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Luminescent lanthanide helicates self-assembled from ditopic ligands bearing phosphonic acid or phosphoester units

Luminescent lanthanide helicates self-assembled from ditopic ligands bearing phosphonic acid or phosphoester units
Luminescent lanthanide helicates self-assembled from ditopic ligands bearing phosphonic acid or phosphoester units
A series of hexadentate ditopic receptors incorporating benzimidazole moieties have been designed, which are fitted with phosphonic acid or phosphoethylester coordinating units. In addition, poly(oxyethylene) pendants have been introduced on the benzimidazole backbone of two ligands to increase water solubility. The ligands self-assemble with lanthanide ions under stoichiometric conditions, yielding triple-stranded homobimetallic helicates, as ascertained by mass spectrometry and UV-visible titrations. The helicates display large thermodynamic stability, for example, log beta(23) approximately 21-24 for all the Eu(III) complexes. Photophysical measurements reveal sensitization of the metal-centered luminescence in the europium and terbium complexes, which is modulated by the nature of the ligand. Hydration numbers determined by the lifetime method are essentially zero. The Eu((5)D(0)) lifetimes are long and reach values up to 3.2 ms, while quantum yields as high as 25% are obtained in water at pH 7.4. Back transfer limits the sensitization efficiency for Tb(III) luminescence, and both lifetimes and quantum yields are much smaller. The properties of the helicates are discussed with respect to those self-assembled from ligands bearing carboxylate coordinating units.
0020-1669
10687-10696
Chauvin, Anne-Sophie
ea95a3c0-b8f0-430e-9b4b-a257303ea55f
Comby, Steve
545d9674-ce80-4a07-afca-5d8bb56cc9b7
Baud, Matthias
8752d519-3d33-43b6-9a77-ab731d410c2e
De Piano, Cyntia
85cba6c5-0643-4446-9ffa-ccab2a1d4f11
Duhot, Céline
8848d1eb-4236-4d09-a245-a2ff6db7aa11
Bünzli, Jean-Claude G.
748e7028-ed05-4d92-b63e-b2ea2005d29b
Chauvin, Anne-Sophie
ea95a3c0-b8f0-430e-9b4b-a257303ea55f
Comby, Steve
545d9674-ce80-4a07-afca-5d8bb56cc9b7
Baud, Matthias
8752d519-3d33-43b6-9a77-ab731d410c2e
De Piano, Cyntia
85cba6c5-0643-4446-9ffa-ccab2a1d4f11
Duhot, Céline
8848d1eb-4236-4d09-a245-a2ff6db7aa11
Bünzli, Jean-Claude G.
748e7028-ed05-4d92-b63e-b2ea2005d29b

Chauvin, Anne-Sophie, Comby, Steve, Baud, Matthias, De Piano, Cyntia, Duhot, Céline and Bünzli, Jean-Claude G. (2009) Luminescent lanthanide helicates self-assembled from ditopic ligands bearing phosphonic acid or phosphoester units. Inorganic Chemistry, 48 (22), 10687-10696. (doi:10.1021/ic901424w). (PMID:19839576 )

Record type: Article

Abstract

A series of hexadentate ditopic receptors incorporating benzimidazole moieties have been designed, which are fitted with phosphonic acid or phosphoethylester coordinating units. In addition, poly(oxyethylene) pendants have been introduced on the benzimidazole backbone of two ligands to increase water solubility. The ligands self-assemble with lanthanide ions under stoichiometric conditions, yielding triple-stranded homobimetallic helicates, as ascertained by mass spectrometry and UV-visible titrations. The helicates display large thermodynamic stability, for example, log beta(23) approximately 21-24 for all the Eu(III) complexes. Photophysical measurements reveal sensitization of the metal-centered luminescence in the europium and terbium complexes, which is modulated by the nature of the ligand. Hydration numbers determined by the lifetime method are essentially zero. The Eu((5)D(0)) lifetimes are long and reach values up to 3.2 ms, while quantum yields as high as 25% are obtained in water at pH 7.4. Back transfer limits the sensitization efficiency for Tb(III) luminescence, and both lifetimes and quantum yields are much smaller. The properties of the helicates are discussed with respect to those self-assembled from ligands bearing carboxylate coordinating units.

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More information

e-pub ahead of print date: 19 October 2009
Published date: 16 November 2009

Identifiers

Local EPrints ID: 400519
URI: https://eprints.soton.ac.uk/id/eprint/400519
ISSN: 0020-1669
PURE UUID: 2947e72e-be4c-4b10-8e42-f0b97ddfae4c
ORCID for Matthias Baud: ORCID iD orcid.org/0000-0003-3714-4350

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Date deposited: 21 Sep 2016 15:35
Last modified: 14 Jul 2018 00:28

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