Salt-bridge and canonical charge solvated complexes of neutral proline (Pro) and Pb(II), [Pb(Pro)](2+), are discussed for the first time. Although thermochemically stable with respect to their corresponding deprotonated forms [Pb(Pro-H)](+), the dicationic complexes are not observed experimentally. Indeed, for the deprotonated complexes a disagreement between IRMPD results and theoretical calculations was reported. We perform an exhaustive DFT assessment to correctly predict the experimental findings, and to rationalize why [Pb(Pro)](2+) complexes are not observed. The deprotonation is likely to occur through a highly exergonic proton transfer between [Pb(Pro)](2+) and a water molecule resulting in the observed [Pb(Pro-H)](+) singly charged ion. (C) 2014 Elsevier B.V. All rights reserved.