96555-79-2Relevant academic research and scientific papers
Phototransformations of Bridgehead-Substituted Dibenzobarrelenes Steady-State and Laser Flash Photolysis Studies
Pratapan, S.,Ashok, K.,Cyr, D. R.,Das, P. K.,George, M. V.
, p. 5512 - 5517 (2007/10/02)
The photochemistry of bridgehead-substituted dibenzobarrelene derivatives 1a-f has been investigated by steady-state photolysis, product analysis, and laser flash photolysis. 4b- or 8b-substituted dibenzosemibullvalenes or products derived thereof were formed in the course of irradiation of 9-(hydroxymethyl)-, 9-ethyl-, and 9-benzyl-substituted dibenzobarrelenes. 9-Cyclopentyl-substituted dibenzobarrelene upon irradiation gave the corresponding 4b-substituted dibenzosemibullvalene and dibenzocyclooctatetraene, whereas from the photolyzates of 9-isopropyl- and 9-cyclohexyl-substituted dibenzobarrelenes the corresponding dibenzocyclooctatetraenes were obtained as the only isolable products.The 337.1-nm laser flash photolysis of 1a-f in benzene results in the formation of their triplets in high yields (ΦT = 0.7-1.0).The triplets possess short lifetimes (0.03-2.2 μs) and are readily quenchable by oxygen, di-tert-butyl nitroxide, and ferrocene (kgT = (0.2-8) X 109 M-1s-1).In spite of high ΦT's, some of the dibenzobarrelene substrates are reluctant to undergo the barrelene-semibullvalene rearrangement under steady-state irradiation; this appears to be related to the unusually short lifetimes of their triplets; that is, decay modes other than those eventually leading to dibenzosemibullvalenes are available to these triplets.
Steady-State and Laser Flash Photolysis Studies of Bridgehead-Substituted Dibenzobarrelenes.
Murty, Bulusu A. R. C.,Pratapan, Sreedharan,Kumar, Challa V.,Das, Paritosh K.,George, Manapurathu V.
, p. 2533 - 2538 (2007/10/02)
The photochemistry of bridgehead-substituted dibenzobarrelenes 1a-h (Scheme I) has been investigated by steady-state photolysis, product analysis, and time-resolved laser flash photolysis. 4b-Substituted dibenzosemibullvalenes 8b,c,f,g are formed as major photoproducts from dibenzobarrelenes 1b,c,f,g,bearing acetoxy, formyl, ethyl, and methoxy 9 -bridgehead substituents, whereas 8b-substituted dibenzosemibullvalenes (or products derived from them) (7 and 6e) are formed from 9-hydroxy- and 9-cyano-substituted dibenzobarrelenes 1a,e.Laser flash photolysis gives rise totransient phenomena attributable to the triplets of dibenzobarrelenes (ΦT = 0.2-0.7 in benzene).These are characterized by broad and diffuse absorption spectra, short lifetimes (0.07-11 μs), and varying degrees of quenchability by azulene, ferrocene, β-carotene, and p-methoxyphenol.The rate constants for triplet quenching by the latter quenchers as well as oxygen and di-tert-butylnitroxy radicals are presented.
