A specific 2,4-disubstituted-adamantane interaction with plasma-grown aluminum oxide. Inelastic-electron-tunneling spectroscopy study

The interaction of several mono- and disubstituted adamantanes with plasma-grown aluminum oxide has been studied using inelastic-electron-tunneling (IET) spectroscopy. The IET spectra evidence the chemisorption of 2,4-adamantanedione onto the aluminum oxide surface as the carboxylate anion of bicyclic acid ketone I, which is formed by ring opening of the b-diketone. In the case of 4-hydroxy-2-adamantanone (II), no ring opening to the corresponding bicyclic acid is obsd. II is chemisorbed as aluminum alkoxide through condensation. Stabilization by addnl. hydrogen bonding between the aluminum oxide and the keto group seems to be required since 1-adamantanol, 2-adamantanol and 2-adamantanone do not adsorb onto the aluminum oxide. Even 5-hydroxy-2-adamantanone is not bonded to the surface, indicating the necessity of a specific 2,4-disubstituted adamantane bidentate interaction with aluminum oxide.