Structure and properties of redox active self-assembled monolayers formed from norbornylogous bridges

Three different length rigid norbornylogous bridges with terminal ferrocene moieties were synthesized. Pure self-assembled monolayers (SAMs) of the norbornylogous bridges and SAMs with the bridges diluted using either hydroxyl-terminated or methyl-terminated diluents were formed for each length of norbornylogous bridge. The SAMs were imaged with scanning tunneling micrsocopy (STM) and the electrochemical properties were investigated. It was found that SAMs composed of only norbornylogous bridges were crystalline-like, while in mixed SAMs, where the norbornylogous bridge was diluted, the ferrocene stood above the surface of the diluent because of the rigidity of the norbornylogous bridges and were homogeneously distributed across the surface. Further, the rate of electron transfer of the norbornylogous bridges was observed to be similar to an alkanethiol-derived ferrocene whose construct was designed to be as close as possible to that of the norbornylogous bridge. Finally, the rate of electron transfer for the norbornylogous bridges in a diluted SAM was slower with a hydroxyl-terminated diluent than with a methyl-terminated diluent.