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In this work, new doped Nafion membranes with enhanced proton conductivity were prepared to be used as proton exchange membranes in fuel cells. New dopants derived from arylmono-or bisphosphonic acid were prepared and incorporated into the new membranes using impregnation or casting methods. Proton conductivities were assessed by Electrochemical Impedance Spectroscopy (EIS), at different temperatures and relative humidity (RH) conditions, in order to evaluate the influence of the structure and the method of the preparation on proton transport. The membranes prepared by casting showed higher proton conductivities than commercial Nafion membrane at all temperatures and relative humidity conditions studied. The [1,4-phenylenebis(hydroxymethanetriyl)]tetrakis(phosphonic acid) (BP2) showed the best proton conductivity with a value of 87 mS cm −1. The values obtained for the activation energy (E a) for proton conduction suggests that transport occurs via both Grotthuss and vehicular mechanisms.

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A series of indazoles substituted at the N-1 and N-2 positions with estercontaining side chains -(CH 2 ) n CO 2 R of different lengths (n = 0-6, 9, 10) are described. Nucleophilic substitution reactions on halo esters (X(CH 2 ) n CO 2 R) by 1H-indazole in alkaline solution lead to mixtures of N-1 and N-2 isomers, in which the N-1 isomer predominates. Basic hydrolysis of the ester derivatives allowed the synthesis of the corresponding indazole carboxylic acids. All compounds were fully characterised by multinuclear NMR and IR spectroscopies, MS spectrometry and elemental analysis; the NMR spectroscopic data were used for structural assignment of the N-1 and N-2 isomers. The molecular structure of indazol-2-yl-acetic acid (5b) was determined by X-ray diffraction, which shows a supramolecular architecture involving O2-H...N1 intermolecular hydrogen bonds.

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