Syntheses and structural determination of the nine-coordinate rare earth metal complexes: [TbIII(Eg3a)(H2O)2] · 4.5H2O and K[TbIII(Edta)(H2O)3] · 5H2O

Two title complexes, [TbIII(Eg3a)(H2O)2] · 4.5H2O (I) (H3Eg3a = 3-carboxymethyl-6, 9-dioxa-3,12-diazatetradecanedioic acid) and K[TbIII(Edta)(H2O)3] · 5H2O(II) (H4Edta = ethylenediamine-N,N,N′,N′-tetraaceti acid), were prepared and characterized by FT-IR, elemental analyses, TGA-DTA-DTG, and single-crystal X-ray diffraction technique. For I, the Tb3+ ion is nine-coordinated by an Eg3a ligand and two coordination water molecules, yielding a monocapped square-antiprismatic (MCSAP) conformation. Complex I crystallizes in the monoclinic system with P21/c space group. The crystal data are as follows: a = 9.237(3), b = 10.018(3), c = 23.580(7) Å, β = 99.021(5)°, V = 2155.2(11) Å3, Z = 4, ρ = 1.822 Mg m−3, μ = 3.353 mm−1, F(000) = 1180, R1 = 0.0445 and wR2 = 0.1034 for 4262 observed reflections with I ≥ 2σ(I). For II, the Tb3+ ion is nine-coordinated by an Edta ligand and three coordinate water molecules also yielding a MCSAP conformation. Complex II crystallizes in the orthorhombic system with Fdd2 space group. The crystal data are as follows: a = 19.373(5), b = 35.429(10), c = 12.114(3) Å, V = 8315(4) Å3, Z = 16, ρ = 2.014 Mg m−3, μ = 2.014 mm−1, F(000) = 5024, R1 = 0.0224 and wR2 = 0.0557 for 3189 observed reflections with I ≥ 2σ(I). The potassium cations bridge the coordination spheres yielding many infinite long 1-D zigzag-type chains. The molecular structure of I is more stable than that of II. According to thermal analyses, the collapsing temperatures of crystal structure are 314°C for I and 348°C for II, which indicates that the crystal structure of II is more stable.