Near-threshold electron transfer in anion-nucleobase clusters: Does the identity of the anion matter?

TY - JOUR

T1 - Near-threshold electron transfer in anion-nucleobase clusters

T2 - Does the identity of the anion matter?

AU - Cercola, Rosaria

AU - Matthews, Edward

AU - Dessent, Caroline E.H.

N1 - © 2019 Informa UK Limited, trading as Taylor & Francis Group. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details.

PY - 2019/3/24

Y1 - 2019/3/24

N2 - Laser dissociation spectroscopy of I − ·adenine (I − ·A) and H 2 PO − 3 ·adenine (H 2 PO − 3 ·A) has been utilised for the first time to explore how the anion identity impacts on the excited states. Despite strong photodepletion, ionic photofragmentation is weak for both clusters, revealing that they decay predominantly by electron detachment. The spectra of I − ·A display a prominent dipole-bound excited state in the region of the detachment energy which relaxes to produce deprotonated adenine. In contrast, near-threshold photoexcitation of H 2 PO − 3 ·A does not access a dipole-bound state, but instead displays photofragmentation properties associated with ultrafast decay of an adenine-localised π→π* transition. Notably, the experimental electron detachment onset of H 2 PO − 3 ·A is around 4.7 eV, which is substantially lower than the expected detachment energy of an ion-dipole complex. The low value for H 2 PO − 3 ·A can be traced to initial ionisation of the adenine followed by significant geometric rearrangement on the neutral surface. We conclude that these dynamics quench access to a dipole-bound excited state for H 2 PO − 3 ·A and subsequent electron transfer. H 2 PO − 3 ·A represents an important new example of an ionic cluster where ionisation occurs from the neutral cluster component and where photodetachment initiates intra-molecular hydrogen atom transfer.

AB - Laser dissociation spectroscopy of I − ·adenine (I − ·A) and H 2 PO − 3 ·adenine (H 2 PO − 3 ·A) has been utilised for the first time to explore how the anion identity impacts on the excited states. Despite strong photodepletion, ionic photofragmentation is weak for both clusters, revealing that they decay predominantly by electron detachment. The spectra of I − ·A display a prominent dipole-bound excited state in the region of the detachment energy which relaxes to produce deprotonated adenine. In contrast, near-threshold photoexcitation of H 2 PO − 3 ·A does not access a dipole-bound state, but instead displays photofragmentation properties associated with ultrafast decay of an adenine-localised π→π* transition. Notably, the experimental electron detachment onset of H 2 PO − 3 ·A is around 4.7 eV, which is substantially lower than the expected detachment energy of an ion-dipole complex. The low value for H 2 PO − 3 ·A can be traced to initial ionisation of the adenine followed by significant geometric rearrangement on the neutral surface. We conclude that these dynamics quench access to a dipole-bound excited state for H 2 PO − 3 ·A and subsequent electron transfer. H 2 PO − 3 ·A represents an important new example of an ionic cluster where ionisation occurs from the neutral cluster component and where photodetachment initiates intra-molecular hydrogen atom transfer.

KW - electron attachment

KW - electronic excitation

KW - gas phase

KW - Nucleobase

KW - photodissociation

UR - http://www.scopus.com/inward/record.url?scp=85063371857&partnerID=8YFLogxK

U2 - 10.1080/00268976.2019.1596327

DO - 10.1080/00268976.2019.1596327

M3 - Article

AN - SCOPUS:85063371857

SN - 0026-8976

JO - Molecular Physics: An International Journal at the Interface Between Chemistry and Physics

JF - Molecular Physics: An International Journal at the Interface Between Chemistry and Physics

ER -