Metal–organic frameworks constructed from three kinds of new Fe-containing secondary building units

Three new Fe-containing MOFs, H3O[Fe5(BTC)3(OAc)2(DMF)2]·H2O 1, [FeNa(m-BDC)2]·NH2(CH3)2 2 and [N(CH3)4]2[Fe3(HBTC)(BTC)2(H2O)]·5.5H2O 3 (BTC = 1,3,5-benzenetricarboxylate, m-BDC = 1,3-benzene-dicarboxylate), have been synthesized from the solvothermal reactions of iron salts and carboxylate ligands. The framework of 1 is constructed from two kinds of secondary building units (SBUs): the sinusoidal chain of iron octahedra SBU [Fe2(COO)6]n2n− and paddle-wheel SBU [Fe2(COO)4(DMF)]. Compound 1 represents the first example of Fe-containing MOFs constructed from two kinds of SBUs. The framework of 2 is built from zigzag-chain SBUs [FeNa(COO)6]n3n− and m-BDC linkers. The framework of 3 is formed by linear tri-nuclear iron SBUs [Fe3(COO)8(H2O)]2− and triangular BTC linkers. To our knowledge, the Fe-containing sinusoidal chain SBU in 1, zigzag-chain SBU in 2 and linear tri-nuclear iron SBU in 3 are found in Fe-containing MOFs for the first time. Magnetic investigation indicates the present of antiferromagnetic exchange interaction within the iron units of compounds.