Competitive collision-induced dissociation

Fig. 5. Zero pressure extrapolated cross sections for the competitive collision-induced dissociation processes of (H20)Na+(NH3) with xenon in the threshold region as a function of kinetic energy in the center-of-mass frame (lower axis) and laboratory frame (upper axis). Solid lines show the best fits to the data using the model of Eq. (7) convoluted over the neutral and ion kinetic energies and the internal energies of the reactants, using common scaling factors. Dashed lines show the model cross sections in the absence of experimental energy broadening for reactants with an internal energy of 0 K. Adapted from [45]...

ICR-FTMS experiments have been employed to derive thermodynamic information using several approaches ( ). These include studies of exothermic and endothermic ion-molecule reactions, equilibration studies, competitive collision-induced dissociation reactions, and photodissociation studies. Exothermic reactions involving therma-lyzed (cooled by an inert buffer gas) ions provide brackets on metal-ligand bond enthalpies, as illustrated by Equation 44 which implies that D(Fe-C5H4 ) > 66 kcal/mol. Endothermic reactions can also be studied in the manner described above for ion beam experi-... 

In this review we discuss five techniques involving Fourier transform mass spectrometry (FTMS) for determining qualitative and quantitative metal ion-ligand bond energies. These include (i) exothermic ion-molecule reactions, (ii) equilibrium measurements, (iii) competitive collision-induced dissociation, (iv) endothermic ion-molecule reactions, and (v) photodissociation. A key advantage of the FTMS methodology is its ion and neutral manipulation capabilities which permit the formation and study of a limitless number of interesting metal-ion systems. 

Main fragmentations occurring both in the ion source, and in metastable and collision-induced dissociation (CID) experiments involve the losses of a hydrogen atom, HCN, and MeCN. These are competitive processes, whose abundances depend on the position of the nitrogen in the pyridine ring. Stable isotope labeling showed that the loss of HCN occurs from the five-membered ring (Scheme 1). 

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