Lanthanide complexes circular polarized luminescence

Complexes of lactic acid with a wide variety of metal ions are known and their stability constants have been determined. A variety of techniques has been used in the study of the species formed in the solutions of this hydroxy acid and inorganic ions. Electrochemical and spectrophoto-metric methods have been used with the main aim of determining stability constants of the complex ions. CD and optical rotatory dispersion (ORD) have also proved to be powerful methods in studying, for instance, Mo, Mo , Cu" and Co", as well as lanthanide complexes. Very recently, Brittain et used circularly polarized luminescence (CPL) techniques in the study... 

The Pfeiffer effect, the outer-sphere interaction of a chiral substrate with a rapidly interconverting racemic solution of a chiral lanthanide complex, can be investigated by measurement of the luminescence dissymmetry factor (the ratio of circularly polarized luminescence to total luminescence) for Eu or Tb " complexes. Thus the racemic D chiral complexes [M(dpa)3], where M = Eu or Tb, interact in an outer-sphere manner with the following optically active spiecies cationic chiral transition metal complexes, ascorbic acid, aminocarboxylates, tartrates, amines and phenols. Association constants can be obtained from limiting values of the dissymmetry factors. In some cases, inner-sphere complexation can be demonstrated, as judged by changes in the general nature of the circularly polarized luminescence spectrum and pH irreversibility of the complexation. 

Lanthanide complexes as chiral probes exploiting circularly polarized luminescence 12CSR7673. 

A number of lanthanide complexes have been shown to exhibit circularly polarized luminescence (CPL—the differential spontaneous emission of left- and right-circularly polarized light). In the absence of any externally applied fields, CPL is exhibited only by systems that have net chirality in their structures or are subject to chiral perturbations by their environment. CPL exhibited by the Af-Af transitions of chiral lanthanide systems provides a sensitive probe of coordination and structure in solution. Applications are limited to systems which possess some element of chirality, but in many cases this merely requires that > 1 ligand of interest has a chiral atom or carries a chiral label (such as a chiral substituent group). ... 

This volume of the Handbook on the Physics and Chemistry of Rare Earths adds five new chapters to the science of rare earths, compiled by researchers renowned in their respective fields. Volume 34 opens with an overview of ternary intermetallic systems containing rare earths, transition metals and indium (Chapter 218) followed by an assessment of up-to-date understanding of the interplay between order, magnetism and superconductivity of intermetallic compounds formed by rare earth and actinide metals (Chapter 219). Switching from metals to complex compounds of rare earths, Chapter 220 is dedicated to molecular stmctural studies using circularly polarized luminescence spectroscopy of lanthanide systems, while Chapter 221 examines rare-earth metal-organic frameworks, also known as coordination polymers, which are expected to have many practical applications in the future. A review discussing remarkable catalytic activity of rare earths in site-selective hydrolysis of deoxyribonucleic acid (DNA) and ribonucleic acid, or RNA (Chapter 222) completes this book. 

Petoud S, Muller G, Moore EG et al (2007) Brilliant Sm, Eu, Tb, and Dy chiral lanthanide complexes with strong circularly polarized luminescence. J Am Chem Soc 129 77-83... 

Lunkley JL, Shirotani D, Yamanari K, Kaizaki S, Muller G. Chiroptical Spectra of a Series of Tetrakis((-i-)-3-heptafluatDbutylyrylcamphorato)lanthanide(in) with an Encapsulated Alkali Metal Ion Circularly Polarized Luminescence and Absolute Chiral Structures for the Eu(III) and Sm(ni) Complexes. Inorg Chem 2011 2011 (50) 12724—12732. 

Brittain HG. Circularly Polarized Luminescence Studies of Chiral Lanthanides Complexes. Pract Spectrosc 1991 12 179-200. 

Muller G, Riehl JP. Use of Induced Circularly Polarized Luminescence (CPL) fiom Racemic D3 Lanthanide Complexes to Determine the Absolute Configuration of Amino Adds. J Eluores-cence 2005 15 553-558. 

Bruce JI, Parker D, Lopinski S, Peacock RD. Survey of Eactors Determining the Circularly Polarized Luminescence of Macrocychc Lanthanide Complexes in Solution. Chirality 2002 14 562-567. 

This analysis was made possible by our ability to measure CPL from racemic solutions of lanthanide complexes through use of circularly polarized excitation [12,45-47]. The varied lifetime of the lanthanide (III) ions allow for some insight concerning the lability of complexes of this type. For example, we have shown that although no CPL is detected in the luminescence from tris-terdentate complexes of Tb(III) and Eu(III) with oxydiacetate (ODA), CPL is observed from DytDPA -, indicating that, indeed, this complex is D3 in aqueous solution, but that only for the short lived Dy(III) ion (x = 20 psec) is the photoprepared enantiomerically-enriched excited state maintained throughout the emission lifetime [45]. 

The interaction of aspartic acid and other ligands with complexes of Tb " with edta and related ligands has also been studied and association constants determined. The complex formation between Tb " or Eu " and (r)-( — )-l,2-propanediaminetetraacetic add or (r,r)-trons-1,2-cyclohexanediaminetetraacetic acid has been similarly investigated. The pH dependence of the circularly polarized and total luminescence shows a drastic configurational change of the chelate system at pH 10.5-11, corresponding, it is believed, to formation of hydroxide complexes. Tlie technique of magnetic-field-induced circularly polarized emission has been introduced for lanthanide ions the mechanisms of lanthanide transition intensities are also discussed in the paper. 

Kitchen JA, Barry DE, Mercs L, Albrecht M, Peacock RD, Gunnlaugsson T. Circularly Polarized Lanthanide Luminescence from Langmuir-dJlodgett Films Formed from Optically Active and Amphiphihc Eu -Based Self-Assembly Complexes. Angew Chem Int Ed 2012 51 704-708. 

The first two chapters of this work cover theoretical and practical aspects of the emission process, the spectroscopic techniques and the equipment used to characterize the emission. Chapter 3 introduces and reviews the property of circularly polarized emission, while Chapter 4 reviews the use of lanthanide ion complexes in bioimaging and fluorescence microscopy. Chapter 5 covers the phenomenon of two-photon absorption, its theory as well as applications in imaging, while Chapter 6 reviews the use of lanthanide ions as chemo-sensors. Chapter 7 introduces the basic principles of nanoparticle upconversion luminescence and its use for bioimaging and Chapter 8 reviews direct excitation of the lanthanide ions and the use of the excitation spectra to probe the metal ion s coordination environment in eoordination compounds and biopolymers. Finally, Chapter 9 describes the formation of heterobimetallic complexes, in whieh the lanthanide ion emission is promoted through the hetero-metal. 

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