Nature of chiral-induced equilibrium shifts in racemic labile lanthanide complexes

Wu, Shao-Yi; Hilmes, Gary L.; Riehl, James P.

doi:10.1021/j100343a022

Cited by 20 publications

(15 citation statements)

References 4 publications

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“…For instance, opposite CPL signs have been found by distinct research groups concerning the addition of chiral sugars such as D-ribose or D-mannose to racemic solutions of [Eu(DPA) 3 ] 3− and [Tb(DPA) 3 ] 3− . One can conclude that the diverse outcomes reported could result from experimental conditions not precisely controlled,27,28,36,38 as pointed out by recent measurements 33,34,40,41. In particular, an instrument limitation has also been advanced as a possible reason for the observation of an opposite CPL sign which would have a consequent influence on the conclusions of the studies, especially for measurements of very small luminescence dissymmetry factors.…”

Section: Introductionmentioning

confidence: 98%

“…From the measurements performed in the last few years,33,34 one can conclude that simple substitutions of similar groups such as minor modifications of the alkyl group of l -histidine amino acid derivatives do not change the overall chirality of the perturbation, but no correlation has been observed with different underivatized amino acids. Further contradictions have been found in the literature regarding the source of this complex mechanism responsible for the equilibrium shift28,36 while attempting to correlate the sign of the CPL to some element of the chiral structure of simple or complex sugars,27,37 or in the use of mixed–ligand lanthanide complexes38,39 containing more than one type of ligand. For instance, opposite CPL signs have been found by distinct research groups concerning the addition of chiral sugars such as D-ribose or D-mannose to racemic solutions of [Eu(DPA) 3 ] 3− and [Tb(DPA) 3 ] 3− .…”

Section: Introductionmentioning

confidence: 99%

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Importance of hydrogen‐bonding sites in the chiral recognition mechanism between racemic D₃ terbium(III) complexes and amino acids

et al. 2008

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The perturbation of the racemic equilibrium of luminescent D 3 terbium(III) complexes with chelidamic acid (CDA), a hydroxylated derivative of 2,6-pyridine-dicarboxylic acid (DPA), by added chiral biomolecules such as L-amino acids has been studied using circularly polarized luminescence and 13 C NMR spectroscopy. It is shown in this work that the chiral-induced equilibrium shift of [Tb (CDA) 3 ] 6− by L-amino acids (i.e. L-proline or L-arginine) was largely influenced by the hydrogenbonding networks formed between the ligand interface of racemic [Tb(CDA) 3 ] 6− and these added chiral agents. The capping of potential hydrogen-bonding sites by acetylation in L-proline led to a ∼100-fold drop in the induced optical activity of the [Tb(CDA) 3 ] 6− :N-acetyl-L-proline system. This result suggested that the hydrogen-bonding networks serve as the basis for further noncovalent discriminatory interactions between racemic [Tb(CDA) 3 ] 6− and added L-amino acids.

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Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Importance of hydrogen‐bonding sites in the chiral recognition mechanism between racemic D₃ terbium(III) complexes and amino acids

et al. 2008

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“…[9,10] This chiral induction, which operates at the chiral metal center, is called the Pfeiffer effect and is attributed to an outer-sphere chiral discrimination phenomenon. [11] If the chiral probe is an enantiopure quencher (e.g., metalloproteins, vitamin B 12 , etc. ), then the enantioselective quenching of lanthanide luminescence can be studied.…”

Section: Introductionmentioning

confidence: 99%

Lanthanide Class of a Trinuclear Enantiopure Helical Architecture Containing Chiral Ligands: Synthesis, Structure, and Properties

Lama

Mamula

Kottas

et al. 2007

Chemistry A European J

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The pinene-bipyridine carboxylic derivatives (+)- and (-)-HL, designed to form configurationally stable lanthanide complexes, proved their effectiveness as chiral building blocks for the synthesis of lanthanide-containing superstructures. Indeed a self-assembly process takes place with complete diastereoselectivity between the enantiomerically pure ligand L(-) and Ln(III) ions (La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er), thus leading to the quantitative formation of a trinuclear supramolecular architecture with the general formula [Ln(3)(L)(6)(mu(3)-OH)(H(2)O)(3)](ClO(4))(2) (abbreviated as tris(Ln[L](2))). This class of C(3)-symmetrical compounds was structurally characterized in the solid state and solution. Electrospray (ES) mass spectrometric and (1)H NMR spectroscopic analyses indicated that the trinuclear species are maintained in solution (CH(2)Cl(2)) and are stable in the investigated concentration range (10(-2)-10(-6) m). The photophysical properties of the ligand HL and its tris(Ln[L](2)) complexes were studied at room temperature and 77 K, thus demonstrating that the metal-centered luminescence is well sensitized both for the visible and near-IR emitters. The chiroptical properties of tris(Ln[L](2)) complexes were investigated by means of circular dichroism (CD) and circularly polarized luminescence (CPL). A high CD activity is displayed in the region of pi-pi* transitions of bipyridine. CPL spectra of tris(Eu[(+)-L](2)) and tris(Tb[(+)-L](2)) present large dissymmetry factors g(em) for the sensitive transitions of Eu(III) ((5)D(0)-->(7)F(1), g(em)=-0.088) and Tb(III) ((5)D(4)-->(7)F(5), g(em)=-0.0806). The self-recognition capabilities of the system were tested in the presence of artificial enantiomeric mixtures of the ligand. (1)H NMR spectra identical to those of the enantiomerically pure complexes and investigations by CD spectroscopic analysis reveal an almost complete chiral self-recognition in the self-assembly process, thus leading to mixtures of homochiral trinuclear structures.

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“…[27][28][29] In both associated and dissociated models of discrimination, the Pfeiffer effect studies show that the BROWN AND HOPKINS discrimination increases as the amino acid concentration increases. If the data shown in Table 1 Table 1 show concentration-dependent chiral discrimination that has the opposite trend of the Pfeiffer effect studies.…”

Section: Concentration Dependencementioning

confidence: 99%

“…27 A study using L-histidine to perturb the racemization of Tb(dpa) 3 3À (i.e., the Pfeiffer effect) demonstrates that the chiral discrimination increases with increasing L-histidine concentration. 28 This concentration-dependent behavior was attributed to each L-histidine interacting with multiple Tb(dpa) 3 3À complexes (i.e., the dissociated model). Another study showed that the Pfeiffer effect between praeseodymium (III) tris (oxydiacetate) (Pr(ODA) 3 3À ), a similar propeller-blade like complex, and L-proline also showed an increase of chiral discrimination with increasing proline concentration.…”

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confidence: 99%

Chiral Discrimination by Ionic Liquids: Impact of Ionic Solutes

Brown

Hopkins

2015

Chirality

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Chiral ionic liquids hold promise in many asymmetric applications. This study explores the impact of ionic solutes on the chiral discrimination of five amino acid methyl ester-based ionic liquids, including L- and D-alanine methyl ester, L-proline methyl ester, L-leucine methyl ester, and L-valine methyl ester cations combined with bis(trifluoromethanesulfonimide) anion. Circularly polarized luminescence spectroscopy was used to study the chiral discrimination by measuring the racemization equilibrium of a dissymmetric europium complex, Eu(dpa)3(3-) (where dpa = 2,6-pyridinedicarboxylate). The chiral discrimination measured was dependent on the concentration of Eu(dpa)3(3-) and this concentration-dependence was different in each of the ionic liquids. Ionic liquids with L-leucine methyl ester and L-valine methyl ester even switched enantiomeric preference based on the solute concentration. Changing the cation of the Eu(dpa)3(3-) salt from tetrabutylammonium to tetramethylammonium ion also affected the chiral discrimination demonstrated by the ionic liquids.

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Nature of chiral-induced equilibrium shifts in racemic labile lanthanide complexes

Cited by 20 publications

References 4 publications

Importance of hydrogen‐bonding sites in the chiral recognition mechanism between racemic D₃ terbium(III) complexes and amino acids

Importance of hydrogen‐bonding sites in the chiral recognition mechanism between racemic D₃ terbium(III) complexes and amino acids

Lanthanide Class of a Trinuclear Enantiopure Helical Architecture Containing Chiral Ligands: Synthesis, Structure, and Properties

Chiral Discrimination by Ionic Liquids: Impact of Ionic Solutes

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Nature of chiral-induced equilibrium shifts in racemic labile lanthanide complexes

Cited by 20 publications

References 4 publications

Importance of hydrogen‐bonding sites in the chiral recognition mechanism between racemic D3 terbium(III) complexes and amino acids

Importance of hydrogen‐bonding sites in the chiral recognition mechanism between racemic D3 terbium(III) complexes and amino acids

Lanthanide Class of a Trinuclear Enantiopure Helical Architecture Containing Chiral Ligands: Synthesis, Structure, and Properties

Chiral Discrimination by Ionic Liquids: Impact of Ionic Solutes

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Importance of hydrogen‐bonding sites in the chiral recognition mechanism between racemic D₃ terbium(III) complexes and amino acids

Importance of hydrogen‐bonding sites in the chiral recognition mechanism between racemic D₃ terbium(III) complexes and amino acids