Enantioselectivity in Niii Schiff-base complexes derived from amino-acids and (S)-o-N-N-benzylprolylaminobenzophenone. Molecular structure of several chiral Niii Schiff-base complexes, circular dichroism and molecular mechanics studiesElectronic supplementary information (ESI) available: Table SI–1: Deviations of coordinating atoms O(2), N(1), N(2), N(3) from the best least squared plane in complexes. Fig. SI–1: Conformations of rings A–C in complexes. Fig. SI–2: Relative positions of atoms in the coordination plane of complexes. See http://www.rsc.org/suppdata/dt/b5/b503786g/

Autor: Pessoa, J. Costa, Correia, I., Galvão, A., Gameiro, A., Felix, V., Fiuza, E.
Zdroj: Dalton Transactions; 2005, Vol. 2005 Issue: 13 p2312-2321, 10p
Abstrakt: Several Niii complexes derived from (S)-o-N-N-benzylprolylaminobenzophenone (S)-BBP and amino acids of general formula Ni(S)-BBP-l-or d--aa were prepared. The crystal and molecular structures of Ni(S)-BBP-Gly, Ni(S)-BBP-l-Ser and Ni(S)-BBP-l-aaIm aaIm l-2-amino-3-imidazol-1-ylpropanoate were determined by X-ray diffraction analysis. In the three complexes the nickel atoms display a square-planar coordination and the overall structure around the metal indicates that the entire Schiff-base ligands form quite rigid frameworks. Molecular mechanics calculations were carried out for complexes Ni(S)-BBP-Gly, Ni(S)-BBP-Ser and Ni(S)-BBP-aaIm containing either the l- or d-amino acid forms, and the factors controlling the stereoselectivity are discussed. Several other Ni(S)-BBP-l-aa complexes are also prepared and their circular dichroism spectra in solution and of the solids dispersed in KBr disks are measured and discussed. In agreement with other studies in solution with similar Ni(S)-BBP-aa complexes, the Cotton effects for the bands with λmaxat 520–530 nm are positive when the amino acids have the l-configuration at the α-carbon. The same is observed in this work for the solid-state CD spectra of all compounds.
Databáze: Supplemental Index
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