Paramagnetism and Fluorescence of Zinc(II) Tripyrrindione: A Luminescent Radical Based on a Redox-Active Biopyrrin
| Autor: | Andrei V. Astashkin, Ritika Gautam, Steven J. Petritis, Elisa Tomat |
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| Rok vydání: | 2018 |
| Předmět: |
Models
Molecular Free Radicals Pyridones Dimer Radical Dipyrone chemistry.chemical_element 02 engineering and technology Zinc 010402 general chemistry Photochemistry Crystallography X-Ray Ligands 01 natural sciences Redox Fluorescence law.invention Inorganic Chemistry chemistry.chemical_compound law Coordination Complexes Physical and Theoretical Chemistry Electron paramagnetic resonance Molecular Structure Ligand 021001 nanoscience & nanotechnology 0104 chemical sciences chemistry Unpaired electron 0210 nano-technology Oxidation-Reduction |
| Zdroj: | Inorganic chemistry. 57(24) |
| ISSN: | 1520-510X |
| Popis: | 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, ΦF = 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. |
| Databáze: | OpenAIRE |
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