Two One-Dimensional Copper-Oxalate Frameworks with the Jahn–Teller Effect: [(CH₃)₃NH]₂[Cu(μ-C₂O₄)(C₂O₄)]·2.5H₂O (I) and [(C₂H₅)₃NH]₂[Cu(μ-C₂O₄)(C₂O₄)]·H₂O (II)

Abstract

Two one-dimensional oxalate-bridged Cu(II) ammonium salts, [(CH3)3NH]2[Cu(μ-C2O4)(C2O4)]·2.5H2O (I) and [(C2H5)3NH]2[Cu(μ-C2O4)(C2O4)]·H2O (II) were obtained and characterized. They were composed of ammonium: (CH3)3NH+ in (I), (C2H5)3NH+ in (II), [Cu(μ-C2O4)(C2O4)2−]n and H2O. The Jahn–Teller-distorted Cu(II) is octahedrally coordinated by six O atoms from three oxalates and forms a one-dimensional zigzag chain. The hydrogen bonds between ammonium, the anion and H2O form a three-dimensional network. There is no hydrogen bond between the anion chains. They were insulated at 20 °C with a relative humidity of 40%. Ferromagnetic and weak-ferromagnetic behaviors were observed in I and II, separately. No long-range ordering was observed above 2 K.

Keywords

• Jahn–Teller effect
• Cu(II)
• oxalate
• crystal structure
• conductivity
• magnetism