Ion-molecule reactions in a quadrupole ion trap as a probe of the gas-phase structure of metal complexes

Abstract

A method is described in which the coordination number in metal complexes can be determined using ion–molecule reactions in a quadrupole ion trap mass spectrometer. Complexes of first‐row transition metals in the +2 oxidation state, including manganese through zinc, are electrosprayed, isolated in the ion trap and allowed to react with gases. The coordination number is ascertained by observing the reagent ligands that successfully react with the complex. It was generally observed that six‐coordinate complexes are unreactive, five‐coordinate complexes react with pyridine and ethylamine, four‐coordinate complexes react with pyridine, ethylamine and ammonia and threecoordinate complexes react with all the reagent ligands studied, including water and methanol. The order of reactivity for a given complex reacting with the various reagent ligands is found to follow the order of the electron‐donating ability of the reagent ligands. In addition, the effect of the metal center on the reactivity of the complexes in the gas phase is analogous to solution‐phase trends; electronic structure strongly influences the gas‐phase reactions. These results were then used to predict the complexation behavior of novel podand ligands for which condensed phase information is not available. The results indicate that ion–molecule chemistry in the gas phase may be useful in predicting the interactions between novel multidentate ligands and metals in solution. © 1998 John Wiley & Sons, Ltd.

Evaluation of metal-mediated DNA binding of benzoxazole ligands by electrospray ionization mass spectrometry

“…Likely, the attached water molecule is dislodged during collisional activation, but then rapidly reattaches before ion detection. This type of solvent adduction process has been commonly observed for transition-metal complexes in a quadrupole ion trap [23][24][25][26][27]. This was the same fragmentation pattern observed for the dissociation of the watersolvated 1:1 complexes containing 6, 7, and 8 and a transition-metal.…”

Conformation-dependent hydrophobic photolabeling of the nicotinic receptor: Electrophysiology-coordinated photochemistry and mass spectrometry

“…These deviations cannot be explained by ion statistics, inability to effectively isolate the monoisotopic fragments, fluctuation in radio frequency isolation of an ion, or mass shift stemming from dissociative collisions between analyte ions and buffer gas (51)(52)(53). Instead, we have determined, by analyzing synthetic BP-photolabeled peptides, that the BP moiety underwent a phenyl rearrangement and ketone formation, losing two hydrogen atoms and producing species that were 2 Da lower in mass than predicted (54).…”

Ions generated from uranyl nitrate solutions by electrospray ionization (ESI) and detected with fourier transform ion-cyclotron resonance (FT-ICR) mass spectrometry

“…Ion-molecule reactions in the gas-phase have been used extensively to gain information on the chemistry and reactivity of metals in coordination complexes, as well as the structures of these metal-ligand complexes [25][26][27][28][29][30][31][32][33][34]. In our studies, D 2 O and adventitious CD 3 OD were used as neutral reaction partners with several of the more abundant ions in Figure 1c to assess the degree of coordinative unsaturation of the uranyl in each of the selected species.…”