Stereochemically Distinct Cyclotetrasiloxanes Containing 3‑Pyridyl Moieties and Their Functional Coordination Polymers


Synthesis of new cyclotetrasiloxane scaffolds containing peripherally functionalized 3-pyridyl moieties, [MeSiO­(CHCH<sup>3</sup>Py)]<sub>4</sub> (L<sup>1</sup>) and [MeSiO­(CH<sub>2</sub>CH<sub>2</sub><sup>3</sup>Py)]<sub>4</sub> (L<sup>2</sup>), and their reactivity studies with certain d<sup>10</sup> metal ions are reported. The ligand L<sup>1</sup> is obtained by the Heck-coupling reaction of tetramethyl tetravinyl tetrasiloxane (D<sub>4</sub><sup>vi</sup>) and 3-bromopyridine in the presence of the Pd(0) catalysts. The as-synthesized ligand L<sup>1</sup> shows the presence of three stereoisomers, <i>cis–trans–cis</i> (L<sup>1A</sup>), <i>cis–cis–trans</i> (L<sup>1B</sup>), and all-<i>trans</i> (L<sup>1C</sup>), which are quantitatively separated by column chromatography. Subsequent reduction of L<sup>1A</sup>, L<sup>1B</sup>, and L<sup>1C</sup> with triethylsilane in the presence of catalytic amounts of Pd/C leads to the formation of the ligands L<sup>2A</sup>, L<sup>2B</sup>, and L<sup>2C</sup> with retention of stereochemistry due to the precursor moieties. Treatment of ZnI<sub>2</sub> with L<sup>1A</sup> gives a one-dimensional coordination framework [(L<sup>1A</sup>)<sub>4</sub>(ZnI<sub>2</sub>)<sub>2</sub>]<sub>∞</sub>, <b>1</b>. These 1D-chains are further connected by π–π stacking interactions between the pyridyl groups of the adjacent chains leading to the formation of a three-dimensional network with the topology of a PtS net. The reaction of silver nitrate with ligand L<sup>1B</sup> gives a chain like one-dimensional cationic coordination polymer {[(L<sup>1B</sup>)<sub>4</sub>Ag<sub>2</sub>]·2NO<sub>3</sub>·H<sub>2</sub>O·CH<sub>3</sub>OH }<sub>∞</sub>, <b>2</b>, consisting of two different kinds of 32-membered macrocycles. Treatment of the all-<i>trans</i> ligand L<sup>2C</sup> with copper­(I) iodide salt results in the formation of a cubane-type Cu<sub>4</sub>I<sub>4</sub> cluster MOF [(L<sup>2C</sup>)<sub>4</sub>Cu<sub>4</sub>I<sub>4</sub>]<sub>∞</sub>, <b>3</b>, in a two-dimensional 4-connected uninodal sql/Shubnikov tetragonal plane net topology represented by the Schläfli symbol {4<sup>4</sup>.6<sup>2</sup>}. This MOF displays a thermochromic luminescence behavior due to Cu<sub>4</sub>I<sub>4</sub> clusters showing an orange emission at 298 K and a blue emission at 77 K

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oai:figshare.com:article/3101602Last time updated on 2/12/2018

This paper was published in FigShare.

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