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Tom Waters

ARC APD Research Fellow

CONTACT DETAILS:

Address: Bio21 Institute, School of Chemistry, University of Melbourne, Parkville, VIC, 3010 Australia

Room: Bio21 Inst., 522

Email: waterst@unimelb.edu.au

Field of expertise

My research focuses on the gas phase reactivity of a range of inorganic anions. The major techniques employed are mass spectrometry, photoelectron spectroscopy, and theoretical chemistry calculations.

Mass Spectrometry

Electrospray ionisation allows solution phase ions to be transferred to the gas phase, where they can be trapped inside a quadrupole ion trap mass spectrometer. This allows the gas-phase reactivity of well-defined species to be examined in the absence of solvent and counterions (Figure 1). Research is focused on defining the complex reactivity of metal oxide cluster anions, with particular emphasis on investigating the effect of cluster size and composition on reactivity. A broad aim is to provide a better understanding of the reactivity of metal oxide surfaces, which are important in many heterogeneous catalytic reactions. We have developed a number of gas phase catalytic cycles that are similar to known condensed phase processes (Figure 1).^1-3

a) Electrospray of mixtures of [MoO4]2- and [WO4]2- b) Gas phase catalytic cycle

Figure 1. a) Electrospray of mixtures of [MoO₄]^2- and [WO₄]^2- allows unusual species such as [MoWO₇]^2- to be examined; b) Gas phase catalytic cycle for oxidation of methanol to formaldehyde with metavanadate [VO₃]^- as the catalyst and dioxygen as the terminal oxidant.

Photoelectron Spectroscopy

Photoelectron spectroscopy provides information about the electronic structure of gaseous species. Prof. Lai-Sheng Wang’s group at Pacific Northwest National Laboratory (USA) have developed an electrospray ionisation photoelectron spectroscopy apparatus (http://www.tricity.wsu.edu/~physics/). Some previous research has focused on metal-dithiolene centers^4-6 and a range of metal oxide anions (Figure 2).^7-9 We aim to correlate electronic and structural information from photoelectron spectroscopy experiments with reactivity data from mass spectrometry experiments.

a) Photoelectron spectrum of [Ni(mnt)2]2- b) Systematic variation of the metal centre

Figure 2. a) Photoelectron spectrum of [Ni(mnt)₂]^2-;. The molecular orbital pictures are from theoretical calculations; b) Systematic variation of the metal centre and charge state across a common series of species.

Theoretical Calculations

Theoretical calculations based on Density Functional Theory (DFT) provide insights into the geometric and electronic structures of inorganic species, as well as the mechanism and energetics of gas phase reactions (Figure 3). Such calculations aid with an interpretation of experimental data from mass spectrometry and photoelectron spectroscopy experiments.

a) Calculated potential energy surface b) Structure of key intermediates and transition states

Figure 3. a) Calculated potential energy surface for the reaction between [VO₃]^- and CH₃OH; b) Structure of key intermediates and transition states. The same reaction was also examined experimentally (Figure 1).

Selected Publications:

Waters, T.; O’Hair, R. A. J.; Wedd, A. G. J. Am. Chem. Soc. 2003, 125, 3384-3396.
Waters, T.; Khairallah, G. H.; Wimala, S. A. S. Y.; Ang, Y. C.; O’Hair, R. A. J.; Wedd, A. G. Chem. Comm. 2006, 4503-4505.
Waters, T.; O’Hair, R. A. J.; Wedd, A. G. Inorg. Chem. 2005, 44, 3356-3366.
Waters, T.; Wang, X. B.; Yang, X.; Zhang, L.; O’Hair, R. A. J.; Wang, L. S.; Wedd, A. G. J. Am. Chem. Soc. 2004, 126, 5119-5129.
Waters, T.; Woo, H. K.; Wang, X. B.; Wang, L. S. J. Am. Chem. Soc. 2006, 128, 4282-4291.
Waters, T.; Wang, X. B.; Woo, H. K.; Wang, L. S. Inorg Chem. 2006, 45, 5841-5851.
Waters, T.; Wang, X. B.; Li, S.; Kiran, B.; Dixon, D. A.; Wang, L. S. J. Phys. Chem. A. 2005, 109, 11771-11780.
Waters, T.; Huang, X.; Wang, X. B.; Woo, H. K.; O’Hair, R. A J.; Wedd, A. G.; Wang, L. S. J. Phys. Chem. A. 2006, 110, 10737-10741.
Huang, X.; Zhai, H. J.; Waters, T.; Li, J.; Wang, L. S. Angew. Chem. Int. Ed. 2006, 45, 657-660.

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