Sen Ananya, Dessent Caroline E H
Department of Chemistry, University of York, Heslington, York YO10 5DD, United Kingdom.
J Chem Phys. 2014 Dec 28;141(24):241101. doi: 10.1063/1.4904259.
We present UV laser action spectra (220-300 nm) of isolated nucleobase-bound Pt(II)(CN)4(2-) complexes, i.e., Pt(CN)4(2-)⋅M, where M = uracil, thymine, cytosine, and adenine. These metal complex-nucleobase clusters represent model systems for identifying the fundamental photophysical and photochemical processes occurring in photodynamic platinum (II) drug therapies that target DNA. This is the first study to explore the specific role of the nucleobase in the photophysics of the aggregate complex. Each of the complexes studied displays a broadly similar absorption spectra, with a strong λmax ∼ 4.7 eV absorption band (nucleobase localized chromophore) and a subsequent increase in the absorption intensity towards higher spectral-energy (Pt(CN)4(2-) localized chromophore). However, strikingly different band widths are observed across the series of complexes, decreasing in the order Pt(CN)4(2-)⋅Thymine > Pt(CN)4(2-)⋅Uracil > Pt(CN)4(2-)⋅Adenine > Pt(CN)4(2-)⋅Cytosine. Changes in the bandwidth of the ∼4.7 eV band are accompanied by distinctive changes in the photofragment product ions observed following photoexcitation, with the narrower-bandwidth complexes showing a greater propensity to decay via electron detachment decay. We discuss these observations in the context of the distinctive nucleobase-dependent excited state lifetimes.
我们展示了分离出的核碱基结合的Pt(II)(CN)4(2-)配合物，即Pt(CN)4(2-)⋅M（其中M = 尿嘧啶、胸腺嘧啶、胞嘧啶和腺嘌呤）的紫外激光作用光谱（220 - 300 nm）。这些金属配合物 - 核碱基簇代表了用于识别在靶向DNA的光动力铂（II）药物治疗中发生的基本光物理和光化学过程的模型系统。这是第一项探索核碱基在聚集配合物光物理中特定作用的研究。所研究的每种配合物都显示出大致相似的吸收光谱，具有一个强的λmax ∼ 4.7 eV吸收带（核碱基定位发色团）以及随后吸收强度向更高光谱能量的增加（Pt(CN)4(2-)定位发色团）。然而，在这一系列配合物中观察到了显著不同的带宽，其顺序为Pt(CN)4(2-)⋅胸腺嘧啶 > Pt(CN)4(2-)⋅尿嘧啶 > Pt(CN)4(2-)⋅腺嘌呤 > Pt(CN)4(2-)⋅胞嘧啶。∼4.7 eV带的带宽变化伴随着光激发后观察到的光碎片产物离子的显著变化，带宽较窄的配合物显示出通过电子脱离衰变衰减的更大倾向。我们在独特的核碱基依赖性激发态寿命的背景下讨论这些观察结果。
