Formation of p-Phenylenediamine-Crown Ether-[PMo12O40]4- Salts

Akutagawa, T., Endo, D., Imai, H., Noro, S., Cronin, L. and Nakamura, T. (2006) Formation of p-Phenylenediamine-Crown Ether-[PMo12O40]4- Salts. Inorganic Chemistry, 45(21), pp. 8628-8637. (doi:10.1021/ic060857i)

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Electron transfer from the electron donor of p-phenylenediamine (PPD) to the electron acceptor of (H+)3[PMo<sub>12</sub>O<sub>40</sub>]<sup>3</sup>- forms a one-electron-reduced Keggin cluster of [PMo<sub>12</sub>O<sub>40</sub>]<sup>4</sup>-, bearing a S = 1/2 spin, while proton transfer from the proton donor of (H<sup>+</sup>)3[PMo<sub>12</sub>O<sub>40</sub>]<sup>3</sup>- to the proton acceptor of PPD yielded mono- and diprotonated cations of 4-aminoanilinium (HPPD<sup>+</sup>) and <i>p</i>-phenylenediammonium (H2PPD2+). By introduction of crown ether receptors during the crystallization process, supramolecular cations of (HPPD<sup>+</sup>)(crown ethers) and/or (H2PPD2<sup>+</sup>)(crown ethers) were successfully introduced into three new -[PMo<sub>12</sub>O<sub>40</sub>]<sup>4</sup>- salts of (H2PPD2<sup>+</sup>)2([12]crown-4)4[PMo<sub>12</sub>O<sub>40</sub>]<sup>4</sup>- (1), (HPPD+)4([15]crown-5)4[PMo<sub>12</sub>O<sub>40</sub>]<sup>4</sup>- (2), and (HPPD+)2(H2PPD2+)([18]crown-6)4[PMo<sub>12</sub>O<sub>40</sub>]<sup>4</sup>- (3) as the countercation. The protonated states of PPD and molecular-assembly structures of the supramolecular cations depended on the size of the crown ethers. In salt 3, a novel mixed-protonated state of HPPD+ and H2PPD2+ was confirmed to be complexed in the cation structure. According to the changes in the cation structures, the anion arrangements were modulated from those of the two-dimensional layer for salt 1 to the isolated cluster for salts 2 and 3. The temperature-dependent magnetic susceptibilities of salts 1-3 were consistent with the isolated spin arrangements of [PMo<sub>12</sub>O<sub>40</sub>]<sup>4</sup>-. The electronic spectra of salts 1-3 indicated the intervalence optical transition from pentavalent MoV to hexavalent MoVI ions within the [PMo<sub>12</sub>O<sub>40</sub>]<sup>4</sup>- cluster. Temperature-dependent electron spin resonance spectra of salt 2 revealed the delocalization-localization transition of the S = 1/2 spin at 60 K. The spin on the [PMo<sub>12</sub>O<sub>40</sub>]<sup>4</sup>- cluster was localized on a specific Mo<sup>V</sup> site below 60 K, which was thermally activated with an activation energy of 0.015 eV.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Cronin, Professor Lee
Authors: Akutagawa, T., Endo, D., Imai, H., Noro, S., Cronin, L., and Nakamura, T.
Subjects:Q Science > QD Chemistry
College/School:College of Science and Engineering > School of Chemistry
University Centres > Glasgow Materials Research Initiative
Journal Name:Inorganic Chemistry

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