相对论效应对光敏抗癌铂配合物吸收光谱的影响
Investigating the influence of relativistic effects on absorption spectra for platinum complexes with light-activated activity against cancer cells
摘要：
首次研究了光活化化学疗法（PACT）的两个原型配合物trans-trans-trans-trans-cis-[Pt（N3）2（OH）2（NH3）2]和cis-trans-cis-[Pt（N3）2（OH）2（NH3）2]的紫外-可见光谱的相对论效应。第一步通常是合理化的紫外-可见光谱的含时密度泛函理论（TD-DFT）是一个不可或缺的工具。我们进行了TD-DFT计算与一系列系统的非相对论（NR），标量相对论（SR），和四分量（4c）的哈密顿量。在4c和NR框架内计算的光谱之间存在很大的差异，而最强烈的特征（在低于300 nm的较高能量下发现）可以在SR框架内合理地再现。然而，在4c框架中引入的自旋轨道耦合会强烈影响潜在的跃迁：虽然这会影响光谱中的强度和强度较低的跃迁，但这种影响在300 nm以上的较低能量下的较弱跃迁中最为明显。由于所研究的复合物被激活的波长超过300 nm的光，采用明确包括自旋-轨道耦合的方法可能是至关重要的合理化的激活机制。所有的计算都是用CAM-B3 LYP和B3 LYP泛函进行的;我们通常发现前者与实验光谱相比表现最好。
英文摘要：
We report the first investigation of relativistic effects on the UV-vis spectra of two prototype complexes for so-called photo-activated chemotherapy (PACT), trans-trans-trans-[Pt(N3)2(OH)2(NH3)2] and cis-trans-cis-[Pt(N3)2(OH)2(NH3)2].In PACT, design of new drugs requires in-depth understanding of the photo-activation mechanisms. A first step is usually to rationalize their UV-vis spectra for which time-dependent density functional theory (TD-DFT) is an indispensable tool. We carried out TD-DFT calculations with a systematic series of non-relativistic(NR), scalar-relativistic (SR), and four-component (4c) Hamiltonians. Large differences are found between spectra calculated within 4c and NR frameworks, while the most intense features (found at higher energies below 300 nm) can be reasonably well reproduced within a SR framework. Yet the underlying transitions can be strongly influenced by spin-orbit coupling introduced in the 4c framework: while this can affect both intense and less intense transitions in the spectra, the effect is most pronounced for weaker transitions at lower energies, above 300 nm. Since the investigated complexes are activated with light of wavelengths above 300 nm, employing a method with explicit inclusion of spin-orbit coupling may be crucial to rationalize the activation mechanism. All calculations were carried out with both the CAM-B3LYP and B3LYP functionals; we generally find the former to perform best in comparison with experimental spectra.
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