Effect of mixed-ligand complex formation on the ionization of the pyrrole hydrogens of histamine and histidine

Imre Sóvágó, Tamás Kiss, Arthur Gergely

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Equilibrium studies have been carried out by pH titrimetry to determine the stability constants of the parent complexes of CuII NiII and ZnII with histamine and histidine, and of the mixed-ligand complexes of these with, glycine, ethylenediamine, 4,5-dihydroxybenzene-1,3- disulphonate, and 2,2′-bipyridyl. From titrations in an alkaline medium it is concluded that nickel(II) and zinc(II) ions do not affect the ionization of the pyrrole hydrogen significantly compared to the free ligand, but Cu II decreases the relevant pKvalues in the parent complexes by about three orders of magnitude. As a consequence of charge-transfer processes, the deprotonation can also be in-fluenced significantly by the formation of mixed-ligand complexes.

Original languageEnglish
Pages (from-to)964-968
Number of pages5
JournalJournal of the Chemical Society, Dalton Transactions
Issue number8
Publication statusPublished - Dec 1 1978


ASJC Scopus subject areas

  • Chemistry(all)

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