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

Abstract

High-throughput screening for asymmetric catalysts has stimulated an interest in optically-based enantiomeric-excess (<i>ee</i>) sensors, primarily for their improved time and cost efficiency when compared to the standard HPLC analysis. We present herein substituent-effect studies on a recently reported Zn(II) multicomponent assembly that is used for chiral, secondary alcohol <i>ee</i> detemination. The systematic altering of assemblies formed from select substituted pyridyl ligands pointed to the conclusion that steric effects dominate the mode of interaction at the pyridyl 3- and 6- positions. From these results we identified a new Zn(II)-centered multicomponent assembly with a higher dynamic range than previously reported. Calibration curves of the CD signals resulting from the new assembly led to an <i>ee</i> assay with a 1.7% error. To further the utility of the new assembly, a correlation was developed between alcohol substituent size to the respective enantiopure CD value.