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The Radical Cation of anti ‐Tricyclooctadiene and Its Rearrangement Products
Author(s) -
Bally Thomas,
Bernhard Stefan,
Matzinger Stephan,
Truttmann Leo,
Zhu Zhendong,
Roulin JeanLuc,
Marcinek Andrzej,
Gebicki Jerzy,
Williams Ffrancon,
Chen GuoFei,
Roth Heinz D.,
Herbertz Torsten
Publication year - 2000
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/(sici)1521-3765(20000303)6:5<849::aid-chem849>3.0.co;2-t
Subject(s) - chemistry , radiolysis , photochemistry , valence (chemistry) , cyclobutadiene , spectroscopy , radical ion , bicyclic molecule , yield (engineering) , quantum yield , ionization , dimer , radical , medicinal chemistry , fluorescence , ion , organic chemistry , molecule , materials science , physics , quantum mechanics , metallurgy
The anti dimer of cyclobutadiene ( anti‐ tricyclo[4.2.0.0 2,5 ]octa‐3,7‐diene, TOD ) is subjected to ionization by γ ‐irradiation in Freon matrices, pulse radiolysis in hydrocarbon matrices, and photoinduced electron transfer in solution. The resulting species are probed by optical and ESR spectroscopy (solid phase) as well as by CIDNP spectroscopy (solution). Thereby it is found that ionization of anti‐ TOD invariably leads to spontaneous decay to two products, that is bicyclo[4.2.0]octa‐2,4,7‐triene ( BOT ) and 1,4‐dihydropentalene (1,4‐ DHP ), whose relative yield strongly depends on the conditions of the experiment. Exploration of the C 8 H 8 . + potential energy surface by the B3LYP/6‐31G* density functional method leads to a mechanistic hypothesis for the observed rearrangements which involves a bifurcation between a pathway leading to the simple valence isomer, BOT . + , and another one leading to an unprecedented other valence isomer, the anti form of the bicyclo[3.3.0]octa‐2,6‐diene‐4,8‐diyl radical cation ( anti ‐ BOD . + ). The latter product undergoes a very facile H‐shift to yield the radical cation of 1,3a‐dihydropentalene (1,3a‐ DHP . + ) which ultimately rearrranges by a further H‐shift to the observed product, 1,4‐ DHP . + .