Enantiomeric NMR signal separation behavior and mechanism of samarium(III) and neodymium(III) complexes with (S,S)‐ethylenediamine‐N,N'‐disuccinate

Abstract

Enantiomeric H and 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 (D) and δ (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 δ (D) and δ (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 (D) and δ (L) values with greater signal broadening compared to the samarium(III) complex.

The robust, readily available cobalt(iii) trication [Co(NH2CHPhCHPhNH2)3]3+ is a progenitor of broadly applicable chirality and prochirality sensing agents

“…NMR methods can be divided into three principal categories: chiral derivatizing agents (CDAs), 8 – 12 , 14 , 15 paramagnetic chiral lanthanide shift reagents (CLSRs), 16 and chiral solvating agents (CSAs). 8 , 10 – 13 Over the past few years, the last approach has attracted increasing attention.…”

<p>A Chelate-Free Nano-Platform for Incorporation of Diagnostic and Therapeutic Isotopes</p>

“…These relaxometric changes are mainly due to the use of high concentration of metals for HIR process. Most of the metals used in these studies (eg, Tb, Eu, Sm, Y, Lu, Sr, Mo and Ba) [54][55][56][57][58][59][60][61][62] are strong paramagnetic and hence at these concentrations may affect both r 1 and r 2 measurements. However, in the case of radiolabelled FH NP for clinical diagnostic imaging, the concentration of the radiometal is usually in nano or even pico-M (eg, for labeling 92.5 MBq of 89 Zr, m Zr ≈ 6.25 pM).…”

Enantiomeric NMR signal separation mechanism and prediction of separation behavior for a praseodymium (III) complex with (S,S)‐ethylenediamine‐N,N‐disuccinate

“…The total substrate concentration [S] t was plotted as a function of reciprocal of δ − δ 0 to give δ b from the slope and K from the intercept. [6,26] Figure 3 shows the above plots for 0.01 M of the Pr(III) complex by using chemical shifts of β-protons of D-and L-alanine. The obtained δ b and K values for the enantiomers are listed in Table 3.…”

“…In the previous study, the δ b and K values were compared between the samarium(III) and neodymium(III) complexes with the potentially hexadentate ligand having two chiral centers, (S,S)-ethylenediamine-N,N 0 -disuccinate ((S,S)-EDDS), to form the stable complexes, and it is revealed that a difference in the δ b values is the main factor for the enantiomeric signal separations, where the downfield shifts of δ b and the difference in the δ b values between the enantiomers for the neodymium(III) complex are much larger than those for the samarium(III) complex. [26] However, more serious signal broadening was induced by a neodymium(III) ion compared with a samarium(III) ion. Therefore, it is suggested that the neodymium(III) and samarium(III) complexes can be used complementarily for higher and lower substrate concentration ratios to the lanthanide(III) complexes, respectively.…”