Fischer photochemical

F. Momicchioli, I. Baraldi and E. Fischer,/. Photochem. Photobiol. A Chem. 48,... 

In attempts to understand the photochemical reactions of Fischer carbene complexes, several matrix isolation and flash photolysis studies have been conducted using both Cr and W (but not Mo) complexes [5-11]. Although the complexes studied and conditions used varied, several general conclusions were drawn ... 

Diacyl peroxides undergo thermal and photochemical decomposition to give radical intermediates (for a recent review, see Hiatt, 1971). Mechanistically the reactions are well understood as a result of the many investigations of products and kinetics of thermal decomposition (reviewed by DeTar, 1967 Cubbon, 1970). Not surprisingly, therefore, one of the earliest reports of CIDNP concerned the thermal decomposition of benzoyl peroxide (Bargon et al., 1967 Bargon and Fischer, 1967) and peroxide decompositions have been used more widely than any other class of reaction in testing theories of the phenomenon. 

The role of a second liquid phase in photochemical sulphoxidation of paraffins with SO2 and O2 mixtures may also be cited, where water is used to extract sulphonic acid to prevent formation of di- and poly-sulphonic acids (Fischer, 1978). 

Acknowledgement. It is great pleasure to express my sincere thanks to my colleagues, past and present members of the Staff of the Photochemical Laboratory for the fine collaboration I enjoyed in these and other topics, in particular to my old-time friend Professor E. Fischer and to my colleagues and associates Drs. D. Gegiou, A. Bromberg, R. Korenstein, Sh. Sharafi-Ozeri,... 

In an attempt to probe further into the complex photochemical system involved, the isomerization of stilbenes adsorbed on silica gel was examined.9 It was observed that the time required for establishment of the photostationary state was significantly increased (by a factor of 3) and that the composition of the photostationary state changed from 93y cis isomer in cyclohexane solution to 60% cis isomer in the silica gel matrix. Though not definitive, this evidence supports Fischer s triplet mechanism, 53 as we have previously reported.9... 

Among the first 18-electron (18e) Fischer-type metal carbene complexes to be used as part of an olefin metathesis catalyst system were W[=C(OMe)Et](CO)5 with BU4NCI (for pent-l-ene)79, and W[=C(OEt)Bu](CO)5 with TiCLt (for cyclopentene)80. These complexes may also be activated thermally, e.g. for the polymerization of alkynes81, or photochemically, e.g. for the ROMP of cycloocta-1,5-diene82. The essential requirement is that a vacancy be created at the metal centre to allow the substrate to enter the coordination sphere. Occasionally the substrate may itself be able to displace one of the CO ligands. 

Laroff GP, Fischer H (1973) The enol of acetone during photochemical reaction of 3-hydroxy-4-methyl-2-butanone and of acetone. Helv Chim Acta 56 2011 -2020 Lehni M, Fischer H (1983) Effects of diffusion on the self-termination kinetics of isopropylol radicals in solution. Int J Chem Kinet 15 733-757... 

Fischer, M.A. and Black, H.S., Modification of membrane composition, eicosanoid metabolism, and immunoresponsiveness by dietary omega-3 and omega-6 fatty acid sources, modulators of ultraviolet-carcinogenesis, Photochem. Photobiol., 54, 381, 1991. 

Bosch M, Fischer C, Cai C, Liakatas I, Jager M, Bosshard Ch, Gunter P (1999) Photochemical stability of highly nonlinear optical chromophores for electro-optic applications. In Organic thin films for photonics applications. Optical Society of America, Washington DC, p 75... 

Scheme 5.18 Photochemical transformations of Fischer-type chromium carbene complexes.

Bucking M, Dickson EFG, Farahani M, Fischer F, Holmes D, Jori G, et al. Quantification of the selective retention of palladium octabutoxynaphthalocyanine, a potential photo-thermal drug, in mouse tissues. J Photochem Photobiol B Biol 2000 58 87-93. 

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