Self-Assembled Fullerene-Derivative Monolayers on a Gold Substrate Using Phenanthroline-Au Interactions

Abstract

Bromination of commercially available 5,6-dimethyl-1,10-phenanthroline with N-bromosuccinimide led to the formation of 5,6-bis(bromomethyl)-1,10-phenanthroline, a new compound, in 33% isolated yield. Conversion of the brominated compound to its corresponding o-quinodimethane intermediate was accomplished by reaction with tetrahexylammonium iodide. Reaction of this intermediate with C60 in refluxing toluene resulted in the formation of the final product, phenanthrolyl[60]fullerene, compound 1, in a 43% isolated yield. Spontaneous self-assembly of 1,10-phenanthroline on a Au(111) surface resulted in the formation of well-ordered monolayers. Addition of 1 to these monolayers resulted in the intercalation of the phenanthrolyl group directly into the stacks. Self-assembly from a solution of 1 containing small amounts of 1,10-phenanthroline resulted in the formation of a secondary layer of fullerene moieties. Since the fullerene diameter is approximately 1.0 nm and the phenanthroline-phenanthroline distances are about 0.33 nm (almost exactly 1/3), the fullerene packing is approximately commensurate with that of the phenanthrolines.