4 research outputs found

    Assembly of Mn-Containing Unprecedented Selenotungstate Clusters with Photocatalytic H<sub>2</sub> Evolution Activity

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    The reaction of Na<sub>2</sub>WO<sub>4</sub> and Na<sub>2</sub>SeO<sub>3</sub> in the presence of MnCl<sub>2</sub> under moderately acidic conditions yielded two unprecedented tungstoselenites: dimeric K<sub>2</sub>Na<sub>10</sub>[K<sub>2</sub>⊂{MnSe<sub>4</sub>W<sub>23</sub>O<sub>85</sub>(H<sub>2</sub>O)<sub>6</sub>}]·29H<sub>2</sub>O (<b>1</b>) and trimeric wheel-shaped K<sub>2</sub>Na<sub>10</sub>[K<sub>2</sub>⊂{Mn<sub>3</sub>Se<sub>7</sub>W<sub>39</sub>O<sub>131</sub>(OH)<sub>20</sub>(H<sub>2</sub>O)<sub>2</sub>}]·60H<sub>2</sub>O (<b>2</b>). The assemblies of <b>1</b> and <b>2</b> are based upon the structure directing effects of Se<sup>IV</sup> heteroatoms for generating diverse well-defined vacancy selenotungstate precursors during the formation. The polyoxoanion of <b>1</b> contains two novel Wells–Dawson-type-like {Se<sub>2</sub>W<sub>11</sub>} fragments, which are constructed from novel {SeW<sub>4</sub>} and {SeW<sub>7</sub>} species derived from Wells–Dawson-type {α-Se<sub>2</sub>W<sub>14</sub>} fragments and one disorder of Mn/W center. The polyoxoanion of <b>2</b> exhibits a crown-type structure composed of a [Se<sub>6</sub>W<sub>38</sub>O<sub>120</sub>(OH)<sub>18</sub>(H<sub>2</sub>O)<sub>2</sub>]<sup>6–</sup> “host” (abbreviated as {Se<sub>6</sub>W<sub>38</sub>}) encapsulating SeO<sub>3</sub><sup>2–</sup>-modified Mn/W and two K<sup>+</sup> “guests”. Remarkably, the crown {Se<sub>6</sub>W<sub>38</sub>} shell remains a new type of {Se<sub>2</sub>W<sub>12</sub>}-based trimeric aggregate in the polyoxometalates chemistry. The two compounds were characterized by single-crystal X-ray structure analysis, IR spectroscopy, thermogravimetric, UV/vis spectroscopy, and ESI–MS. Moreover, their photocatalytic H<sub>2</sub> evolution activity was also investigated

    Side Group of Poly(3-alkylthiophene)s Controlled Dispersion of Single-Walled Carbon Nanotubes for Transparent Conducting Film

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    Controlled dispersion of single-walled carbon nanotubes (SWCNTs) in common solvents is a challenging issue, especially for the rising need of low cost flexible transparent conducting films (TCFs). Utilizing conductive polymer as surfactant to facilitate SWCNTs solubility is the most successful pragmatic approach to such problem. Here, we show that dispersion of SWCNT with polymer significantly relies on the length of polymer side groups, which not only influences the diameter distribution of SWCNTs in solution, also eventually affects their effective TCF performance. Surfactants with longer side groups covering larger nanotube surface area could induce adequate steric effect to stabilize the wrapped SWCNTs against the nonspecific aggregation, as discerned by the optical and microscopic measurements, also evidenced from the resultant higher electrokinetic potential. This approach demonstrates a facile route to fabricate large-area SWCNTs-TCFs exhibiting high transmittance and high conductivity, with considerable uniformity over 10 cm Ă— 10 cm

    pH-Controlled and Sulfite Anion-Directed Assembly of a Family of Cerium(III)-Containing Polyoxotungstates Clusters

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    A versatile one-pot strategy was employed to synthesize five cerium­(III)-containing polyoxotungstate nanoclusters through pH-controlled and sulfite anion-directed assembly: [C<sub>2</sub>H<sub>8</sub>N]<sub>3</sub>Na<sub>7</sub>[Ce<sub>2</sub>(H<sub>2</sub>O)<sub>6</sub>W<sub>22</sub>O<sub>72</sub>(OH)<sub>4</sub>]·20H<sub>2</sub>O (<b>1</b>) at pH 5.0; [C<sub>2</sub>H<sub>8</sub>N]<sub>8</sub>Na<sub>16</sub>[Ce<sub>4</sub>(H<sub>2</sub>O)<sub>12</sub>W<sub>44</sub>O<sub>144</sub>(OH)<sub>12</sub>]·23H<sub>2</sub>O (<b>2</b>) at pH 4.5; [C<sub>2</sub>H<sub>8</sub>N]<sub>2</sub>Na<sub>4</sub>Ce<sub>2</sub>[Ce<sub>2</sub>(H<sub>2</sub>O)<sub>10</sub>W<sub>28</sub>O<sub>92</sub>(OH)<sub>2</sub>]·27H<sub>2</sub>O (<b>3</b>) at pH 2.8–3.3; [C<sub>2</sub>H<sub>8</sub>N]<sub>2</sub>Na<sub>7</sub>[{α-SW<sub>7</sub>O<sub>28</sub>}­{Ce<sub>2</sub>(H<sub>2</sub>O)<sub>6</sub>}­(W<sub>3</sub>O<sub>6</sub>)­{α-SW<sub>9</sub>O<sub>32</sub>}­{α-SW<sub>9</sub>O<sub>31</sub>(OH)}]·18H<sub>2</sub>O (<b>4</b>) at pH 2.5; [C<sub>2</sub>H<sub>8</sub>N]<sub>2</sub>Na<sub>18</sub>[Ce<sub>2</sub>(H<sub>2</sub>O)<sub>9</sub>W<sub>36</sub>O<sub>110</sub>(OH)<sub>12</sub>]<sub>2</sub>·30H<sub>2</sub>O (<b>5</b>) at pH 1.5. These compounds were characterized by single-crystal X-ray structure analysis, IR spectroscopy, thermogravimetric (TG) analysis, X-ray photoelectron spectroscopy (XPS), and electrospray ionization mass spectrometry (ESI-MS). Moreover, their electrochemical properties were investigated. Single-crystal X-ray structure analysis revealed that <b>1</b> and <b>2</b> were di- and tetra-cerium­(III)-bridged polyoxotungstates, constructed from two different types of lacunary {W<sub>11</sub>} units. <b>3</b> composed of the well-known cerium­(III)-stabilized {W<sub>28</sub>} unit and organic amine–sodium–cerium cations, was isolated in the pH range 2.8–3.3. In this reaction system, the SO<sub>3</sub><sup>2–</sup> anion acted as a heteroanion template at a lower pH 2.5. <b>4</b> was isolated by the combination of cerium­(III) centers and SO<sub>3</sub><sup>2–</sup> heteroanion template, which is the first lanthanide-containing polyoxotungstates with sulfur heteroatoms, and the 4f metal cerium­(III) centers in <b>4</b> both have eight-coordinated modes and the SO<sub>3</sub><sup>2–</sup> heteroanion templates display μ<sub>7</sub> and μ<sub>9</sub> coordination modes. At a much lower pH 1.5, the polyanion of <b>5</b> was obtained, two triangular-shaped {W<sub>36</sub>} subunits were bridged by the cerium­(III) ions, resulting in the largest lanthanide-containing iso-polyoxotungstates known to date

    Assembly of Keggin-/Dawson-type Polyoxotungstate Clusters with Different Metal Units and SeO<sub>3</sub><sup>2–</sup> Heteroanion Templates

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    Using a pH-dependent synthetic approach, the combination of different simple metal salts or metal coordination complexes with SeO<sub>3</sub><sup>2–</sup> heteroanion templates was employed to synthesize five distinct assemblies of Keggin-/Dawson-type tungstoselenites: (C<sub>2</sub>H<sub>8</sub>N)<sub>10</sub>KNa­[(α-SeW<sub>9</sub>O<sub>34</sub>)­{Zr­(H<sub>2</sub>O)}­{WO­(H<sub>2</sub>O)}­(WO<sub>2</sub>)­(SeO<sub>3</sub>)­{α-SeW<sub>8</sub>O<sub>31</sub>Zr­(H<sub>2</sub>O)}]<sub>2</sub>­·14H<sub>2</sub>O (<b>1</b>) at pH = 1.3; (C<sub>2</sub>H<sub>8</sub>N)<sub>10</sub>KNa<sub>5</sub>­[(Se<sub>2</sub>W<sub>18</sub>O<sub>60</sub>)<sub>2</sub>­(μ<sub>2</sub>-O)<sub>4</sub>]­·12H<sub>2</sub>O (<b>2</b>) at pH = 2.5; (C<sub>2</sub>H<sub>8</sub>N)<sub>4</sub>Na<sub>4</sub>­[Se<sub>2</sub>W<sub>18</sub>O<sub>62</sub>­(H<sub>2</sub>O)<sub>2</sub>]­·13H<sub>2</sub>O (<b>3</b>) at pH = 3.6; (C<sub>2</sub>H<sub>8</sub>N)<sub>4</sub>­K<sub>3</sub>Na<sub>10</sub>­[(α-SeW<sub>9</sub>O<sub>33</sub>)<sub>2</sub>­{Ce<sub>2</sub>(CH<sub>3</sub>COO)­(H<sub>2</sub>O)<sub>3</sub>W<sub>3</sub>O<sub>6</sub>}­(α-Se<sub>2</sub>W<sub>14</sub>O<sub>52</sub>)]·26H<sub>2</sub>O (<b>4</b>) at pH = 4.5; K<sub>10</sub>Na<sub>5</sub>­[(α-SeW<sub>9</sub>O<sub>33</sub>)<sub>2</sub>­{Ce<sub>2</sub>(H<sub>2</sub>O)<sub>4</sub>W<sub>3</sub>O<sub>6</sub>}­{α-Se<sub>2</sub>W<sub>14</sub>O<sub>51</sub>(OH)}]­·24H<sub>2</sub>O (<b>5</b>) at pH = 4.5. All five compounds were characterized by single-crystal X-ray structure analysis, IR spectroscopy, thermogravimetric, UV/vis spectroscopy, and ESI-MS. Moreover, their electrochemical properties were investigated. Keggin-type polyoxoanion of <b>1</b> remains the first reported Zr-containing tungstoselenites based on {α-SeW<sub>9</sub>} building blocks. X-ray analysis revealed that the 4d metal Zr centers have seven- and eight-coordinated modes, and SeO<sub>3</sub><sup>2–</sup> acts as the templates as well as the linkers. With the increasing of the pH, Dawson-type polyoxoanions of <b>2</b> and <b>3</b> based on the first reported basic lacunary {α-Se<sub>2</sub>W<sub>14</sub>} building blocks are obtained by using 3d-4f metal coordination complexes. Polyoxoanions of <b>4</b> and <b>5</b> remain similar structures stabilized by the 4f metal Ce centers at pH = 4.5 and that contain the basic Keggin-type {α-SeW<sub>9</sub>} and Dawson-type {α-Se<sub>2</sub>W<sub>14</sub>} building blocks in <b>1</b>–<b>3</b> at the same time, presenting the mixed multiple lacunary building blocks being combined into the single polyoxoanion architecture. Furthermore, the density functional theory calculations have been performed on polyoxoanions of <b>1</b> and <b>5</b> as the representatives to investigate their electronic properties
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