Jean-Claude Bunzli - Tuning the self-assembly of lanthanide triple stranded heterobimetallic helicates by ligand design

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      Publication Details (including relevant citation   information):

      Jensen,T.B., Scopelliti,R., Bunzli,J.C.G. Dalton   Transactions 2008 (8) 1027-1036

      Abstract: The heterobitopic ligands L-AB4 and   L-AB5 have been designed and synthesised with the ultimate aim of   self-assembling dual-function lanthanide complexes containing   either a magnetic and a luminescent probe or two luminescent   probes emitting at different wavelengths. They react with   lanthanide ions to form complexes of composition   [Ln(2)(L-ABX)(3)](6+) of which three (X = 4; Ln = Pr, Nd, Sm)   have been isolated and characterised by means of X-ray   diffraction. The unit cells contain triple-stranded helicates in   which the three ligand strands are wrapped tightly around the two   lanthanide ions. In acetonitrile solution the ligands form not   only homobimetallic, but also heterobimetallic complexes of   composition [Ln(1)Ln(2)(LABX)(3)](6+) when reacted with a pair of   different lanthanide ions. The yield of heterobimetallic   complexes is analyzed in terms of both the difference in ionic   radii of the lanthanide ions and of the inherent tendency of the   ligands to form high percentages of head-head-head (HHH)   helicates in which all three ligand strands are oriented in the   same direction with respect to the Ln-Ln vector. The latter is   very sensitive to slight modi. cations of the tridentate   coordinating units

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