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.

Caged peroxide: An octanuclear nickel complex, which exhibits peroxide in an unprecedented μ6‐(η1)3 coordination mode, was prepared (see structure: only the Ni8 unit with the central peroxo ligand and the bridging oxygen atoms is shown; green Ni, red O). This mode of binding finally completes the series of symmetrical μn‐(η1)n/2 peroxide binding modes in complexes.

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