Hydrated metal-oxide versus dihydroxide structures of [MO2H2]+ cations with MFe, Co, and Ni

Interaction of FeO- with water: anion photoelectron spectroscopy and theoretical calculations

The interactions of FeO^- with water molecules were studied by using photoelectron spectroscopy and density functional theoretical calculations. It is found that a dihydroxyl species, Fe(OH)₂^-/0, can be formed when FeO^-/0 interacts with the first water molecule. The complexes formed via the interactions between FeO^-/0 and n water molecules can be viewed as Fe(OH)₂(H₂O)_n-1^-/0, in which (n - 1)H₂O molecules interact with a Fe(OH)₂ core. For Fe(OH)₂^-/0 and Fe(OH)₂(H₂O)^-, the Fe(OH)₂ unit has two conformers with the two OH groups oriented differently. The vertical detachment energies (VDEs) of FeO₂H₂(H₂O)_n-1^- (n = 1-4) are measured to be 1.25 ± 0.04, 1.66 ± 0.04, 2.06 ± 0.04, and 2.37 ± 0.04 eV, respectively, by experiment. It is also worth mentioning that in the FeO₂H₂(H₂O)^- anion the water molecule interacts with the Fe(OH)₂ core by forming a hydrogen bond with one of the OH groups, while in neutral FeO₂H₂(H₂O), the water molecule interacts with the Fe atom of the Fe(OH)₂ core via its O atom.

Interaction of TiO2(-) with water: photoelectron spectroscopy and density functional calculations

The interactions of titania with water molecules were studied via photoelectron spectroscopy and density functional calculations of TiO(OH)2(-) and Ti(OH)4(H2O)n(-) (n = 0-5) clusters which are corresponding to the TiO2(H2O)(-) and TiO2(H2O)n+2(-) (n = 0-5) systems, respectively. Experimental observation and theoretical calculations confirmed that TiO(OH)2(-) was produced when TiO2(-) interacts with one water molecule, and Ti(OH)4(H2O)n(-) (n = 0-5) were produced successively when TiO2(-) interacts with two or more water molecules. The structures of Ti(OH)4(H2O)n(-) with n = 4, 5 are slightly different from those of n = 1-3. The structures of Ti(OH)4(H2O)1-3(-) can be viewed as the water molecules interacting with the Ti(OH)4(-) core through hydrogen bonds; however, in Ti(OH)4(H2O)4,5(-), one of the water molecules interacts directly with the Ti atom via its oxygen atom instead of a hydrogen bond and distorted the Ti(OH)4(-) core.

Reactivity of hydrated monovalent first row transition metal ions M(+)(H2O)n, M = V, Cr, Mn, Fe, Co, Ni, Cu, Zn, toward molecular oxygen, nitrous oxide, and carbon dioxide

The reactions of hydrated monovalent transition metal ions M(+)(H(2)O)(n), M = V, Cr, Mn, Fe, Co, Ni, Cu, Zn, toward molecular oxygen, nitrous oxide, and carbon dioxide were studied by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. Clusters containing monovalent chromium, cobalt, nickel, or zinc were reactive toward O(2), while only hydrated cobalt was reactive toward N(2)O. A strongly size dependent reactivity was observed. Chromium and cobalt react very slowly with carbon dioxide. Nanocalorimetric analysis, (18)O(2) exchange, and collision induced dissociation (CID) experiments were done to learn more about the structure of the O(2) products. The thermochemistry for cobalt, nickel, and zinc is comparable to the formation of O(2)(-) from hydrated electrons. These results suggest that cobalt, nickel, and zinc are forming M(2+)/O(2)(-) ion pairs in the cluster, while chromium rather forms a covalently bound dioxygen complex in large clusters, followed by an exothermic dioxide formation in clusters with n ≤ 5. The results show that hydrated singly charged transition metal ions exhibit highly specific reactivities toward O(2), N(2)O, and CO(2).

Ion-mobility mass spectrometry of complexes of nickel and acetonitrile

Mono- and dications of microsolvated nickel complexes of acetonitrile are probed by means of ion-mobility mass spectrometry. Specifically, the complexes [(CH3CN)nNi]+, [(CH3CN)nNi]2+, [(CH3CN)nNiOH]+, and [(CH3CN)nNiCl]+ (n = 0–6) are compared to each other and their reactions with background water are probed. In general, the arrival times of the ions in the ion-mobility experiment linearly increase with the mass-to-charge ratio, but for the smaller, more reactive complexes, the arrival times are notably larger than expected from their mass. This effect is attributed to the markedly larger reactivity of these particular ions, as reflected in both charge-separation processes as well as adduct formation upon interaction with background water.

Theoretical study of the microhydration of mononuclear and dinuclear uranium(VI) species derived from solvolysis of uranyl nitrate in water

The structures and energetics of mononuclear and dinuclear uranium species formed upon speciation of uranyl(VI) nitrate, UO(2)(NO(3))(2), in water are investigated by quantum chemistry using density functional theory and the wavefunction-based methods (MP2, CCSD, CCSD(T)). We provide a discussion of the basic coordination patterns of the various mono- and dinuclear uranyl compounds [(UO(2))(m)(X,Y)(2m-1)(H2O)(n)](+) (m = 1, 2; n = 0-4) found in a recent mass spectrometric study (Tsierkezos et al., Inorg Chem 2009, 48, 6287). The energetics of the complexation of the uranyl dication to the counterions OH(-) and NO(3) (-) as well as the degradation of the dinuclear species were studied by reference to a test set of 16 representative molecules with the MP2 method and the B3LYP, M06, M06-HF, and M06-2X DFT functionals. All DFT functionals provide structures and energetics close to MP2 results, with M06 family being slightly superior to the standard B3LYP functional.

Large effect of a small substitution: competition of dehydration with charge retention and coulomb explosion in gaseous [(bipy(R))Au(mu-O)2Au(bipy(R))]2+ dications

Dinuclear gold(III) clusters with a rhombic Au(2)O(2) core and 2,2'-bipyridyl ligands substituted in the 6-position (bipy(R)) are examined by tandem mass spectrometry. Electrospray ionization of the hexafluorophosphate salts affords the complexes [(bipy(R))Au(mu-O)(2)Au(bipy(R))](2+) as free dications in the gas phase. The fragmentation behavior of the mass-selected dications is probed by means of collision-induced dissociation experiments which reveal an exceptionally pronounced effect of substitution. Thus, for the parent compound with R = H, i.e., [(bipy)Au(mu-O)(2)Au(bipy)](2+), fragmentation at the dicationic stage prevails to result in a loss of neutral H(2)O concomitant with an assumed rollover cyclometalation of the bipyridine ligands. In marked contrast, all complexes with alkyl substituents in the 6-position of the ligands (bipy(R) with R = CH(3), CH(CH(3))(2), CH(2)C(CH(3))(3), and 2,6-C(6)H(3)(CH(3))(2)) as well as the corresponding complex with 6,6'-dimethyl-2,2'-dipyridyl as a ligand exclusively undergo Coulomb explosion to produce two monocationic fragments. It is proposed that the additional steric strain introduced to the central Au(2)O(2) core by the substituents on the bipyridine ligand, in conjunction with the presence of oxidizable C-H bonds in the substituents, crucially affects the subtle balance between dication dissociation under maintenance of the 2-fold charge and Coulomb explosion into two singly charged fragments.

Density functional theory for transition metals and transition metal chemistry

We introduce density functional theory and review recent progress in its application to transition metal chemistry. Topics covered include local, meta, hybrid, hybrid meta, and range-separated functionals, band theory, software, validation tests, and applications to spin states, magnetic exchange coupling, spectra, structure, reactivity, and catalysis, including molecules, clusters, nanoparticles, surfaces, and solids.