The coordination of sterically hindered bases to metalloporphyrins

Robert G. Little*, Brian M. Hoffman, James A. Ibers

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


The coordination of sterically hindered nitrogenous bases to octaethylporphinatocobalt(II), (Co(OEP)), has been studied by epr techniques. It is shown that, despite reports in the literature to the contrary, 2,4,6-trimethylpyridine (s-collidine) and 2,6-dimethylpyridine (2,6-lutidine) do not coordinate to cobalt porphyrins. On the basis of progressive purification of the s-collidine it is shown that previous reports of its coordination result from the presence of impurities in the material. We have also found that 2-methylpyridine (2-picoline) at best coordinates weakly. This work, along with the results of independent structural studies, shows that the trigger mechanism for the allosteric linkage of hemoglobin cannot apply unmodified to cobalt-substituted hemoglobin.

Original languageEnglish (US)
Pages (from-to)207-215
Number of pages9
JournalBioinorganic Chemistry
Issue number3
StatePublished - Apr 1974

ASJC Scopus subject areas

  • Biochemistry


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