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Chirality at metal and helical ligand folding in optical isomers of chiral bis(naphthaldiminato)nickel(ii) complexes.
- Source :
-
Dalton Transactions: An International Journal of Inorganic Chemistry . 1/14/2016, Vol. 45 Issue 2, p667-680. 14p. - Publication Year :
- 2016
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Abstract
- Enantiopure bis[{(R or S)-N-1-(Ar)ethyl-2-oxo-1-naphthaldiminato-κ2N,O}]nickel(ii) complexes {Ar = C6H5 (1R or 1S), p-OMeC6H4 (2R or 2S), and p-BrC6H4 (3R or 3S)} are synthesized from the reactions between (R or S)-N-1-(Ar)ethyl-2-oxo-1-naphthaldimine and nickel(ii) acetate. Circular-dichroism spectra and their density-functional theoretical simulation reveal the expected mirror image relationship between the enantiomeric pairs 1R/1S and 3R/3S in solution. CD spectra are dominated by the metal-centered Λ- or Δ-chirality of non-planar four-coordinated nickel, this latter being in turn dictated by the ligand chirality. Single crystal structure determination for 1R and 1S shows that there are two symmetry-independent molecules (A and B) in each asymmetric unit that give a Z′ = 2 structure. Two asymmetric and chiral bidentate N^O-chelate Schiff base ligands coordinate to the nickel atom in a distorted square planar N2O2-coordination sphere. The conformational difference between the symmetry-independent molecules arises from the “up-or-down” folding of the naphthaldiminato ligand with respect to the coordination plane, which creates right- (P) or left-handed (M) helical conformations. Overall, the combination of ligand chirality, chirality at the metal and ligand folding gives rise to discrete metal helicates of preferred helicity in a selective way. Cyclic voltammograms (CV) show an oxidation wave at ca. 1.30 V for the [Ni(L)2]/[Ni(L)2]+ couple, and a reduction wave at ca.−0.35 V for the [Ni(L)2]/[Ni(L)2]− couple in acetonitrile. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 14779226
- Volume :
- 45
- Issue :
- 2
- Database :
- Academic Search Index
- Journal :
- Dalton Transactions: An International Journal of Inorganic Chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 111924493
- Full Text :
- https://doi.org/10.1039/c5dt03940a