Syntheses and crystal structures of the cerium-based coordination polymers poly[(acetic acid)bis­(μ-5-carb­oxy­thio­phene-2-carboxyl­ato)bis­(μ-thio­phene-2,5-di­carboxyl­ato)dicerium(III)] and poly[(μ-acetato)­aqua­(μ4-thio­phene-2,5-di­carboxyl­ato)cerium(III)]

Abstract

In the crystal structures of the title compounds, the Ce^III cations are eightfold coordinated and linked into three-dimensional frameworks by ligands based on different deprotonated derivates of 2,5-thio­phenedi­carb­oxy­lic acid. Both compounds exhibit O—H⋯O hydrogen bonds.

The title compounds, [Ce₂(C₆H₃SO₄)₂(C₆H₂SO₄)₂(CH₃COOH)]_n (1) and [Ce(CH₃COO)(C₆H₂SO₄)(H₂O)]_n (2) were synthesized by solvothermal reaction of Ce(NO₃)₃·6H₂O with 2,5-thio­phenedi­carb­oxy­lic acid (H₂TDC, C₆H₄SO₄) and acetic acid in aceto­nitrile or ethanol/water, respectively. These compounds were obtained as single crystals among other crystalline phases. Both compounds belong to the family of three-dimensional coordination polymers. The asymmetric unit of 1 consists of two Ce^III cations, two TDC²⁻ dianions, two HTDC⁻ anions and one acetic acid ligand, all of them located in general positions. The two Ce^III cations are each coordinated by eight oxygen atoms in the form of distorted square anti­prisms. These are bridged by carboxyl­ate and carb­oxy­lic acid groups, forming mono-periodic hybrid inorganic building units (IBUs), which are connected into a three-dimensional network by the TDC²⁻ and HTDC⁻ ligands. Compound 2 has an asymmetric unit composed of one Ce^III cation, one TDC²⁻ dianion, one acetate anion and one water mol­ecule in general positions. The cerium atom is eightfold coordinated by oxygen atoms. Edge-sharing CeO₈ polyhedra form a dinuclear IBU (Ce₂O₁₄). This IBU is bridged by six TDC²⁻ linkers to nine other IBUs, forming a three-dimensional framework. Both title compounds exhibit additional O—H⋯O hydrogen bonds. Powder X-ray diffraction shows that both compounds were not obtained as pure phases.