Effect of oxygen-enhanced intersystem crossing on the observed efficiency of formation of singlet oxygen

McLean, Andrew J.; McGarvey, David J.; Truscott, T. George; Lambert, Christopher; Land, Edward J.

doi:10.1039/ft9908603075

Cited by 80 publications

(50 citation statements)

References 21 publications

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“…The singlet oxygen quantum yield value obtained for T(NAF)PP (0.60) is comparable to that of TPP (0.62), is somewhat higher than that found with T(OH)PP (0.46) (25) and almost twice the value for Photofrin II (0.32) (35). The value obtained for the fraction of triplets quenched by oxygen giving rise to singlet oxygen ( S Δ = Φ Δ / Φ T = 0.79) is in agreement with the typical values found for porphyrins (0.76 ± 0.02) (36).…”

Section: Resultssupporting

confidence: 89%

A New Nonconjugated Naphthalene Derivative ofMeso‐tetra‐(3‐hydroxy)‐phenyl‐porphyrin as a Potential Sensitizer for Photodynamic Therapy

Fonseca

Arranja

Urbano

et al. 2010

Photochem & Photobiology

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A new 5,10,15,20-tetra-(phenoxy-3-carbonyl-1-amino-naphthyl)-porphyrin was prepared by an isocyanate condensation reaction and its photophysical properties fully evaluated, both in terms of photostability and singlet oxygen production. It shows considerably enhanced photostability when compared with the parent 5,10,15,20-tetra-(3-hydroxy-phenyl)-porphyrin, with the photodegradation quantum yields for T(NAF)PP and T(OH)PP being 4.65×10(-4) and 5.19×10(-3) , respectively. Its photodynamic effect in human carcinoma HT-29 cells was evaluated. The new porphyrin showed good properties as a sensitizer in photodynamic therapy with an in vitro cytotoxicity IC(50) value of 6.80μg mL(-1) for a 24h incubation. In addition to the potential of this compound, the synthetic route used provides possibilities of extension to a wide range of new sensitizers.

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Section: Resultssupporting

confidence: 89%

A New Nonconjugated Naphthalene Derivative ofMeso‐tetra‐(3‐hydroxy)‐phenyl‐porphyrin as a Potential Sensitizer for Photodynamic Therapy

Fonseca

Arranja

Urbano

et al. 2010

Photochem & Photobiology

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“…The φ ∆ value for TPP in DMF was obtained using as reference TPP in benzene (φ ∆ ) 0.62). 43 Pulse radiolysis experiments were carried out at the Free Radical Research Facility, Daresbury, U.K., using 200 ns to 2 µs high-energy electron pulses from a 12 MeV linear accelerator (LINAC), passed through solutions in a 2.5 cm optical path length quartz cuvette attached to a flow system. 44,45 All solutions were bubbled with argon for 30-40 min before experiments.…”

Section: Methodsmentioning

confidence: 99%

Photophysics of an Indigo Derivative (Keto and Leuco Structures) with Singular Properties

et al. 2006

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Spectral and photophysical properties of the indigo derivative Cibalackrot in keto and reduced (leuco) forms were studied by absorption spectra, fluorescence and pulse radiolysis and compared with the structurally similar indigo. With the keto form of this dye, fluorescence (φ F ) 0.76) and intersystem crossing (φ T ) 0.11) are dominant, whereas with indigo, efficient internal conversion (φ IC ) 0.99) is observed, probably involving proton transfer through intramolecular hydrogen bonds. With Cibalackrot, this pathway is blocked, supporting the above model for indigo. With the reduced form of Cibalackrot, more than 98% of the absorbed quanta are dissipated through S 1 ∼∼f S 0 internal conversion, which contrasts with leuco-indigo, where fluorescence (φ F ) 0.35), internal conversion (φ IC ) 0.53) and intersystem crossing (φ T ) 0.12 5 ) are found to be competitive. In addition, a synthetic precursor of Cibalackrot (preCiba) was also investigated. This has a rigid molecular structure (with a moiety identical to Cibalackrot and the other to indigo), but intra-or intermolecular proton transfer is allowed between adjacent carbonyl and N-H groups. With this precursor in its keto structure the photophysical parameters are generally very close to those of the keto form of indigo, and different from those of Cibalackrot. A more detailed investigation of the time-decay profiles of preCiba in dioxane (and with added water and D 2 O) has shown that these follow biexponential laws with a shorter component of 14-25 ps, which appears associated with a risetime at longer wavelength emissions (and to a positive preexponential at shorter emission wavelengths) and a longer lived (decay) component of 104-130 ps. In the steady-state spectra of preCiba, the variation with temperature reveals a blue shift of the emission maxima, which is interpreted as the presence (simultaneous emission) of two species (keto and enol) in the excited state. Indigo and deuterated indigo are also found to present a similar behavior. The overall data are interpreted as to be due to an excited-state process involving the proton transfer between keto and enol forms. Rate constants with values of 7 × 10 10 s -1 for preCiba and 1.6 × 10 11 s -1 for deuterated indigo were obtained. This inverse isotope effect is justified on the basis of the proposed model for proton-transfer excited-state deactivation.

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“…In order to obtain the zero level, O,(lA,) phosphorescence was quenched by adding DABCO. Singlet molecular oxygen quantum yields were calculated by comparison with H,TPP as reference compound (QA = 0.62 in benzene (35) where I si the phosphorescence signal, I,, is the zero level signal and A the absorbance at the excitation wavelength. The sub-and supraindexes s and r stand for sample and reference, respectively.…”

Section: Methodsmentioning

confidence: 99%

Photophysical and Aggregation Studies of t‐Butyl‐Substituted Zn Phthalocyanines

Fernández

Awruch

Dicelio

1996

Photochem & Photobiology

108

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Three potential photosensitizers for photodynamic therapy: tetra-t-butyl phthalocyaninato Zn(II), tetrakis-(1,ldimethyl-2-phthalimido)ethylphthalocyaninato Zn(II), and tetrakis-(l,l-dimethyl-2-amino)ethylphthalocyaninato Zn(II), have been studied in homogeneous organic media. Dimerization constants and monomer and dimer spectra have been determined. Fluorescence, triplet and singlet oxygen quantum yields were measured and the photophysical characterization of the triplet state was performed for the three dyes. These parameters were evaluated in connection with aggregation results.

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Effect of oxygen-enhanced intersystem crossing on the observed efficiency of formation of singlet oxygen

Cited by 80 publications

References 21 publications

A New Nonconjugated Naphthalene Derivative ofMeso‐tetra‐(3‐hydroxy)‐phenyl‐porphyrin as a Potential Sensitizer for Photodynamic Therapy

A New Nonconjugated Naphthalene Derivative ofMeso‐tetra‐(3‐hydroxy)‐phenyl‐porphyrin as a Potential Sensitizer for Photodynamic Therapy

Photophysics of an Indigo Derivative (Keto and Leuco Structures) with Singular Properties

Photophysical and Aggregation Studies of t‐Butyl‐Substituted Zn Phthalocyanines

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