Title: Heteropolynuclear metallomesogens
Authors: Binnemans, Koen
Lodewyckx, Katleen #
Issue Date: 2003
Conference: 31. Arbeitstagung Flüssigkristalle location:Mainz (Germany) date:19-21 March 2003
Abstract: Mixed f-d metallomesogens are an intriguing new class of materials, since they combine specific magnetic interactions of f-d coordination compounds with the properties of liquid crystals. Furthermore, from a materials processing point of view, such f-d metallomesogens could be advantageous because of the strong tendency of the lanthanide-based metallomesogens to form a glassy state on cooling rather than to crystallise, and thus giving the possibility to freeze-in the mesomorphic order, whereas common non-mesomorphic f-d coordination complexes are obtained as crystalline powders. In order to obtain these heteropolynuclear f-d metallomesogens, our approach consisted of modifying the structures of previously described non-mesomorphic f-d complexes in such a way that a sufficient structural anisotropy was obtained for the formation of mesophases.
We describe in this contribution the synthesis and characterisation of heteropolynuclear metallomesogens containing both a transition metal ion and a lanthanide ion [1]. We synthesised adducts between a mesomorphic Cu(salen) complex (salen = 2,2’-N,N’-bis(salicylidene) ethylenediamine) and a lanthanide nitrate. Different stoichiometries were found, depending on the lanthanide ion: [Ln(NO3)3{Cu(salen)}2], for Ln = La – Nd, and [Ln(NO3)3Cu(salen)] for Ln = Sm – Lu. This stoichiometry corresponds to that of similar unsubstituted complexes [2]. The compounds exhibit a wide temperature-range hexagonal columnar mesophase (ColH) with rather low melting temperatures. Although the clearing point could be observed for the parent Cu(salen) complex, the mixed f-d complexes decomposed before clearing. For the corresponding adducts to the nickel complex of the substituted salen ligand, only trinuclear species were observed. The nickel-lanthanide complexes have a higher thermal stability than the corresponding copper-lanthanide complexes, in the sense that the former do not decompose at the clearing point.

[1] K. Binnemans, K. Lodewyckx, B. Donnio and D. Guillon, Chem. Eur. J.
2002, 8, 1101.
[2] M.L. Kahn, T.M. Rajendiran, Y. Jeannin, C. Mathonière, O. Kahn, C.R. Acad. Sci, II C 2000, 3, 131.
Description: oral presentation by Koen Binnemans
Publication status: published
KU Leuven publication type: AMa
Appears in Collections:Molecular Design and Synthesis
# (joint) last author

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