Lanthanide Metalloligand Strategy toward d–f Heterometallic Metal–Organic Frameworks: Magnetism and Symmetric-Dependent Luminescent Properties

On the basis of lanthanide metalloligands, [Ln­(ODA)₃]^3– (H₂ODA = oxydiacetic acid), three series of d–f heterometallic metal–organic frameworks, {[Co­(H₂O)₆]·[Ln₂(ODA)₆Co₂]·6H₂O}_<i>n</i> [<b>1</b>; Ln = Gd (<b>1a</b>), Dy (<b>1b</b>), and Er (<b>1c</b>)], {[Ln₂(ODA)₆Cd₃(H₂O)₆]·<i>m</i>H₂O}_<i>n</i> [<b>2</b>; Ln = Pr (<b>2a</b>), Nd (<b>2b</b>), Sm (<b>2c</b>), Eu (<b>2d</b>), and Dy (<b>2e</b>), <i>m</i> = 9, 6, or 3], and {[Cd­(H₂O)₆]·[Ln₂(ODA)₆Cd₂]·<i>m</i>H₂O}_<i>n</i> [<b>3</b>; Ln = Dy (<b>3a</b>), Ho (<b>3b</b>), Er (<b>3c</b>), Tm (<b>3d</b>), and Lu (<b>3e</b>), <i>m</i> = 6 or 12], were designed and synthesized by a solvent volatilization and hydrothermal method. Magnetic investigation of <b>1</b> reveals the ferromagnetic interactions between the metal ions. In <b>2</b>, Ln^III ions occupied the inversion centers, which are confirmed by the fact that the emission intensity ratio of ⁵D₀ → ⁷F₁ to ⁵D₀ → ⁷F₂ of the Eu^III ion is much more than 3 in <b>2d</b>. It is worth noting that, in <b>2d</b>, the intensity ratio <i>I</i>(⁵D₀→⁷F₁)/<i>I</i>(⁵D₀→⁷F₂) could decrease significantly upon the introduction of different hydrophilic guest molecules, which implies that the luminescent properties of <b>2d</b> have a strong dependence on the geometry of the first coordination sphere of the Eu^III ion