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.

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Birnessite-type layered manganese oxides were prepared using various approaches for the design and fabrication of supercapacitor electrodes: (i) Oxidized carbon-MnO2 nanocomposites were obtained from birnessite precipitated in the presence of the oxidized forms of four different carbon types: graphite, acetylene black, high surface area active carbon and fullerene. (ii) films were anodically deposited at the surface of inexpensive stainless steel foils. MnSO4 plating solutions were electrolyzed at various potentials and for various durations. Preparation conditions are shown to affect the oxide structure, morphology (surface area), and chemical composition (content of Mn3+, Mn4+). Consequently, they also greatly affect the electrochemical capacitance performances of the prepared electrode materials.

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(1), 2 reported in our paper as new compounds, were previously known 1,2 but were prepared by different methods from ours. We deeply regret any confusion that resulted from the omission of these citations; refs 1 and 2 cited here are in addition to those listed in our original paper.