title: Enantiomeric NMR signal separation behavior and mechanism of samarium(III) and neodymium(III) complexes with (S,S)-ethylenediamine-N,N'-disuccinate.
abstract: Enantiomeric1H and13C NMR signal separation behaviors of various α-amino acids and DL-tartarate were investigated by using the samarium(III) and neodymium(III) complexes with (S,S)-ethylenediamine-N,N'-disuccinate as chiral shift reagents. A relatively smaller concentration ratio of the lanthanide(III) complex to substrates was suitable for the neodymium(III) complex compared with the samarium(III) one, striking a balance between relatively greater signal separation and broadening. To clarify the difference in the signal separation behavior, the chemical shifts of β-protons for fully bound D- and L-alanine (δb(D) and δb(L)) and their adduct formation constants (Ks) were obtained for both metal complexes. Preference for D-alanine was similarly observed for both complexes, while it was revealed that the difference between the δb(D) and δb(L) values is the significant factor to determine the enantiomeric signal separation. The neodymium(III) and samarium(III) complexes can be used complementarily for higher and smaller concentration ranges of substrates, respectively, because the neodymium(III) complex gives the larger difference between the δb(D) and δb(L) values with greater signal broadening compared to the samarium(III) complex.
authors.affiliation: Graduate School of Science and Engineering, University of Toyama, Toyama, Japan.
authors.forename: Sen-Ichi
authors.identifier: http://orcid.org/0000-0001-8222-9842
authors.initials: SI
authors.lastname: Aizawa
authors.affiliation: Graduate School of Science and Engineering, University of Toyama, Toyama, Japan.
authors.forename: Masaru
authors.initials: M
authors.lastname: Okano
authors.affiliation: Graduate School of Science and Engineering, University of Toyama, Toyama, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Kidani
mesh_terms: D005029:Ethylenediamines / Q000737:chemistry*; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D009354:Neodymium / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D012493:Samarium / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D005029:Ethylenediamines; D008024:Ligands; D009942:Organometallic Compounds; D009354:Neodymium; D012493:Samarium; C031234:ethylenediamine
keywords: chiral shift reagent; enantiomeric signal separation mechanism; neodymium(III) complex; samarium(III) complex