Structures of electrosprayed Pb(Uracil-H)+ complexes by infrared multiple photon dissociation spectroscopy

The structures of three ion molecule complexes of [Pb(Ura-H)(+) have been explored by infrared multiple photon dissociation (IRMPD) spectroscopy in the gas phase. A complex of [Pb(Ura-H)(+) with uracil, [Pb(Ura-H)(Ura)](+), or the singly or doubly water solvated complexes, [Pb(Ura-H)(H2O)(+) and [Pb(Ura-H)(H2O)2](+), have been irradiated with tunable infrared radiation in the N-H/O-H stretching region (3200-4000 cm(-1)) to produce IRMPD spectra which were compared with IR spectra computed using B3LYP/6-31+G(d,p) for various isomers. In all cases, the computed spectra for the lowest energy structures agree very well with the experimental IRMPD spectrum. Results show that all complexes involved a [Pb(Ura-H)](+) core which is deprotonated at N3 and has lead bound to either N3 and 04 or N3 and O2. Our results suggest that the [Pb(Ura-H)](+) structure that is deprotonated at N1 and lead is bound to N1 and 02 is not an significant contributor to the electrosprayed complexes. [Pb(Ura-H)(Ura)](+) was found to have a four-coordinate lead. The water molecules in [Pb(Ura-H)(H2O)](+) and [Pb(Ura-H)(H2O)(2)](+) were determined to be directly coordinated to lead, the first also hydrogen bonded to one carbonyl oxygen. (C) 2011 Published by Elsevier B.V.