2 research outputs found
Synthesis and Characterization of Molecular Hexagons and Rhomboids and Subsequent Encapsulation of Keggin-Type Polyoxometalates by Molecular Hexagons
Structural control among hexagonal
(trimer), rhomboidal (dimer), and infinite-chain supramolecular complexes
with three different supporting ligands of ethylenediamine (en), <i>N</i>,<i>N</i>,<i>N</i>′,<i>N</i>′-tetramethylethylenediamine (en*), and 1,2-bisÂ(diphenyl)Âphosphinoethane
(dppe) [(en)ÂPdÂ(L)]<sub>3</sub>(OTf)<sub>6</sub> <b>1t·OTf</b>, [(en*)ÂPdÂ(L)]<sub>2</sub>(PF<sub>6</sub>)<sub>4</sub> <b>2d·PF</b><sub><b>6</b></sub>, and [(dppe)ÂPdÂ(L)Â(OTf)<sub>2</sub>]<sub>∞</sub> <b>3·OTf</b> (OTf = trifluoromethane sulfonate;
L = 1,3-bisÂ(4-pyridylethynyl)Âbenzene) in the solid and solution states
was investigated. The encapsulation of a large Keggin-type polyoxometalate
[α-PW<sub>12</sub>O<sub>40</sub>]<sup>3–</sup> by these
complexes was also examined. As the steric bulkiness of the supporting
ligands increased in the order of en < en* < dppe, the hexagonal,
rhomboidal, and infinite-chain structures were obtained, as confirmed
by X-ray crystallography. In solution, equilibrium between the molecular
hexagon (<b>1t·OTf</b>/<b>2t·PF</b><sub><b>6</b></sub>) and the molecular rhomboid (<b>1d·OTf</b>/<b>2d·PF</b><sub><b>6</b></sub>) was observed in
the en/en* ligand systems, whereas <b>3·OTf</b> with the
dppe ligand did not exhibit equilibrium and instead existed as a single
species. These phenomena were established by cold-spray ionization
mass spectroscopy (CSI-MS) and <sup>1</sup>H diffusion ordered NMR
spectroscopy (DOSY). The addition of the highly negatively charged
Keggin-type phosphododecatungstate [α-PW<sub>12</sub>O<sub>40</sub>]<sup>3–</sup> to a solution of <b>2t/2d·PF</b><sub><b>6</b></sub> resulted in the encapsulation of the tungstate
species in the cavity of the molecular hexagon to form {[(en*)ÂPdÂ(L)]<sub>3</sub>[⊃α-PW<sub>12</sub>O<sub>40</sub>]}Â(PF<sub>6</sub>)<sub>3</sub> <b>2t·</b>[α-PW<sub>12</sub>O<sub>40</sub>]<sup>3–</sup>, as confirmed by a combination of <sup>1</sup>H and <sup>31</sup>P DOSY and CSI-MS spectral data
Synthesis and Characterization of Molecular Hexagons and Rhomboids and Subsequent Encapsulation of Keggin-Type Polyoxometalates by Molecular Hexagons
Structural control among hexagonal
(trimer), rhomboidal (dimer), and infinite-chain supramolecular complexes
with three different supporting ligands of ethylenediamine (en), <i>N</i>,<i>N</i>,<i>N</i>′,<i>N</i>′-tetramethylethylenediamine (en*), and 1,2-bisÂ(diphenyl)Âphosphinoethane
(dppe) [(en)ÂPdÂ(L)]<sub>3</sub>(OTf)<sub>6</sub> <b>1t·OTf</b>, [(en*)ÂPdÂ(L)]<sub>2</sub>(PF<sub>6</sub>)<sub>4</sub> <b>2d·PF</b><sub><b>6</b></sub>, and [(dppe)ÂPdÂ(L)Â(OTf)<sub>2</sub>]<sub>∞</sub> <b>3·OTf</b> (OTf = trifluoromethane sulfonate;
L = 1,3-bisÂ(4-pyridylethynyl)Âbenzene) in the solid and solution states
was investigated. The encapsulation of a large Keggin-type polyoxometalate
[α-PW<sub>12</sub>O<sub>40</sub>]<sup>3–</sup> by these
complexes was also examined. As the steric bulkiness of the supporting
ligands increased in the order of en < en* < dppe, the hexagonal,
rhomboidal, and infinite-chain structures were obtained, as confirmed
by X-ray crystallography. In solution, equilibrium between the molecular
hexagon (<b>1t·OTf</b>/<b>2t·PF</b><sub><b>6</b></sub>) and the molecular rhomboid (<b>1d·OTf</b>/<b>2d·PF</b><sub><b>6</b></sub>) was observed in
the en/en* ligand systems, whereas <b>3·OTf</b> with the
dppe ligand did not exhibit equilibrium and instead existed as a single
species. These phenomena were established by cold-spray ionization
mass spectroscopy (CSI-MS) and <sup>1</sup>H diffusion ordered NMR
spectroscopy (DOSY). The addition of the highly negatively charged
Keggin-type phosphododecatungstate [α-PW<sub>12</sub>O<sub>40</sub>]<sup>3–</sup> to a solution of <b>2t/2d·PF</b><sub><b>6</b></sub> resulted in the encapsulation of the tungstate
species in the cavity of the molecular hexagon to form {[(en*)ÂPdÂ(L)]<sub>3</sub>[⊃α-PW<sub>12</sub>O<sub>40</sub>]}Â(PF<sub>6</sub>)<sub>3</sub> <b>2t·</b>[α-PW<sub>12</sub>O<sub>40</sub>]<sup>3–</sup>, as confirmed by a combination of <sup>1</sup>H and <sup>31</sup>P DOSY and CSI-MS spectral data