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Structure and Chirality in Sulfur-Containing Amino Acids Adsorbed on Au(111) Surfaces

2015; American Chemical Society; Volume: 119; Issue: 18 Linguagem: Inglês

10.1021/acs.jpcc.5b00380

1932-7455

Tatiana Popa, Irina Paci,

Spectroscopy and Quantum Chemical Studies

Chiral self-assembly is governed by a complex interplay between molecular asymmetry and intermolecular and molecule–substrate interactions. In this work, we examined extended systems of enantiomerically pure and racemic cysteine, homocysteine, and methionine and their self-assembly on Au(111), using a classical parallel tempering Monte Carlo approach. We found that, for all of the amino acids considered here, the Au(111) substrate provided insufficient configurational restriction to promote chiral recognition upon adsorption. Molecules tethered to the surface were able to sample a broad range of configurations, and form complex networks of hydrogen bonds. Upon dissociative adsorption, rosette structures and chains with small local enantiomeric excess were observed, while nondissociative processes led to formation of solution-type racemic aggregates. Given the important role played by the surface in the chiral recognition process, we propose that a four-step interaction model (Booth et al. Chirality 1997, 9, 96) is more appropriate for such systems than the more traditional three-point contact model.