Rational model for chiral recognition in a silica-based chiral column: Chiral recognition of N-(3,5-dinitrobenzoyl)phenylglycine-terminated alkylsilane monolayer by 2,2,2-trifluoro-1-(9-anthryl)ethanol derivatives by chemical force microscopy

Direct measurement of the chemical force between chiral molecules was investigated by chemical force microscopy (CFM). 2,2,2-Trifluoro-1-(9-anthryl) ethanol (TFAE) and N-(3,5-dinitrobenzoyl)phenylglycine (DNBP), a well-known pair of enantiomers, were strongly immobilized on the surface of the cantilever tip and the substrate surface, respectively, by the use of aminosilane, to propose a chiral stationary phase model system of a silica-based chiral column. The modification of TFAE on a cantilever tip and DNBP on the substrate surface was confirmed by x-ray photoelectron spectroscopic and time-of-flight secondary ion mass spectrometric measurements. The force curve between (R or 5)-TFAE and (R or S)-DNBP enantiomers were measured using the force measurement mode scanning force microscopy to determine the magnitude of the interaction. The histograms of the adhesion force for a different chirality pair [(R)-ATEA vs (S)-DNBP and (S)-ATEA vs (R)-DNBP] showed a broader distribution than those for the identical chirality pair [(R)-ATEA vs (R)-DNBP and (S)-ATEA vs (S)-DNBP]. Since CFM measurement cans recognize the difference of in nanonewton forces, the results can be regarded as a rational design for chiral recognition in a silica-based chiral column.