From self-assembly to charge transport with single molecules - an electrochemical approach

Structure formation and self-assembly of physisorbed and chemisorbed organic monolayers will be describedon electrified solid-liquid interfaces employing in-situ scanning tunneling microscopy (STM) and surface-enhancedinfrared spectroscopy (SEIRAS) in combination with electrochemical techniques. We present first a casestudy on self-assembly by directional hydrogen bonding and its interplay with the electrode potential choosingaromatic carboxylic acids, with an emphasis on 1,3,5-benzene-tricarboxylic acid (TMA). Structure and electricalcharacteristics of chemisorbed organic monolayers involving the formation of covalent bonds with the substratesurface will be discussed for a series of 4-methyl-4'-(n-mercaptoalkyl)biphenylson Au(111) electrodes. In an attempt to explore single molecule properties, such as charge transport andredox-mediated tunneling, we subsequently introduce an STM-based technique to construct symmetric and asymmetricmetal/(single) molecule/metal junctions. Employing α,ω-alkanedithiols and redox-active derivatives of viologens we demonstratenovel transport and single molecule electrochemical studies, which bear unique novel perspectives for fundamentalas well as applied investigations.