Second Ionization Energies of Gaseous Iron Oxides and Hydroxides:  The FeO_mH_n²⁺ Dications (m = 1, 2; n ≤ 4)

Abstract

The energetics of selected dicationic iron oxides and hydroxides FeO m H n 2+ (m = 1, 2; n ≤ 4) are probed by charge-stripping mass spectrometry in conjunction with ab initio calculations employing the B3LYP/6-311+G* level of theory. Specifically, Fe+, FeO+, FeOH+, Fe(H2O)+, [Fe,O2,H2]+, (H2O)FeOH+, and Fe(H2O)2 + and their respective dications are examined. In most cases, reasonable agreement between experiment and theory is found, and discrepancies can be attributed to interferences in the experimental study. Nevertheless, some shortcomings of the theoretical approach are obvious. Combination of experimental and theoretical results leads to adiabatic ionization energies of the monocationic iron compounds: IEa(FeO+) = 18.3 ± 0.4 eV, IEa(FeOH+) = 17.0 ± 0.4 eV, IEa(Fe(H2O)+) = 14.3 ± 0.5 eV, IEa((H2O)FeOH+) = 15.6 ± 0.5 eV, and IEa(Fe(H2O)2 +) = 12.6 ± 0.4 eV. In the case of [Fe,O2,H2]+, structural isomerism and isobaric interferences give rise to a composite charge-stripping peak and prevent the experimental determination of the ionization energy. Interestingly, the computational results suggest a reversed order of stabilities for the mono- and dicationic [Fe,O2,H2]+/2+ isomers, i.e., Fe(OH)2 + > (H2O)FeO+ > Fe(H2O2)+ versus Fe(H2O2)2+ > (H2O)FeO2+ > Fe(OH)2 2+. The ion energetics are used to assess the effects of ligation on the stabilities of the iron dications. While the covalent Fe−O and Fe−OH bonds decrease with increasing oxidation state of the metal, the interactions with water are dominated by electrostatic contributions. On average, solvation by water lowers the second ionization energy of the iron compounds studied by as much as 1.6 ± 0.3 eV

Innocent and Less‐Innocent Solvent Ligands: A Systematic Investigation of Cationic Iron Chloride/Alcohol Complexes by Electrospray Ionization Mass Spectrometry Complemented by DFT Calculations

“…In this respect, we refer to a related study of iron hydroxide ions. [15] Thus, the bond dissociation energy BDE(Fe + -OH 2 ) = 1.3 eV is significantly smaller than BDE(HOFe + -OH 2 ) = 2.3 eV and a corresponding Born-Haber cycle implies that BDE-(H 2 OFe + -OH) = 4.8 eV exceeds BDE(Fe + -OH) = 3.8 eV by the same amount. Hence, we conclude that solvation of the metal cation also increases the bond energies to covalent ligands as indicated by the increased AEs associated with the loss of Cl.…”

Energetics of the Ligated Vanadium Dications VO2+, VOH2+, and [V,O,H2]2+

“…Further, OVF 3 was used as an independent precursor for VO in the EI mode. [2,36,39] The reagents used in FAB, and OVF 3 were used as received (Strem). In the energy-resolved CS measurements, B(1)-only selected monocations M were collided with O 2 in front of E(1), and the dication signals M 2 were recorded by scanning E(1) at improved energy resolutions E/DE 3000 ± 10 000.…”

Formation of iron complexes from trifluoroacetic acid based liquid chromatography mobile phases as interference ions in liquid chromatography/electrospray ionization mass spectrometric analysis

“…(CH 3 CN) 2 .OH, corresponding to mass 159.0770; propenenitrile cluster (C 3 H 3 N) 3 , corresponding to mass 159.0529; and (CH 3 COO) 2 (CH 3 CN), corresponding to mass 159.0531. We can rule out the first three clusters as the mass error from the measured mass of 159.0502 is quite large, even though neutral and charged iron hydroxides, such as FeO, FeOH, Fe(H 2 O), Fe(OH)H 2 O and FeO m H n , are involved in the redox chemistry of iron in the aqueous media and clusters of acetonitrile and water have also been observed . Clusters of CH 3 COO with Fe have been observed in ESI when a SS tip was used.…”

“…We therefore explored the possibility of neutral 159 being a cluster of several solvent components present in the LC effluent at the time of ESI. There are several possibilities: a [12] and clusters of acetonitrile and water have also been observed. [13] Clusters of CH 3 COO with Fe have been observed in ESI when a SS tip was used.…”