IR spectroscopic properties of H(MeOH)n+ clusters in the liquid phase: Evidence for a proton wire

Abstract

The long-standing problem of understanding the nature of the "excess proton" in acidified water is simplified by studying the proton in methanol. The 3D network of hydrogen bonds in H(aq)+ is reduced to a ID problem. Infrared spectroscopic characterization of linear chain methanol proton solvates in H(CH3OH)n+ for n = 2-8 provides insight into some of the puzzling IR spectral features associated with O-H-O vibrations. These include the virtual disappearance of otherwise strong bands from H-bonded methanol molecules adjacent to symmetrical O-H +-O groups. The data indicate that a chain of up to four O-H⋯-O bonds either side of this group can act as an electrical wire to separate positive charge. This suggests a refinement of the Grotthuss proton-hopping mechanism for explaining the anomalously high mobility of H + in Hbonded media. © 2008 Wiley-VCH Verlag GmbH & Cu. KGaA.