Effect of ligand and bridge substitution on chiral recognition of 1-phenylethylammonium cation by an anionic binuclear Ni(II) complex
| Autor: | Tanmay Dutta, Chandani Rani Das, Manabendra Ray |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
chemistry.chemical_classification
Methionine 010405 organic chemistry Stereochemistry Ligand Diastereomer Bridging ligand 010402 general chemistry 01 natural sciences 0104 chemical sciences Amino acid Inorganic Chemistry chemistry.chemical_compound chemistry Materials Chemistry Physical and Theoretical Chemistry Solubility Enantiomeric excess Histidine |
| Zdroj: | Inorganica Chimica Acta. 486:367-376 |
| ISSN: | 0020-1693 |
| Popis: | Chiral recognition is an important phenomenon. Identifying factors those influences recognition and resolution have significance in multiple areas. Earlier, we had reported recognition and resolution (30% ee) of 1-phenylethylammonium cation using an anionic binuclear Ni(II) complex of a l -histidine derived ligand. We have now synthesized its l -methionine analogue and also substituted the bridging acetate to benzoate. Substitution of amino acid and subsequent reaction with racemic 1-phenylethylamine resulted in isolation of crystals of both possible diastereoisomers (1 and 2) as a conglomerate. This is different from l -histidine analogue which showed pseudo racemate formation. HPLC experiments on the bulk of the crystals showed 30% ee. On the other hand, substitution of both the amino acid and bridging ligand resulted in isolation of crystals of single diastereoisomer (3). HPLC experiment on the bulk of the crystals showed an improved 58% ee. Thus, changes in amino acid changed the mechanism of crystal formation without improving the enantiomeric excess (ee) but the changes in bridge almost doubled the % ee. To understand the reasons, the complexes 1–3 were structurally characterized and compared with previously reported l -histidine analogue. Comparison showed, the absence of strong imidazole-carboxylate H-bonding in the present system narrowed the solubility difference between diastereomers, which may have resulted in the formation of conglomerate. On the other hand, changing the bridging acetate to benzoate increase the number of inter molecular non-covalent interactions which may have influenced the improved chiral enhancement. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Full Text from ScienceDirect