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complexes the indole chromophore was found to be the protondonating substituent. The spectral shifts of these complexes, and thus the relative strength of the hydrogen bond, are shown to give a reasonable linear correlation with the basicities of the partners as measured by the respective proton affinities. This correlation was also found to hold in general for substituted indoles. The use of the gas-phase proton affinity, which has previously been found to be sensitive to the polarizability of the attached alkyl groups, has made it possible to compare the important interaction components in terms of Morokuma's energy decomposition analysis. We have interpreted the ordering of indole hydrogen-bonded spectral shifts in terms of the interplay of both electrostatic interaction and polarization interaction components. It appears that for weakly bonded systems such as those containing indole as the proton donor, polarization forces can become important in determining electronic spectral shifts.We have also shown that indole and species such as halocarbons that are important in anesthetic activity can participate in hy-drogen bonds where the indole moiety is the proton acceptor. This observation provides a unique opportunity to investigate the dynamics of such biological processes in an isolated environment. Further investigations on these hydrogen-bonded indoles are currently in progress in our laboratory.Acknowledgment. The financial support of the Natural Sciences and Engineering Research Council of Canada and the Petroleum Research Fund, administered by the American Chemical Society, is gratefully acknowledged. We wish to thank Dr. R. Houriet for providing us with unpublished values of proton affinities and Prof. A. G. Harrison for helpful discussions.

Both heterogeneous and homogeneous catalyses of water oxidation to 02 have been recently reported for metal oxides1 and aquo-or hydroxo-metal complexes.2 One of the more efficient systems involves cobalt(II) catalysis of water oxidation by Ru-(bpy)33+ (£°(Ru(bpy)33+/2+) = 1.26 V), which occurs above pH ~52a (eq 1). We have studied the kinetics and product distri-Ru(bpy)33+ + V2H20 = Ru(bpy)32+ + H++ >/402 (1)

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R~(bpy),~' (bpy = 2,2'-bipyridyl) has been covalently attached to n-type Sn02 via condensation of surface hydroxyl groups with ruthenium (4-(trichlorosilylethyl)-4'-methyl-2,2'-bipyridine)bis(2,2'-bipyridine) bis(hexafluorophosphate)). A thick coating (-1000 layers, based on the surface hydroxyl group concentration) was produced, presumably via oligomerization of hydrolyzed -SiCI3 groups. The coating, which was stable to organic solvents as well as to aqueous acids and bases, gave reversible cyclic voltammograms, with peak potentials shifted slightly from those of aqueous R~(bpy),~+, but the number of electroactive molecules corresponded only to a few layers. The coated electrode gave a photocurrent about twice that observed for SnO, in contact with aqueous 4 mM R~(bpy),~+, with a slightly red-shifted excitation spectrum. Only a small fraction of the electroactive molecules appeared to participate in excited-state electron transfer, although a steady-state current was supported, presumably by slow electron transfer from the outer layers. Prolonged illumination produces extensive hydrolysis of the outer layers of the coating, but a modest reduction of electroactivity, and only a slight decrease in photocurrent. The photocurrent increases with applied potential, then reaches a plateau, and falls off again near the reduction potential of Ru(bpy)32t*; the falloff is attributed to back-electron transfer via tunnelling through the thin space charge layer.

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