Enantiospecific Electrodeposition of Chiral CuO Films from Copper(II) Complexes of Tartaric and Amino Acids on Single-Crystal Au(001)

Abstract

Chiral films of CuO were electrochemically deposited onto achiral Au(001) using chiral precursors such as tartaric acid and the amino acids alanine and valine to complex the Cu(II). The chirality of the electrodeposited films was dictated by the chiral solution precursor. X-ray diffraction pole figures and azimuthal scans, in conjunction with stereographic projections, were used to determine the absolute configuration and enantiomeric excess of the chiral CuO films. CuO films grown from l-tartaric acid have a (11̄1̄) orientation with an enantiomeric excess of 95%, while the films grown from d-tartaric acid have a (1̄11) orientation with an enantiomeric excess of 93%. CuO films grown from chiral amino acids have two types of chiral orientations, each showing lower enantiomeric excess compared with the films deposited from tartaric acid. The films grown from l-alanine and l-valine solution have an excess of the (1̄11) and (1̄1̄1̄) orientations, while the films grown from d-alanine and d-valine have an excess of (11̄1̄) and (111). Films of CuO deposited from a solution of achiral glycine consist of a racemic mixture of the (1̄11) and (11̄1̄) orientations. Chiral CuO films deposited on both single-crystal Au(001) and polycrystalline Au films were shown to exhibit chiral recognition for the electrochemical oxidation of tartaric acid.