Quadrupole ion trap studies of the structure and reactivity of transition metal ion pair complexes

Electrospray ionization mass spectrometry was used to investigate complex formation of different metal complexes in a continuous-flow ligand-exchange reactor. A computer program was developed based on normal equilibrium calculations to predict the formation of various metal-ligand complexes. Corresponding to these calculations, infusion electrospray mass spectrometric experiments were performed to investigate the actual complex formation in solution. The data clearly show good correlation between the theoretically calculated formation of metal-ligand complexes and the experimental mass spectrometric data. Moreover, the approach demonstrates that the influence of the pH can be investigated using a similar approach. Indirectly, these infusion experiments provide information on relative binding constants of different ligands towards a metal-ion. To demonstrate this, a continuous-flow ligand-exchange detection system with mass spectrometric detection was developed. Injection of ligands, with different affinity for the metal-ion, into the reactor shows good correlation between binding constants and the response in the ligand-exchange detection system. Additional information on the introduced ligand, and the complexes formed after introduction of the ligand, can be obtained from interpretation of the mass spectra. , novel detection methods are necessary. Conventional techniques to study these interactions and complexes are infrared spectroscopy, X-ray diffraction, and nuclear magnetic resonance spectroscopy (NMR) [4], but these techniques have several drawbacks. The use of electrospray ionization mass spectrometry (ESI-MS) for studying metal-ions, metal-ligand interactions and metal complexes is readily recognized [5]. Using MS as a detection technique offers the advantage of being, in general, more sensitive than NMR and X-ray diffraction and opens up the possibility to screen complex samples. Moreover, MS enables simultaneous monitoring the response of ligand-exchange reactions and additionally obtaining chemical information about the specific compound [6,7].Today, MS is often used in studying host-guest complexes [8 -10], structural elucidation by collisioninduced dissociation (CID) MS [11,12], and studying relative binding constants of ligands to metal-ions [13,14]. Additionally, due to the liquid-based ionization in the ESI process, it is suitable for studying liquid-phase reactions, e.g., ligand-exchange reactions [6,7], which enables the study of complex systems.In general, the assumption is made of a good correlation between complexes formed in solution and what is observed in the mass spectrum [15]. FAB-MS and ESI-MS have been used in the past to evaluate binding selectivities of various compounds, e.g., caged crown ethers to metal-ions [16]. An excellent correlation between obtained ESI mass spectral data and expected binding selectivities has been reported in several papers [13,17,18], although several parameters should be kept in mind. For a good correlation between complex formation in solution and what i...

Section: Infusion Experiments (Cu(ii) and 22=-bipyridyl)supporting

confidence: 77%

Metal-complex formation in continuous-flow ligand-exchange reactors studied by electrospray mass spectrometry

Krabbe

Boer

Zwan

et al. 2007

“…For species in which the complex contained the nitrate anion and coordinating alcohol molecules, multiple CID stages caused the elimination of two alcohol molecules and nitric acid to leave an ion pair composed Regardless of the coordinating anion, ESI produced gas-phase uranyl complexes that contained three solvent molecules, whether alcohol or H 2 O. Work by Vachet and Callahan [14] has suggested that the nitrate anion, within gas-phase transition metal complexes, is primarily a bidentate ligand. The acceptance of three additional ligands by the uranyl-nitrate ion pair is consistent with a hypothesis that ESI produces a gasphase complex with a pentagonal bipyramidal conformation reminiscent of the structure of uranyl complexes in the solution phase [5][6][7][8][9][10][11].…”

Section: Discussionmentioning

confidence: 99%

“…To gain a better understanding of the intrinsic interactions between different uranyl species and solvent, we have begun an investigation of uranyl-anion complexes in the gas phase using ion-trap mass spectrometry (IT-MS). Several recent reports have demonstrated that intrinsic metal and metal complex chemistry can be investigated by the (controlled) addition of reagent gas to an ion trap [12][13][14][15][16][17][18][19][20][21][22], or by way of the presence of H 2 O and other small molecule contaminants within the He bath gas used to collisionally cool ions and improve trapping efficiency [23][24][25]. The reactions of uranium ions in the gas phase have been the subject of several earlier investigations.…”

mentioning

confidence: 99%

Elucidation of the collision induced dissociation pathways of water and alcohol coordinated complexes containing the uranyl cation

Stipdonk

Anbalagan

Chien

et al. 2003

Multiple-stage tandem mass spectrometry was used to characterize the dissociation pathways for complexes composed of (1) the uranyl ion, (2) nitrate or hydroxide, and (3) water or alcohol. The complex ions were derived from electrospray ionization (ESI) ϩ . The abundance of the species was greater than expected based on previous experimental measurements of the (slow) hydration rate for UO 2 ϩ when stored in the ion trap. To account for the production of the hydrated product, a reductive elimination reaction involving reactive collisions with water in the ion trap is proposed. T he speciation and reactivity of uranium is a topic of sustained interest because species-dependent chemistry [1] controls processes ranging from nuclear fuel processing [2] to mobility and fate in the geologic subsurface [3,4]. The solution chemistry of uranium is dominated by the uranyl dication, UO 2 2ϩ , which is known to form complexes with a range of ligands [1]. Specific interaction with solvent will significantly influence the physico-chemical behavior of the uranyl ion and its complexes, and this has motivated investigations of complex composition and stability using infrared spectroscopy and extended X-ray absorption fine structure [5][6][7][8][9][10][11]. Unfortunately, explicit control over the interactions of solvent and nonsolvent ligands with the uranyl ion is difficult, which makes the study of species-dependent uranium behavior complicated. To gain a better understanding of the intrinsic interactions between different uranyl species and solvent, we have begun an investigation of uranyl-anion complexes in the gas phase using ion-trap mass spectrometry (IT-MS). Several recent reports have demonstrated that intrinsic metal and metal complex chemistry can be investigated by the (controlled) addition of reagent gas to an ion trap [12][13][14][15][16][17][18][19][20][21][22], or by way of the presence of H 2 O and other small molecule contaminants within the He bath gas used to collisionally cool ions and improve trapping efficiency [23][24][25]. The reactions of uranium ions in the gas phase have been the subject of several earlier investigations. Studies by , and by Schwarz and coworkers [30] have probed the reactions between U ϩ and UO ϩ and organic compounds such as alkanes and alcohols. Armentrout and Beauchamp [31] investigated the oxidation of U ϩ using small molecules such as O 2 , CO, CO 2 , COS, and

“…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.…”

Section: Ion-molecule Reactions In the Gas-phase With D 2 O And Cd 3 mentioning

confidence: 99%

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

Pasilis

Somogyi

Herrmann

et al. 2006

Electrospray ionization (ESI) of uranyl nitrate solutions generates a wide variety of positively and negatively charged ions, including complex adducts of uranyl ions with methoxy, hydroxy, and nitrate ligands. In the positive ion mode, ions detected by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry are sensitive to instrumental tuning parameters such as quadrupole operating frequency and trapping time. Positive ions correspond to oligomeric uranyl nitrate species that can be characterized as having a general formula of