Home
Resources
Publications
Tripyridinophane Platform Containing Three Acetate Pendant Arms: An Attractive Structural Entry for the Development of Neutral Eu(III) and Tb(III) Complexes in Aqueous Solution

Tripyridinophane Platform Containing Three Acetate Pendant Arms: An Attractive Structural Entry for the Development of Neutral Eu(III) and Tb(III) Complexes in Aqueous Solution

Nadine Leygue, Chantal Galaup, Alberto Lopera, Estefanía Delgado-Pinar, René M Williams, Heinz Gornitzka, Jurriaan M Zwier, Enrique García-España, Laurent Lamarque, Claude Picard

Inorg Chem. 2020 Jan 21;59(2):1496-1512.

PMID: 31913029

Abstract:

We report a detailed characterization of Eu3+ and Tb3+ complexes derived from a tripyridinophane macrocycle bearing three acetate side arms (H3tpptac). Tpptac3- displays an overall basicity (∑ log KiH) of 24.5, provides the formation of mononuclear ML species, and shows a good binding affinity for Ln3+ (log KLnL = 17.5-18.7). These complexes are also thermodynamically stable at physiological pH (pEu = 18.6, pTb = 18.0). It should be noted that the pGd value of Gd-tpptac (18.4) is only slightly lower than that of commercially available MRI contrast agents such as Gd-dota (pGd = 19.2). Moreover, a very good selectivity for these ions over the endogenous cations (log KCuL = 14.4, log KZnL = 12.9, and log KCaL = 9.3) is observed. The X-ray structure of the terbium complex shows the metal coordinated by the nine N6O3 donor set of the ligand and one inner-sphere water molecule. DFT calculations result in two Eu-tpptac structures with similar bond energies (ΔE = 0.145 eV): one structure in which the water is coordinated to the metal ion and one structure in which the water molecule is farther away from the ion, bound to the ligand with an OH-π bond. By detailed luminescence experiments, we demonstrate that the europium complex in aqueous solution presents a hydration equilibrium between nine-coordinate, dehydrated [Eu-tpptac]0 and ten-coordinate, monohydrated [Eu-tpptac(H2O)]0 species. A similar trend is observed for the terbium complex. Despite the presence of this hydration equilibrium, the H3tpptac ligand sensitizes Eu3+ and Tb3+ luminescence efficiently in buffered water at physiological pH. Particularly, the terbium complex displays a long excited-state lifetime of 2.24 ms and an overall quantum yield of 33% with a brightness of 3600 M-1 cm-1. Such features of Ln3+ complexes of H3tpptac indicate that this platform appears to be particularly appealing for the further development of luminescent lanthanide labels.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP100587926	Terbium(III) acetate hydrate		100587-92-6	Price
AP62667645	Europium(III) acetate hydrate		62667-64-5	Price

As a specialist in analytical chemical Products, Alfa Chemistry offers consumers a wealth of raw materials and a full range of technologies and services.

QUICK LINKS

HEADQUARTERS

Tel:

Fax:

Email: