Lanthanide Anionic Metal–Organic\nFrameworks\nContaining Semirigid Tetracarboxylate Ligands: Structure, Photoluminescence,\nand Magnetism

Abstract

A series of lanthanide anionic metal–organic frameworks,\n[NH₂(CH₃)₂]­[Ln­(MDIP)­(H₂O)] (Ln = Pr (<b>1</b>), Nd (<b>2</b>), Sm (<b>3</b>), Eu (<b>4</b>), Gd (<b>5</b>), Tb (<b>6</b>),\nDy (<b>7</b>); H₄MDIP = methylenediisophthalic acid)\nand [NH₂(CH₃)₂]­[Ln­(MDIP)­(H₂O)]·0.5NH­(CH₃)₂ (Ln = Er (<b>8</b>), Tm (<b>9</b>), Yb (<b>10</b>)), have been synthesized\nand characterized. In compounds <b>1</b>–<b>7</b>, the adjacent Ln³⁺ ions are intraconnected to form infinite\nmetal-carboxylate oxygen chain-shaped building blocks along the [001]\ndirection. In compounds <b>8</b>–<b>10</b>, MDIP\nligands bridge dinuclear lanthanide centers to form three-dimensional\nframeworks which can be rationalized as a (4,8)-connected topological\nnet with the Schläfli symbol of (4¹⁰.6¹⁴.8⁴)­(4⁵.6)₂. Dimethylamine cations\noccupy the vacancy of all the compounds as counterions. The photophysical\nproperties of trivalent Pr, Nd, Sm, Eu, Tb, Dy, Er, Yb compounds at\nroom temperature were investigated and showed that MDIP is an efficient\nsensitizer of the luminescence of both the Tb³⁺ ion emitting\nvisible light and the Yb³⁺ ion emitting in the near-IR.\nAntiferromagnetic interactions between Gd³⁺ ions were observed\nfrom magnetic susceptibility data.