When complexed with a strong inorganic acid such as sulfuric or phosphoric acid, ®lms of polybenzimidazole (PBI) show two types of behaviour, depending on the time of immersion in the corresponding acid bath. The ®rst type, prepared at shorter doping times, has conductivity in the range 10 25 ±10 24 S cm 21 , whilst the second, of conductivity w10 23 S cm 21 is formed after more prolonged immersion. The `switch-over' from one state to the other is at 10±11 h in H 3 PO 4 , and 2±3 h in H 2 SO 4 . PBI has a remarkable capacity to concentrate H 3 PO 4 and, even in an acid bath of concentration 3 mol dm 23 , the acid concentration within a PBI membrane is ca. 14.5 mol dm 23 . IR spectroscopy performed on hydrated PBI membranes as a function of temperature, and on acid-complexed membranes as a function of the amount of sorbed acid con®rms proton transfer from H 3 PO 4 to the imino groups of PBI and, at high doping levels, the presence of undissociated H 3 PO 4 .

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Chlorine trioxide, Cl(2)O(6), reacts with Au metal, AuCl(3), or HAuCl(4).nH(2)O to yield the well-defined chloryl salt, ClO(2)Au(ClO(4))(4). The crystal and molecular structure of ClO(2)Au(ClO(4))(4) was solved by a Rietveld analysis of powder X-ray diffraction data. The salt crystallizes in a monoclinic cell, space group C2/c, with cell parameters a = 15.074(5), b = 5.2944(2), and c = 22.2020(2) A and beta = 128.325(2) degrees. The structure displays discrete ClO(2)(+) ions lying in channels formed by Au(ClO(4))(4)(-) stacks. Au is located in a distorted square planar environment: Au-O = 1.87 and 2.06 A. [ClO(4)] groups are monodentate with ClO(b) = 1.53 and ClO(t) = 1.39 A (mean distances; O(b), oxygen bonded to Au; O(t), free terminal oxygen). A full vibrational study of the Au(ClO(4))(4)(-) anion is supported by DFT calculations.