TimothГ©e Lathion, Alexandre FГјrstenberg, CГ©line Besnard, Andreas Hauser, Azzedine Bousseksou, Claude Piguet.This article is cited by 194 publications. The use of 3d metal ions as a noncovalent tripodal spacer for lanthanide podates is discussed together with the crucial role played by carboxamide groups for the control of structural, electronic, and photophysical properties. The preparation of the segmental ligand L 2 from the new asymmetric synthon 6-( N, N-diethylcarbamoyl)pyridine-2-carboxylic acid is described together with its crystal and molecular structure (C 33H 33N 7O, monoclinic, P2 1/ c, Z = 4). Improved resistance toward hydrolysis also results from the use of carboxamide groups, and no change in luminescence is observed for 5+ in moist acetonitrile. Photophysical measurements and quantum yields in acetonitrile indicate that the terminal N, N-diethylcarbamoyl group in L 2 favors efficient intramolecular L 2 в†’ Eu(III) energy transfers leading to strong Eu-centered red luminescence. The separation of contact and pseudocontact contributions to the 1H-NMR paramagnetic shifts of the axial complexes 5+ (Ln = Ce, Pr, Nd, Sm, Eu, Tm, Yb) establishes that the triple helical structure is maintained in solution. Zn(II) occupies the distorted pseudooctahedral capping coordination site defined by the three bidentate binding units while Eu(III) lies in the resulting вЂњfacialвЂќ pseudotricapped trigonal prismatic site produced by the three remaining tridentate units as exemplified by luminescence measurements using the Eu(III) structural probe. The crystal structure of (ClO 4)(CF 3SO 3) 4(CH 3CN) 4 ( 13 EuZnC 111H 111N 25O 19F 12S 4Cl, monoclinic, C2/ c, Z = 8) shows the wrapping of the three ligands L 2 about a pseudo- C 3 axis passing through the metal ions. The segmental ligand 2-1,1вЂ-dimethyl-5,5вЂ-methylene-2вЂ-(5-methylpyridin-2-yl)bis (L 2) reacts with stoichiometric amounts of Ln(III) (Ln = Laв€’Nd, Smв€’Tb, Tmв€’Lu, Y) and Zn(II) in acetonitrile to yield quantitatively and selectively the heterodinuclear triple-helical complexes 5+ under thermodynamic control.

Mingliu font dream of mirrors online