Abstract
A family of bis[(R or S)-N-1-(Ar)ethylsalicylaldiminato-κ(2) N,O]-Δ/Λ-zinc(II) {Ar=C(6) H(5) (ZnRL(1) or ZnSL(1) ), p-CH(3) OC(6) H(4) (ZnRL(2) or ZnSL(2) ) and p-ClC(6) H(4) (ZnRL(3) or ZnSL(3) )} compounds was synthesized and investigated by multiple methods. They feature Λ/Δ-chirality-at-metal induction along the pseudo-C(2) axis of the molecules. The chirality induction is quantitative in the solid state, explored by X-ray crystallography and powder X-ray diffraction (PXRD), where R or S-ligated complexes diastereoselectively yield Λ or Δ-configuration at the metal. On the other hand, Λ and Δ-diastereomers co-exist in solution. The Λ⇆Δ equilibrium is solvent- and temperature-dependent. Electronic circular dichroism (ECD) spectra confirm the existence of a diastereomeric excess of Λ-ZnRL(1-3) or Δ-ZnSL(1-3) in solution. DSC analysis reveals thermally induced irreversible phase transformation from a crystalline solid to an isotropic liquid phase. ECD spectra were reproduced by DFT geometry optimizations and time-dependent DFT (TD-DFT) calculations, providing ultimate proof of the dominant chirality atmetal in solution.