Impact of 1,10-Phenanthroline-Induced Intermediate Valence on the Luminesence of Divalent Europium Halides.

Starting from EuX2 (X = Cl, Br, I), we systematically investigated a variety of divalent europium complexes containing bidentate 1,10-phenanthroline (Phen) ligands. Depending on the Eu/Phen ratio, mono-, di-, and polynuclear complexes are formed, with the latter yielding one-dimensional ∞1[EuBr2(phen)] chains. Seven new divalent europium complexes, [Eu(phen)4(H2O)]Br2·2MeCN, [Eu(phen)4]I2·1.7Tol, [EuBr(phen)3]2Br2·4MeCN, [EuCl2(phen)2]2·2MeCN, [EuBr2(phen)2]2, [EuI2(phen)2]2, and [EuBr2(phen)]x, are presented in this work. All species show remarkable optical properties based on a partial electron transfer from the EuII center to the Phen ligand. The photophysical characterization is further supported by electrochemistry studies in order to describe the intermediate valence of the Eu center.

Selenous Acid in an Aromatic Framework: Insights Into a Temperature-Sensitive Internal Redox System from the Solid State.

We report on a new compound composed of a phenanthroline network in which emerging channels are alternately occupied by selenous acid (H2SeO3) and dioxane molecules. The material undergoes a variety of structural changes due to both its redox activity as well as its thermal decomposition. We investigate an internal redox system of the incorporated selenous acid and the aldehyde groups of the phenanthroline framework. The reduction process of the selenium species was further elucidated by cyclic voltammetry, while the oxidation process was also monitored by 1H NMR spectra. The thermal behavior reveals that the material can undergo a reversible, topotactic transition due to dioxane and water (de)intercalation.