Aromatic ketones as standards for singlet molecular oxygen photosensitization. Time-resolved photoacoustic and near-IR emission studies

Martí, Cristina; Jürgens, Oriol; Cuenca, Oriol; Casals, Mercè; Nonell, Santi

doi:10.1016/1010-6030(96)04321-3

Cited by 185 publications

(175 citation statements)

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“…By laser-induced optoacoustic spectroscopy, Schmidt et al determined a second value of 186 AE 5 kJ mol À1 in toluene [3]. By the same technique, though a different detector arrangement and data-handling procedures, our group obtained a similar value, 178 AE 8 kJ mol À1 [4]. It is important to point out that both works derived the E T value assuming a triplet quantum yield F T of unity, since laser-induced optoacoustic spectroscopy only affords the value of the product F T E T .…”

supporting

confidence: 56%

On the Phosphorescence of 1H-Phenalen-1-one

Flors

Nonell

2001

HCA

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Dedicated to Professor AndreÂ M. Braun, on the occasion of his 60th birthday Combining the effects of heavy atom and low temperature, the phosphorescence spectrum from 1H-phenalen-1-one has been unveiled. The 0-0 band is located at 649 nm in methylcyclohexane and shifted to 646 nm in ethanol, which sets the triplet-energy level to 185 and 186 kJ´mol À1 , respectively. The emission is unambiguously identified as phosphorescence originating from 1H-phenalen-1-one through complementary transient absorption and emission studies. The quantum yield for triplet formation is confirmed to be unity.1. Introduction. ± 1H-Phenalen-1-one (hereafter phenalenone, also called perinaphthenone, PN) is a universal reference for sensitization of singlet oxygen, O 2 (a 1 D g ), owing to its solubility in a large variety of solvents and its high quantum yield for singlet oxygen production, F D , which is close to 0.95 in most solvents investigated so far ranging from H 2 O to cyclohexane [1 ± 5]. Another important property of PN is its high photostability and its low rate constant for O 2 (a 1 D g ) quenching, e.g., 3.2 Â 10 4 m À1 s À1 in perfluorodecalin [6]. The molecular structure and absorption spectrum are shown in Fig. 1.The triplet-energy value of PN, E T , remains a matter of debate in the literature. In 1991, Oliveros et al. proposed a value of 220 kJ mol À1 for the triplet energy, derived from phosphorescence measurements [1]. It was later shown that their emission originated from a PN photoproduct (vide infra). By laser-induced optoacoustic spectroscopy, Schmidt et al. determined a second value of 186 AE 5 kJ mol À1 in toluene [3]. By the same technique, though a different detector arrangement and data-handling procedures, our group obtained a similar value, 178 AE 8 kJ mol À1 [4]. It is important to point out that both works derived the E T value assuming a triplet quantum yield F T of unity, since laser-induced optoacoustic spectroscopy only affords the value of the product F T E T . However, the value reported by Schmidt et al. is probably close to the correct one, since, later, Schmidt and Bodesheim were able to observe a transient emission at 650 nm, which they identified as PN phosphorescence on the basis of its quenching by oxygen [7]. In fact, the authors demonstrated in their paper that PN is able to photosensitise singlet sigma oxygen, O 2 (b 1 S g ), which lies at 157 kJ mol À1 . This value should, therefore, be regarded as a lower limit for phenalenones triplet energy. The lack of spectral information in their work still leaves open the question of where the triplet-energy level lies.Recently, by emission spectroscopy at 77 K, Okutsu et al. showed that the emission reported by Oliveros et al. was due to a photoproduct formed by abstraction of a solvent

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supporting

confidence: 56%

On the Phosphorescence of 1H-Phenalen-1-one

Flors

Nonell

2001

HCA

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“…On the basis of the LIOAS experiments, we have evaluated the values of some parameters (reported in Table 2). The values of α and K 1 evaluated on the basis of the Marti et al approach [48] are in very good accordance with those estimated on the basis of the Rudzki-Small et al method [49] and describe how much absorbed energy is dissipated by the systems in prompt processes at a time shorter than 0.4 µs; these parameters evidently show that about 40 % to 60 % of excitation is deactivated as a result of thermal relaxation in prompt processes. The sum of K i (i = 1, 2) is less than 1 indicating that other processes in the molecules could also contribute to deactivation [49].…”

Section: Pas and Lioas Experimentssupporting

confidence: 67%

“…The α and K i values (evaluated from Eqs. (3) and (4)) are similar as expected [48,49] and give insight into the fast non-radiative processes occurring in a time range shorter than 0.4 µs (in the resolution time range of our LIOAS device). As seen, more than 50 % of the absorbed energy in samples 1 and 2 is converted promptly into heat.…”

Section: Pas and Lioas Experimentssupporting

confidence: 54%

“…The LIOAS measurements were carried out at 20 • C in a nitrogen atmosphere. The photothermal data were analyzed using two methods: Marti et al and Rudzki et al which are widely described in the literature [48,49]. Marti's approach [48] gives information on a part of the energy changed into heat promptly (expressed by α parameter) in the time range from 0 µs to 0.4 µs (resolution of the LIOAS device) with the use of…”

Section: Materials and Experimental Methodsmentioning

confidence: 99%

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Triplet Thermal Relaxation Study as a Probe of Weak Interdimers of Porphyrin Derivatives

2011

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This article deals with results concerning the study of interacting dyes which are able to create weak interdimers. Two groups of organic systems: phthalocyanines (di-ethanol-amine and di-octane-amine) and pyridyl porphyrins (zinc, copper, and free-base) covalently linked to polyethylene glycol (PEG) in water and organic solvents (dioxane, dimethylsulfoxide) were investigated. Absorption, fluorescence, and photoacoustics were used as experimental methods but particular attention was paid to light-induced optoacoustic spectroscopy to follow the dye's triplet population and triplet thermal relaxation to study intermolecular interactions. It has been shown that even the weak interactions of the organic dyes under study is not detectable by absorption and only slightly by fluorescence is it possible to follow interactions by complementary photothermal methods. The results obtained for selected phthalocyanines and covalent porphyrin-polymer samples evidently show that the lightinduced optoacoustic experiment is a perfect tool in the detection of weakly interacting aggregates.

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“…(AE 0.005). TPP in cyclohexane with F TPP D 0.73 (determined against phenalenone in cyclohexane, with F D 0.91 AE 0.03, as recommended in [41]) was used as a reference. Phenalenone was also used in all four solvents with a value of F D considered identical to that in cyclohexane.…”

Section: Experimental Partmentioning

confidence: 99%

Time-Resolved Thermodynamic Profile upon Photoexcitation of a Nitrospiropyran in Cycloalkanes and of the Corresponding Merocyanine in Aqueous Solutions

Williams

Klihm

Braslavsky

2001

HCA

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Dedicated to Professor AndreÂ M. Braun on the occasion of his 60th birthdayThe photoconversion of 2',3'-dihydro-6-nitro-1',3',3'-trimethylspiro[2H-1-benzopyran-2,2'-indole] (Sp) to its open merocyanine form (Mc) in a series of aerated cycloalkanes (cyclopentane, cyclohexane, and trans-and cis-decalin) and of the protonated merocyanine (McH ) to Sp in aqueous solution were studied by laser-induced optoacoustic spectroscopy (LIOAS). The (11 AE 2) ml mol À1 expansion determined for the ring closure is due to deprotonation of McH plus the reaction of the ejected proton with the monoanion of malonic acid (added to stabilize Mc), an intrinsic expansion and a small electrostriction term. The energy difference between Sp and initial McH is (282 AE 110) kJ mol À1 . An intrinsic contraction of À (47 AE 15) ml mol À1 occurs upon ring opening, forming triplet 3 Mc in the cycloalkanes, whereas no volume change was detected for the 3 Mc to Mc relaxation. Electrostriction decreases the 3 Mc energy, (165 AE 18) kJ mol À1 , to 135 kJ mol À1 . The difference in the values of the ring-opening (Sp to Mc) reaction enthalpy in cycloalkanes as derived from the temperature dependence of the Sp > Mc equilibrium, (29 AE 8) kJ mol À1 , and from the LIOAS data, À (9 AE 25) kJ mol À1 , is due to the formation of Mc-Sp aggregates during steady-state measurements. The Sp-sensitized singlet molecular oxygen, O 2 ( 1 D g ), quantum yield (average F D 0.58 AE 0.03) derived from the near-IR emission of O 2 ( 1 D g ), was taken as a measure of Mc production in the cycloalkanes. These solvents, albeit troublesome in their handling, provide an additional series for the determination of structural volume changes in nonaqueous media, besides the alkanes already used.Introduction. ± The knowledge of the structural volume changes in photochemical reactions [1] is not just of academic interest, but also represents a challenge regarding the possibility of creating materials displaying a reversible volume response towards light [2]. Our major interest in this area is the relationship between the structural volume changes and the type of photoreaction, in order to understand the origin of the molecular structural changes upon excitation of biological photoreceptors [3].A quantitative correlation was found between the reaction structural volume changes determined by laser-induced optoacoustic spectroscopy (LIOAS) [4] and the entropy changes of the reaction for intramolecular photoinduced electron-transfer reactions of Ru II bipyridyl cyano complexes as well as for photoinduced intermolecular electron-transfer reactions between Ru(bpy) 3 2 and the methyl viologen cation, in both cases in aqueous solution containing various monovalent salts. Based on the constancy of the reaction free energy, the changes were attributed to an entropy-enthalpy

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Aromatic ketones as standards for singlet molecular oxygen photosensitization. Time-resolved photoacoustic and near-IR emission studies

Cited by 185 publications

References 47 publications

On the Phosphorescence of 1H-Phenalen-1-one

On the Phosphorescence of 1H-Phenalen-1-one

Triplet Thermal Relaxation Study as a Probe of Weak Interdimers of Porphyrin Derivatives

Time-Resolved Thermodynamic Profile upon Photoexcitation of a Nitrospiropyran in Cycloalkanes and of the Corresponding Merocyanine in Aqueous Solutions

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