The photodynamic therapy (PDT) related photophysical properties of five palladium(II) porphyrins with increasing steric demand of the meso-substituents were investigated by steady state and time-resolved absorption and luminescence spectroscopy. The steric strain of the meso-substituents is reflected in a bathochromic shift of the B-band in the absorption spectra. In contrast to free-base porphyrins, the palladium(II) complexes exhibit only a very weak fluorescence with Φ Fl ~ 10-4. Instead, the corresponding triplet states of the porphyrins are formed via inter system crossing (ISC) with a quantum yield ΦISC of nearly unity. A phosphorescence quantum yield ΦISC of 10-4 was determined assuming dynamic quenching. The triplet state of all compounds is efficiently quenched by molecular oxygen, generating singlet molecular oxygen with a quantum yield of ΦΔ ~ 0.85. The various substitution patterns exerted no significant influence on the ISC rates or singlet oxygen quantum yields. Significant differences, on the other hand, were observed with respect to the triplet lifetimes, with a tendency of longer lifetimes for the porphyrins with sterically more demanding substituents (in air-saturated solution). All porphyrins were successfully incorporated into liposomes. The phototoxic activity of three compounds was investigated in cell suspensions. The use of the new porphyrinato-palladium(II) in PDT applications is discussed.

中文翻译：

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构象扭曲的钯 (II) 卟啉的 PDT 相关光物理性质

通过稳态和时间分辨吸收和发光光谱研究了五种钯 (II) 卟啉的光动力疗法 (PDT) 相关光物理性质，其中内观取代基的空间需求增加。介观取代基的空间应变反映在吸收光谱中 B 波段的红移。与游离碱卟啉相比，钯 (II) 配合物仅表现出非常微弱的荧光，Φ佛罗里达州~ 10-4. 相反，卟啉的相应三重态是通过系统间交叉 (ISC) 形成的，量子产率 Φ国际标准委员会几乎统一。A 磷光量子产率 Φ国际标准委员会10 个-4假设动态淬火确定。所有化合物的三重态都被分子氧有效猝灭，产生量子产率为Φ的单重态分子氧Δ~ 0.85。各种取代模式对 ISC 速率或单线态氧量子产率没有显着影响。另一方面，在三重态寿命方面观察到显着差异，具有空间上要求更高的取代基的卟啉具有更长寿命的趋势（在空气饱和溶液中）。所有的卟啉都成功地掺入了脂质体。在细胞悬液中研究了三种化合物的光毒活性。讨论了新卟啉钯 (II) 在 PDT 应用中的用途。