Thiacalix[4]arene-functionalized molecular clusters involving the Keggin-type PM <sub>4</sub>Mo <sub>8</sub> (M = Co, Ni) motif: Electrochemical and photothermal conversion properties
Qing Zhao, Dong-Ao Mao, Liangliang Huang, Kun Zhou, Hongrui Tian, Bao-Kuan Chen, Yanfeng Bi
Abstract
Four new thiacalixarene-functionalized polyoxometalate clusters, [Na<sub>2.5</sub>(H<sub>2</sub>O)<sub>2.5</sub>Co<sub>4</sub>(TC4A)PMo<sub>8</sub>O<sub>32</sub>][(CH<sub>3</sub>)<sub>2</sub>NH<sub>2</sub>]<sub>4.5</sub>(CH<sub>3</sub>OH)(DMF)<sub>1.5</sub>(H<sub>2</sub>O) (PCo<sub>4</sub>Mo<sub>8</sub>-<strong>1, </strong>H<sub>4</sub>TC4A = <em>p-tert</em>-Butylthiacalix[4]arene<strong>)</strong>, [H<sub>4</sub>Ni<sub>4</sub>(TC4A)PMo<sub>8</sub>O<sub>32</sub>][(CH<sub>3</sub>)<sub>2</sub>NH<sub>2</sub>]<sub>3</sub>(DMF)<sub>4</sub>(CH<sub>3</sub>OH)<sub>2</sub> (H<sub>2</sub>O)<sub>2</sub> (PNi<sub>4</sub>Mo<sub>8</sub>-<strong>2)</strong>, and [M<sub>4</sub>(TC4A)PMo<sub>8</sub>VO<sub>33</sub>][N(CH<sub>3</sub>)<sub>4</sub>]<sub>2</sub>[HN(CH<sub>3</sub>)<sub>3</sub>][(CH<sub>3</sub>)<sub>2</sub>NH<sub>2</sub>](DMF)<sub>2</sub>(CH<sub>3</sub>OH)<sub>5 </sub><strong> </strong>(M= Co, PCo<sub>4</sub>Mo<sub>8</sub>V-<strong>3</strong>; M = Ni, PNi<sub>4</sub>Mo<sub>8</sub>V-<strong>4</strong>), were synthesized under solvothermal conditions and characterized by single-crystal X-ray diffraction, respectively. These four clusters were characterized by Keggin-type PM<sub>4</sub>Mo<sub>8</sub> motifs, which confer redox properties similar to those of PMo<sub>12</sub>O<sub>40</sub><sup>3−</sup> (PMo<sub>12</sub>) while providing superior structural stability and electrocatalytic reduction of IO<sub>3</sub><sup>−</sup>. The substitution of four metal ions, along with the capping TC4A ligand and VO unit, significantly modulated visible-light absorption, enhancing photothermal conversion in the solid state and organic solutions The efficiency of photothermal conversion revealed that the absorption of visible light relies on electron transfer pathways, which can be discerned through band gap analysis, DFT calculations, and XPS measurements.