A europium(III)-N,N,N′,N′-tetrakis(2-pyridylmethyl)-(R)-propylenediamine complex as a new chiral lanthanide NMR shift reagent for aqueous neutral solution

Abstract

A new chiral lanthanide shift reagent [EuIWl2(R)-tppn}]C1O4 which is structurally characterized by X-ray crystallography, resolves the enantiomer signals of a-amino acids in neutral aqueous solution and affords a good relation between the relative signal position of enantiomers and their absolute configurations.

Assignment of absolute configuration using chiral reagents and NMR spectroscopy

“…With Eu(tppn), the a-proton, a-methyl, b-methyl, and g-hydrogen resonances have empirical trends that correlate with the absolute stereochemistry. 177 Subsequent studies show that the use of the Ce(III) 178 and La(III) 179 complexes of tppn reduce the broadening while still showing the same trends needed to assign the absolute configuration. Empirical trends are observed with the Ha 176 or a-methyl signal 180 of a-methylamino acids with Eu(pdta).…”

“…The use of Sm(tfc) 3 , which causes smaller shifts but less broadening than Eu(III), provides sufficient discrimination and the same trends necessary to reliably assign the configuration. 175 Water-soluble lanthanide chelates of (R)-or (S)-propylenediaminetetraacetate (57) [Eu(pdta)] 176 and N,N,N 0 ,N 0 -tetrakis(pyridylmethyl)-(R)-propylene diamine (86) [Eu(tppn)] 177 can be used to assign the absolute configuration of underivatized aamino acids. With Eu(tppn), the a-proton, a-methyl, b-methyl, and g-hydrogen resonances have empirical trends that correlate with the absolute stereochemistry.…”

Bonding Study on the Chemical Separation of Am(III) from Eu(III) by S-, N-, and O-Donor Ligands by Means of All-Electron ZORA-DFT Calculation

“…We set the hydration complex for both Eu and Am ions as [M III (H 2 O) 9 ] 3+ , because the most stable oxidation state for them in solution is trivalent 18 3+ , we refer to the X-ray coordinates of [Eu III (TPEN′)Cl 2 ] (ClO 4 ) (TPEN′ = N,N,N′,N′-tetrakis(2-pyridylmethyl)-(R)-propylenediamine) for both systems and replace two Cl atoms with two H 2 O molecules. 25 For [M III {(R 2 PO 2 ) 2 H} 3 ], we construct the molecular geometry whose coordination sphere is octahedral based on the literature, 5 because its X-ray structure is not available. The metal ion is chelated by dimeric phosphinic acid bridged through the hydrogen bond, ←OP(R 2 )OH---OP(R 2 )O − →.…”

Water‐soluble calix[4]resorcinarenes as chiral NMR solvating agents for bicyclic aromatic compounds

“…In this report, we compare the effectiveness of 1-4 as chiral NMR solvating agents for a series of water-soluble compounds with bicyclic naphthyl (5-7), indane (8), dihydroindole (9), and indole (10-12) rings. Compounds 2-4 are often superior to 1 as chiral NMR solvating agents for these bicyclic compounds.…”