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Enantiomeric NMR signal separation behavior and mechanism of samarium(III) and neodymium(III) complexes with ( S , S )‐ethylenediamine‐ N , N '‐disuccinate
Author(s) -
Aizawa SenIchi,
Okano Masaru,
Kidani Takahiro
Publication year - 2017
Publication title -
chirality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.43
H-Index - 77
eISSN - 1520-636X
pISSN - 0899-0042
DOI - 10.1002/chir.22681
Subject(s) - chemistry , samarium , neodymium , lanthanide , enantiomer , ethylenediamine , reagent , stereochemistry , inorganic chemistry , organic chemistry , laser , ion , physics , optics
Enantiomeric 1 H and 13 C 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 (δ b (D) and δ b (L)) and their adduct formation constants ( K s) 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 δ b (D) and δ b (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 δ b (D) and δ b (L) values with greater signal broadening compared to the samarium(III) complex.