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

Abstract

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](+).