Banaszek Maciej, Golec Barbara, Rybakiewicz-Sekita Renata, Kowalski Jarosław, Szczodry Piotr, Dutkiewicz Natalia, Waluk Jacek, Gorski Aleksander
Faculty of Mathematics and Science, Cardinal Stefan Wyszyński University, Dewajtis 5, Warsaw 01-815, Poland.
Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, Warsaw 01-224, Poland.
J Phys Chem B. 2025 Jun 5;129(22):5491-5500. doi: 10.1021/acs.jpcb.5c02423. Epub 2025 May 28.
Photostability is a crucial parameter in applications based on light-matter interactions. In this work, we demonstrate that photodegradation efficiency can be strongly decreased by altering the thermodynamic and kinetic characteristics of a chromophore. Photobleaching quantum yields have been determined for a series of free-base octaethylporphyrins and their palladium metallocomplexes gradually substituted by phenyl groups at the positions. Due to increased oxidation potential of palladium porphyrins, photostability is improved in comparison with zinc or magnesium derivatives. A spectacular effect is observed for nonplanar palladium derivatives in which the triplet lifetime in deoxygenated solution is shortened by 3 orders of magnitude with respect to planar porphyrins. Comparison of photodestruction efficiencies in oxygen-containing and degassed toluene samples shows a hundred-fold decrease of photobleaching quantum yields for nonplanar palladium porphyrins, reaching an extremely low value of less than 10. In contrast, free-base, nonplanar porphyrins are less stable than the planar analogues in nondegassed toluene. Finally, planar free-base and palladium porphyrins become significantly less photostable in the degassed solution because the triplet decay time increases by 3 orders of magnitude compared to oxygen-containing samples.
光稳定性是基于光与物质相互作用的应用中的一个关键参数。在这项工作中，我们证明了通过改变发色团的热力学和动力学特性，可以显著降低光降解效率。已经测定了一系列在β位逐渐被苯基取代的游离碱八乙基卟啉及其钯金属配合物的光漂白量子产率。由于钯卟啉的氧化电位增加，与锌或镁衍生物相比，其光稳定性得到了提高。对于非平面钯衍生物，观察到了一个显著的效果，即在脱氧溶液中，其三线态寿命相对于平面卟啉缩短了3个数量级。在含氧和脱气甲苯样品中光破坏效率的比较表明，非平面钯卟啉的光漂白量子产率降低了一百倍，达到了极低的值，小于10⁻⁵。相比之下，在未脱气的甲苯中，游离碱非平面卟啉比平面类似物更不稳定。最后，平面游离碱和钯卟啉在脱气溶液中的光稳定性显著降低，因为与含氧样品相比，三线态衰变时间增加了3个数量级。
