Electrospray ionization has been used for engendering gas-phase 1:1 complexes of deprotonated glycine (Gly-H) − and the atomic transition metal dications Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ and Zn 2+ , as well as Pb 2+ that we reported previously. The CID-resolved spectra of these complexes with (Gly-H) − could be compared with that of (Gly-H) − in the absence of the metal cation in order to assess the importance of metal bond activation by M 2+ within [M(Gly-H)] + . Four channels were distinguished in the dissociation of the transition metal dication complexes: CO loss, H 2 O loss, CO 2 loss and H 2 O+CO loss. The results were rationalized in terms of the properties of the metal center. The capacity to activate bonds was found to decrease from Fe 2+ to Zn 2+ leading to an increase in CO 2 loss. Metal dications with empty valence orbitals have high capacities to activate the NH bond and induce a proton transfer from NH 2 to COO − , favoring carboxyl structures. In essence, the number of electrons in the valence shell of the metal dication influences its capacity to activate bonds and determines the position of the proton in the complexes at eiher nitrogen or oxygen, generating carboxylate and carboxyl structures, respectively. Secondary loss of CO 2 was found to be influenced by the ionization energy or proton affinity of the metal.