Synthesis and Characterization of New Fluorene-Based Singlet Oxygen Sensitizers

Abstract

The synthesis, photophysical characterization, and determination of singlet oxygen quantum yields (Phi(Delta)) for a class of fluorene derivatives with potential application in two-photon photodynamic therapy (PDT) is reported. It has been demonstrated that these compounds possess the ability to generate singlet oxygen (1O2) upon excitation. A photochemical method, using 1,3-diphenylisobenzofuran (DPBF) as 1O2 chemical quencher, was employed to determine the singlet oxygen quantum yields (Phi(Delta)) of the fluorene-based photosensitizers in ethanol. Phi(Delta) values ranged from 0.35 to 0.75. These derivatives may have potential application as two-photon photosensitizers when pumped via two-photon excitation in the near-IR spectral region.

Dynamic quenching of porphyrin triplet states by two-photon absorbing dyes: Towards two-photon-enhanced oxygen nanosensors

“…Here k e° is the frequency factor, ΔG * ET is the free energy of activation for the ET step, and ΔG ET is the driving force of the ET reaction. ΔG * ET can be further expressed using the Marcus-Hush theory [33] in terms of ΔG ET and reorganization energy λ: (5) Experimentally determined k q 's and their decimal logarithms (log k q ) were plotted against the corresponding driving forces ΔG ET (Fig. 7).…”

“…Molecular devices capable of generation of triplet states upon two-photon (2P) excitation have been the focus of several recent studies, including construction of 2P agents for photodynamic therapy [2,3,4,5] and 2P phosphorescent oxygen nanosensors [1,6]. Phosphorescent probes used in biological oxygen measurements [7] are based on metalloporphyrins, whose 2P absorption (2PA) cross-sections (σ 2 ) are very small, and their ability to generate emissive triplet E-mail: vinograd@mail.med.upenn.edu.…”

Photostability of D–π–A nonlinear optical chromophores containing a benzothiazolium acceptor

“…The rate constant k Q for 1 O 2 quenching (relative reactivity index β Q = k d / k Q ; in this case β Q includes both physical and chemical quenching) by 1 – 7 necessary for more accurate Φ 1 O 2 determination were calculated based on inhibition of DPIBF oxidation ( β = 1.1 × 10 −4 M in MeOH29, 30) by competitive 1 O 2 quenching31, 32 using the following equations (in the primary model we replaced the concentrations with the corresponding absorbances): and by monitoring the decrease of the DPIBF absorption band at different quencher concentration using Young's kinetic technique:33 …”

Photo-induced proton transfer in fluorene- and carbazole-based compounds as red- and orange-light-emitting molecules: A TD-DFT study

“…Many possible applications of fluorene and its heteroanalogues, namely, carbazole, dibenzofuran, and dibenzothiophene, making use of their photochemical features have been described in recent times. The useful electronic properties of these materials make them promising candidates for use in such diverse technologies as organic light-emitting diodes, thin-film transistors, chemical sensors, photovoltaics, photorefractives, holography, electronic data storage, and electroluminescent devices [32][33][34][35][36][37][38][39]. The nanofibrils fabricated from the carbazole exhibit strong blue fluorescence upon excitation under UV light.…”