Synthesis and structural determination of mononuclear eight-coordinate (EnH)[LuIII(Egta)] · 2H2O and 2D ladder-like nine-coordinate (EnH2)[YIII(Egta)(H2O)]2 · 6H2O

Abstract

Two novel lanthanide complexes, (EnH)[LuIII(Egta)] · 2H2O (I) and (EnH2)[YIII(Egta)H2O]2 · 6H2O (II), where En = ethylenediamine and H4Egta = ethyleneglycol-bis-(2-aminoethylether)-N,N,N′,N′-tetraacetic acid, have been successfully synthesized through direct heating reflux and their molecular crystal structures were determined by FT-IR spectroscopy, thermal analysis and single crystal X-ray diffraction techniques (CIF files CCDC nos. 966211 (I) and 966210 (II)). X-ray diffraction reveals that I has a eight-coordinate mononuclear structure with distorted square antiprismatic conformation. The reason that the Lu(III) adopts a eight-coordinate conformation is the small ionic radius and more f-orbital electrons, which generates a relatively small coordination number. Complex I crystallizes in a orthorhombic system with Pca21 space group. The crystal data are as follows: a = 22.4933(14), b = 9.1067(7), c = 10.6450(5) A and V = 2180.5(2) A3. Complex II takes nine-coordinated structure with a monocapped square antiprism, and crystallizing in the monoclinic crystal system with P21/c space group. The cell dimensions are as follows: a = 12.9600(11), b = 12.6209(12), c = 16.9151(15) A, β = 122.021(2)° and V = 2345.8(4) A3. Each ethylenediammonium (EnH 2 2+ ) cation in (EnH2)[YIII(Egta)H2O]2 · 6H2O (II) connects three adjacent [YIII(Egta)(H2O)] 2 2- anions through hydrogen bonds. While in II, there are two types of EnH 2 2+ cations, which form hydrogen bonds with the neighboring [YIII(Egta)(H2O)] 2 2- anions, leading to the formation of a 2D ladder-like layer structure. The results showed that the ionic radius of rare earth metals play a crucial role in crystal and molecular structure of their complexes.