Tropolonato complexes

The antimicrobial activity of Bi(III) against the bacterium Helicobacter pylori appears to be important for its antiulcer activity (458). This organism may be involved in other conditions such as cancer. The mechanism of antimicrobial activity may involve interference in Fe(III) or Zn(II) biochemical pathways. Bismuth(III) is not known to bind to DNA. Attempts to synthesize new Bi(III) complexes with activity against H. pylori include those of Keppler et al. (459), who have found that Bi(III)-tropolonato complexes such as 98 are highly active... 

As might be expected for chelating 0,0 donor ligands it is the intermediate trivalent state of osmium which is stabilized by /J-diketonates (as is the case for catechols, p. 597, and tropolonato complexes, p. 597). In the presence of rc-acceptor chelates such as bipy, phen and terpy the II state is favoured, while with halides the IV state is preferred. The apparent absence of an osmyl complex, e.g. 0s02acac2, is surprising. 

Various tropolonato complexes of protoactinium have been synthezised and characteriz-ed 2 . However, no thermochemical data (including emf and hence AG) are seemingly available, even though there are simple redox reactions interrelating these species. 

Some of the isolated simple tropolonato complexes grouped by their charge, metal oxidation state and stoichiometry are listed in Tables 1-3. 

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