Stereoselective association of binuclear metallacycles in coordination polymers

Kholbystov, A. N., Brett, M. T., Blake, A. J., Champness, N. R., Gill, P. M.W., O'Neill, D. P., Teat, S. J., Wilson, C. and Schröder, M. (2003) Stereoselective association of binuclear metallacycles in coordination polymers. Journal of the American Chemical Society, 125(22), pp. 6753-6761. (doi: 10.1021/ja029048y) (PMID:12769586)

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Abstract

A series of structurally related binuclear metallacycles [Cd(NO3)2L]2, where L is an angular exo-bidentate ligand, have been synthesized. Each metallacycle contains two coordinatively unsaturated, chiral metal centers within a single molecule, and the assembly of these metallacycles into polymeric framework structures has been studied systematically for the first time. Stereoselective homochiral association of [Cd(NO3)2L]2 leads to the formation of helical coordination polymers, whereas meso type association results in nonhelical chain structures. The type of stereoselective aggregation depends on the conditions of self-assembly as well as on ligand functionality. Both helical and nonhelical polymeric complexes have been isolated for the metallacycle [Cd(NO3)2(2,4‘-pyacph)]2 (2,4‘-pyacph = 2,4‘-(4-ethynylphenyl)bipyridyl). Homochiral association results in the formation of helical [Cd(NO3)]∞ chains which link the binuclear [Cd(NO3)2(2,4‘-pyacph)]2 metallacycles into racemic two-dimensional sheets which contain both P and M [Cd(NO3)]∞ helices. In contrast, meso-association leads to the formation of nonhelical one-dimensional chains. It is shown that the product of homochiral association is predominately formed at room temperature and that of meso-association is generated at elevated temperatures. Thus, it may be concluded that the homochiral association appears to be energetically less favorable than the meso-association, a conclusion that has been confirmed by theoretical calculations of the crystal lattice energy. Several high-yield syntheses of bipyridyl-type ligands used for metallacyclic assembly are also reported.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Wilson, Dr Claire
Authors: Kholbystov, A. N., Brett, M. T., Blake, A. J., Champness, N. R., Gill, P. M.W., O'Neill, D. P., Teat, S. J., Wilson, C., and Schröder, M.
College/School:College of Science and Engineering > School of Chemistry
Journal Name:Journal of the American Chemical Society
Publisher:American Chemical Society
ISSN:0002-7863
ISSN (Online):1520-5126
Published Online:10 May 2003

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