Threshold collision-induced dissociation TCID

The determination of thermochemistry using threshold collision-induced dissociation (TCID) relies on a deceptively simple experiment determine the energy threshold for the endothermic reaction (Eq. 1), the dissociation of the molecular ion AB+ ... 

Gas-phase studies of ligand coordination to anionic metals are much less extensive than for cationic complexes. One comprehensive study was conducted by Sunderlin, Wang, and Squires who examined the anionic TM carbonyl complexes for V, Cr, Mn, Fe, Co, and Ni. BDEs for sequential addition of CO to M were measured using threshold collision-induced dissociation (TCID) methods described below. Comparison of TM carbonyl BDEs among isoelectronic species showed that the ordering was usually Z)[(CO) cM —CO]>Z)[(CO)xM—CO]>Z)[(CO) cM —CO], a trend easily rationalized on the basis of 7r-backdonation. Cases where a different order was observed could be imderstood as metals having different electronic states, e.g., Ni" " (3d , D) vs. Fe Ap Jid, F). 

Complementary experimental approaches, such as threshold collision-induced dissociation (TCID), yield more direct information on the transition states in peptide fragmentation chemistry [19]. 

TCID, threshold collision-induced dissociation A tandem MS experiment used to measure the threshold at which a fragmentation reaction starts to occur allows one to determine activation barriers and binding energies. 

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