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Enantioselective Chemisorption on Model Chirally Modified Surfaces: 2-Butanol on alpha-(1-Naphthyl)ethylamine/Pd(111)
Boscoboinik, J. A.
Tysoe, W. T.
Published by: Journal of Physical Chemistry C
Volume, Number, Pages: 113 31 13877-13885
Accession Number: WOS:000268478700061
The enantioselective adsorption of propylene oxide and 2-butanol is explored on alpha(1-naphthyl)-ethylamine (.NEA) covered Pd(111) using temperature-programmed desorption (TPD), reflection-absorption infrared spectroscopy (RAIRS), and scanning tunneling microscopy (STM). The saturation coverage of NEA is similar to 0.1 monolayers (ML), and it thermally decomposes to desorb hydrogen and HCN. 2-Butanol adsorbs enantioselectively on NEA-rnodified Pd(111), while propylene oxide does not, emphasizing the importance of hydrogen-bonding interactions. An enantioselectivity ratio, ER, of similar to 2 (corresponding to an ee of similar to 33%) is found at an NEA coverage of similar to 0.055 ML, where 2-butanol adsorbs on the Pd(111) substrate. A second regime is found in which 2-butanol adsorbs on an NEA-covered surface with a maximum ER similar to 1.8 (corresponding to an ee of similar to 29%). This interaction appears to cause the NH2 group to reorient to facilitate hydrogen bonding interactions between 2-butanol and the amine group, and the heat of adsorption of similar to 35 kJ/mol is typical of -OH center dot center dot center dot NH2 hydrogen bond strengths.