Luminescent Dinuclear Lanthanide Complexes of 5-Me-HXTA

Abstract

The synthesis and characterization of a series of anionic homobimetallic lanthanide complexes of the septadentate chelate 5-Me-HXTA (N,N-(2 hydroxy-5-methyl-1,3-xylylene)bis(N-(carboxymethyl)glycine) is described (Ln = Nd, Sm, Eu, Tb, Dy, Ho, Er, Yb). Single X-ray crystallography confirms that the complexes exist as discrete dimeric pairs in the solid state. Proton NMR, diffusion-ordered spectroscopy, and luminescence solution studies suggest that the binuclear stoichiometry is retained in aqueous solution over a range of analytically useful concentrations. The phenolic chromophores effectively sensitize the visible and near-infrared lanthanide-centered emission in the terbium, neodymium, and ytterbium derivatives, giving rise to particularly long-lived green and near-infrared emission. The terbium complex displays a high quantum yield of around 50% in aqueous solution with a low detection limit of 1 x 10(-12) M, rendering this compound a potential candidate for time-resolved applications.

Features of the Molecular Structure and Luminescence of Rare-Earth Metal Complexes with Perfluorinated (Benzothiazolyl)phenolate Ligands

“…The europium complex 5 , in contrast to the non-emissive non-fluorinated analog, revealed a weak metal-centered luminescence in a THF solution at 616 nm, corresponding to the 5 D 0 → 7 F 2 transition (Figure 8). This observation is consistent with the known fact of quenching the luminescence of europium by phenol-substituted ligands due to the appearance in the complex of LMCT states and the low reduction potential of the Eu (III) ion [47]. The complexes Nd, Er, and Yb showed luminescence in the NIR region upon 405 nm laser excitation (Figure 9).…”

Paramagnetic DOSY: An Accurate Tool for the Analysis of the Supramolecular Interactions between Lanthanide Complexes and Proteins

“…Relaxation enhancements that are observed on nuclei located close to paramagnetic centers can be problematic for the determination of accurate diffusion coefficients by NMR . The main reason is that fast relaxation induces a line broadening that may be detrimental not only to the resolution, but also to the actual sensitivity of experimental data . In order to check the feasibility of diffusion measurements on paramagnetic tris‐dipicolinate lanthanide complexes, a reproducibility study was carried on for [Na] 3 [Yb(DPA) 3 ].…”

Lanthanide Contraction within a Series of Asymmetric Dinuclear [Ln2] Complexes

“…[24] The literature contains some series of dinuclear complexes of lanthanides, which usually contain fewer members. [30][31][32][33] From the point of view of the single-ion structure, such series should not be much more informative than mononuclear ones, considering that in these complexes both metals are structurally equal. It would be interesting to analyze individually and collectively the effect of lanthanide contraction of systems that contain more than one noncrystallographically equivalent metal.…”