Lu Tian, Shao Pin, Mathew Iswarya, Sand Andrew, Sun Wenfang
Department of Chemistry and Molecular Biology, North Dakota State University, Fargo, North Dakota 58105, USA.
J Am Chem Soc. 2008 Nov 26;130(47):15782-3. doi: 10.1021/ja807021n.
Texaphyrins are pentaazadentate macrocycles with interesting photophysical properties and potential applications as nonlinear optical (NLO) materials, photosensitizers, magnetic resonance imaging (MRI) contrasting reagents, and radiation sensitizers, etc. To further red-shift the Q-like band of the texaphyrins, a benzotexaphyrin with an extensively delocalized pi-electron system was synthesized for the first time. Its photophysical characteristics were systematically investigated. Due to the extended pi-conjugation, the Q(0,0) band of benzotexaphyrin bathochromically shifts to 810 nm, and it emits at 825 nm with a singlet excited-state lifetime of 895 ps. Its triplet excited-state energy is estimated to be 119 kJ/mol. The triplet excited-state lifetime is approximately 2.2 micros, and the quantum yield of the triplet excited-state formation is 0.78. It also exhibits a triplet-triplet transient absorption in the region 505-590 nm. In addition, benzotexaphyrin exhibits high efficiency in generating singlet oxygen in methanol (Phi(Delta) = 0.65). Therefore, benzotexaphyrin could potentially be a NIR photosensitizer and emitter for photodynamic therapy and bioimaging applications.
特沙卟啉是具有有趣光物理性质的五氮杂齿大环化合物，作为非线性光学（NLO）材料、光敏剂、磁共振成像（MRI）造影剂和辐射增敏剂等具有潜在应用价值。为了进一步使特沙卟啉的类Q带发生红移，首次合成了一种具有广泛离域π电子体系的苯并特沙卟啉。对其光物理特性进行了系统研究。由于π共轭的扩展，苯并特沙卟啉的Q(0,0)带发生红移至810 nm，在825 nm处发射，单重激发态寿命为895 ps。其三重激发态能量估计为119 kJ/mol。三重激发态寿命约为2.2微秒，三重激发态形成的量子产率为0.78。它在505 - 590 nm区域还表现出三重态-三重态瞬态吸收。此外，苯并特沙卟啉在甲醇中产生单线态氧的效率很高（Φ(Δ)=0.65）。因此，苯并特沙卟啉有可能成为用于光动力疗法和生物成像应用的近红外光敏剂和发射体。
