A Simple Method for the Determination of Enantiomeric Excess and Identity of Chiral Carboxylic Acids

Abstract

The association between an achiral copper(II) host (1) and chiral carboxylate guests was studied using exciton-coupled circular dichroism (ECCD). Enantiomeric complexes were created upon binding of the enantiomers of the carboxylate guests to the host, and the sign of the resultant CD signal allowed for determination of the configuration of the studied guest. The difference in magnitudes and shapes of the CD signals, in conjunction with linear discriminant analysis (LDA), allowed for the identity of the guest to be determined successfully. A model was created for the host:guest complexes which successfully predicts the sign of the observed CD signal. Further, Taft parameters were used in the model, leading to rationalization of the observed magnitudes of the CD signals. Finally, the enantiomeric excess (ee) of unknown samples of three chiral carboxylic acid guests was determined with an average absolute error of ± 3.0%.

Synthesis and structural analyses of phenylethynyl-substituted tris(2-pyridylmethyl)amines and their copper(ii) complexes

“…One helical twist over another will dominate when a chiral ligand is bound in solution, thereby giving rise to a Cotton effect in the circular dichroism spectra. 28 In the lack of a chiral ligands, the helical twists would be rapidly interconverting, a phenomenon that cannot occur in the solid state.…”

From substituent effects to applications: enhancing the optical response of a four-component assembly for reporting ee values

“…For example, various stereodynamic systems that utilize circular dichroism (CD) for ee determination have been published 12,13,17. Recently, our group developed a chiral alcohol sensor involving a multicomponent assembly that incorporates the alcohol into a hemiaminal ether ( 1 ) under equilibrium conditions13–15 (Fig.…”

Russian Nesting Doll Complexes of Molecular Baskets and Zinc Containing TPA Ligands

“…16 For instance, one can use Zn(II) or Cu(II) complexes of chiral TPA for rapid determination of enantiomeric excess of alcohols, carboxylic acids and amines. [17][18][19][20] In this vein, dynamic propeller chirality in TPA ligands has been controlled with an alkyl substituent at the stereogenic benzylic carbon ( Figure 1A). The alkyl group acts as a relay auxiliary to, via van der Waals interactions, promote the exclusive formation of right-or left-handed stereoisomer.…”