title: Structure-selective recognition by voltammetry: enantiomeric determination of amines using azophenolic crowns in aprotic solvent.
abstract: The enantiomeric recognition of amines by voltammetry using electroactive macrocyclic molecules, nitroazophenolic crown ethers, is reported. The oxidation potential of the nitroazophenol moiety in nitroazophenols with 18-crown-6 sensitively depends on the structure of alkyl amines. Based on this phenomenon, enantiomeric amines and even the quantitative assay of the R/S ratio in enantiomeric mixtures can be selectively recognized by using 18-crown-6 azophenol (3-H) with chiral centers. In the case of phenylglycinol, the association constants (K) of 3-H for the R and S forms have an R/S value of 3.5. The peak potential of the R form in square-wave voltammograms reproducibly differs from that of the S form by 32 mV, within which the peak potential linearly varies with the enantiomeric ratio. Free energy perturbation and molecular dynamics simulation provide deeper understanding of the enantiomeric recognition in this system. The theoretical analysis indicates that the free energy difference between diastereomeric complexes agrees well with the experimental results, and the pi-pi or charge-charge interaction plays a key role in enantiomeric recognition.
authors.affiliation: Department of Chemistry, Seoul National University, Seoul 151-747, Korea.
authors.forename: Kyungmin
authors.initials: K
authors.lastname: Chun
authors.forename: Tae Hyun
authors.initials: TH
authors.lastname: Kim
authors.forename: One-Sun
authors.initials: OS
authors.lastname: Lee
authors.forename: Keiji
authors.initials: K
authors.lastname: Hirose
authors.forename: Taek Dong
authors.initials: TD
authors.lastname: Chung
authors.forename: Doo Soo
authors.initials: DS
authors.lastname: Chung
authors.forename: Hasuck
authors.initials: H
authors.lastname: Kim
mesh_terms: D000588:Amines / Q000032:analysis*; D043844:Crown Ethers / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000588:Amines; D043844:Crown Ethers; D012997:Solvents