Two novel high-dimensional iron(ii) coordination polymers modeled by semi-rigid tetrapyridines

Abstract

Two new iron(II) coordination polymers with the formula [Fe(TPOM)(SCN)₂]·2(HN(CH₃)₂)·4(H₂O) (1, TPOM = tetrakis(4-pyridyloxymethylene)methane) and [Fe(TPOM2)(SCN)₂]·2(CH₃OH) (2, TPOM2 = tetrakis(3-pyridyloxymethylene)methane), have been synthesized and characterized by elemental analysis, IR spectroscopy, TGA, magnetic measurements and X-ray single-crystal diffraction. Compound 1 crystallizes in the orthorhombic space group Cccm, and exhibits a 3D porous pts framework in which the Fe^II(NCS)₂ units are linked by the tetra-topic TPOM ligands. In contrast, compound 2 crystallizes in the monoclinic space group C2/c, whose crystal structure consists of a 2D sheet formed by the connection of Fe^II(NCS)₂ units and tetra-topic TPOM2 ligands. Interestingly, every 2D sheet interleavingly stacks over each other to totally construct a [4] tiling structure with a plane net signature of [122]₄[4·4·4·4]. Temperature-dependent SQUID under variable external pressure and X-ray diffraction measurements indicate that the iron(II) ions in 1 and 2 remain in the high spin state over the temperature range of 2–300 K.