Absolute configurational assignment of self-organizing asymmetric tripodal ligand-metal complexes

Chirality. 1997;9(5-6):616-22. doi: 10.1002/(SICI)1520-636X(1997)9:5/6<616::AID-CHIR32>3.0.CO;2-P.

Abstract

The solution configuration of labile coordination complexes may be difficult to determine, even in cases in which the solid state structure is known. We have previously synthesized a series of chiral ligands which form pseudo-C3-symmetric complexes with ZnII and CuII salts that possess an available electrophilic coordination site. Molecular modeling of ZnII complexes of the chiral ligand N,N-bis[(2-quinolyl)methyl]-1-(2-pyridyl)ethanamine (alpha-MeBQPA) showed that the spatial arrangement of the heterocyclic arms is controlled by a substituent on one methylene arm, resulting in the adoption of an enantiomeric conformation displaying a propeller-like asymmetry. In this paper we report the application of the exciton chirality method to the determination of the conformation of asymmetric metal-ligand complexes in solution. There is a good correlation between the predicted and the observed Cotton effects, demonstrating that the geometry in solution closely resembles that predicted by computational simulations and those obtained by X-ray crystallographic studies of metal complexes with racemic and enantiomerically pure ligands. The X-ray crystallographic structure of the first optically pure complex in this series is reported.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Circular Dichroism
  • Copper*
  • Crystallography, X-Ray
  • Ligands*
  • Models, Molecular
  • Molecular Conformation
  • Pyridines / chemical synthesis
  • Pyridines / chemistry*
  • Quinolines / chemical synthesis
  • Quinolines / chemistry*
  • Solutions
  • Solvents
  • Spectrophotometry
  • Stereoisomerism
  • Zinc*

Substances

  • Ligands
  • N,N-bis((2-quinolyl)methyl)-1-(2-pyridyl)ethanamine
  • Pyridines
  • Quinolines
  • Solutions
  • Solvents
  • Copper
  • Zinc