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.
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 Pt(IV)(CN)6(2-)·Ur and Pt(II)(CN)4(2-)·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 (λmax = 4.90 and 4.70 eV) that we assign primarily to excitation of the Ur π-π* localized chromophore. Distinctive UV photofragmentation products are observed for the complexes, with Pt(IV)(CN)6(2-)·Ur photoexcitation resulting in complex fission, while Pt(II)(CN)4(2-)·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.
Department of Chemistry, University of York, Heslington, York YO10 5DD, United Kingdom.
Ananya
A
Sen
Department of Chemistry, University of York, Heslington, York YO10 5DD, United Kingdom.
Caroline E H
CE
Dessent
Pt complex photochemistry; laser photodissociation; multiply charged anions; nucleobase photochemistry; photodynamic therapy; uracil photophysics