High chiral recognition in α-amino-acid and -ester complexation

Peacock, Stephen C.; Cram, Donald J.

doi:10.1039/c39760000282

Cited by 38 publications

(19 citation statements)

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“…Circularly polarized phosphorescence from transition metal complex has been reported for Cr(en) 3 (ClO 4 ) 3 (en=ethylenediamine), Cr(en) 3 Cl 3 and Rh(en) 3 Cl 3 ⋅NaCl ⋅ 6H 2 O in crystal state . Very similar dissymmetry factors have been reported for the CPL and CD spectra of Ru(2,2′‐bipyridine) 3 2+ .…”

Section: Helicenes and Helicenoidssupporting

confidence: 68%

Circularly Polarized Luminescence and Circular Dichroisms in Small Organic Molecules: Correlation between Excitation and Emission Dissymmetry Factors

2018

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by the recent rapid growth of interest in circularly polarized luminescence (CPL) of organic molecules, we have collected all the reliable CPL, as well as the corresponding circular dichroism (CD), data measured in fluid solutions. To analyze the correlation between CPL and CD, we employed the absorption and luminescence dissymmetry factors (g abs and g lum ) of the p-p* transition reported for chiral organic molecules of various categories, including planar chiral cyclophanes and helicenes, axially chiral biaryls and spiro compounds, and pointand axially chiral BODIPY derivatives. In rigid p-systems, the absorption and fluorescence spectra are often mirror images of each other with a small Stokes shift, reflecting the minimal conformational relaxation in the emissive excited state, which should also affect the chiroptical properties in the excited state and be better sensed by CPL. However, no comprehensive efforts have hitherto been made to correlate the two relevant chiroptical properties, i. e. CPL versus CD, and also to quantitatively elucidate the effects of conformational relaxation in the excited state on the CPL behavior. The global linear regression analysis of all the reported g abs and g lum values, though fairly scattered (see TOC), led us to a quantitative relationship: j g lum j = 0.81 j g abs j (r 2 = 0.60), which demonstrates that the CPL dissymmetry factor is proportional to, and smaller than, the CD dissymmetry factor. A closer look revealed that the slope of the plot, or the proportional coefficient, is a critical function of the class of compounds, varying from 0.99 for cyclophanes to 0.93 for biaryls, to 0.77 for BODIPYs, and then to 0.61 for helicenes/ helicenoids. The scattered g lum -g abs plot and the general trend g lum g abs appear to be inherent to the CPL of organic molecules in their isolated states, originating from the conformational flexibility, vibrational contribution, and Stokes shift that differ in each category.The absorption and emission intensities are proportional to the relevant dipole strength D, which is defined by Equation (7):In isotropic solutions, the electric quadrupole moment is cancelled out in R and generally small and negligible for D. The dissymmetric factors g abs and g lum are thus given by [Eq. (8)]:

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Section: Helicenes and Helicenoidssupporting

confidence: 68%

Circularly Polarized Luminescence and Circular Dichroisms in Small Organic Molecules: Correlation between Excitation and Emission Dissymmetry Factors

2018

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“…Chemoselectivity in binding the target analyte is important-rejecting competing charge-dense ions for example-and stereoselectivity is also required so that the potential difference that builds up at the aqueous-membrane interface is proportional to the activity of the ion and its enantiomeric purity. Earlier work on chiral sensors had examined certain lipophilic chiral crown ethers as ionophores 2 and although enantioselective sensors for chiral primary amines were defined, chemoselectivity was very modest (severe Na + /K + interference) and N-alkyl substitution compromised the N-H ... O binding interaction.…”

Section: Chiral Sensorsmentioning

confidence: 99%

“…An early example of such an interaction with a synthetic neutral ionophore involves the complexation of a primary ammonium ion, RN + H 3 with the lone-pairs of C 3 -related ether oxygen atoms in an 18-crown-6 derivative. 2 Receptors that are rich in p-electron density may also serve as the hydrogen-bond acceptor: 3 in the enzyme acetylcholine esterase the interactions between the cationic NMe 3 head group of acetylcholine and the hydrophobic p-electrons of Trp-84 are believed to contribute over 20 kJ mol 21 to the overall free energy of binding. 4 Whilst cation-p interactions are undoubtedly an important binding interaction in supramolecular chemistry, for an N + -CH group as a hydrogen bond donor the interaction with ether oxygens is more energetically favourable.…”

Section: Introductionmentioning

confidence: 99%

Selective complexation and sensitive analysis of charge diffuse cationic species using lipophilic cyclodextrins

Parker¹,

Kataky²

1997

Chem. Commun.

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“…Unter allen untersuchten Ionophoren fallt besonders die Verbindung 9 von Cram et al [23] auf, welche auch bei Verteilungs-und Chromatographie-Versuchen dieser Autoren die hischste Enantiomerenselektivitat aufwies. Alle anderen untersuchten chiralen Ionophoren zeigen eine eher bescheidene Enantiomerenselektivitat.…”

Section: So Lasst Sich Die Emk Der Messketteunclassified

Elektrochemische Untersuchungen über das enantiomerenselektive Verhalten von chiralen Ionophoren in flüssigen Membranen

Thoma¹,

Viviani‐Nauer²,

Schellenberg³

et al. 1979

Helvetica Chimica Acta

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The enantiomer selectivity of a series of chiral neutral ionophores was investigated by electrochemical methods using ionophore-solvent-polymer membranes and chiral ammonium salts as substrates. The potentiometrically determined enantiomer selectivities are in good agreement with the results of electrodialytic transport studies. Einleitung. -Beobachtungen des ionenselektiven Verhaltens von elektrisch neutralen, lipophilen Naturstoffen wie von Valinomycin und von den Makrotetroliden [I] fuhrten in den letzten 10 Jahren zu einer sturmischen Entwicklung im Entwurf von Modellverbindungen mit Selektivitat fur vorgegebene Ionen. So sind eine grosse Anzahl Liganden vornehmlich mit Selektivitat fur Alkali-und Erdalkaliionen hergestellt worden [2-51. In Anlehnung an die Pionierarbeiten von Pedersen haben besonders Cram et al. [6-81 chirale Liganden hoher Enantiomerenselektivitat fur chiral monosubstituierte Ammonium-Ionen bereitet. Ein enantiomerenselektives elektromotorisches Verhalten in Membranen konnte jedoch erst kiirzlich bei Ionophoren vom Typ 1-3 nachgewiesen werden [9]. Das Studium dieses Verhaltens ist deshalb interessant, wed es sich um Modelle fur die stereospezifischen Transporte von chiralen biogenen Ammonium-Ionen unter biologischen Bedingungen handelt. In der vorliegenden Abhandlung berichten wir iiber die Methodik und iiber einige Ergebnisse der elektrochemischen Untersuchungen von chiralen Liganden auf ihr enantiomerenselektives Verhalten als Ionophoren. Diese Untersuchungen beruhen auf friiheren Arbeiten aus unserem Laboratorium iiber das ionenselektive Verhalten der Ionophoren in Fliissigmembranen [9] [ 101. Theoretische Grundlagen. -Unter gewissen Voraussetzungen [ 10-131 ist die Ionenselektivitiit von Membranen, die aus einem elektrisch neutralen lipophilen Ionophor in einem in Wasser schwer loslichen organischen Losungsmittel bestehen, durch die Komplexbildung des Ionophors mit den Ionen in der Membrane gegeben.

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High chiral recognition in α-amino-acid and -ester complexation

Cited by 38 publications

References 0 publications

Circularly Polarized Luminescence and Circular Dichroisms in Small Organic Molecules: Correlation between Excitation and Emission Dissymmetry Factors

Circularly Polarized Luminescence and Circular Dichroisms in Small Organic Molecules: Correlation between Excitation and Emission Dissymmetry Factors

Selective complexation and sensitive analysis of charge diffuse cationic species using lipophilic cyclodextrins

Elektrochemische Untersuchungen über das enantiomerenselektive Verhalten von chiralen Ionophoren in flüssigen Membranen

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