Super-charged porphyrazines: Synthesis and physical properties of octacationic tetraazaporphyrins

Máirín E. Anderson*, Anthony G.M. Barrett, Brian M. Hoffman

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

45 Scopus citations

Abstract

We report the synthesis of octacationic macrocycles based on the porphyrazine (tetraazaporphyrin) core. The first stage is the synthesis of Mg(II) 2,3,7,8,12,13,17,18-octakis(4-pyridyl)porphyrazine, [Mgpz(pyr)8], and the parent [H2pz(pyr)8]. Both compounds are freely soluble in aqueous acid due to protonation of the pyridyl groups but with concomitant loss of Mg2+ by the latter. Methylation of [H2pz(pyr)8] gives the octacation, 2,3,7,8,12,13,17,18-octakis(N-methyl-4-pyridiniumyl)porphyrazine, [H2pz(Me-pyr)8]8+, which is freely soluble in water as the chloride salt. The peripheral charges greatly lower the pKa values of the pyrrole protons of [H2pz(Me-pyr)8]8+ in aqueous solution. Global fitting of optical pH titration curves gives pKa values for the first and second deprotonations of 6.3 and 8.8 in 2.0 M NaCl and 4.1 and 5.6 at 0.1 M NaCl. The analysis further gives the UV - visible spectra of the [H2pz(Me-pyr)8]8+, [Hpz(Me-pyr)8]7+, and [pz(Me-pyr)8]6+ species. The free-base compound [H2pz(Me-pyr)8]8+ rapidly incorporates a variety of metal ions (Ba(II), Cd(II), Co(II), Cu(II), Mn(III), Ni(II), Pd(II), and Zn(II)) to form [Mpz(Me-pyr)8]8+. We present the complete synthesis and characterization of the [Nipz(Me-pyr)8]8+ and [Cupz(Me-pyr)8]8+ derivatives.

Original languageEnglish (US)
Pages (from-to)6143-6151
Number of pages9
JournalInorganic chemistry
Volume38
Issue number26
DOIs
StatePublished - 1999

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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