Recognition Of Chiral Substrates Using Novel Chiral Cu(II) And Zn(II) Complexes
Enantioselective recognition is a key step in chiral resolution and transformation in biological, pharmacological and industrial processes. Coordinatively unsaturated chiral metal complexes with desired chemical properties are good candidates as chiral receptors to discriminate between coordinating enantiomeric analytes. In an effort to understand such recognitions and develop new catalysts, new chiral bi- and tridentate carboxylate rich ligands and their Zn(II) and Cu(II) complexes have been synthesized. The ligands and metal complexes have been characterized using several spectroscopic techniques such as NMR, ESI-quadrupole/TOF-MS and UV-Vis. Relentless effort in growing single crystal of the complexes suitable for X-ray diffraction is underway. Based on 1H and 13C NMR and UV-Vis investigation, the metal complexes have shown enantioselectivity towards biologically relevant substrates such as chiral amino acids and sugars. Substrates under investigation range from simple L/D alanine to the more complex sugars such as L/D glucose, L/D mannose and L/D xylose, as well as the polyalcohol xylitol. Based on the pKapp values and observed coordination induced shifts (CIS) the metal complexes Zn[S-15]- favors D-sugars and Zn[S-14]- shows a greater chiral recognition than their R counter parts toward the S chiral guest substrates such as L-alanine and L-phenylalanine. Although, the supramolecular interaction between Zn[R-13]- and sugars present a less chiral recognition than what we reported in 2015 using a chiral ligand such as 17.