Subedi Dili R, Reid Ryan, D'Souza Patrick F, Nesterov Vladimir N, D'Souza Francis
Department of Chemistry, University of North Texas, 1155 Union Circle, #305070, Denton, TX 76203-5017, USA.
Chempluschem. 2022 Feb 23;87(4):e202200010. doi: 10.1002/cplu.202200010.
A series of meso-substituted with aromatic (=tolyl, pyrenyl, fluorenyl, naphthyl, and triphenylamine) substituents, platinum (Pt), and palladium (Pd) porphyrins have been synthesized and characterized by spectroscopic and single-crystal X-ray diffraction studies to probe structure-reactivity aspects on the electrochemical redox potentials, and phosphorescence quantum yields and lifetimes. In the X-ray structures, the aromatic meso-substituents were rotated to some extent from the planarity of the porphyrin ring to minimize steric hindrance. Both Pt and Pd porphyrins revealed higher electrochemical redox gaps as compared to their free-base porphyrin analogs as a result of the harder oxidation and reduction processes. The ability of both Pt and Pd porphyrins to generate singlet oxygen was probed by monitoring the photoluminescence of O at 1270 nm. Higher quantum yields for both triplet sensitizers compared to their free-base analogs were witnessed. Singlet oxygen quantum yields close to unity were possible to achieve in the case of Pt and Pd porphyrins bearing triphenylamine substituents at the meso-position. The present study brings out the importance of different meso-substituents on the triplet porphyrin sensitizers in governing singlet oxygen quantum yields; a key property of photosensitizers needed for photodynamic therapy, chemical synthesis, and other pertinent applications.
一系列中位被芳香族（=甲苯基、芘基、芴基、萘基和三苯胺）取代基取代的铂（Pt）和钯（Pd）卟啉已被合成，并通过光谱和单晶X射线衍射研究进行了表征，以探究其在电化学氧化还原电位、磷光量子产率和寿命方面的结构-反应性。在X射线结构中，芳香族中位取代基从卟啉环平面旋转了一定程度，以最小化空间位阻。由于氧化和还原过程更难，Pt和Pd卟啉与其游离碱卟啉类似物相比，显示出更高的电化学氧化还原能隙。通过监测1270 nm处O的光致发光，探究了Pt和Pd卟啉产生单线态氧的能力。与游离碱类似物相比，两种三线态敏化剂的量子产率都更高。对于在中位带有三苯胺取代基的Pt和Pd卟啉，单线态氧量子产率有可能接近1。本研究揭示了不同的中位取代基对三线态卟啉敏化剂在控制单线态氧量子产率方面的重要性；单线态氧量子产率是光动力疗法、化学合成及其他相关应用所需光敏剂的关键性质。
