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Quantum yields of photosensitized production of singlet oxygen.,
Quantum yields of photosensitized production of singlet oxygen, from porphyrins and related species.,
Quantum yields of photosensitized production of singlet oxygen, from drugs, dyes, polymers, etc.,

Quantum Yields for the Photosensitized Formation of the Lowest Electronically Excited Singlet State of Molecular Oxygen in Solution

Francis Wilkinson
Department of Chemistry,
University of Technology, Loughborough,
Leicestershire, LE11 3TU, UK
and
W. Phillip Helman and Alberta B. Ross
Radiation Chemistry Data Center,
Radiation Laboratory,
University of Notre Dame,
Notre Dame, IN 46556

J. Phys. Chem. Ref. Data 22: 113-262 (1993)


Quenching of excited singlet and triplet states of many substances by ground state molecular oxygen produces singlet oxygen, the lowest electronically excited singlet state of molecular oxygen, O2(1DELTAg). The fractions of singlet and triplet states quenched which produce singlet oxygen and the quantum yields of formation of singlet oxygen in fluid solutions have been critically compiled. Methods for determining yield parameters have been reviewed. Data have been compiled from the literature through 1991. Photosensitizers such as aromatic hydrocarbons, aromatic ketones and thiones, quinones, coumarins, fluoresceins, transition metal complexes, and heterocyclics are included in Table 1. Porphyrins and phthalocyanines are included in Table 2. Other materials which have been investigated for singlet oxygen production, such as dyes and drugs, are collected in Table 3 along with heterogeneous systems such as polymer-bound photosensitizers.

Data Tables


1. Quantum yields of photosensitized production of singlet oxygen. 317 entries
2. Quantum yields of photosensitized production of singlet oxygen, from porphyrins and related species. 229 entries
3. Quantum yields of photosensitized production of singlet oxygen, from drugs, dyes, polymers, etc. 208 entries
4. Selected reference values for phiDELTA and fDELTAT

Contents of Tables 1-3

Quantitative data for photosensitized singlet oxygen production are given in three tables containing 1,600 separate entries for 750 chemical species. The main table (Table 1) contains data for 316 compounds which convert molecular oxygen into singlet oxygen via their excited triplet and/or singlet states with varying efficiencies. Porphyrins and related species have been collected into Table 2. An additional table (Table 3) has been provided for dyes, polymers and some other species which, although they are ill-defined, are of interest for various biomedical, environmental, and industrial applications. The arrangement of the tables is alphabetic by the chemical names of the photosensitizers. Common names have been used for a few compounds, otherwise, systematic names have been entered. Inverted names have been used in most cases so that substituted acetophenones, anthracenes, fluoresceins, etc. are grouped. Data for each photosensitizer are grouped by solvent and listed in reverse chronological order.

Oxygen concentrations are given when they have been reported, or else 'air' or 'O2' to indicate that the solution was air- or oxygen-saturated.

The Solvent line gives the solvent or mixture of solvents with the proportions (volume:volume) and the pH or pD, if reported. Heterogeneous systems are identified, e.g. as micellar (mic), and the surfactant present is given in the Comments.

Values in the quantum yield line (phiDelta) may be tagged with a superscript T to denote quantum yields representing 100% quenching of T1, or ST representing 100% quenching of both S1 and T1. Most of the quantum yields tagged T are for type T sensitizers which have the proportion of S1 quenched by O2 = 0. However limiting yields of singlet oxygen production from T1 have been obtained in other cases by adjusting oxygen concentrations or by correcting for oxygen quenching of the sensitizer singlet states. Evaluation of the proportion of S1 quenched by O2 and the proportion of T1 quenched by O2 has enabled the determination of phiDeltaT and phiDeltaST.

The fraction of T1 yielding singlet oxygen (fDeltaT) is known through phiT(S) when the proportion of T1 quenched by O2 has been measured for type T sensitizers.

Some details of the determination are given in the Comments line. Abbreviations and symbols are listed for chemical species which have been used as reference sensitizer (S'), triplet donor (TD), triplet acceptor (TA), actinometer (AC), and acceptor of singlet oxygen (A). Values for phiDelta and fDeltaT of the reference sensitizer which have been used to obtain the tabulated data are given. Quantum yields and extinction coefficients for the triplet states have been included when their values have been used for obtaining the singlet oxygen yields. Temperature is included in the Comment if it has been reported to be outside the range of about 20-25o C.

Often fDeltaT or phiDelta have been determined relative to the known value for another sensitizer so that the values depend on the standard values chosen for the reference sensitizer. It would be desirable to obtain the best possible values for fDeltaT and phiDelta for the reference sensitizers based on the measured values which have been reported. Unfortunately fDeltaT for each sensitizer depends on the solvent (on pH etc.) and so it is necessary to treat the values for each solvent separately. For sensitizers other than type T, values of phiDelta depend on the concentration of oxygen. For those classes of sensitizer (e.g. type ST and TC) we must therefore treat separately the values for each solvent saturated with air and oxygen, respectively. Values reported as ratios with respect to the value for a reference sensitizer, are often of greater accuracy than values obtained by methods used to measure fDeltaT and phiDelta which do not give a ratio but may depend on other photophysical parameters. It has to be recognised that no accurate set of phiT values, however, is available.

In some cases only ratios of phiDelta have been reported. We have converted reported ratios into absolute values by using the averages from Table A.2.1 when available, or using apparently accepted standards from the literature, or using a standard value inferred from other reported data. Footnote b in the tables identifies reference values used in this work to calculate absolute values from reported ratios.

Abbreviations and Symbols.

Full Introduction.

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