220863-25-2Relevant academic research and scientific papers
Behavior of biradicals generated from a Norrish type-I reaction of 2,2- diphenylcycloalkanones. Chain-length dependence and magnetic field effects
Suzuki, Itsuko,Tanaka, Ryoko,Yamaguchi, Akinori,Maki, Shin-Ichiro,Misawa, Hiroaki,Tokumaru, Katsumi,Nakagaki, Ryoichi,Sakuragi, Hirochika
, p. 103 - 113 (2007/10/03)
The reaction course of acyl-diphenylmethyl biradicals (α-oxo-ω, ω- diphenyl-α,ω-alkanediyl biradicals), O=C↑(CH2)η-2-C↑Ph2 (3BR-η), generated from the Norrish type-I reaction of 2,2-diphenylcycloalkanones (CK- η) with various ring sizes in methanol, is switched from intramolecular disproportionation (n = 6, 7), giving a diphenylalkenal, to acylphenyl 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. The magnetic field dependence of the lifetimes of 3BR-η (η = 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 > 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.
