title: A simple thermodynamic model for rationalizing the formation of self-assembled multimetallic edifices: application to triple-stranded helicates.
abstract: Reaction of the bis-tridentate ligand bis[1-ethyl-2-[6'-(N,N-diethylcarbamoyl)pyridin-2'-yl]benzimidazol-5-yl]methane (L2) with Ln(CF(3)SO(3))(3).xH(2)O in acetonitrile (Ln = La-Lu) demonstrates the successive formation of three stable complexes [Ln(L2)(3)](3+), [Ln(2)(L2)(3)](6+), and [Ln(2)(L2)(2)](6+). Crystal-field independent NMR methods establish that the crystal structure of [Tb(2)(L2)(3)](6+) is a satisfying model for the helical structure observed in solution. This allows the qualitative and quantitative beta23 (bi,Ln1,Ln2)characterization of the heterobimetallic helicates [(Ln(1))(Ln(2))(L2)(3)](6+). A simple free energy thermodynamic model based on (i) an absolute affinity for each nine-coordinate lanthanide occupying a terminal N(6)O(3) site and (ii) a single intermetallic interaction between two adjacent metal ions in the complexes (DeltaE) successfully models the experimental macroscopic constants and allows the rational molecular programming of the extended trimetallic homologues [Ln(3)(L5)(3)](9+).
authors.affiliation: Contribution from the Department of Inorganic, Analytical, and Applied Chemistry, University of Geneva, 30 quai E. Ansermet, CH-1211 Geneva 4, Switzerland.
authors.forename: Kornelia
authors.initials: K
authors.lastname: Zeckert
authors.forename: Josef
authors.initials: J
authors.lastname: Hamacek
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Rivera
authors.forename: Sébastien
authors.initials: S
authors.lastname: Floquet
authors.forename: André
authors.initials: A
authors.lastname: Pinto
authors.forename: Michal
authors.initials: M
authors.lastname: Borkovec
authors.forename: Claude
authors.initials: C
authors.lastname: Piguet