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

Abstract

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 PtCl₆^2- 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 PtCl₆^2-∙thymine and PtCl₆^2-∙adenine complexes also display very prominent delayed electron emission bands. These results mirror recent results on the related Pt(CN)₄^2-∙nucleobase complexes. The observation of delayed electron emission bands in the PtCl6 2-∙nucleobase spectra obtained in this work, as for the previously studied Pt(CN)₄^2-∙nucleobase complexes, is attributed to onephoton 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 inmore » the 266 nm spectra is linked to fundamental differences in the individual nucleobase photophysics at this excitation energy. Here, 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 timescale long enough to allow autodetachment.« less

Authors:

Sen, Ananya ^[1]; Matthews, Edward M.  ^[1];

• Search DOE PAGES for author "Matthews, Edward M."
• Search DOE PAGES for ORCID "0000-0001-5095-621X"

Hou, Gao-Lei ^[2]; Wang, Xue-Bin  ^[2];

• Search DOE PAGES for author "Wang, Xue-Bin"
• Search DOE PAGES for ORCID "0000-0001-8326-1780"

Dessent, Caroline E. H. ^[1]

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+ Show Author Affiliations

1. Univ. of York (United Kingdom)
2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

Publication Date:

Wed Nov 11 00:00:00 EST 2015

Research Org.:

Pacific Northwest National Laboratory (PNNL), Richland, WA (United States). Environmental Molecular Sciences Laboratory (EMSL)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences, and Biosciences Division; USDOE Office of Science (SC), Biological and Environmental Research (BER)

OSTI Identifier:

1243269

Alternate Identifier(s):

OSTI ID: 1225769

Report Number(s):

PNNL-SA-113578
Journal ID: ISSN 0021-9606; JCPSA6; 48585; KC0301050

Grant/Contract Number:  

AC05-76RL01830; 208589-BIOIONS; KC0301050-16248

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Chemical Physics

Additional Journal Information:

Journal Volume: 143; Journal Issue: 18; Journal ID: ISSN 0021-9606

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Environmental Molecular Sciences Laboratory; Isomerism; Nucleobases; Autoionization; Coulomb barrier; Ions and properties; Photoelectron spectroscopy; Basis sets; Thymine; Gas phase; Density functional theory