Zinc porphyrins photosensitization reactions

Sn02 semiconducting electrodes are photosensitized by zinc porphyrin complexes but the zinc species is consumed in a competing dimerization reaction.1166... 

In related studies of metal ions, Krasnovski learned that the oxides of titanium, zinc, or tungsten possess high photosensitizing activity in redox reactions comparable to the activity of porphyrins and chlorophylls 15). 

There are several excellent photosensitizers one of them is [Ru(bpy)3]2+ [6]. There are two optical isomers in this complex one is A [Ru(bpy)3]2+ and the other is A-[Ru(bpy)3]2 +, as shown in Scheme 1. Thus one can expect to perform the stereoselective electron transfer reaction with A- and A-[Ru(bpy)3]2 +. Unfortunately, however, the racemization of [Ru(bpy)3]2+ is induced photochemically [7]. The reasonable way to suppress the photoracemiza-tion of this complex is to introduce the optically active organic functional group into the transition metal complexes, as will be discussed in Sec. II.B. The other photosensitizer that is useful for the photoinduced electron transfer reaction is the copper(I) complexes with 1,10-phenanthroline and their derivatives [8,9]. Zinc(II) porphyrin is also an excellent photosensitizer for photoinduced electron transfer reaction [10]. In these complexes, molecular chirality does not exist, unlike in [Ru(bpy)3]2 +. Thus one must introduce some chiral functional group into these compounds, to use these complexes as chiral photosensitizers. 

The interplay of different dye molecules present during the electrodeposition reactions of dye-modified ZnO was studied for zinc complexes of tetrasulfonated phthalocyanine (TSPcZn, Figure 4.4a) and tetraphenylporphyrin (TSTPPZn) in which case both dyes (Figure 4.4b) were simultaneously adsorbed to form a hybrid material with ZnO [258]. The typical absorption bands for both dyes were detected. Films of TSPcZn/ZnO consisted of larger particulate domains when compared with TSTPPZn/ZnO or (TSTPPZn + TSPcZn)/ZnO. The presence of the porphyrin stabilized the phthalocyanine on the ZnO since a greater amount of TSPcZn was adsorbed. In the photosensitization of ZnO, TSPcZn and TSTPPZn worked... 

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