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A Mechanistic Study of the Dynamic Quenching of the Excited State of europium(III) and terbium(III) Macrocyclic Complexes by Charge- Or Electron Transfer

A Mechanistic Study of the Dynamic Quenching of the Excited State of europium(III) and terbium(III) Macrocyclic Complexes by Charge- Or Electron Transfer

Filip Kielar, Craig P Montgomery, Elizabeth J New, David Parker, Robert A Poole, Siobhan L Richardson, Philip A Stenson

Org Biomol Chem. 2007 Sep 21;5(18):2975-82.

PMID: 17728864

Abstract:

Dynamic quenching of the metal-based excited state of Eu(III) and Tb(III) complexes of sixteen different macrocyclic ligands has been studied. Quenching by urate, ascorbate and selected catechols is most effective for Tb(III) systems, and involves intermediate formation of an excited state complex (exciplex) between the electron-poor heterocyclic sensitising moiety incorporated into the ligand (tetraazatriphenylene, azaxanthone or a pyrazoyl-azaxanthone) and the electron-rich reductant. The process is sensitive to steric inhibition created by the local ligand environment; quenching is reduced as temperature increases as exciplex formation is entropically disfavoured. In contrast, iodide quenches each complex studied according to a classical collisional encounter model; increasing temperature enhances the rate of quenching, and the process is more sensitive to local electrostatic fields generated by ligand substitution, conforming to a traditional Stern-Volmer kinetic model. Quenching may be inhibited by protein association, allowing the identification of candidates for use as optical imaging probes in cellulo.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP13813406	Terbium(III) iodide		13813-40-6	Price

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