Heterodinuclear metalloporphyrin

The present paper describes the mechanism of porphyrin metalation in the presence of catalyst with special emphasis on the reaction intermediates including heterodinuclear metalloporphyrin, mixed-valence metalloporphyrin, and sandwich-metalloporphyrin with 18-crown-6. 

The homodinuclear mercury(ll) porphyrin dissociates to a 1 1 mercury(ll) porphyrin which reacts with zinc(ll) or copper(Il) to form the corresponding heterodinuclear metalloporphyrin. The final step is the dissociation of mercury(ll) from the corresponding heterodinuclear metalloporphyrin. Interestingly ki, ks, and k4 values for zinc(II) are almost the same as for copper(II), while the rate k-2lk. for copperfll) is about 80 times as high as for zinc(II). These findings are consistent with the proposed reaction mechanism. The reaction paths for ki, k%, and k involve only the dissociation of mercury(II) and thus they are independent of the nature of incoming metal ions. On the other hand the reaction path for k2 depends on characteristics of incoming metal ions, because it involves coordination of these metal ions to form heterodinuclear metalloporphyrins. 

Heterodinuclear metalloponhyrin, postulated in the metalloporphyrin fomiation catalyzed by mercury(II) or cadmium(Il)10 12 was detected kinetically in the reaction of zincfll) or copper(ll) with homodinuclear mercury(II) porphyrin complex of Hg2tpps2 - The following biphasic reaction was observed ... 

Recently, ESR spectroscopy has been used to study srlver(II) porphyrins. Aggregation in metalloporphyrins, in tetrachloroethane (TCE) and 2-methyltetrahydrofuran (MTHF) has been studied at 77 K. In MTHF a well-resolved signal due to monomeric Ag mesoporphyrm(IX) dimethyl ester (MPD) was observed. In TCE, however, additional signals on the monomer spectrum and a g = 4 signal with a partially resolved structure were found when the gain was increased. The g = 4 signal was ascribed to the AM = 2 transition of the dimeric [Ag"MPD]2. In an equimolar molar mixture of Cu MPD and Ag MPD a heterodinuclear complex was formed. 

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