Generation and dissociation of oxygen‐ and chloride‐bridged iron(III) and manganese(III) tetraphenylporphyrin dimer ions in the gas phase

Electrospray ionization mass spectrometry (ESI/MS) has allowed the discovery of novel dimer ions emerging from solutions of metalloporphyrin salts and their investigation by collision‐induced dissociation (CID) with N 2 molecules. ESI mass spectra have been recorded for the formation of the oxygen or chloride‐bridged dimer ions [(FeTPP) 2 OH] + , [(MnTPP) 2 OH] + , [(FeTPP) 2 Cl] + and [(MnTPP) 2 Cl] + derived from various solutions of FeTPPCl and MnTPPCl salts. The CID of [(FeTPP) 2 OH] + proceeds mainly by neutral loss of (FeTPP)OH to form [FeTPP] + and, to a minor extent, to form the charge‐reversed products. The CID of [(MnTPP) 2 OH] + exhibits exclusively the product ion [MnTPP] + by loss of neutral (MnTPP)OH. [(FeTPP) 2 Cl] + and [(MnTPP) 2 Cl] + dissociate by loss of (Fe/MnTPP)Cl to give rise to [Fe/MnTPP] + . [(FeTPP) 2 O] + and [(FeTPP) 2 OH] + were generated from a solution of the dimer, (FeTPP) 2 O. Dissociation of [(FeTPP) 2 O] + yields two product ions, [FeTPP] + and [(FeTPP)O] + , with higher onsets compared to the equivalent fragments formed from [(FeTPP) 2 OH] + . Copyright © 2009 John Wiley & Sons, Ltd.