15min:
INFRARED SPECTRA OF K+(TRYPTAMINE)(H2O)_n=1-4 AND K+(TRYPTAMINE)(H2O)_n=0-2Ar.

AMY L. NICELY AND JAMES M. LISY, Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801.

A balance of competing electrostatic and hydrogen bonding interactions directs the structure of hydrated gas-phase cluster ions. In K+(Tryptamine) cluster ions, a favorable electrostatic interaction between the potassium cation and the tryptamine NH2 lone pair stabilizes the high-energy Gph(in) and Gpy(in) conformers of neutral tryptamine. Previous studies of Tryptamine(H2O)n clusters indicate that the hydrating water molecules stabilize the neutral minimum energy Gpy(out) tryptamine conformer. In this scheme, the first water molecule interacts directly with the NH2 lone pair and is located to the side of the tryptamine monomer. By incorporating a potassium cation, however, the minimum energy tryptamine cdotswater configuration is disrupted in order to maximize the electrostatic interactions with the cation, shifting so that the tryptamine cdotswater interaction includes a pi-hydrogen bond between the water and the phenyl ring of tryptamine. The infrared photodissociation spectra of K+(Tryptamine)(H2O)_n=1-4 and K+(Tryptamine)(H2O)_n=0-2Ar will be presented along with parallel ab initio and thermodynamics calculations to assist with the identification of the isomers present in each experiment.