Optical Chirality Sensing with an Auxiliary-Free Earth-Abundant Cobalt Probe

Broadly useful chiroptical enantiomeric excess (ee) sensing remains challenging and typically involves carefully designed molecular receptors or supramolecular assemblies. Herein, we report on the enantioselective sensing of 35 amino acids, amino phosphonic acids, hydroxy acids, amino alcohols, and diamines with an auxiliary-free cobalt probe. Chiroptical analysis of the enantiomeric composition and concentration of minute sample amounts was achieved with high accuracy by using earth-abundant cobalt salts and hydrogen peroxide as the oxidant. Despite the absence of an auxiliary ligand, the cobalt assay is applicable to aromatic and aliphatic compounds and yields strong CD signals at high wavelengths. This method obviates the general prerequisite for chromophoric metal ligands to generate chiroptical signals through ECCD (exciton-coupled circular dichroism) effects or through analyte-to-ligand chirality induction, and it offers operational simplicity, cost efficiency, waste reduction, and speed.