Poly(arylisocyanides) as Versatile, Enantiodiscriminating Alignment Media for Small Molecules.

Area of Science:

• Organic Chemistry
• Analytical Chemistry
• Materials Science

Background:

• Residual dipolar couplings (RDCs) provide valuable structural information for small molecules.
• Chiral alignment media are crucial for studying enantiomers using RDCs.
• Existing alignment methods have limitations in scope and precision.

Purpose of the Study:

• To develop and validate amino acid-derived lyotropic liquid crystalline (LLC) phases as chiral alignment media.
• To measure residual dipolar couplings (RDCs) of small chiral organic molecules with high precision.
• To investigate the potential for differentiating enantiomers using these chiral LLC phases.

Main Methods:

• Synthesis of amino acid-derived polyarylisocyanides to form LLC phases.
• Preparation of anisotropic samples in CDCl3 for NMR measurements.
• Measurement of deuterium quadrupolar splittings and RDCs using F2-coupled HSQC spectra.

Main Results:

• LLC phases exhibited excellent orienting properties for diverse chiral analytes.
• Precise RDCs up to ±40 Hz were extracted from NMR spectra.
• Diastereomorphous interactions between the chiral environment and enantiomers were observed.
• Differential order effects were particularly evident for ketones and alcohols.

Conclusions:

• Amino acid-derived LLC phases are effective chiral alignment media for RDC measurements.
• The method allows for accurate structural elucidation of chiral organic molecules.
• This approach offers a promising route for distinguishing enantiomers based on differential RDC values.