title: Cation-π interactions in protonated phenylalkylamines.
abstract: Phenylalkylamines of the general formula C6H5(CH2)nNH2 (n = 1-4) have been delivered to the gas phase as protonated species using electrospray ionization. The ions thus formed have been assayed by IRMPD spectroscopy in two different spectroscopic domains, namely, the 600-1800 and the 3000-3500 cm(-1) regions using either an IR free electron laser or a tabletop OPO/OPA laser source. The interpretation of the experimental spectra is aided by density functional theory calculations of candidate species and vibrational frequency analyses. Protonated benzylamine presents a relatively straightforward instance of a single stable conformer, providing a trial case for the adopted approach. Turning to the higher homologues, C6H5(CH2)nNH3(+) (n = 2-4), more conformations become accessible. For each C6H5(CH2)nNH3(+) ion (n = 2-4), the most stable geometry is characterized by cation-π interactions between the positively charged ammonium group and the aromatic π-electronic system, permitted by the folding of the polymethylene chain. The IRMPD spectra of the sampled ions confirm the presence of the folded structures by comparison with the calculated IR spectra of the various possible conformers. An inspection of the NH stretching region is helpful in this regard.
authors: Dipartimento di Chimica e Tecnologie del Farmaco, Università degli Studi di Roma La Sapienza , P. le A. Moro 5, I-00185 Roma, Italy.
authors: Barbara
authors: B
authors: Chiavarino
authors: Maria Elisa
authors: ME
authors: Crestoni
authors: Markus
authors: M
authors: Schütz
authors: Aude
authors: A
authors: Bouchet
authors: Susanna
authors: S
authors: Piccirillo
authors: Vincent
authors: V
authors: Steinmetz
authors: Otto
authors: O
authors: Dopfer
authors: Simonetta
authors: S
authors: Fornarini
mesh_terms: D000814:Aniline Compounds / Q000737:chemistry*; D001596:Benzylamines / Q000737:chemistry; D002412:Cations / Q000737:chemistry*; D003198:Computer Simulation; D006860:Hydrogen Bonding; D008956:Models, Chemical; D011522:Protons; D013055:Spectrophotometry, Infrared / Q000295:instrumentation / Q000379:methods; D014732:Vibration
chemical_list: D000814:Aniline Compounds; D001596:Benzylamines; D002412:Cations; D011522:Protons; C030796:benzylamine