Mononuclear single helices of lanthanum(III) and europium(III). Metal dependent diastereomeric excess
De, S., Drew, M. G. B. and Datta, D. (2010) Mononuclear single helices of lanthanum(III) and europium(III). Metal dependent diastereomeric excess. Inorganica Chimica Acta, 363 (14). pp. 4123-4126. ISSN 0020-1693
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To link to this article DOI: 10.1016/j.ica.2010.05.016
Using the 1: 2 condensate of benzildihydrazone and 2-acetylpyridine as a tetradentate N donor ligand L, LaL(NO3)(3) (1) and EuL(NO3)(3) (2), which are pale yellow in colour, are synthesized. While single crystals of 1 could not be obtained, 2 crystallises as a monodichloromethane solvate, 2 center dot CH2Cl2 in the space group Cc with a = 11.7099(5) angstrom, b = 16.4872(5) angstrom, c = 17.9224(6) angstrom and beta = 104.048(4)degrees. From the X-ray crystal structure, 2 is found to be a rare example of monohelical complex of Eu(III). Complex 1 is diamagnetic. The magnetic moment of 2 at room temperature is 3.32 BM. Comparing the FT-IR spectra of 1 and 2, it is concluded that 1 also is a mononuclear single helix. H-1 NMR reveals that both 1 and 2 are mixtures of two diastereomers. In the case of the La(III) complex (1), the diastereomeric excess is only 10% but in the Eu(III) complex 2 it is 80%. The occurrence of diastereomerism is explained by the chiralities of the helical motif and the type of pentakis chelates present in 1 and 2.