title: IR spectrum of the protonated neurotransmitter 2-phenylethylamine: dispersion and anharmonicity of the NH3(+)-π interaction.
abstract: The structure and dynamics of the highly flexible side chain of (protonated) phenylethylamino neurotransmitters are essential for their function. The geometric, vibrational, and energetic properties of the protonated neutrotransmitter 2-phenylethylamine (H(+)PEA) are characterized in the N-H stretch range by infrared photodissociation (IRPD) spectroscopy of cold ions using rare gas tagging (Rg = Ne and Ar) and anharmonic calculations at the B3LYP-D3/(aug-)cc-pVTZ level including dispersion corrections. A single folded gauche conformer (G) protonated at the basic amino group and stabilized by an intramolecular NH(+)-π interaction is observed. The dispersion-corrected density functional theory calculations reveal the important effects of dispersion on the cation-π interaction and the large vibrational anharmonicity of the NH3(+) group involved in the NH(+)-π hydrogen bond. They allow for assigning overtone and combination bands and explain anomalous intensities observed in previous IR multiple-photon dissociation spectra. Comparison with neutral PEA reveals the large effects of protonation on the geometric and electronic structure.
authors.affiliation: Institut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstrasse 36, D-10623 Berlin, Germany. dopfer@physik.tu-berlin.de.
authors.forename: Aude
authors.initials: A
authors.lastname: Bouchet
authors.forename: Markus
authors.initials: M
authors.lastname: Schütz
authors.forename: Barbara
authors.initials: B
authors.lastname: Chiavarino
authors.forename: Maria Elisa
authors.initials: ME
authors.lastname: Crestoni
authors.forename: Simonetta
authors.initials: S
authors.lastname: Fornarini
authors.forename: Otto
authors.initials: O
authors.lastname: Dopfer
mesh_terms: D006860:Hydrogen Bonding; D008958:Models, Molecular; D008968:Molecular Conformation; D018377:Neurotransmitter Agents / Q000737:chemistry*; D010627:Phenethylamines / Q000737:chemistry*; D011522:Protons; D011789:Quantum Theory; D013055:Spectrophotometry, Infrared
chemical_list: D018377:Neurotransmitter Agents; D010627:Phenethylamines; D011522:Protons; C029261:phenethylamine