A water molecule exhibits characteristic properties on the basis of hydrogen bonding. In the past decade, single water molecules placed in non-hydrogen-bonding environments have attracted growing attention. To reveal the fundamental properties of a single water molecule, endohedral fullerene H2 O@C60 is an ideal and suitable model. We examined the electronic properties of H2 O@C60 by performing single-molecule measurements. The conductance of a single molecular junction based on H2 O@C60 was found to be comparable to that of empty C60 . The observed values were remarkably higher than those obtained for conventional molecular junctions due to the effective hybridization of the π-conjugated system to the metal electrode. Additionally, the results undoubtedly exclude the possibility of electrostatic contact of entrapped H2 O with the carbon wall of C60 . We finally concluded that H2 O entrapped inside a C60 cage can be regarded as an electrostatically isolated molecule.
Keywords: break junction technique; electron transfer; endohedral fullerene; molecular electronics; singe-molecule studies.
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