Collision-induced dissociation of tetraphenyl iron and manganese porphyrin ions by electrospray ionization mass spectrometry

Tetraphenyl iron(III) and manganese(III) porphyrin chloride (FeTPPCl and MnTPPCl) are studied by electrospray ionization tandem mass spectrometry (ESI/MS/MS). Removal of the chloride counter ion from these salts results in intense [FeTPP]+ and [MnTPP]+ ions that lose hydrogen and peripheral phenyl rings upon multi-collision-induced dissociation (CID). Dissociation pathways are probed as a function of collision-offset voltage with onset measurements. Onset voltages generally are higher for [MnTPP]+. While primary losses of benzene, biphenyl and hydrogen occur concomitantly at low collision voltages, losses of hydrogen from the secondary and higher-order ions occur at higher collision voltages. Comparisons are made with previous measurements using surface-induced dissociation, photodissociation and electron impact.