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Photochemistry of 1,1-diazenes. Direct and sensitized photolyses of N-(2,2,5,5-tetramethylpyrrolidyl)nitrene, dl-N-(2,5-diethyl-2,5-dimethylpyrrolidyl)nitrene, and N-(2,2,6,6-tetramethylpiperidyl)nitrene

Schultz, Peter G. and Dervan, Peter B. (1982) Photochemistry of 1,1-diazenes. Direct and sensitized photolyses of N-(2,2,5,5-tetramethylpyrrolidyl)nitrene, dl-N-(2,5-diethyl-2,5-dimethylpyrrolidyl)nitrene, and N-(2,2,6,6-tetramethylpiperidyl)nitrene. Journal of the American Chemical Society, 104 (24). pp. 6660-6668. ISSN 0002-7863. http://resolver.caltech.edu/CaltechAUTHORS:20160511-153909487

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Abstract

The photochemistry of the l, 1-diazenes N-(2,2,5,5-tetramethylpyrrolidyl)nitrene (1), d/-N-(2,5-diethyl-2,5-dimethylpyrrolidyl) nitrene (2), and N-(2,2,6,6-tetramethylpiperidyl)nitrene (3) is reported. The fluorescence spectrum of 1,1-diazene 1 has a 0-0 band at 607 nm, which is the maximum. The spacing between the peaks at 607 and 672 nm corresponds to the N=N stretch of S0 consistent with the 1638-cm^(-1) stretch obtained from the infrared spectrum of 1. The fluorescence quantum yields are Φ_F = 2 X 10^(-3) (MTHF, -78 °C), 7 x 10^(-3) (MTHF, -196 °C), and l X 10^(-3) (EPA, -196 °C). The fluorescence lifetime of 1 is T_F = 2.3 x 10^(-8) s (CFCl_3, -196 °C). Direct irradiation of 1 (466-610 nm, -78 °C) affords four hydrocarbon products, 54% 4, 44% 5, 2% 6 + 7 and tetrazene 8. Triplet-sensitized photodecomposition afforded 74% 4, 24% 5, 2% 6 + 7 and tetrazene 8. An approximate quantum yield for decomposition on direct irradiation is Φ_D = 1.1 x 10^(-2). From S_1, kN_2 is >3.4 X 10^5 s^(-1), and reaction of S_0 with S_1. k_(DIM) is >4.2 x 10^7 L mo1^(-1) s^(-1) (at -78 °C). The spectrum of 1,1-diazene 2 reveals a structured absorption with λmax 507 nm and a 0-0 band at 568 nm (ε = 20). The vibrational spacing is 1270 cm^(-1). The fluorescence spectrum of 1,1-diazene 2 has a 0-0 band at 620 nm, which is the maximum. The spacing between the maxima at 620 and 690 nm corresponds to the N=N stretch of S_0 consistent with the 1630-cm^(-1) stretch obtained for the infrared spectrum of 2. The fluorescence quantum yield Φ_F = 9 X 10^(-3) (MTHF, -196 °C). The direct and sensitized irradiation of 2 in the visible affords hydrocarbon products 14-19 and tetrazene 20 in different ratios. The retention of stereochemistry in the cyclobutane products in the direct and sensitized photodecomposition was 98 and 68%, respectively, similar to the spin correlation effect seen in corresponding 1,2-diazene isomer. This indicates that for 2 (and by extension 1) k_(isc) << k_(N2), consistent with a large S_1-T_1 gap in 1,1-diazenes. For 1,1-diazene 3 the fluorescence spectrum has a single maximum at 684 nm. The fluorescence quantum yield Φ_F = 4 X 10^(-4) (MTHF, -196 °C). The estimated fluorescence lifetime is T_F = 4 X 10^(-9)s. Direct irradiation of 3 in the visible at -78 °C afforded three hydrocarbon products, 29% 21, 3% 22, 68% 23 and tetrazene 25.


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http://dx.doi.org/10.1021/ja00388a031DOIArticle
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Additional Information:© 1982 American Chemical Society. Received February 26, 1982. We are grateful to the National Science Foundation for generous support. Contribution No. 6594 from the Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125.
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Division of Chemistry and Chemical Engineering6594
Record Number:CaltechAUTHORS:20160511-153909487
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20160511-153909487
Official Citation:Photochemistry of 1,1-diazenes. Direct and sensitized photolyses of N-(2,2,5,5-tetramethylpyrrolidyl)nitrene, dl-N-(2,5-diethyl-2,5-dimethylpyrrolidyl)nitrene, and N-(2,2,6,6-tetramethylpiperidyl)nitrene Peter G. Schultz and Peter B. Dervan Journal of the American Chemical Society 1982 104 (24), 6660-6668 DOI: 10.1021/ja00388a031
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ID Code:67030
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Deposited By: Victoria Brennan
Deposited On:19 May 2016 21:25
Last Modified:19 May 2016 21:25

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