Vanadyl Porphyrin Speciation Based on Submegahertz Ligand Proton Hyperfine Couplings

Mannikko, Donald; Stoll, Stefan

doi:10.1021/acs.energyfuels.9b00867

Cited by 23 publications

(21 citation statements)

References 47 publications

(86 reference statements)

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“…More importantly, a recent study by Mannikko and Stoll reported the use of sub-megahertz hyperfine couplings to speciate the substitution pattern in a series of vanadyl porphyrin model compounds. 64…”

Section: Resultsmentioning

confidence: 99%

Elucidating the Geometric Substitution of Petroporphyrins by Spectroscopic Analysis and Atomic Force Microscopy Molecular Imaging

et al. 2019

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Determination of the molecular structures of petroporphyrins has been crucial to understand the diagenetic pathways and maturation of petroleum. However, these studies have been hampered by their structural complexity and the challenges associated with their isolation. In comparison to the skeletal macrocyclic structures, much less is known about the substitutions, which are more sensitive to the maturation and diagenesis pathways. While these isolated vanadyl petroporphyrins largely consist of etioporphyrin and deoxophylloerythroetioporphyrin as expected, surprisingly, we find evidence that one or a few β hydrogens are present in petroporphyrins of low carbon numbers using a combination of ultraviolet–visible spectroscopy, Fourier transform ion cyclotron resonance mass spectrometry, and non-contact atomic force microscopy. Petroporphyrins with β hydrogens were not anticipated on the basis of their biological precursors. The data support dealkylation under catagenesis but not transalkylation or random alkylation of the β and meso positions, despite the fact that more complex porphyrin structures are formed.

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Section: Resultsmentioning

confidence: 99%

Elucidating the Geometric Substitution of Petroporphyrins by Spectroscopic Analysis and Atomic Force Microscopy Molecular Imaging

et al. 2019

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“…For future research, a detailed analysis of the structure and surrounding of vanadyl complexes (porphyrinic and nonporphyrinic) and radicals by more sophisticated EPR techniques would provide clues to the fabrication receipts and the evolution/degradation of embalming materials. First, electron nuclear double resonance (ENDOR) spectroscopy will provide additional information on the evolution of VO-P complexes by probing hyperfine interactions with 1 H nuclei of metallic complexes and radicals . Second, pulse-EPR methods will allow direct measurements of relaxation times T 1 and T 2 and measurement of small hyperfine intera c tions with 14 N, 13 C, 31 P, and 33 S nuclei. ,, However, the ease of use of standard continuous-wave X-band EPR spectroscopy (recording a spectrum takes only a few minutes) and the ubiquity of vanadyl geoporphyrins VO-P and radicals in bitumen open the door to the easy characterization of bitumen in all types of archeological artifacts.…”

Section: Conclusion and Perspectivementioning

confidence: 99%

Nondestructive Analysis of Mummification Balms in Ancient Egypt Based on EPR of Vanadyl and Organic Radical Markers of Bitumen

et al. 2020

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The black matter employed in funeral context by ancient Egyptian is a complex mixture of plant-based compounds with variable amounts of bitumen. Asphaltene, the most resistant component of bitumen, contain Vanadyl porphyrins and carbonaceous radicals which can be used as paramagnetic probes to investigate embalming materials without sample preparation. Electron Paramagnetic Resonance (EPR) at X-band, combining in-phase and out-of-phase detection schemes, provides new information in a non-destructive way about the presence, the origin, and the evolution of bitumen in these complex materials. It is found that the relative EPR intensity of radicals and vanadyl porphyrins is sensitive to the origin of the bitumen. The presence of non-porphyrinic vanadyl complexes in historical samples is likely due to the complexation of VO2+ ions by carboxylic functions at the interface between bitumen and other biological components of the embalming matter. The absence of such oxygenated vanadyl complex in natural bitumen and in one case of historical human mummy acquired by a museum in the 19th century reveals a possible, non-documented, ancient restoration of this mummy by pure bitumen. The linear correlation between in-phase and out-of phase EPR intensities of radicals and vanadyl porphyrins in balms and in natural bitumen, reveals a nanostructuration of radicals and vanadyl porphyrin complexes, which was not affected by the preparation of the balm. This points to the remarkable chemical stability of paramagnetic probes in historical bitumen in ancient Egypt. File list (2) download file view on ChemRxiv BackMatter_EPR.pdf (1.68 MiB) download file view on ChemRxiv Supporting Information.pdf (1.32 MiB)Non-destructive analysis of mummification balms in Ancient Egypt, based on EPR of vanadyl and organic radical markers of bitumen.

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“…The values A// = 2.6 MHz and AꞱ = 0.3 MHz measured for VO-P correspond to the values known for the hydrogen Hmeso of porphyrin in vanadyl porpyrin complexes. 33,34 It must be noticed that additional ENDOR features that would be expected at A// = 1.3 MHz and AꞱ = 0.4 MHz for hydrogen of pyrrole groups, 34,35 are not observed in our ENDOR spectra.…”

Section: Resultsmentioning

confidence: 61%

Insight into the structure of black coatings of ancient Egyptian mummies by advanced EPR spectroscopy of vanadyl complexes.

Dutoit

Binet

Vezin

et al. 2021

Preprint

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Advanced EPR techniques such as ENDOR and pulsed EPR are used to investigate the enigmatic black coatings of ancient Egyptian mummies, consisting in a complex and heterogeneous mixtures of conifer resins, wax, fat and oil with variable amounts of bitumen. Natural bitumen always contains traces of vanadyl porphyrin complexes that we used here as internal probes to explore the nanoscale environment of V4+ ions in these black coatings by hyperfine spectroscopy. Four types of vanadyl porphyrins were identified from the analysis of 14N hyperfine interactions. Three types (referred to as VO-P1, VO-P2 and VO-P3) are present in natural bitumen from the Dead Sea, among which VO-P1 and VO-P2 are also present in black coatings of mummies. The absence of VO-P3 in mummies, which is replaced by another complex VO-P4, may be due to its transformation during preparation of the black matter for embalming. Analysis of 1H hyperfine interaction shows that bitumen and other natural substances are intimately mixed in these black coatings, with bitumen aggregate sizes not larger than a few nanometres.

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Vanadyl Porphyrin Speciation Based on Submegahertz Ligand Proton Hyperfine Couplings

Cited by 23 publications

References 47 publications

Elucidating the Geometric Substitution of Petroporphyrins by Spectroscopic Analysis and Atomic Force Microscopy Molecular Imaging

Elucidating the Geometric Substitution of Petroporphyrins by Spectroscopic Analysis and Atomic Force Microscopy Molecular Imaging

Nondestructive Analysis of Mummification Balms in Ancient Egypt Based on EPR of Vanadyl and Organic Radical Markers of Bitumen

Insight into the structure of black coatings of ancient Egyptian mummies by advanced EPR spectroscopy of vanadyl complexes.

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