Chiral analysis, such as determination of identity, concentration, and relative ratio of optically active (chiral) molecules, plays an indispensable role in contemporary synthetic, medicinal, and biological chemistry. Here, we describe the selective control of metal-centered chirality in an octahedral geometry to prepare negatively charged Al(III) complexes, which can be used as versatile (1)H NMR chiral solvating agents for both positively and negatively charged chiral molecules in polar or nonpolar solvents. During the formation of ion pairs between the Al(III) complexes and the chiral analytes such as amines and carboxylic acids, the metal-centered chirality in the Al complexes plays a crucial role in providing anisochronous chemical shifts to the (1)H NMR spectra. As a chiral solvating agent, Al(III) complexes display an unprecedentedly broad substrate scope, good solvent compatibility, and operational simplicity.

A rational approach for generating 1,1'-binaphthalene-like axial chirality of a small organic receptor, 2,2'-dihydroxybenzil is presented. The receptor combines with 2 equiv of monodentate primary amines to form a diimine, of which axial chirality is controlled by steric strain with moderate (1.4:1) to good (4.7:1) stereoselectivity. The observed circular dichroism (CD) spectra have been closely simulated by TD-DFT computations and can be used for determining the absolute chirality and enantiomeric excess of primary amines.

2,2'-Dihydroxybenzil is demonstrated to be a highly diastereoselective stereodynamic receptor for the chiral recognition of amino alcohols. The receptor by forming diimine compounds with amino alcohols showed good (11:1) to excellent (>50:1) diastereoselectivity in chloroform. The existence of intramolecular hydrogen bonding with amino alcohols only in an axial conformer is demonstrated by H NMR and CD spectroscopy, X-ray crystallography, and DFT computations. The exciton chirality method can be used with diazo-attached 2,2'-dihydroxybenzil.

A chiral aluminum solvating agent (CASA) was demonstrated to be a general and efficient reagent for 1H NMR chiral analysis of alcohols. The sodium salt of the CASA (CASA-Na) showed a complete baseline peak separation of the hydroxyl group for various chiral alcohols including primary, secondary, and tertiary alcohols with alkyl and aryl substituents in CD3CN. Due to the weak intermolecular interaction, 1H NMR measurement at low temperature (-40 to 10 °C) was required.