Magnetic moments: The orientation of the title single‐molecule magnet was investigated by magnetic single crystal and luminescence characterization, supported by ab initio calculations, and was found to be governed by the position of the hydrogen atoms of the apical water molecules. This finding suggests that simple magneto‐structural correlations can give misleading clues for research in molecular magnetism as well as in the design of MRI contrast agents.

Heteronuclear lanthanide terephthalate coordination polymers with the general chemical formula [Ln2–2xLn′2x(bdc)3(H2O)4]∞, for which bdc2– symbolizes benzene‐1,4‐dicarboxylate (or terephthalate) and Ln and Ln′ represent trivalent rare earth ions, were synthesized and structurally characterized. Analysis of the Y/Lu compounds by 89Y and 13C solid‐state NMR spectroscopy was carried out, and the results support the hypothesis of randomly distributed lanthanide ions. The spectroscopic and colorimetric properties of this family of compounds were investigated in detail. The resulting data demonstrate that this series of compounds presents highly tunable luminescence properties and clearly indicate that intermetallic deactivation processes play an important role in the emission mechanism. Playing with intermetallic distances allows one to tune the color and the brightness of the lanthanide emission in these coordination polymers.

Reactions in water between mixtures of rare earth ions (Ln =Y, La-Tm, except Pm) and the sodium salt of terephthalic acid lead to an infinite family of isostructural heteropolynuclear coordination polymers. The monophasic character of the synthesized powders as well as the isostructurality of the heteropolynuclear compounds with the previously described mononuclear [Tb(2)(C(8)H(4)O(4))(3)(H(2)O)(4)](infinity) are ascertained on the basis of the X-ray powder diffraction diagrams. One family of heterodinuclear compounds has been studied in detail, that is, [(La(2-x)Y(x))(C(8)H(4)O(4))(3)(H(2)O)(4)](infinity) with 0 < or = x < or = 2. This study demonstrates the random character of the spatial distribution of the metallic ions. In order to demonstrate the high modularity of the physical properties, the solid-state luminescent properties of the compounds of general formula [(Eu(2-x)Tb(x))(C(8)H(4)O(4))(3)(H(2)O)(4)](infinity) with 0 < or = x < or = 2 have been studied and compared to those of the corresponding mixtures of [(Eu(2))(C(8)H(4)O(4))(3)(H(2)O)(4)](infinity) and [(Tb(2))(C(8)H(4)O(4))(3)(H(2)O)(4)](infinity). In order to confirm the general character of these studies, the compound containing in equal proportions all 13 rare earth ions between La and Tm (except Pm) plus Y has been synthesized and characterized. At last, the solid-state luminescent properties of compounds belonging to the ternary system [(Ce(2-x-y)Eu(x)Tb(y))(C(8)H(4)O(4))(3)(H(2)O)(4)](infinity) with x + y < or = 2 are briefly described.