3.1. Sc Group 6772 3.2. Ti Group 6773 3.3. V Group 6775 3.4. Cr Group 6776 3.5. Mn Group 6777 3.6. Fe Group 6779 3.7. Co Group 6780 3.8. Ni Group 6782 3.9. Cu Group 6782 3.10. Zn Group 6784 3.11. Lanthanide Group 6784 3.12. Actinide Group 6785 3.13. Periodic Trends on Bonding and Reactivity 6785 4. Ionic Mononuclear Transition Metal Oxide Species 6787 4.1. Cations 6788 4.2. Anions 6790 4.2.1. Monoxide Anions 6790 4.2.2. Dioxide Anions 6791 4.2.3. Oxygen-Rich Anions 6792 5. Multinuclear Transition Metal Oxide Clusters 6792 5.1. Sc Group 6793 5.2. Ti Group 6793 5.3. V Group 6793 5.4. Cr Group 6797 5.5. Mn Group 6798 5.6. Fe Group 6798 5.7. Co Group 6798 5.8. Ni Group 6798 5.9. Cu Group 6799 6. Summary 6800 7. Acknowledgments 6800 8. References 6800

Spectroscopic and theoretical studies of transition metal oxides and dioxygen complexes.

The geometrical structures of the ground states of triniobium monoxide, Nb3O, and its cation, Nb3O+, have been determined by an experimental and theoretical study. Vibrationally resolved photoelectron spectra of an Nb3O cluster beam were obtained at 100 and 300 K using the pulsed field ionization‐zero electron kinetic energy technique. The spectra were simulated by calculating multidimensional Franck–Condon factors using the geometries and harmonic vibrational frequencies obtained from density functional theory for the minimum energy structures of the ion and neutral molecule. The rather remarkable agreement between the experiment and the simulated spectra establishes that Nb3O and Nb3O+ have planar C2v structures with the oxygen atom bridging two niobium atoms. These are the most complex transition metal cluster structures to date to be characterized by gas phase spectroscopic techniques.

The structure of Nb3O and Nb3O+ determined by pulsed field ionization–zero electron kinetic energy photoelectron spectroscopy and density functional theory

Density functional theory (DFT) calculations are applied to study the structure and bonding properties of groups 3–7 transition metal oxide clusters M
 x=1–3O
 and Scx=4–6O
 with 2y − nx + q = 1, in which n is the number of metal valence electrons and q is the charge number. These clusters include MO2, M
 2O3
 +, M
 2O4
 −, and M
 3O5 (M = Sc, Y, La); MO2
 +, MO3
 −, M
 2O4
 +, M
 2O5
 −, M
 3O6
 +, and M
 3O7
 − (M = Ti, Zr, Hf), and so on. The obtained lowest energy structures of most of these clusters are with character of oxygen-centered radical (O·). That is, the clusters contain oxygen atom(s) with the unpaired electron being localized on the 2p orbital(s). Chromium and manganese oxide clusters (except CrO4
 −) do not contain O· with the adopted DFT methods. The binding energies of the radical oxygen with the clusters are also calculated. The DFT results are supported by available experimental investigations and predict that a lot of other transition metal oxide clusters including those with mixed-metals (such as TiVO5 and CrVO6) may have high oxidative reactivity that has not been experimentally identified. The chemical structures of radical oxygen over V2O5/SiO2 and MoO3/SiO2 catalysts are suggested and the balance between high reactivity and low concentration of the radical oxygen in condensed phase catalysis is discussed.

Transition metal oxide clusters with character of oxygen-centered radical: a DFT study

The vibrationally resolved 488 nm negative ion photoelectron spectra of V3O, Nb3O, and Ta3O provide measurements of their electron affinities, vibrational frequencies, and low-lying electronic state energies. The electron affinities increase smoothly down the triad with values (eV) of 1.218±0.008 for V3O, 1.393±0.006 for Nb3O, and 1.583±0.010 for Ta3O. The metal–oxygen symmetric stretching fundamental frequencies are 750±20, 710±15, and 710±15 cm−1, respectively, for the neutral clusters and 770±20 cm−1 for V3O−. Lower frequency symmetric modes are also active, with frequencies (±15 cm−1) of 415 and 340 cm−1 for V3O, 320 cm−1 for Nb3O, 225 cm−1 for Ta3O, and of 355, 300, and 215 cm−1 (±20 cm−1), respectively, for their anions. Weaker transitions also showing vibrational structure are observed to excited states at 3350±30 cm−1 for V3O, 4300±100 and 6190±120 cm−1 for Nb3O, and 3180±40 and 3870±50 cm−1 for Ta3O. The spectra indicate that the extra electrons in the anions occupy essentially nonbonding orbital...

Negative ion photoelectron spectroscopy of the group 5 metal trimer monoxides V3O, Nb3O, and Ta3O

Gas phase activation of carbon dioxide by niobium and niobium monoxide cations

The He I photoelectron spectra of NbO and TaO have been recorded. In both cases four main bands were observed which can be attributed to ionization of the isolated metal monoxide molecule. Bands associated with other oxides or the metal were not observed.Assignment of the photoelectron spectra of NbO and TaO was made with the aid of Hartree–Fock–Slater (HFS) calculations and by comparison with the known photoelectron spectrum of VO. The first adiabatic ionization energies of NbO and TaO have been measured as 7.91 ± 0.02 eV and 8.61 ± 0.02 eV, respectively. Suggestions are made to explain the poor agreement between previous mass-spectrometric values for the first ionization energy of each oxide.

High-temperature photoelectron spectroscopy. A study of niobium monoxide and tantalum monoxide

X-ray photoelectron and infrared spectroscopy have been used to investigate the chemical composition of some ammonium uranates, all of which were prepared by the direct titration of uranyl nitrate solution with ammonia. Some correlation is found between the U(4f) binding energy and the pH of the solution used to prepare the uranates, and the v3 asymmetric stretching frequency for the uranyl (UO22+) ion. All samples showed the presence of ammonium ions and possibly two types of hydroxide species. Strong retention of nitrate ions was also observed for all samples.

An X-Ray Photoelectron Spectroscopic Study of Some Ammonium Uranates

X-ray photoelectron spectroscopy (X.p.s.) using depth profiling and angle-resolved studies has been used to investigate the surface of borided zirconium. The study shows that there is considerable surface oxidation which may seriously limit some practical applications of the borided sample.

X-ray photoelectron spectroscopic study of the surface of borided zirconium

X-ray photoelectron spectroscopy has been used to observe the free surface segregation of impurities in samples of platinum and palladium. Heating in vacuo to 600°C promoted the surface segregation of silver, gold, and carbon in platinum and the surface segregation of silver and sulfur in palladium. All species segregated in their elemental form. The core level binding energies of the silver and gold segregants were lower than those measured for the corresponding pure metal states.

An X-Ray Photoelectron Spectroscopic Study of the Free Surface Segregation of Impurities in Platinum and Palladium

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High-temperature photoelectron spectroscopy. A study of niobium monoxide and tantalum monoxide

An X-Ray Photoelectron Spectroscopic Study of Some Ammonium Uranates

X-ray photoelectron spectroscopic study of the surface of borided zirconium

X-ray photoelectron spectroscopic study of the surface of borided zirconium

An X-Ray Photoelectron Spectroscopic Study of the Free Surface Segregation of Impurities in Platinum and Palladium