Formation of Perfluoroalkyl Fullerene Alkylphosphonic Acid Self-Assembled Monolayers on Aluminum Oxide

The possibility of fabricating self-assembled monolayers (SAMs) from alkylphosphonic acids functionalized with trifluoromethyl derivatives of C60 on a metal oxide surface has been demonstrated in this work. Using several trifluoromethylfullerenes (TMFs) of different compositions and isomeric structures, we explored their relative reactivities in the Bingel-Hirsch cycloaddition reactions with 11-(diethoxyphosphoryl)undecyl methyl malonate for the first time. Only two isomers of C60(CF3)10 showed fairly selective monoadduct formation, whereas compounds with lower CF3 content showed no selectivity. Converting the phosphonic ester into a phosphonic acid moiety enabled the successful formation of self-assembled monolayers of the TMF-alkylphosphonic acid on aluminum oxide surfaces. Comparison with analogous SAMs made with underivatized C60 showed that TMFs form more hydrophobic surfaces.