln(Ⅲ) Ln(Ⅲ) distances of 3.742 and 3.684 for 3 and 4, respectively. Magnetic studies show that the antiferromagnetic CuⅡ-LnⅢ interactions occur in 1 (J CuGd = 0.21 cm-1 ) and 2. The antiferromagnetic interaction occurs in complex 3 with J CuGd = 0.82 cm-1 and J GdGd = 0.065 cm-1 , while dominant ferromagnetic interaction occurs in complex 4.
