| Abstract
| - The phase formation of 4,4‘-bipyridine (4,4‘-BP) and its coadsorption with interfacial water on quasi-Au(111) film electrodes (20 nm) from 0.05 M KClO4 has been studied employing in-situ surface enhancedinfrared reflection adsorption spectroscopy (SEIRAS). Organic molecules form, dependent on the electrodepotential and in the absence of Faradaic reactions, three monolayers of distincly different orientation. Thehigh coverage adlayer I is composed of perpendicularly oriented 4,4‘-BP molecules coordinated with onenitrogen atom to the underlying positively charged electrodes (C2v symmetry). Changing the electrodepotential toward negative values causes two first-order phase transitions giving rise to two low-coverageorganic adlayers. These transitions are accompanied by an in-plane tilting of the N-coordinated molecule.The conclusions on the interfacial orientation of 4,4‘-BP are supported by a comparative analysis of in situSEIRAS, surface enhanced Raman spectroscopy, and sum frequency generation spectra. SEIRAS spectraalso indicate that 4,4‘-BP is coadsorbed with water molecules and modifies the interfacial hydrogen-bonded network of the later. The nature of these interactions and their consequences for the creation offunctionalized adlayers on metal electrodes are compared with related N-heterocyclic molecules.
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