Ion Site Substitution\nin a Sulfonylcalix[4]arene-Supported\nLn<sub>8</sub> (Ln = Tb and Eu) Coordination Wheel with Tunable Luminescence

Lanthanide coordination clusters (LCCs), namely, [Ln<sub>8</sub>(TC4A-SO<sub>2</sub>)<sub>4</sub>(TA)<sub>2</sub>(DMF)<sub>4</sub>(H<sub>2</sub>O)<sub>10</sub>] (solvents) (Ln<sub>8</sub> = <b>Tb</b><sub><b>8</b></sub>, <b>Eu</b><sub><b>8</b></sub>, <b>Tb</b><sub><b>4</b></sub><b>Eu</b><sub><b>4</b></sub>; H<sub>4</sub>TC4A-SO<sub>2</sub> = <i>p</i>-<i>tert</i>-butylsulfonylcalix[4]arene; H<sub>4</sub>TA = dl-tartaric acid), were synthesized via the\nsolvothermal method and were characterized by single-crystal X-ray\ndiffraction. Ln<sub>8</sub> is a wheel-shaped framework built from\nfour cone-shaped mononuclear units (Ln<sup>III</sup>-TC4A-SO<sub>2</sub>) and four bridging-Ln<sup>III</sup> ions with two tartrates located\nin the center serving as “spokes”. <b>Tb</b><sub><b>8</b></sub> exhibits an extraordinary luminescence quantum\nyield (QY<sub>s</sub>) of 53.3% in the solid state under the excitation\nof 370 nm, while <b>Eu</b><sub><b>8</b></sub> cannot emit\nunder similar conditions. Furthermore, <b>Tb</b><sub><b>8</b></sub> shows concentration-dependent emission in a methanol solution\nwith the best luminescence QY<sub>l</sub> of 61.8%, representing one\nof the best luminescent Tb-based coordination clusters. The Eu ions\ncan be rationally doped in the Tb ring (<b>Tb</b><sub><i>x</i></sub><b>Eu</b><sub><b>8–<i>x</i></b></sub>, 4 ≤ <i>x</i> < 8) by a stoichiometric\nratio on specific sites to tune the emission color output, which reveals\nthe efficient energy transfer from <sup>5</sup>D<sub>4</sub>-<sup>7</sup>F<sub>5</sub> and <sup>5</sup>D<sub>4</sub>-<sup>7</sup>F<sub>6</sub> levels of Tb<sup>III</sup> to the <sup>5</sup>D<sub>0</sub> level of Eu<sup>III</sup>. This work presents a unique method of\ncontrolling the fabrication and tunable luminescence of LCCs.