Design and syntheses of hybrid supramolecular architectures: based on [Fe(C2O4)3]3− metallotectons and diverse organic cations

Abstract

Employing [Fe(C₂O₄)₃]³⁻ (C₂O₄²⁻ = oxalate) metallotectons as building units, a series of 3D iron–organic compounds with formulae [K(H-L₁)₂{Fe(C₂O₄)₃}·2H₂O] 1, [(H-Phen){Fe (C₂O₄)₂}(Phen)·3H₂O] 2, [(H₂-L₂)₂{Fe₂(C₂O₄)₃Cl₄}] 3, [K(H₂-L₃){Fe(C₂O₄)₃}·2H₂O] 4, [K(H₂-L₄){Fe(C₂O₄)₃}·H₂O] 5, [(H-L₅){Fe(C₂O₄)(L₅)}] 6, [(H₂-L₆)₂{Fe₂(C₂O₄)₄(OH)₂}·2H₂O] 7, [(H-L₇)₄{Fe(C₂O₄)₃}Cl·2H₂O] 8 (with L₁ = 2-methylbenzimidazole, Phen = 1,10-phenanthroline, L₂ = 1,4-bis(imidazol-1-ylmethyl)benzene, L₃ = 1,4-bis((2-methylimidazol-1-yl)methyl)benzene, L₄ = 1,1′-butane-1,4-diylbis(1H-imidazole), H-L₅ = 1H-benzotriazole, L₆ = 1,2-ethylenediamine, L₇ = melamine) have been synthesized and characterized by single-crystal X-ray diffraction. Compounds 1 and 5 possess different 2D [KFe(C₂O₄)₃]²⁻ layers. Compound 2 features a 2D hydrogen bonded network completed by trimer water clusters and [Fe(C₂O₄)₂(Phen)]⁻ anions via hydrogen bonds. Compounds 3–6 feature a series of 2D layers, which are further extended into a 3D supramolecular structure through C–H⋯O hydrogen bonds. Distinct [Fe₂(C₂O₄)₃Cl₄]⁴⁻ units and [Fe₂(C₂O₄)₄(OH)₂]⁴⁻ units are shown in compounds 3 and 7, respectively. Trinary hydrogen bonds and double hydrogen bonds are simultaneously displayed in 8 as well as N–H⋯Cl and O–H⋯Cl hydrogen bonds. Furthermore, in order to examine the thermal stability of all compounds, TGA was carried out.