engleski

Chirality induction in ML2 metal complexes with amino acid substituted bis(2-picolyl)amine ligands

Metal complexes of tridentate ligands L with ML2 stoichiometry can form several six-coordinated geometrical isomers: meridional, trans-facial, and delta or lambda cis-facial. For the rigid terpyridyne ligand (L = terpy), the meridional isomer of the corresponding M(terpy)2 metal complexes is strongly preferred, while complexes with the more flexible bis(2-picolyl)amine ligand (L = bpa) could form both meridional and facial isomers. Interestingly, however, all reported single crystal structures M(R-bpa)2 complexes with substituents R ≠ H reveal only cis-facial geometry, even with very bulky substituents where a trans-geometry might be expected due to sterical hindrance. Continuing our interest in metal complexes with nitrogen ligand amino acid bioconjugates, we present herein the synthesis and characterization of L1 – L5 and their ML or ML2 complexes with M = Zn(II), Co(II) or Ni(II). Particular attention will be paid to possible inter-strand hydrogen bonding and chirality induction in the ML2 complexes.

metal complexes; bioconjugates; amino acids; nitrogen ligands

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