Mapping the UV photophysics of platinum metal complexes bound to nucleobases: Laser spectroscopy of isolated Uracil·pt(CN)₄^2- and Uracil·Pt(CN)₆^2- complexes

TY - JOUR

T1 - Mapping the UV photophysics of platinum metal complexes bound to nucleobases

T2 - Laser spectroscopy of isolated Uracil·pt(CN)42- and Uracil·Pt(CN)62- complexes

AU - Sen, Ananya

AU - Dessent, Caroline E H

PY - 2014/10/2

Y1 - 2014/10/2

N2 - We report the first UV laser spectroscopic study of isolated gas-phase complexes of platinum metal complex anions bound to a nucleobase as model systems for exploring at the molecular level the key photophysical processes involved in photodynamic therapy. Spectra of the PtIV(CN)62-·Ur and PtII(CN)42-·Ur complexes were acquired across the 220-320 nm range using mass-selective photodepletion and photofragment action spectroscopy. The spectra of both complexes reveal prominent UV absorption bands (max = 4.90 and 4.70 eV) that we assign primarily to excitation of the Ur localized chromophore. Distinctive UV photofragmentation products are observed for the complexes, with PtIV(CN)62-·Ur photoexcitation resulting in complex fission, while PtII(CN)42-·Ur photoexcitation initiates a nucleobase proton-transfer reaction across 4.4-5.2 eV and electron detachment above 5.2 eV. The observed photofragments are consistent with ultrafast decay of a Ur localized excited state back to the electronic ground state followed by intramolecular vibrational relaxation and ergodic complex fragmentation.

AB - We report the first UV laser spectroscopic study of isolated gas-phase complexes of platinum metal complex anions bound to a nucleobase as model systems for exploring at the molecular level the key photophysical processes involved in photodynamic therapy. Spectra of the PtIV(CN)62-·Ur and PtII(CN)42-·Ur complexes were acquired across the 220-320 nm range using mass-selective photodepletion and photofragment action spectroscopy. The spectra of both complexes reveal prominent UV absorption bands (max = 4.90 and 4.70 eV) that we assign primarily to excitation of the Ur localized chromophore. Distinctive UV photofragmentation products are observed for the complexes, with PtIV(CN)62-·Ur photoexcitation resulting in complex fission, while PtII(CN)42-·Ur photoexcitation initiates a nucleobase proton-transfer reaction across 4.4-5.2 eV and electron detachment above 5.2 eV. The observed photofragments are consistent with ultrafast decay of a Ur localized excited state back to the electronic ground state followed by intramolecular vibrational relaxation and ergodic complex fragmentation.

KW - laser photodissociation

KW - multiply charged anions

KW - nucleobase photochemistry

KW - photodynamic therapy

KW - Pt complex photochemistry

KW - uracil photophysics

UR - http://www.scopus.com/inward/record.url?scp=84907807140&partnerID=8YFLogxK

U2 - 10.1021/jz501749j

DO - 10.1021/jz501749j

M3 - Article

AN - SCOPUS:84907807140

SN - 1948-7185

VL - 5

SP - 3281

EP - 3285

JO - JOURNAL OF PHYSICAL CHEMISTRY LETTERS

JF - JOURNAL OF PHYSICAL CHEMISTRY LETTERS

IS - 19

ER -