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.