Photoinduced kinetic analysis

Kinetic analysis of photoinduced interfacial charge transfer processes in colloidal semiconductor systems is frequently complex. Indeed, it is diffi-... 

Kinetic analysis gives additional information related to the reactivity of the free radicals obtained during the processes following a photoinduced electron transfer process. A variation in radical reactivity could be caused, for example, by their stability or their reactivity with monomer, as in the case of photoinitiation by 4-carboxybenzophenone-sulfur-containing carboxylic acid of free-radical polymerization [184]. 

Photoamination of la with ammonia and aliphatic primary amines (RNH ) in the presence of m-DCB in MeCN-HjO (9 1) was kinetically analyzed by Yasuda and coworkers. The fluorescence of la was quenched by m-DCB at a diffusion-controlled limit, but not at all by RNHj, and photoamination of la with RNH did not occur in the absence of m-DCB. Therefore, an initiation process for photoamination is the photoinduced electron transfer from la to m-DCB. For kinetic analysis, Scheme 6.37, involving the nucleophilic addition of RNH to the cationic intermediate, was postulated. As the cationic species, the cation radical of la (D ) and the ion pair [D /... 

An analysis of the kinetic characteristics of photochromic quinones showed that the photochromic transformations of methylnaphthoquinone, alkyl- and acyloxyan-thraquinones in solution at room temperature were observed in the microsecond range. As a consequence, these compounds may be of theoretical interest in the future. The photochromic aryloxyanthraquinones are characterized by a lifetime of the photoinduced form that reaches several minutes in solution and several hours in polymer films at room temperature, which makes them acceptable for a number of applications. In this regard, of special interest are photochromic naphthacenequi-... 

In the present ehapter we consider the inter- or intramolecular photoinduced electron transfer phenomenon. We mainly focus on photoinduced electron transfer processes that lead to the photoinitiation of polymerization, and on processes initiated by photoredueed or photooxidized excited states. We concentrate especially on a description of the kinetic schemes, a description of the reactions that follow the primary proeess of eleetron transfer, and the characteristics of intermediates formed after electron transfer. Understanding the complexity of the processes of photo-initiated polymerization requires a thorough analysis of the examples illustrating the meehanistie aspects of the formation of free radicals with the ability to start polymerization. 

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