The excitation energies, singlet-triplet energy gap and spin-orbit coupling constants for Zn-, GaCl-, Pd-, and Pt- tetrasulfonyl phthalocyanines complexes (ZnPc, GaClPc, PdPc, and PtPc) have been computed by using the density functional theory and employing the M06 exchange-correlation functional. Results show that these systems possess interesting photophysical properties, which make them possible photosensitizers to be proposed in photodynamic therapy (PDT). Absorption energies of all the complexes examined have been found falling inside the so-called therapeutic window (550–800 nm). Singlet-triplet energy gap values are higher than those required for the production of cytotoxic molecular oxygen and the spin-orbit coupling constants are such as to ensure an efficient spin orbit intersystem crossing. The obtained data are consistent with the experimental oxygen singlet quantum yields. The platinum complex appears to be the most effective candidate to propose for PDT.

中文翻译：

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含有重原子的四磺酰基酞菁作为光动力治疗中可能的光敏剂的光物理性质

使用密度泛函理论计算了 Zn-、GaCl-、Pd- 和 Pt- 四磺酰基酞菁配合物（ZnPc、GaClPc、PdPc 和 PtPc）的激发能、单重态三重态能隙和自旋轨道耦合常数并采用 M06 交换相关函数。结果表明，这些系统具有有趣的光物理特性，这使得它们可能成为光动力疗法 (PDT) 中提出的光敏剂。已发现所有检查过的配合物的吸收能量落在所谓的治疗窗口（550-800 nm）内。单重态-三重态能隙值高于产生细胞毒性分子氧所需的值，并且自旋轨道耦合常数确保有效的自旋轨道系统间交叉。所得数据与实验氧单线态量子产率一致。铂络合物似乎是建议用于 PDT 的最有效候选者。