Mercury metalloporphyrins

Speciation studies have been focused on relatively few elements, mainly aluminum, antimony, arsenic, chromium, lead, mercury, selenium, and tin. The primary species of these elements studied with ICP-MS detection are presented in Table 3 and they include different oxidation states, alkylated metal and/or metalloid compounds, selenoaminoacids, and selenopeptides. In addition, applications in studies of the pharmacokinetics of metal-based drugs (Pt, V, Au), metalloporphyrins (Ni, V, Fe, etc.), heavy metals in phytochelatins (Cd, Cu, Zn, Hg, etc.) and in humic substances should be mentioned. 

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 ... 

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. 

The change in absorbance at 564 nm (absorption maximum of Hg2(tpps)2-) is smaller than for the second-step reaction. This finding points to one mercury(II) ion remaining in the intermediate. The increase in absorbance at 551 nm during the first-step reaction suggests the coordination of zinc(II) to form the hetrodinuclear metalloporphyrin. 

Neither of these metalloporphyrins has been found in crude oil, however. Mercury forms porphyrin complexes with mesoporphyrin but the complexes are decomposed by water. The extraction of crude oil C-1 with distilled water removed insignificant amounts of Hg, thus indicating that Hg is not present in the oil as a porphyrin complex. Arsenic also shows a higher concentration in the low-molecular-weight fraction than in the 1000-4000 fraction. This is consistent with the previous conclusion that part of the As in crude oil is present in low-molecular-weight compounds such as alkyl or aryl arsines. 

Diethvldithiocarbamato Mercury (II). The incorporation of metal-ligand complexes within polymeric membranes for the development of new anion sensors is not limited to the use of metalloporphyrins. Indeed, recent studies with the Hg (II) complex of diethyldithiocarbamate (Hg(DDC)2) have yielded a new membrane electrode with relatively high... 

The electrochemistry of metalloporphyrins at the start of the 1960s involved, in large part, measurements of standard redox potentials for naturally occurring complexes in aqueous buffered media [14], The choice of an aqueous solvent was often dictated by the biological relevance of the compounds available for study, while the choice of the measurement technique (potentiome-try or polarography at a dropping mercury electrode) was necessitated by the type of available electrochemical instrumentation, virtually all of which was homemade and... 

The electrochemistry of zinc, cadmium, and mercury porphyrins is uncomphcated and only macrocycle-centered electrode reactions are observed in nonaqueous solvents [7, 21]. Metalloporphyrins with this type of metal ion have been studied in some detail, but the best characterization of the electrochemical reaction products has been obtained with zinc porphyrins... 

The metalloporphyrin system can also mediate in the oxidation of mercury to ion. 

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