Structures and Bonding Properties of Gold–Arg-Cys Complexes: DFT Study of Simple Peptide-Coated Metal

We present the structures, bonding characteristics, and infrared spectra of the gold surface (111)–Arg-Cys (Arg-Cys@Au(111)) complex calculated by a periodic plane wave DFT technique. We examine the detailed features of bonding between the gold surface and dipeptide. The dipeptide is revealed to form a covalent bond via the −SH group with 2–3 gold atoms, and also weak noncovalent interactions via the carboxyl and guanidine side chain lying more or less parallel to the gold surface. The S–H bond dissociates as a result of the S––(Au)n bond formation, with the hydrogen atom binding to the guanidine moiety. The acidic proton stays at the carboxyl group in the most stable structure of Arg-Cys@Au(111). The calculated infrared spectra are compared with experimental observations reported by Petoral and Uvdal (Colloids Surf., B 2002, 25, 335).