Oxochlorin frameworks confining a β-hydroxyketone moiety
Nivedita Chaudhri1,2, Matthew J Guberman-Pfeffer3, Matthias Zeller4
1Department of Chemistry, University of Connecticut, Storrs, CT 06269-3060, USA. c.bruckner@uconn.edu.
Dalton Transactions (Cambridge, England : 2003)
|July 23, 2024
Summary
Meso-hydroxyoxochlorins feature an acetylacetonate-like moiety but do not chelate transition metals due to aromaticity concerns. Halochromic properties reveal protonation sites, supported by computational analysis.
Area of Science:
- Organic Chemistry
- Coordination Chemistry
- Photochemistry
Background:
- Meso-hydroxyoxochlorins possess acetylacetonate (acac)-like moieties within their chromophore structures.
- These moieties exhibit enol forms and strong intramolecular hydrogen bonding between enol and beta-ketone groups.
Purpose of the Study:
- To investigate the metal-chelating capabilities of the acac-like functionality in meso-hydroxyoxochlorins.
- To understand the electronic properties and protonation/deprotonation sites within these molecules.
Main Methods:
- X-ray diffraction studies to analyze crystal structures and hydrogen bonding.
- Testing the chelation of 3d and 4d transition metal ions.
- Halochromism studies to probe protonation sites.
- Computational analysis to support experimental findings.
Main Results:
- Meso-hydroxyoxochlorins, despite having acac-like structures, do not effectively chelate transition metal ions.
- Chelation is hindered by the perturbation of porphyrinic chromophore aromaticity, outweighing metal binding energies.
- Halochromic properties indicate specific protonation/deprotonation sites within the molecules.
Conclusions:
- The unique structure of meso-hydroxyoxochlorins prevents metal chelation due to aromaticity preservation.
- Protonation/deprotonation behavior is linked to the chromophore's electronic structure and stability.
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