Monolayers derived from a crown ether fullerene derivative

A benzo-18-crown-6-methanofullerene derivative, 1, was compressed into stable monolayers at the air-water interface in a Langmuir trough, even when spread on a pure water subphase. However, the stability and integrity of the monolayer increased considerably in the presence of 1 M K+ in the water subphase. The UV-Vis spectra of this monolayer at the air-water interface were recorded and they were observed to exhibit time-dependent changes. These time dependent changes were observed in the absence and in the presence of irradiation, thus indicating that the changes were not the result of polymerization, as was originally desired. The changes are most likely due to aggregation of the fullerene derivative at the air-water interface. The same compound (1) was also capable of forming an organized monolayer via molecular recognition with a surface derived from Au (111) modified with -S-(CH2)(2)-NH3+ groups. Cystamine spontaneously forms a stable self-assembled monolayer (SAM) in the presence of an Au (111) surface. This SAM was shown to be capable of inducing the formation of a secondary SAM of 1 via the interactions between the positively charged -NH3+ groups and the crown ethers present in the fullerene derivatives. A total coverage of approximately 75% of the gold surface was calculated from the measured electrochemical response of the surface-confined fullerene derivative.