Apparent activation of H 2 O and elimination of H 2 from gas‐phase mixed‐metal complexes containing silver, calcium and deprotonated glycine

Rationale Ion trap mass spectrometry was used to study the reactivity of species derived from gas‐phase, mixed‐metal complexes, [Ag 2 Xx(Gly‐H) 3 ] + , where Xx = Ca, Mg, Sr and Ag, and in particular the apparent activation of an H 2 O ligand added during an ion‐molecule reaction. Methods Precursor [Ag 2 Xx(Gly‐H) 3 ] + complexes were formed by electrospray ionization (ESI) using spray solutions in which AgNO 3 , XxNO 3 and glycine were mixed in a 1:1:3 molar ratio. Specific species for study of ion‐molecule reactions were created in a “top down” fashion using collision‐induced dissociation (CID). Ion‐molecule reactions were performed by selective isolation and storage in a linear ion trap, where reactions with adventitious H 2 O can occur. Results Multiple stages of CID of [Ag 2 Ca(Gly‐H) 3 ] + resulted in the formation of [AgHCa(Gly‐H)] + . An ion‐molecule reaction of this ion produced a peak 16 mass units higher which is hypothesized to be a result of addition of H 2 O followed by loss of H 2 . This reaction was studied further by replacing Ca with Mg, Sr and Ag; as well as by incorporating deuterium‐labelled glycine into the complex. Conclusions The experimental results showed the following pattern for the apparent rates of reaction: Mg > Sr > Ca. When silver is the only metal present there is an addition of water but no loss of H 2 . DFT and MP2 calculations help identify plausible pathways for decomposition of H 2 O and formation of H 2 . Copyright © 2015 John Wiley & Sons, Ltd.