Spectral Sensitization of Dediazoniation by the 2-electron-transfer system meso-tetraphenylporphinato-dichlorostannate(IV)/10-methyl-9-Phenyl-9.10-dihydro-acridine
✍ Scribed by Prof. Dr. H. G. O. Becker; Dipl.-Chem. Katrin Grossmann
- Book ID
- 105353669
- Publisher
- John Wiley and Sons
- Year
- 1990
- Tongue
- English
- Weight
- 547 KB
- Volume
- 332
- Category
- Article
- ISSN
- 1615-4150
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✦ Synopsis
Abstract
The photoreduction of meso‐tetraphenylporphinatodichlorostannate(IV) (SnCl~2~TPP) by 9‐phenyl‐10‐methyl‐9,10‐dihydro‐acridine (ACH) in 1,2‐dichloroethane/acetonitrile 1:1 (v/v) under argon proceeds only with a low quantum yield in spite of the fact that ACH is in other cases an excellent 2‐electron donor. The reason may be the formation of a triplet exciplex which opens a new deactivation channel. Evidence for such an exciplex is given by means of the WARE treatment of flash‐photolytic experiments and quantum yields of dediazoniation, K~eq~ ≈ 650 M^−1^ and τ~exc~ = 46 μs.
The exciplex reacts fast with p‐N,N‐dimethylamino‐benzenediazonium tetrafluoroborate (k~r~ = 4.1 × 10^8^ M^−1^ s^−1^) under electron transfer leading to dediazoniation. At high ACH concentrations (8 × 10^−3^ M) the dediazoniation gives even at very low diazonium salt concentrations (≈ 4 × 10^−5^ M) quantum yields as high as 1.95 (0.37 stemming from sensitization by the SnCl~2~ complex of tetraphenylchlorine present as an impurity of SnCl~2~TPP. SnCl~2~TPP) remains unchanged during the sensitization reaction, i.e. the process is fully photocatalytic.