Water-Free Proton Conduction in Discotic Pyridylpyrazolate-based Pt(II) and Pd(II) Metallomesogens

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• 作者：Cristián Cuerva ; José A. Campo ; Mercedes Cano ; Jesús Sanz ; Isabel Sobrados ; Virginia Diez-Gómez ; Alberto Rivera-Calzada ; Rainer Schmidt
• 刊名：Inorganic Chemistry
• 出版年：2016
• 出版时间：July 18, 2016
• 年：2016
• 卷：55
• 期：14
• 页码：6995-7002
• 全文大小：459K
• 年卷期：0
• ISSN：1520-510X

文摘

In this work we report on water-free proton conductivity in liquid-crystal pyridylpyrazolate-based Pt(II) and Pd(II) complexes [M(pz^R(n,n)py)₂] (pz^R(n,n)py = 3-(3,5-dialkyloxyphenyl)-5-(pyridin-2-yl)pyrazolate, R(n,n) = C₆H₃(OC_nH_2n+1)₂; n = 4, 12, 16, M = Pd; n = 12, M = Pt) with potential application as electrolyte materials in proton exchange membrane fuel cells. The columnar ordering of the complexes in the liquid-crystalline phase opens nanochannels, which are used for fast proton exchange as detected by impedance spectroscopy and NMR. The NMR spectra indicate that the proton conduction mechanism is associated with a novel C–H···N proton transfer, which persists above the clearing point of the material. The highest conductivity of ∼0.5 μS cm^–1 at 180 °C with an activation energy of 1.2 eV is found for the Pt(II) compound in the mesophase. The Pd(II) complexes with different chain length (n = 4, 12, and 16) show lower conductivity but smaller activation energies, in the range of 0.74–0.93 eV.