Covalent Attachment of Porphyrins and Ferrocenes to Electrode Surfaces through Direct Anodic Oxidation of Terminal Ethynyl Groups

摘要

The structural rigidity and suitable electronic properties of the C≡C moiety make the alkynyl group an attractive linkage for electron transfer between redox-active metal centers or between an electrode and a covalently bonded redox-active molecule. Given the wide application of terminal alkynes in molecular derivatization, electrografting methods based on this group hold promise for a diverse collection of molecularly altered electrodes and other metal surfaces. A radical-based electrografting procedure, which requires generation of the alkynyl radical close to the electrode surface, involves the loss of a hydrogen atom from the end carbon. We recently described a two-step method for such a process based on anodic oxidation of a lithio-activated ethynyl group. This process requires the in situ formation of a Li-stabilized carbanion [Eq. (1)], followed by one-electron oxidation [Eq. (2)], thereby producing an ethynyl radical, which reacts with the electrode.