Behavior of Biradicals Generated from a Norrish Type-I Reaction of 2,2-Diphenylcycloalkanones. Chain-Length Dependence and Magnetic Field Effects

DOI DOI PDF 1 Citations 34 References
  • Itsuko Suzuki
    Department of Chemistry, University of TsukubaTsukuba, Ibaraki 305-8571
  • Ryoko Tanaka
    Department of Chemistry, University of TsukubaTsukuba, Ibaraki 305-8571
  • Akinori Yamaguchi
    Department of Chemistry, University of TsukubaTsukuba, Ibaraki 305-8571
  • Shin-ichiro Maki
    Department of Chemistry, University of TsukubaTsukuba, Ibaraki 305-8571
  • Hiroaki Misawa
    Department of Chemistry, University of TsukubaTsukuba, Ibaraki 305-8571
  • Katsumi Tokumaru
    Department of Chemistry, University of TsukubaTsukuba, Ibaraki 305-8571
  • Ryoichi Nakagaki
    Institute for Molecular ScienceMyodaiji, Okazaki 444-8585
  • Hirochika Sakuragi
    Department of Chemistry, University of TsukubaTsukuba, Ibaraki 305-8571

Description

<jats:title>Abstract</jats:title> <jats:p>The reaction course of acyl-diphenylmethyl biradicals (α-oxo-ω,ω-diphenyl-α,ω-alkanediyl biradicals), O=C↑–(CH2)n−2–C↑Ph2 (3BR-n), generated from the Norrish type-I reaction of 2,2-diphenylcycloalkanones (CK-n) with various ring sizes in methanol, is switched from intramolecular disproportionation (n = 6, 7), giving a diphenylalkenal, to acyl-phenyl recombination (n ≥ 9), affording a cyclophane derivative. The behavior of 3BR-9 derived from CK-9 was studied in detail; the photolysis of CK-9 afforded an open-chain and a cyclic decarbonylation product together with an unsaturated aldehyde and a 4-methylene-2,5-cyclohexadienyl ketone (a pre-cyclophane). The photolysis of this ketone gave the same products that arose from the photolysis of CK-9, presenting the possibility that the decarbonylation products and a part of the aldehyde are formed as secondary products during irradiation.</jats:p> <jats:p>The magnetic field dependence of the lifetimes of 3BR-n (n = 12 and 13) generated from CK-12 and 13, respectively, was measured in methanol by means of a pulsed-laser excitation technique. The rate constants for intersystem crossing showed a maximum at a relatively low field strength, which decreased with increasing the field strength to level off to an asymptotic value at &gt; 1.5 kG. The results show that the role of hyperfine coupling in intersystem crossing is less important in these systems, presumably because of the presence of a carbonyl oxygen and the absence of a hydrogen atom at the radical center.</jats:p>

Journal

Citations (1)*help

See more

References(34)*help

See more

Keywords

Details 詳細情報について

Report a problem

Back to top