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Dithizone and its oxidation products: a DFT, spectroscopic, and X-ray structural study
Karel G von Eschwege1, Jeanet Conradie, Annemarie Kuhn
1Department of Chemistry, PO Box 339, University of the Free State, Bloemfontein 9300, South Africa. veschwkg@ufs.ac.za
The Journal of Physical Chemistry. A
|November 23, 2011
Summary
Air oxidation of ortho-fluorodithizone yielded the first X-ray structure of a dithizone disulfide. Computational methods confirmed reaction pathways and explained dithizone
Area of Science:
- Chemical Crystallography
- Computational Chemistry
- Organic Chemistry
Background:
- Dithizone (H2Dz) undergoes oxidation, with its reaction pathway and final product structure previously unconfirmed by X-ray crystallography.
- Understanding the oxidation mechanism and tautomeric forms of dithizone is crucial for its chemical applications.
Purpose of the Study:
- To elucidate the complete oxidation pathway of dithizone, including the characterization of its disulfide intermediate.
- To computationally validate the experimentally observed structures and reaction mechanisms using various theoretical methods.
- To explain the observed solvatochromic and concentratochromic properties of dithizone and its derivatives.
Main Methods:
- Air oxidation of ortho-fluorodithizone to synthesize the dithizone disulfide.
- X-ray crystallography for structural determination of the disulfide intermediate.
- Density Functional Theory (DFT) calculations (OLYP, PW91, B3LYP) and MP2 calculations for electronic structure and reaction pathway analysis.
- Time-dependent DFT (TD-DFT) for predicting spectroscopic properties.
- UV-visible spectroscopy for experimental validation of electronic transitions.
Main Results:
- The first X-ray resolved structure of a dithizone disulfide, (HDz)2, was obtained, completing the structural validation of the dithizone oxidation pathway.
- DFT and MP2 calculations successfully predicted the energetically favored tautomers and structures, aligning with experimental crystallographic data.
- Atomic charge distribution analysis supported the proposed cyclization pathway and crystal packing of the dehydrodithizone tetrazolium salt (Dz).
- TD-DFT accurately explained the solvatochromic properties, linking specific tautomers to the observed colors in different solvents (orange in methanol, green in dichloromethane).
- Concentratochromism of H2Dz was observed in methanol, and computed orbitals/oscillators closely matched experimental UV-visible spectra.
Conclusions:
- The study successfully characterized the dithizone disulfide intermediate and validated the complete oxidation pathway of dithizone using a combination of experimental and computational techniques.
- Theoretical calculations provide robust support for the observed structures and mechanisms, offering insights into the electronic properties and tautomerism of dithizone.
- The findings provide a comprehensive understanding of dithizone's reactivity, electronic behavior, and spectroscopic characteristics, crucial for its further application in chemistry.
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