Abstract
Hydration layers play a key role in many technical and biological systems, but our understanding of these structures remains very limited. Here, we investigate the molecular processes driving hydration of a chiral metal–organic surface, bitartrate on Cu(110), which consists of hydrogen-bonded bitartrate rows separated by exposed Cu. Initially water decorates the metal channels, hydrogen bonding to the exposed O ligands that bind bitartrate to Cu, but does not wet the bitartrate rows. At higher temperature, water inserts into the structure, breaks the existing intermolecular hydrogen bonds, and changes the adsorption site and footprint. Calculations show this process is driven by the creation of stable adsorption sites between the carboxylate ligands, to allow hydration of O–Cu ligands within the interior of the structure. This work suggests that hydration of polar metal–adsorbate ligands will be a dominant factor in many systems during surface hydration or self-assembly from solution.
Highlights
Solvents play an important role in many chemical reactions, as they stabilize reactants, products, and intermediates differently and so alter the reaction rate and chemical selectivity, but our knowledge of their role in heterogeneous processes is remarkably limited.[1]
Water is becoming increasingly important as a “green” solvent to reduce waste, but its role often extends beyond the simple delivery of species to a reaction site, with hydration playing a key role in the formation of solvent−adsorbate complexes that can direct surface chemistry.[2,3]
The contrast of bitartrate in STM images is sensitive to changes in its local configuration, which provides a way to explore the effect of coadsorbed water on the bitartrate structure during hydration, even when the water itself may not be directly visible by STM
Summary
Solvents play an important role in many chemical reactions, as they stabilize reactants, products, and intermediates differently and so alter the reaction rate and chemical selectivity, but our knowledge of their role in heterogeneous processes is remarkably limited.[1] In particular, water is becoming increasingly important as a “green” solvent to reduce waste, but its role often extends beyond the simple delivery of species to a reaction site, with hydration playing a key role in the formation of solvent−adsorbate complexes that can direct surface chemistry.[2,3] techniques to determine chemical identity and adsorbate structure are well developed at solid interfaces, far less is known about the local solvent environment at functional interfaces.[4] In particular, X-ray and spectroscopic probes may provide evidence for global changes in surface hydration,[5−11] detailed molecular scale information is sparse. Understanding the mechanisms by which water restructures or solvates surface species remains a significant challenge.[13,14]
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