Organic–inorganic hybrid materials constructed from inorganic lanthanide sulfate skeletons and organic 4,5-imidazoledicarboxylic acid

Abstract

Five different types of the lanthanide sulfate–carboxylates family, [La₂(SO₄)(Himdc)₂(H₂O)₂] 1, [Gd₂(SO₄)₂(Himdc)(H₂O)₃]·H₂O 2, [Ln₂(SO₄)₂(Himdc)(H₂O)₃]·H₂O (Ln = Gd 3a, Eu 3b), [Eu₆Cu(SO₄)₆(Himdc)₄(H₂O)₁₄] 4, and [Ln(Himc)(SO₄)(H₂O)] (Ln = Eu 5a, Gd 5b, Tb 5c, Dy 5d, Er 5e); H₂imc = 4-imidazolecarboxylic acid, H₃imdc = 4,5-imidazoledicarboxylic acid) have been obtained by hydrothermal reactions of Ln₂O₃, transition metal sulfates and H₃imdc at 170 °C and characterized by means of elemental analyses, IR, TG analysis, luminescence spectroscopy and single crystal X-ray diffraction. The 3D structure of 1 is constructed from alternately linkages of organic {La(Himdc)} layers and inorganic {La₂O₂(SO₄)} layers, with the La atoms as hinges. 2 and 3a/3b both contain alternately arranged 1D left- and right-handed helical {Ln(imdc)} chains bridged by SO₄²⁻ anions to form a 3D framework with 1D rectangle-like channels along the b axis. The structural differences of 2 and 3a/3b lie in the linkages of the SO₄²⁻ anions. Complex 4 consists of 2D tubular Eu–sulfate layers pillared by {Cu(Himdc)₂} units to generate a 3D network. Complexes 5a–5e possess 2D bamboo-raft-like layer structures based on helical tubes. Interestingly, H₂imc comes from the in-situ decarboxylation of H₃imdc in the hydrothermal reactions. The luminescence properties of the complexes 3a, 4, 5a5c, 5d were investigated in solid state at room temperature.