Radical ions in photochemistry 10. The photosensitized (electron-transfer) isomerization of 1,2-diphenylcyclopropanes.

Radical cations and triplet states of 1,2-disubstituted cyclopropanes: comparison of potential surfaces

“…11 About 15 years later, Wong and Arnold first postulated radical cations of cis-1 as intermediates in photoreactions sensitized by naphthalene, 1-cyanonaphthalene, and 1,4-dicyanonaphthalene (DCN, 3). 7 Irradiation of 3 in the presence of cis-1 resulted in an A/E multiplet effect near the benzylic signals of cis-1. This limited (and incomplete) result was used to derive a detailed mechanism for the interconversion of cis-and trans-1, involving a localized, ring-closed radical cation, a ring-opened (1,n) radical cation, and a ring-open triplet state.…”

“…Depending on the nature of the sensitizer different types of intermediates have been invoked. [1][2][3][4][5][6][7][8][9] Hammond and co-workers 1 studied the triplet-sensitized isomerization of cis-and trans-1 shortly after this group first encountered cases of energy transfer, termed "non-vertical", in systems where the resulting triplet states had geometries significantly different from those of the parent ground states. 10 They envisioned a ring-opened triplet state for cis-and trans-1.…”

Regioselective Oxidative Ring Opening of Cyclopropyl Silyl Ethers: A Quantum Chemical Study

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Interestingly aliphatic or aromatic substituted cyclopropyl radical cations are-in absence of nucleophiles-structurally and configurationally stable. This has been demonstrated by CIDNP (chemically induced dynamic nuclear polarization) and by other transient spectroscopic experiments based on photoinduced electron transfer (PET).…”

A novel synthesis of α- and β-morpholino enones by electron transfer sensitized photooxidation of 2-morpholinocyclopropanols

“…Photoinduced electron transfer (ET) cis-trans isomerization and oxidative ring opening of cyclopropanes have been the subject of numerous investigations. 1,2 Dioxolane derivatives and, in some cases, hydroperoxides and chalcones are formed by electron transfer photooxidation of aryl substituted cyclopropanes. Several mechanisms involving the superoxide anion radical, a chain reaction with triplet oxygen, or reaction of triplet oxygen with a 1,3-biradical formed by back electron transfer to the cyclopropane cation radical have been discussed.…”

“…The free energy changes (DG) for the one-electron transfer process from the cyclopropane derivatives to photoexcited 1 TPT* or 1 DCA* were estimated by application of the Rehm-Weller equation [eqn. (1)]. 8 The Coulombic term (e 2 /ea) was neglected…”