UV laser photoactivation of hexachloroplatinate bound to individual nucleobases: In vacuo as molecular level probes of a model photopharmaceutical

TY - JOUR

T1 - UV laser photoactivation of hexachloroplatinate bound to individual nucleobases

T2 - In vacuo as molecular level probes of a model photopharmaceutical

AU - Matthews, Edward

AU - Sen, Ananya

AU - Yoshikawa, Naruo

AU - Bergström, Ed

AU - Dessent, Caroline E H

N1 - © the Owner Societies, 2016. 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. Embargo : 12 months.

PY - 2016/6/14

Y1 - 2016/6/14

N2 - Isolated molecular clusters of adenine, cytosine, thymine and uracil bound to hexachloroplatinate, PtCl6 2-, have been studied using laser electronic photodissociation spectroscopy to investigate photoactivation of a platinum complex in the vicinity of a nucleobase. These metal complex-nucleobase clusters represent model systems for identifying the fundamental photochemical processes occurring in photodynamic platinum drug therapies that target DNA. This is the first study to explore the specific role of a strongly photoactive platinum compound in the aggregate complex. Each of the clusters studied displays a broadly similar absorption spectra, with a strong λmax ∼ 4.6 eV absorption band and a subsequent increase in the absorption intensity towards higher spectral-energy. The absorption bands are traced to ligand-to-metal-charge-transfer excitations on the PtCl6 2- moiety within the cluster, and result in Cl-·nucleobase and PtCl5 - as primary photofragments. These results demonstrate how selective photoexcitation can drive distinctive photodecay channels for a model photo-pharmaceutical. In addition, cluster absorption due to excitation of nucleobase-centred chromophores is observed in the region around 5 eV. For the uracil cluster, photofragments consistent with ultrafast decay of the excited state and vibrational predissociation on the ground-state surface are observed. However, this decay channel becomes successively weaker on going from thymine to cytosine to adenine, due to differential coupling of the excited states to the electron detachment continuum. These effects demonstrate the distinctive photophysical characteristics of the different nucleobases, and are discussed in the context of the recently recorded photoelectron spectra of theses clusters.

AB - Isolated molecular clusters of adenine, cytosine, thymine and uracil bound to hexachloroplatinate, PtCl6 2-, have been studied using laser electronic photodissociation spectroscopy to investigate photoactivation of a platinum complex in the vicinity of a nucleobase. These metal complex-nucleobase clusters represent model systems for identifying the fundamental photochemical processes occurring in photodynamic platinum drug therapies that target DNA. This is the first study to explore the specific role of a strongly photoactive platinum compound in the aggregate complex. Each of the clusters studied displays a broadly similar absorption spectra, with a strong λmax ∼ 4.6 eV absorption band and a subsequent increase in the absorption intensity towards higher spectral-energy. The absorption bands are traced to ligand-to-metal-charge-transfer excitations on the PtCl6 2- moiety within the cluster, and result in Cl-·nucleobase and PtCl5 - as primary photofragments. These results demonstrate how selective photoexcitation can drive distinctive photodecay channels for a model photo-pharmaceutical. In addition, cluster absorption due to excitation of nucleobase-centred chromophores is observed in the region around 5 eV. For the uracil cluster, photofragments consistent with ultrafast decay of the excited state and vibrational predissociation on the ground-state surface are observed. However, this decay channel becomes successively weaker on going from thymine to cytosine to adenine, due to differential coupling of the excited states to the electron detachment continuum. These effects demonstrate the distinctive photophysical characteristics of the different nucleobases, and are discussed in the context of the recently recorded photoelectron spectra of theses clusters.

UR - http://www.scopus.com/inward/record.url?scp=84973603526&partnerID=8YFLogxK

U2 - 10.1039/c6cp01676f

DO - 10.1039/c6cp01676f

M3 - Article

AN - SCOPUS:84973603526

SN - 1463-9076

VL - 18

SP - 15143

EP - 15152

JO - Physical Chemistry Chemical Physics

JF - Physical Chemistry Chemical Physics

IS - 22

ER -