The photolysis of acylphosphine oxides IV. investigations with di-n-butyl-2,6-dichlorobenzoyl phosphine oxide and dicyclohexyl-2,4,6-trimethylbenzoyl phosphine oxide
1991; Elsevier BV; Volume: 58; Issue: 2 Linguagem: Inglês
10.1016/1010-6030(91)85050-q
ISSN1873-2666
AutoresTetsuro Majima, Y. Konishi, Artur Böttcher, Keiji Kuwata, M. Kamachi, W. Schnabel,
Tópico(s)Free Radicals and Antioxidants
ResumoDi-n-butyl-2,6-dichlorobenzoyl phosphine oxide (DCBPO) and dicyclohexyl-2,4,6-trimethylbenzoyl phosphine oxide (TMCPO) undergo α scission on irradiation with UV light: φ(α) 0.3 (DCBPO) and φ(α) 0.2 (TMCPO). Picosecond and nanosecond flash photolysis studies, in conjunction with electron spin resonance (ESR) and optical absorption detection, provide evidence for the formation of phosphinoyl radicals R2· O (R n-butyl or cyclohexyl respectively). From the results, it is inferred that excited singlet states deactivate by two routes: α scission and intersystem crossing to the triplet manifold (φ(T) 0.5 (DCBPO) and φ(T) 0.7 (TMCPO)). The triplets deactivate essentially by intramolecular hydrogen abstraction resulting, to a small extent, in the formation of olefins: φ(1-butene) 0.04 (DCBPO) and φ(cyclohexene) 0.03 (TMCPO). Enolization with subsequent reketonization is the main triplet deactivation route in the case of TMCPO.
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