Trinuclear Lanthanoid Complexes of 1,3,5-Triamino-1,3,5-trideoxy-cis-inositol with a Unique, Sandwich-Type Cage Structure(1).
A variety of trinuclear complexes [M(3)(H(-)(3)L)(2)](3+) [M = Y, La, Eu, Gd, Dy; L = 1,3,5-triamino-1,3,5-trideoxy-cis-inositol (taci) and 1,3,5-trideoxy-1,3,5-tris(dimethylamino)-cis-inositol (tdci)] was prepared as solid materials of the composition M(3)(H(-)(3)L)(2)X(3).pH(2)O.qEtOH (X = Cl, NO(3); 2.5 </= p </= 9; q = 0, 0.33) and characterized by elemental analyses, NMR spectroscopy, and FAB(+) mass spectrometry. The crystal structures of [La(3)(H(-)(3)taci)(2)(H(2)O)(4)Cl]Cl(2).3H(2)O and [Gd(3)(H(-)(3)taci)(2)(H(2)O)(6)]Cl(3).3H(2)O were elucidated by single-crystal X-ray diffraction studies. The La complex crystallizes in the orthorhombic space group Pbca, a = 17.10(2) Å, b = 16.20(4) Å, c = 20.25(4) Å, Z = 8 for C(12)Cl(3)H(38)La(3)N(6)O(13). The Gd complex crystallizes in the monoclinic space group P2(1)/n, a = 10.294(3) Å, b = 15.494(5) Å, c = 19.994(6) Å, beta = 95.36(2) degrees, Z = 4 for C(12)Cl(3)Gd(3)H(42)N(6)O(15). The two complexes exhibited a unique, sandwich-type cage structure, where the two triply deprotonated taci ligands encapsulate an equilateral triangle of the three metal centers. The metal cations are coordinated to the equatorial, terminal amino groups and are bridged by the axial &mgr;(2)-alkoxo groups. The coordination spheres are completed by additional peripheral ligands such as H(2)O or Cl(-) counterions. The coordination number of the metal cations is 8. Magnetic susceptibility measurements of the Gd complex revealed very weak antiferromagnetic coupling interactions between the three Gd centers. Complex formation and species distribution in aqueous solution was investigated by potentiometry and pD-dependent NMR spectroscopy. An exclusive formation of the [Eu(3)(H(-)(3)taci)(2)](3+) unit in solution was found in the range 7 </= pH </= 10. The formation constants were determined for the Y, Eu, Gd, Dy, and Lu complexes with taci. The stability of the lanthanoid complexes increased monotonically with decreasing ionic radius of the metal center.
Hedinger
Roman
R
Laboratorium für Anorganische Chemie, ETH Zentrum, CH-8092 Zürich, Switzerland, Universität des Saarlandes, Fachrichtung Anorganische Chemie, Postfach 15 11 50, D-66041 Saarbrücken, Germany, Institut de Chimie Minérale et Analytique, Université de Lausanne-BCH, CH-1015 Lausanne, Switzerland, Dipartimento di Chimica, Università di Firenze, 50144 Florence, Italy, and Institut für Kristallographie, ETH Zentrum, CH-8092 Zürich, Switzerland.
Ghisletta
Michele
M
Hegetschweiler
Kaspar
K
Tóth
Eva
E
Merbach
André E.
AE
Sessoli
Roberta
R
Gatteschi
Dante
D
Gramlich
Volker
V