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Visible to Near-Infrared Emission from Ln<sup>III</sup>(Bis-oxazoline)–[Mo<sup>V</sup>(CN)<sub>8</sub>] (Ln = Ce–Yb) Magnetic Coordination Polymers Showing Unusual Lanthanide-Dependent Sliding of Cyanido-Bridged Layers

Abstract

Complexes of lanthanides­(III) (Ce–Yb) with 2,2′-bis­(2-oxazoline) (Box) combined with octacyanidomolybdate­(V) gave a series of magneto-luminescent coordination polymers, {[Ln<sup>III</sup>(Box)<sub><i>n</i></sub>(DMF)<sub><i>m</i></sub>]­[Mo<sup>V</sup>(CN)<sub>8</sub>]}·<i>x</i>(solvent) (<b>1</b>–<b>12</b>). They are built of cyanido-bridged layers of a mixed 4- and 8-metal rings topology and show unique sliding of layers dependent on a 4f metal ion. For light lanthanides, dominant phase A, {[Ln<sup>III</sup>(Box)<sub>2</sub>(DMF)<sub>2</sub>]­[Mo<sup>V</sup>(CN)<sub>8</sub>]}·1.5MeCN (Ln = Ce, <b>1</b>; Pr, <b>2</b>; Nd, <b>3</b>), consists of ideally aligned, not shifted layers, giving large channels (13.7 × 14.0 Å). Intermediate lanthanides reveal phase B, {[Ln<sup>III</sup>(Box)<sub>2</sub>(DMF)<sub>2</sub>] [Mo<sup>V</sup>(CN)<sub>8</sub>]}·H<sub>2</sub>O (Ln = Sm, <b>4</b>; Eu, <b>5</b>; Gd, <b>6</b>; Tb, <b>7</b>; Dy, <b>8</b>), of smaller pores (8.4 × 10.6 Å) due to layer-H<sub>2</sub>O hydrogen bonding, which induces sliding of CN<sup>–</sup>-bridged layers. Heavy lanthanides show phase C, {[Ln<sup>III</sup>(Box)­(DMF)<sub>3</sub>]­[Mo<sup>V</sup>(CN)<sub>8</sub>]}·MeCN (Ln = Ho, <b>9</b>; Er, <b>10</b>; Tm, <b>11</b>; Yb, <b>12</b>), with large channels (13.7 × 13.7 Å) of a similar size to light lanthanides. This effect comes from the changes in Ln<sup>III</sup> coordination sphere affecting solvent–layer interactions. Compounds <b>1</b>–<b>12</b> reveal diverse emission depending on the interaction between Ln<sup>III</sup> and Box luminophors. For <b>2</b>–<b>5</b>, <b>9</b>, and <b>12</b>, the ligand-to-metal energy-transfer-induced visible f-centered emission ranging from green for Ho<sup>III</sup>-based <b>9</b>, orange from Sm<sup>III</sup>-based <b>4</b>, to red for Pr<sup>III</sup>- and Eu<sup>III</sup>-containing <b>2</b> and <b>5</b>, respectively. Near-infrared emission was found for <b>2</b>–<b>4</b>, <b>9</b>, and <b>12</b>. Red phosphorescence of Box was detected for Gd<sup>III</sup>-based <b>6</b>, whereas the selective excitation of ligand or Ln<sup>III</sup> excited states resulting in the switchable red to green emission was found for Tb<sup>III</sup>-based <b>7</b>. The materials revealed Ln<sup>III</sup>–Mo<sup>V</sup> magnetic coupling leading to ferromagnetism below 2.0 and 2.2 K for <b>4</b> and <b>7</b>, respectively. The onset of magnetic ordering at low temperatures was found for <b>6</b> and <b>8</b>. Compounds <b>1</b>–<b>12</b> form a unique family of cyanido-bridged materials of a bifunctional magneto-luminescence character combined with dynamic structural features

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