Mixed Metal Phosphonates: Structure and Proton Conduction Manipulation through Various Alkaline Earth Metal Ions
Three new layered mixed metal phosphonates [CoMg(notpH<sub>2</sub>)(H<sub>2</sub>O)<sub>2</sub>]ClO<sub>4</sub>·nH<sub>2</sub>O (<b>CoMg·nH<sub>2</sub>O</b>), [Co<sub>2</sub>Sr<sub>2</sub>(not...
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MDPI AG
2022-11-01
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| Online Access: | https://www.mdpi.com/2073-4352/12/11/1648 |
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| author | Song-Song Bao Nan-Zhu Li Yu-Xuan Wu Yang Shen |
| author_facet | Song-Song Bao Nan-Zhu Li Yu-Xuan Wu Yang Shen |
| author_sort | Song-Song Bao |
| collection | DOAJ |
| description | Three new layered mixed metal phosphonates [CoMg(notpH<sub>2</sub>)(H<sub>2</sub>O)<sub>2</sub>]ClO<sub>4</sub>·nH<sub>2</sub>O (<b>CoMg·nH<sub>2</sub>O</b>), [Co<sub>2</sub>Sr<sub>2</sub>(notpH<sub>2</sub>)<sub>2</sub>(H<sub>2</sub>O)<sub>5</sub>](ClO<sub>4</sub>)<sub>2</sub>·nH<sub>2</sub>O (<b>CoSr·nH<sub>2</sub>O</b>), and [CoBa(notpH<sub>2</sub>)(H<sub>2</sub>O)<sub>1.5</sub>]ClO<sub>4</sub> (<b>CoBa</b>) were synthesized by reacting a tripodal metalloligand Co<sup>III</sup>(notpH<sub>3</sub>) [notpH<sub>6</sub> = C<sub>9</sub>H<sub>18</sub>N<sub>3</sub>(PO<sub>3</sub>H<sub>2</sub>)<sub>3</sub>] with alkaline earth metal ions. Along with an increase in the radius of the alkaline earth metal ions, the 6-coordinate {MgO<sub>6</sub>}, 7-coordinate {SrO<sub>7</sub>}, and 9-coordinate {BaO<sub>9</sub>} geometries are the distorted octahedron, capped triangular prism, and tricapped triangular prism, respectively. Consequently, the metalloligand Co(notpH<sub>2</sub>)<sup>−</sup> adopts variable coordination modes to bind the alkaline earth metal nodes, forming diverse layer topologies in the three mixed metal phosphonates. The AC impedance measurements revealed that the proton conductivities at 25 °C and 95% relative humidity (RH) follow the sequence: <b>CoMg·nH<sub>2</sub>O</b> > <b>CoSr·nH<sub>2</sub>O</b> > <b>CoBa</b>. As expected, <b>CoMg·nH<sub>2</sub>O</b> exhibits a 28-fold enhanced value for proton conductivity (4.36 × 10<sup>−4</sup> S cm<sup>−1</sup>) compared with the previously reported isostructural compound, <b>CoCa·nH<sub>2</sub>O</b>, at 25 °C and 95% RH due to the greater Lewis acid strength of Mg(II) lowering the pKa of the coordinated water. |
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| last_indexed | 2024-03-09T18:24:49Z |
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| spelling | doaj.art-c6396cfed50b4a56b32478852f32b6ad2023-11-24T08:02:28ZengMDPI AGCrystals2073-43522022-11-011211164810.3390/cryst12111648Mixed Metal Phosphonates: Structure and Proton Conduction Manipulation through Various Alkaline Earth Metal IonsSong-Song Bao0Nan-Zhu Li1Yu-Xuan Wu2Yang Shen3State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, ChinaState Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, ChinaState Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, ChinaState Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, ChinaThree new layered mixed metal phosphonates [CoMg(notpH<sub>2</sub>)(H<sub>2</sub>O)<sub>2</sub>]ClO<sub>4</sub>·nH<sub>2</sub>O (<b>CoMg·nH<sub>2</sub>O</b>), [Co<sub>2</sub>Sr<sub>2</sub>(notpH<sub>2</sub>)<sub>2</sub>(H<sub>2</sub>O)<sub>5</sub>](ClO<sub>4</sub>)<sub>2</sub>·nH<sub>2</sub>O (<b>CoSr·nH<sub>2</sub>O</b>), and [CoBa(notpH<sub>2</sub>)(H<sub>2</sub>O)<sub>1.5</sub>]ClO<sub>4</sub> (<b>CoBa</b>) were synthesized by reacting a tripodal metalloligand Co<sup>III</sup>(notpH<sub>3</sub>) [notpH<sub>6</sub> = C<sub>9</sub>H<sub>18</sub>N<sub>3</sub>(PO<sub>3</sub>H<sub>2</sub>)<sub>3</sub>] with alkaline earth metal ions. Along with an increase in the radius of the alkaline earth metal ions, the 6-coordinate {MgO<sub>6</sub>}, 7-coordinate {SrO<sub>7</sub>}, and 9-coordinate {BaO<sub>9</sub>} geometries are the distorted octahedron, capped triangular prism, and tricapped triangular prism, respectively. Consequently, the metalloligand Co(notpH<sub>2</sub>)<sup>−</sup> adopts variable coordination modes to bind the alkaline earth metal nodes, forming diverse layer topologies in the three mixed metal phosphonates. The AC impedance measurements revealed that the proton conductivities at 25 °C and 95% relative humidity (RH) follow the sequence: <b>CoMg·nH<sub>2</sub>O</b> > <b>CoSr·nH<sub>2</sub>O</b> > <b>CoBa</b>. As expected, <b>CoMg·nH<sub>2</sub>O</b> exhibits a 28-fold enhanced value for proton conductivity (4.36 × 10<sup>−4</sup> S cm<sup>−1</sup>) compared with the previously reported isostructural compound, <b>CoCa·nH<sub>2</sub>O</b>, at 25 °C and 95% RH due to the greater Lewis acid strength of Mg(II) lowering the pKa of the coordinated water.https://www.mdpi.com/2073-4352/12/11/1648mixed metal phosphonatesmetalloligandalkaline earth metalproton conduction |
| spellingShingle | Song-Song Bao Nan-Zhu Li Yu-Xuan Wu Yang Shen Mixed Metal Phosphonates: Structure and Proton Conduction Manipulation through Various Alkaline Earth Metal Ions Crystals mixed metal phosphonates metalloligand alkaline earth metal proton conduction |
| title | Mixed Metal Phosphonates: Structure and Proton Conduction Manipulation through Various Alkaline Earth Metal Ions |
| title_full | Mixed Metal Phosphonates: Structure and Proton Conduction Manipulation through Various Alkaline Earth Metal Ions |
| title_fullStr | Mixed Metal Phosphonates: Structure and Proton Conduction Manipulation through Various Alkaline Earth Metal Ions |
| title_full_unstemmed | Mixed Metal Phosphonates: Structure and Proton Conduction Manipulation through Various Alkaline Earth Metal Ions |
| title_short | Mixed Metal Phosphonates: Structure and Proton Conduction Manipulation through Various Alkaline Earth Metal Ions |
| title_sort | mixed metal phosphonates structure and proton conduction manipulation through various alkaline earth metal ions |
| topic | mixed metal phosphonates metalloligand alkaline earth metal proton conduction |
| url | https://www.mdpi.com/2073-4352/12/11/1648 |
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