Photoelectron spectroscopy of hexachloroplatinate-nucleobase complexes: Nucleobase excited state decay observed via delayed electron emission

Journal Article · Sat Nov 14 00:00:00 EST 2015 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.4935171· OSTI ID:22493221

Sen, Ananya; Matthews, Edward M.; Dessent, Caroline E. H., ^[1]; Hou, Gao-Lei; Wang, Xue-Bin ^[2]

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1. Department of Chemistry, University of York, Heslington, York YO10 5DD (United Kingdom)
2. Physical Sciences Division, Pacific Northwest National Laboratory, MS K8-88, P.O. Box 999, Richland, Washington 99352 (United States)

We report low-temperature photoelectron spectra of isolated gas-phase complexes of the hexachloroplatinate dianion bound to the nucleobases uracil, thymine, cytosine, and adenine. The spectra display well-resolved, distinct peaks that are consistent with complexes where the hexachloroplatinate dianion is largely intact. Adiabatic electron detachment energies for the hexachloroplatinate-nucleobase complexes are measured as 2.26-2.36 eV. The magnitudes of the repulsive Coulomb barriers (RCBs) of the complexes are all ∼1.7 eV, values that are lower than the RCB of the uncomplexed PtCl{sub 6}{sup 2−} dianion as a result of charge solvation by the nucleobases. In addition to the resolved spectral features, broad featureless bands indicative of delayed electron detachment are observed in the 193 nm photoelectron spectra of the four clusters. The 266 nm spectra of the PtCl{sub 6}{sup 2−} ⋅ thymine and PtCl{sub 6}{sup 2−} ⋅ adenine complexes also display very prominent delayed electron emission bands. These results mirror recent results on the related Pt(CN){sub 4}{sup 2−} ⋅ nucleobase complexes [A. Sen et al., J. Phys. Chem. B 119, 11626 (2015)]. The observation of delayed electron emission bands in the PtCl{sub 6}{sup 2−} ⋅ nucleobase spectra obtained in this work, as for the previously studied Pt(CN){sub 4}{sup 2−} ⋅ nucleobase complexes, is attributed to one-photon excitation of nucleobase-centred excited states that can effectively couple to the electron detachment continuum, producing strong electron detachment. Moreover, the selective, strong excitation of the delayed emission bands in the 266 nm spectra is linked to fundamental differences in the individual nucleobase photophysics at this excitation energy. This strongly supports our previous suggestion that the dianion within these clusters can be viewed as a “dynamic tag” which has the propensity to emit electrons when the attached nucleobase decays over a time scale long enough to allow autodetachment.

• OSTI ID: 22493221
• Journal Information: Journal of Chemical Physics, Vol. 143, Issue 18; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ADENINES
CARBON NITRIDES
COMPLEXES
COULOMB FIELD
CYANIDES
CYTOSINE
ELECTRON DETACHMENT
ELECTRON EMISSION
ELECTRONS
EV RANGE
EXCITATION
EXCITED STATES
PHOTOELECTRON SPECTROSCOPY
PHOTONS
PLATINUM CHLORIDES
SOLVATION
THYMINE