Studies of gas‐phase reactions of cationic iron complexes of 2‐pyrimidinyloxy‐N‐arylbenzylamines by electrospray ionization tandem mass spectrometry

Abstract

Electrospray ionization triple quadrupole mass spectrometry (ESI-TSQ-MS) and electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) were used to investigate the interesting gas-phase reactions of the cationic iron (Fe) complexes of 2-pyrimidinyloxy-N-arylbenzylamines (1-6), which are generated by ESI when mixing their methanolic solutions. Further studies of these Fe complexes by collision-induced dissociation (CID) show that Fe(III) complexes undergo an interesting gas-phase single electron transfer (SET) reaction to give 1(•+) -6(•+) ,with loss of neutral FeCl(2) , whereas Fe(II) can catalyze gas-phase Smiles rearrangement reactions of compounds 1-6. By using different Fe(II)X(2) salts (X = Cl or Br) with a set of reactants, the role of the counterion (X(-) ) and the structure effect of the reactants on Fe(II)-catalyzed gas-phase Smiles rearrangement reactions are studied. Evidence obtained from by TSQ-MS and FTICR-MS experiments, hydrogen/deuterium (H/D) exchange experiments and theoretical computations supported some unique gas-phase chemistries initiated by introduction of Fe(II) into 1. Importantly, by comparing the distinct gas-phase reaction results of the cationic Fe(III) complexes with those of Fe(II) complexes, the charge state effects of iron on the gas-phase chemistries of Fe complexes are revealed.