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Volumn 121, Issue 40, 1999, Pages 9265-9275

1,3-cyclopentanediyl diradicals: Substituent and temperature dependence of triplet-singlet intersystem crossing

Author keywords

[No Author keywords available]

Indexed keywords

AZO COMPOUND; PENTANE; RADICAL;

EID: 0033552267     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja991362d     Document Type: Article
Times cited : (61)

References (105)
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    • note
    • The bands of the diradicals are broad and the band maxima lie at somewhat shorter wavelengths than the 0-0 transitions of the corresponding monoradicals.
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    • note
    • The mechanism responsible for the spin flip in the 1,3-diradicals 1 and 2 is SOC. The lifetimes of several triplet diradicals 1 and 2, which include the longest- and shortest-lived derivatives and those with heavy atoms, have been measured at various magnetic field strengths up to 5000 G, but no effect was observed within an error of ± 5%. These results preclude any significant contributions from hyperfine coupling, the alternative mechanism for inducing ISC (ref 8).
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    • A correlation between ISC rates and aryl substituent parameters has been previously described for unsymmetrical Norrish-Type-II diradicals in nonpolar solvents, generated photochemically from γ-phenylbutyrophenone derivatives (ref 10a,d). In the polar solvent methanol, the substituents had essentially no influence on the triplet diradical lifetimes.
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    • note
    • The through-bond interaction is due mainly to conjugation through the pseudo-π orbital of the methylene bridge, which affects only the symmetric orbital (Figure 5). The ethylene bridge can be ignored in the orbital-interaction diagram because it influences the symmetric and asymmetric NBMOs in a similar manner.
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    • note
    • AM1 - Δγ|. This procedure gave Δγ = 0.115 ± 0.003 eV for diradicals 1 and 0.114 ± 0.003 eV for diradicals 2.
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    • AB are expected to increase the ionic contributions to the ground-state singlet wave function of nonplanar phenylnitrenes by second-order interactions.
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    • a and ln A, eq 7), then EEC and IKR are synonymous.
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    • AM1 given in Table 1.
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    • note
    • a.
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* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.