Oxygen metal-free macrocycles

Fig. 16.13 Effect of heat treatment on the kinetic current density for oxygen reduction for some Co, Fe, and metal-free macrocycles (Pc phthalocyanine, OEP octaethylporphyrin and TPP tetraphenylporphyrin). All samples were supported on the same carbon black for the pyrolyzed samples, the highest kinetic current densities are given, achieved after a heat treatment at temperatures ranging from 600 to 800°C. Current values were taken from [41], figure 1...

There are a few examples of 02 oxidations catalyzed by zeolite-encapsulated complexes. Encapsulated CoPc was active in the oxidation of propene to aldehyde, whereas the free complex was inactive.76 A triple catalytic system, Pd(OAc)2, benzoquinone, and a metal macrocycle, was used to oxidize alk-enes with molecular oxygen at room temperature.77,78 Zeolite-encapsulated FePc79-81 and CoSalophen80,82 complexes were used as oxygen-activating catalysts. 

An example of a macrocycle with oxygen donors to support a Ti catalyst for lactide polymerization has been reported by Frediani et a/. " The authors described several titanium chloride complexes bearing calix[4]arene ligands, which act as catalysts for solvent-free lactide polymerization (Figure 18). These complexes acted as dual-site catalysts with two polymer chains growing from one metal center. 

The oxidation of hydroquinone to benzoquinone is regarded as a test reaction for evaluation of the catalytic activity of the metal macrocycle oxygen-activating complexes. The oxygen uptake for the oxidation of hydroquinone catalyzed by the free iron phthalocyanine catalyst is depicted in Fig. 1. The catalytic activity of the free iron phthalocyanine was similar to that observed by Backvall, Hopkins, Grennberg, Mader and Awasthi [5]. 

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