The efficient intramolecular sensitisation of terbium(III) and europium(III) by benzophenone-containing ligands

Beeby, Andrew; Bushby, Lisa M.; Maffeo, Davide; Williams, J. A. Gareth

doi:10.1039/b003057k

Cited by 71 publications

(73 citation statements)

References 13 publications

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“…3À (H 2 dpa = dipicolinic acid) in aerated 0.1 m tris(hydroxymethyl)aminomethane (Tris) buffer with an experimental error of 15 % is one of the highest reported to date [10,[54][55][56][57] and the highest value found for terbium complexes containing a water molecule coordinated to the metal centre. The bpatcn 3À chromophore sensitises the Eu ion less efficiently, leading to a quantum yield value f= 5 %, similar to the quantum yield of lanthanide-based commercial luminescent probes.…”

Section: Resultsmentioning

confidence: 89%

Lanthanide Complexes of a Picolinate Ligand Derived from 1,4,7‐Triazacyclononane with Potential Application in Magnetic Resonance Imaging and Time‐Resolved Luminescence Imaging

Nonat

Gateau

Fries

et al. 2006

Chemistry A European J

107

101

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The new potentially octadentate ligand, 1-(carboxymethyl)-4,7-bis[(6-carboxypyridin-2-yl)methyl]-1,4,7-triazacyclononane (H(3)bpatcn), in which two picolinate arms and one acetate arm are connected to the 1,4,7-triazacyclonane core, has been prepared. Potentiometric studies show an increased stability of the Gd(III) complex of H(3)bpatcn (logK(GdL)=15.8(2)) with respect to the Gd(III) complex of the analogous ligand 1,4,7-triazacyclononane-N,N',N''-triacetic acid (H(3)nota) (logK(GdL)=13.7), associated with an increased selectivity of H(3)bpatcn for gadolinium over calcium. The H(3)bpatcn ligand sensitises the terbium ion very efficiently, leading to a long-lived and highly luminescent terbium complex (quantum yield=43 %), in spite of the presence of a coordinated water molecule. (1)H proton NMR studies indicate that the metal ion is rigidly encapsulated by the three arms of the octadentate ligand H(3)bpatcn and that the macrocycle framework remains bound (through the five nitrogen and the three oxygen atoms) even at high temperature. A new theoretical method for interpreting the water proton relaxivity is presented. It is based on recent progresses in the description of the electronic spin relaxation and on an auxiliary probe solute. It replaces the Solomon, Bloembergen and Morgan (SBM) framework, which is questionable at low field, while avoiding resorting to simulations and/or sophisticated theories with additional unknown zero-field splitting (ZFS) parameters. The inclusion of two picolinate groups on a triazacyclononane framework affords the mono-aquo gadolinium complex [Gd(bpatcn)(H(2)O)] with favourable electron-relaxation properties (tau(eff)(S0)=125 ps). The optimisation of the electronic relaxation by ligand design is especially important to achieve high relaxivity in the new generation macromolecular complexes with long rotational correlation times.

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Section: Resultsmentioning

confidence: 89%

Lanthanide Complexes of a Picolinate Ligand Derived from 1,4,7‐Triazacyclononane with Potential Application in Magnetic Resonance Imaging and Time‐Resolved Luminescence Imaging

Nonat

Gateau

Fries

et al. 2006

Chemistry A European J

107

101

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“…The efficiency of ligand-to-lanthanide energy transfer, which requires compatibility between the energy levels of the ligand excited states and the accepting levels of lanthanide ions, is crucial in the design of highperformance probes. [19] Moreover, high quantum yield cannot be obtained without the prevention of nonradiative deactivation of the lanthanide excited states by OÀH oscillators of coordinated or closely diffusing water molecules. The incorporation of suitable chromophores in carefully designed polydentate ligands leads to increased stability of the lanthanide chelate in solution and allows for the metal center to be well protected from water molecules.…”

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confidence: 99%

An Efficient Design for the Rigid Assembly of Four Bidentate Chromophores in Water‐Stable Highly Luminescent Lanthanide Complexes

et al. 2005

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The unique electronic properties of lanthanide ions (longlived luminescence and sharp emission spectra) make them particularly suitable for the development of diagnostic tools in medical analysis. [1,2] Lanthanide complexes are increasingly used for sensor development [3] and as luminescent probes in time-resolved high-throughput assays and fluorescence imaging because of their ability to discriminate between background fluorescence and the target signal.[ ).[ [15][16][17][18] As the Laporte-forbidden 4f-4f transition prevents direct excitation of lanthanide luminescence, lanthanide ions require sensitization by suitable organic chromophores. Furthermore, for practical applications under physiological conditions, the lanthanide ion should be incorporated into highly stable complexes. The efficiency of ligand-to-lanthanide energy transfer, which requires compatibility between the energy levels of the ligand excited states and the accepting levels of lanthanide ions, is crucial in the design of highperformance probes.[19] Moreover, high quantum yield cannot be obtained without the prevention of nonradiative deactivation of the lanthanide excited states by OÀH oscillators of coordinated or closely diffusing water molecules. The incorporation of suitable chromophores in carefully designed polydentate ligands leads to increased stability of the lanthanide chelate in solution and allows for the metal center to be well protected from water molecules. However, the tendency of lanthanide ions to adopt high coordination numbers and their lack of stereochemical preferences make the design of such ligands very challenging.[20] A successful strategy adopted by several investigators relies on tripodal architectures for the organization of three tridentate binding units in nine-coordinate Ln iii complexes. [21][22][23][24][25] The design of polydentate ligands that allow the arrangement of four bidentate moieties around a lanthanide ion has received less attention in spite of the excellent luminescent properties observed for tetrakis complexes of bidentate chomophores, such as quinolinates [26] or tropolonates. [27] Recently, octadentate ligands incorporating four bidentate chromophores have been shown to yield lanthanide complexes with very efficient emissions in the visible or NIR regions. [15,28] The structures of these complexes have not been elucidated, but the highly flexible structure of the backbone that connects the bidentate units suggests nonoptimal protection of the metal center in such systems.Herein, we describe a new and particularly efficient way of assembling four picolinate chromophores around a lanthanide center with a multidentate ligand that yields highly luminescent and water-stable lanthanide complexes. The decadentate ligand N,N,N'N'-tetrakis[(6-carboxypyridin-2-yl)methyl]ethylenediamine (H 4 tpaen) is readily obtained in five steps from commercially available pyridine-2,6-dicarboxylic acid and ethylenediamine in a yield of 26 % (Scheme 1).The water-soluble complexes of tpaen were isolated in 50-60 % yie...

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“…The first strategy is based on alkylation of one nitrogen atom of the cyclen skeleton followed by introduction of remaining acetic acid arms. The alkylation procedures start with monoalkylation of cyclen with chloroacetamide followed by alkylation of three remaining secondary amines, for example, with ethyl bromoacetate [242]. Alternatively, a direct alkylation of t Bu 3 DO3A with bromoacetamide (acetonitrile, K 2 CO 3 ) can be applied [243].…”

Section: Derivatives With Acetamide Pendantsmentioning

confidence: 99%

Synthesis and Characterization of Ligands and their Gadolinium(III) Complexes

Kotek¹,

Kubíček²,

Hermann³

et al. 2013

The Chemistry of Contrast Agents in Medical Magnetic Resonance Imaging

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The efficient intramolecular sensitisation of terbium(III) and europium(III) by benzophenone-containing ligands

Cited by 71 publications

References 13 publications

Lanthanide Complexes of a Picolinate Ligand Derived from 1,4,7‐Triazacyclononane with Potential Application in Magnetic Resonance Imaging and Time‐Resolved Luminescence Imaging

Lanthanide Complexes of a Picolinate Ligand Derived from 1,4,7‐Triazacyclononane with Potential Application in Magnetic Resonance Imaging and Time‐Resolved Luminescence Imaging

An Efficient Design for the Rigid Assembly of Four Bidentate Chromophores in Water‐Stable Highly Luminescent Lanthanide Complexes

Synthesis and Characterization of Ligands and their Gadolinium(III) Complexes

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