Synthesis and characterization of homo- and heteronuclear molecular Al3+ and Th4+ species chelated by the ethylenediaminetetraacetate (edta) ligand

Abstract

Four molecular species chelated by edta have been synthesized from aqueous solutions and characterized by single-crystal X-ray diffraction, infrared spectroscopy, and thermogravimetric analysis. [Th(H₂O)₄(edta)] (Th1) crystallized in monoclinic space group P2₁/c with unit cell parameters of a = 8.5275(5) Å, b = 12.0635(7) Å, c = 15.8825(9) Å, and β = 105.340(2)°. Monoclinic space group C₂ was identified for [Al₂(edta)(OH)₂(H₂O)₂] (Al2) with a = 11.1089(10) Å, b = 9.4830(8) Å, c = 7.6116(7) Å, and β = 112.026(3)°. [Th₄(H₂O)₄Al₁₀(H₂O)₈(OH)₂₈(edta)₄]·Cl₂(H₂O)₂₉ (Th4Al10) formed the triclinic space group P with a = 9.3172(8) Å, b = 16.6099(14) Å, c = 19.5080(14) Å, α = 102.314(3)°, β = 95.615(3)°, and γ = 92.473(3)°. [Th₂(H₂O)₂Al₆(H₂O)₁₀(OH)₁₄(edta)₂]·(NO₃)₄(H₂O)₁₈ (Th2Al6) also crystallized in triclinic space group P with unit cell parameters a = 10.9899(12) Å, b = 11.6107(12) Å, c = 14.3350(17) Å, α = 73.012(4)°, β = 87.411(4)°, and γ = 75.717(4)°. Small molecular species are observed in the Th1 and Al2 compounds, while the metal cations hydrolyze to create nanometer-sized heterometallic clusters in the Th4Al10 and Th2Al6 materials. The topological characteristics of each species are described and related to aqueous speciation in Th⁴⁺, Al³⁺-edta systems.