Correcting the record: the dimers and trimers of trans-N-methylacetamideElectronic supplementary information (ESI) available: Further NMA gas phase and jet spectra, spectra of the d7 isotopologue, experimental details, tables of B97D results, Cartesian B3LYP-D3 coordinates. See DOI: 10.1039/c6cp07989j

• Main Authors: Forsting, Thomas, Gottschalk, Hannes C, Hartwig, Beppo, Mons, Michel, Suhm, Martin A
• Format: Article
• Language: English
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c6cp07989j

The dimer of trans-N -methylacetamide serves as a simple model for hydrogen bonds in peptides, free of any backbone distortions. Its preferred structures represent benchmark systems for an accurate quantum chemical description of protein interactions. The trimer allows for either two linear or three strained hydrogen bonds, with the former being the only structural motif considered so far in the literature, but the latter winning in energy by a large margin due to London dispersion. A combination of linear Raman and infrared supersonic jet techniques with B3LYP-D3/aug-cc-pVTZ quantum chemical predictions corrects earlier tentative spectroscopic assignments based on a hybrid density functional without dispersion correction. Linear Amide I-III infrared spectra of the jet-cooled monomer are compared to those recently obtained by action spectroscopy. Raman jet spectroscopy reveals three N -methylacetamide molecules organizing into a ring structure, previously overlooked in computations.