Ten-Coordinate Neodymium(III) Complexes with Triethylenetetraaminehexaacetic Acid

✍ Scribed by Anna Mondry; Przemysław Starynowicz

• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: English
• Weight: 174 KB
• Volume: 2006
• Category: Article
• ISSN: 1434-1948
• DOI: 10.1002/ejic.200501023

✦ Synopsis

Abstract

The crystal structures and spectroscopic (IR, Raman, UV/Vis) data for the complexes [C(NH~2~)~3~]~2~[Nd(HTTHA)]·3H~2~O (I) and [C(NH~2~)~3~]~3~[Nd(TTHA)]·6H~2~O (II) are presented. Crystals of I are triclinic, P$\bar {1}$, a = 9.998(2), b = 10.730(2), c = 15.557(3) Å, α = 106.89(3)°, β = 90.27(3)°, γ = 93.24(3)°, V = 1594.0(5) Å^3^, Z = 2, while the chiral crystals of II are monoclinic, __P__2~1~, a = 10.157(2), b = 15.958(3), c = 12.788(3) Å, β = 112.68(3)°, V = 1912.5(7) Å^3^, Z = 2. Both structures consist of the complex monomeric anions, guanidinium cations and water of hydration. The Nd^III^ ions are ten‐coordinate. The TTHA ligand coordinates to the Nd^III^ ions with six of its carboxyl oxygen atoms and four nitrogen atoms. Although the coordination environments of both Nd^III^ cations are essentially the same, the spectral results of both crystals reveal the influence of the degree of protonation of the ligand on the Nd^III^ ion. The IR and Raman spectra allowed us to assign some important frequencies. A comparison of the electronic absorption spectra of Nd^III^–TTHA complexes in solution and in single crystals of I and II allows the detection of a small elongation of the Nd–O and Nd–N bonds in these complexes as compared to the [Nd(TTHA)]^3–^ moiety in the previously reported complex Na~3~[Nd(TTHA)]·2.5NaClO~4~·7.617H~2~O and indicates that the coordination geometry of the ten‐coordinate neodymium complex in solution is the same as in the chiral crystal II. The intensities of the f–f transitions in Nd^III^–TTHA solutions and of crystals I and II were analysed on the basis of the Judd–Ofelt theory. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)