Photolysis mechanism electron production

After a substitution step, which occurs by an associative mechanism, the products disproportionate by an electron-transfer process to yield Fe(II) and Fe(0) products.Stepwise carbonyl substitution frcxn Fe (CO) (. by (CF ) P in sunlight proceeds as far as (Fe(CO)2 P(CF )3)3]. High yield syntheses of [Fe(C0)2 (S2CNMe2)2l [Fe (S2CNMe2) 3] from Fe2(C0)g or Fe3(CO) 2 have been reported.A new form of (Ru(CO) ], prepared by photolysis of concentrated solutions of RU3(CO)under carbon monoxide, reacts with phosphines to form [Ru(C0) 1 species (n = 1,2 ... 

Characteristically, the mechanisms formulated for azide decompositions involve [693,717] exciton formation and/or the participation of mobile electrons, positive holes and interstitial ions. Information concerning the energy requirements for the production, mobility and other relevant properties of these lattice imperfections can often be obtained from spectral data and electrical measurements. The interpretation of decomposition kinetics has often been profitably considered with reference to rates of photolysis. Accordingly, proposed reaction mechanisms have included consideration of trapping, transportation and interactions between possible energetic participants, and the steps involved can be characterized in greater detail than has been found possible in the decompositions of most other types of solids. 

It has been proposed that there may be a single-electron-transfer mechanism for the Mukaiyama reaction.62 63 For example, photolysis of benzaldehyde dimethylacetal and 1-trimethylsilyloxycyclohexene in the presence of a typical photoelectron acceptor, tri-phenylpyrylium cation, gives an excellent yield of the addition product. 

A final example of an n-n reaction will be cited to illustrate still another type of reactivity of the n—r excited state. This is the photolysis of frans-dypnorie oxide (XXXII) to afford as the major product the unsaturated alcohol XXXIV (22). In this case the mechanism, as outlined in Chart VI, involves hydrogen abstraction from the methyl group by the m-situated excited carbonyl group the odd electron containing... 

Ito T, Shinohara H, Hatta H, Nishimoto S-l (1999) Radiation-induced and photosensitized splitting of C5-C5 -linked dihydrothymine dimers product and laser flash photolysis studies on the oxidative splitting mechanism. J Phys Chem A 103 8413-8420 ItoT, Shinohara H, Hatta H, Fujita S-l, Nishimoto S-l (2000) Radiation-induced and photosensitized splitting of C5-C5 -linked dihydrothymine dimers. 2. Conformational effects on the reductive splitting mechanism. J Phys Chem A 104 2886-2893 ItoT, Shinohara H, Hatta H, Nishimoto S-l (2002) Stereoisomeric C5-C5 -linked dehydrothymine dimers produced by radiolytic one-electron reduction of thymine derivatives in anoxic solution structural characteristics in reference to cyclobutane photodimers. J Org Chem 64 5100-5108 Jagannadham V, Steenken S (1984) One-electron reduction of nitrobenzenes by a-hydroxyalkyl radicals via addition/elimination. An example of an organic inner-sphere electron-transfer reaction. J Am Chem Soc 106 6542-6551... 

This discussion of acetone is closed without going into detail concerning the various radical reactions at room temperature. Many of them must occur and the overall mechanism is believed to be well understood. Any mechanism which necessarily involves so many steps probably never could be proved to be correct in its entirety. The points we wish to emphasize are mainly that dissociation can occur in more than one way, sometimes from one electronic state and sometimes from another. The relative importances of the various steps are difficult to determine but studies of emission decay, of intermediate concentrations by flash photolysis, and of the yields of all of the products by modern methods such as chromatography and nuclear magnetic resonance permit reasonable mechanisms to be proposed. 

Time resolved laser flash photolysis and electric spin resonance (ESR) spectroscopic investigations were used to get further insight to the reaction mechanism. Both methods demonstrate the formation of do using PET conditions [175,214,215], Upon addition of H donors the signal of do is quenched [214], The oxidation of do is followed by H abstraction from the H donor as shown in Scheme 9. Nucleophilic addition can be excluded because no alkoxyfullerenes were detected at all [173], After reduction of H-do, e.g., by electron transfer from the reduced sensitizer molecule H-do might recombine with R" to the final product. Decay experiments of do by the addition of alcohols support the proposed mechanism of H abstraction as a first step. The involved radical products reveal do as an electrophilic radical. 

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