Paramagnetism and Fluorescence of Zinc(II) Tripyrrindione

A Luminescent Radical Based on a Redox-Active Biopyrrin

Ritika Gautam, Steven J. Petritis, Andrei V. Astashkin, Elisa Tomat

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

The ability of bilins and other biopyrrins to form fluorescent zinc complexes has been known for more than a century; however, the exact identity of the emissive species remains uncertain in many cases. Herein, we characterize the hitherto elusive zinc complex of tripyrrin-1,14-dione, an analogue of several orange urinary pigments. As previously observed for its Pd(II), Cu(II), and Ni(II) complexes, tripyrrindione binds Zn(II) as a dianionic radical and forms a paramagnetic complex carrying an unpaired electron on the ligand π-system. This species is stable at room temperature and undergoes quasi-reversible ligand-based redox chemistry. Although the complex is isolated as a coordination dimer in the solid state, optical absorption and electron paramagnetic resonance spectroscopic studies indicate that the monomer is prevalent in a tetrahydrofuran solution. The paramagnetic Zn(II) tripyrrindione complex is brightly fluorescent (λabs = 599 nm, λem = 644 nm, ωF = 0.23 in THF), and its study provides a molecular basis for the observation, made over several decades since the 1930s, of fluorescent behavior of tripyrrindione pigments in the presence of zinc salts. The zinc-bound tripyrrindione radical is thus a new addition to the limited number of stable radicals that are fluorescent at room temperature.

Original languageEnglish (US)
JournalInorganic Chemistry
DOIs
StateAccepted/In press - Jan 1 2018

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Paramagnetism
paramagnetism
Zinc
zinc
Fluorescence
fluorescence
pigments
Pigments
Bile Pigments
Ligands
ligands
Dione
room temperature
tetrahydrofuran
Dimers
Light absorption
Paramagnetic resonance
electron paramagnetic resonance
optical absorption
Salts

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

Cite this

Paramagnetism and Fluorescence of Zinc(II) Tripyrrindione : A Luminescent Radical Based on a Redox-Active Biopyrrin. / Gautam, Ritika; Petritis, Steven J.; Astashkin, Andrei V.; Tomat, Elisa.

In: Inorganic Chemistry, 01.01.2018.

Research output: Contribution to journalArticle

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