Synthetic Tuning of Redox, Spectroscopic, and Photophysical Properties of {Mo<sub>6</sub>I<sub>8</sub>}<sup>4+</sup> Core Cluster Complexes by Terminal Carboxylate Ligands


The reactions between the tetra-<i>n</i>-butylammonium salt of [{Mo<sub>6</sub>I<sub>8</sub>}­I<sub>6</sub>]<sup>2–</sup> and silver carboxylates RCOOAg (R = CH<sub>3</sub> (<b>1</b>), C­(CH<sub>3</sub>)<sub>3</sub> (<b>2</b>), α-C<sub>4</sub>H<sub>3</sub>O (<b>3</b>), C<sub>6</sub>H<sub>5</sub> (<b>4</b>), α-C<sub>10</sub>H<sub>7</sub> (<b>5</b>), or C<sub>2</sub>F<sub>5</sub> (<b>6</b>)) in CH<sub>2</sub>Cl<sub>2</sub> afforded new carboxylate complexes [{Mo<sub>6</sub>I<sub>8</sub>}­(RCOO)<sub>6</sub>]<sup>2–</sup>. The complexes were characterized by X-ray single-crystal diffraction and elemental analysis, cyclic/differential pulse voltammetry, and IR, NMR, and UV–visible spectroscopies. The emission properties of the complexes <b>1</b>–<b>6</b>, and those of the earlier reported complexes with R = CF<sub>3</sub> (<b>7</b>) and <i>n</i>-C<sub>3</sub>F<sub>7</sub> (<b>8</b>), were studied both in acetonitrile solution and in the solid state. In deaerated CH<sub>3</sub>CN at 298 K, all of the complexes <b>1</b>–<b>8</b> exhibit intense and long-lived emission with the quantum yield and lifetime being 0.48–0.73 and 283–359 μs, respectively. The oxidation (<i>E</i><sub>ox</sub>)/reduction (<i>E</i><sub>red</sub>) potentials of the complexes correlate linearly with the p<i>K</i><sub>a</sub> value of the terminal carboxylate ligands L = RCOO (p<i>K</i><sub>a</sub>(L)). Reflecting the p<i>K</i><sub>a</sub>(L) dependences of <i>E</i><sub>ox</sub>/<i>E</i><sub>red</sub>, the emission energy (ν<sub>em</sub>) of the complexes was also shown to correlate with p<i>K</i><sub>a</sub>(L). The present study successfully demonstrates synthetic tuning of the redox, spectroscopic, and photophysical characteristics of a {Mo<sub>6</sub>I<sub>8</sub>}<sup>4+</sup>-based cluster complex with p<i>K</i><sub>a</sub>(L)

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oai:figshare.com:article/3551895Last time updated on 2/12/2018

This paper was published in FigShare.

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