A series of new rare earth sulfates based on lanthanide contraction and dual organic-amine templating effects

Abstract

Five different types of dual organic-amine templated lanthanide sulfates, [(CH₃)₂NH₂]₆[H₃N(CH₂)₂NH₃][Nd₂(SO₄)₇] (1), [(CH₃)₂NH₂]₃[Eu(SO₄)₃] (2), [(CH₃)₂NH₂]₂[H₃N(CH₂)₂NH₃]_0.5[Ln(SO₄)₃] (3) (LnEu (3a), Gd (3b), Tb (3c)), [(CH₃)₂NH₂]₄[Dy₂(SO₄)₅] (4) and [H₃N(CH₂)₂NH₃]₅[Ln₂(SO₄)₈] (5) (LnDy (5a), Ho (5b), Er (5c), Tm (5d), Yb (5e), Lu (5f)) have been solvothermally obtained by employing dimethylacetamide (DMAc) as solvent and characterized by single-crystal X-ray diffraction, IR spectroscopy, thermal analysis, fluorescent spectra and ICP. The zigzag chain structure of compound 1 is constructed from two types of 4-membered rings (4 MRs) which connect each other alternately by sulfate groups. The one-dimensional (1D) chainlike structure of compound 2 is alternately linked by tetramer [Eu₂(SO₄)₂O₁₀] and 4 MR units. Compounds 3a to 3c are isomorphous and have similar interesting two-dimensional (2D) frameworks fabricated through zigzag chains and 12 MRs, fully protonated ethylenediamine (en) are located in 12 MRs and protonated dimethylamine (dma) are located between the inorganic layers. Compound 4 exhibits a 2D layered structure and the plane layers consist of two types of double stranded chains and 12 MRs. Compounds 5a to 5f are also isomorphous and feature a binuclear lanthanide cluster structure. Although the 12 compounds were synthesized under the same conditions except the rare earth oxide types, they belong to five types of structures and we can clearly see obvious transitivity and uniformity, as the ionic radius decreases, the coordination number of the rare earth elements decreases from 9 to 8 and the lanthanide contraction supports crystal structures concerning a sterically hindered coordination atmosphere. The luminescent properties of compounds 2, 3a and 3c exhibit characteristic europium and terbium luminescence.