title: Synthesis and photophysics of benzotexaphyrin: a near-infrared emitter and photosensitizer.
abstract: 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.
authors.affiliation: Department of Chemistry and Molecular Biology, North Dakota State University, Fargo, North Dakota 58105, USA.
authors.forename: Tian
authors.initials: T
authors.lastname: Lu
authors.forename: Pin
authors.initials: P
authors.lastname: Shao
authors.forename: Iswarya
authors.initials: I
authors.lastname: Mathew
authors.forename: Andrew
authors.initials: A
authors.lastname: Sand
authors.forename: Wenfang
authors.initials: W
authors.lastname: Sun
mesh_terms: D001554:Benzene / Q000737:chemistry*; D015394:Molecular Structure; D055668:Photochemical Processes; D017319:Photosensitizing Agents / Q000138:chemical synthesis* / Q000737:chemistry; D011166:Porphyrins / Q000138:chemical synthesis* / Q000737:chemistry; D013053:Spectrophotometry
chemical_list: D017319:Photosensitizing Agents; D011166:Porphyrins; C442892:texaphyrin; D001554:Benzene