Homo- and heterodimer formation in metalloporphyrins

Banci, Lucia

doi:10.1021/ic00199a031

Cited by 15 publications

(4 citation statements)

References 1 publication

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“…The ESR spectrum of each Cu(II) tetrabenzotetraarylporphyrin is characterized by a prominent g t value ranging from 2.051 to 2.053 (A t ¼ 41-66 as seen in Table 1), values consistent what was previously reported for other Cu(II) porphyrins. [42][43][44] It should be pointed out that the Cu(II) hyper-ne is ill-dened in spectra of the benzo-(TpYPP)Cu derivatives at 110 K in CH 2 Cl 2 (Fig. 2b) and this can be accounted for by aggregation of these porphyrins under the given experimental conditions.…”

Section: Synthesis and Uv-vis Spectramentioning

confidence: 98%

Electrochemistry of nonplanar copper(ii) tetrabutano- and tetrabenzotetraarylporphyrins in nonaqueous media

Fang

et al. 2015

RSC Adv.

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Two series of copper tetraarylporphyrins containing b,b 0 -fused tetrabutano or tetrabenzo groups were synthesized and characterized as to their electrochemistry and spectroelectrochemistry in nonaqueous media. The examined compounds are represented as butano-(TpYPP)Cu II and benzo-(TpYPP)Cu II , where TpYPP is the porphyrin dianion and Y is a CH 3 , H or Cl substituent on the para-position of the four meso-phenyl rings of the compound. Each neutral porphyrin in the two series is ESR active and shows a typical d 9 Cu(II) signal in frozen CH 2 Cl 2 solution. Each Cu(II) porphyrin also undergoes two reversible one-electron reductions and two reversible one-electron oxidations in DMF or CH 2 Cl 2 containing 0.1 M tetra-n-butylammonium perchlorate to give a p-anion radical and dianion upon reduction and a pcation radical and dication upon oxidation. A third one-electron oxidation is also observed for butano-(TpYPP)Cu (Y ¼ CH 3 and H) and benzo-(TPP)Cu in PhCN and this process is assigned to the Cu II /Cu III transition. The reversible half-wave potential for the first oxidation of each compound in both series is shifted negatively by about 500 mV as compared to E 1/2 values for oxidation of the related copper tetraarylporphyrin without the four fused benzo or butano rings while smaller positive shifts of 60 and 300 mV are seen for reduction of the tetrabenzotetraarylporphyrins and tetrabutaotetraarylporphyrins, respectively, as compared to the same redox reactions of the related tetraarylporphyrins. The electrochemically measured HOMO-LUMO gap averages 1.76 AE 0.05 V for benzo-(TpYPP)Cu II , 2.04 AE 0.06 V for butano-(TpYPP)Cu II and 2.33 AE 0.03 for (TpYPP)Cu in CH 2 Cl 2 .

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Section: Synthesis and Uv-vis Spectramentioning

confidence: 98%

Electrochemistry of nonplanar copper(ii) tetrabutano- and tetrabenzotetraarylporphyrins in nonaqueous media

Fang

et al. 2015

RSC Adv.

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“…Synthetic and structural studies tend to focus on V(IV) porphyrin derivatives, 697,698 but a few V(II) 699,700 and V(III) 701 porphyrins structures have been reported. Homo- 702,703 and heterodimers 703 could be observed by EPR spectroscopy at -193 °C. Vanadyl porphyrins provide a convenient model system for the more reactive oxoiron(IV) porphyrinate intermediate in oxygen atom transfers.…”

Section: Vanadium Porphyrinsmentioning

confidence: 99%

The Chemistry and Biochemistry of Vanadium and the Biological Activities Exerted by Vanadium Compounds

et al. 2004

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“…Although the tendency of vanadyl porphyrins to self-dimerize is well documented, [52][53][54][55] the conditions generally present in vacuum residue and asphaltene solutions should not result in any significant dimerization. 44,52 3.2.4. UV/visible Spectroscopy of Authentic Petroporphyrins.…”

Section: The Characterization Of Vanadium Compoundsmentioning

confidence: 99%

“…Symmetrical porphyrins such as VOTPP do not form significant amounts of a dimeric species, while unsymmetrical porphyrins show a higher tendency to aggregate due to the ability to form head-to-toe species. Although the tendency of vanadyl porphyrins to self-dimerize is well documented, − the conditions generally present in vacuum residue and asphaltene solutions should not result in any significant dimerization. , …”

Section: To Be or Not To Be (A Porphyrin)that Is The Question The Ch...mentioning

confidence: 99%

Chemistry and Association of Vanadium Compounds in Heavy Oil and Bitumen, and Implications for Their Selective Removal

2010

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Most crude oils contain traces of vanadium, which cause significant detrimental impact during catalytic conversion and combustion. The concentrations in bitumen and vacuum residue are generally much higher, which poses a problem for the economical upgrading of these feedstocks. These problems are relevant since the world reserves of conventional light oils are dwindling and being replaced by an increasing amount of heavier feedstocks. In this article, the current understanding of the distribution and form of vanadium compounds within vacuum residue is critically discussed. The implications of this chemistry on prospects for new separation methods, other than deasphalting, are considered. Although only a small fraction of the vanadium is contained within the polar resin fraction (i.e., maltenes), this fraction has been most often characterized to determine the chemical form of the vanadium compounds. Various spectroscopic techniques have been used to determine that these resin soluble vanadium compounds exist as metalloporphyrins characterized by their intense absorption of UV/visible radiation. In the case of the asphaltene bound metals, this UV/visible absorbance is not observed and has historically led to their distinction as “non-porphyrins”. However, more recent results using X-ray spectroscopies (EXAFS and XANES), as well as a more in depth analysis of the UV/vis response of metalloporphyrins, indicates that, although these asphaltene-bound vanadium compounds do not exhibit the characteristic UV/visible absorption, they are indeed still bound in a porphyrinic structure. The fact that the majority of the vanadium is contained within the highly aromatic, highly polar asphaltene fraction also poses additional roadblocks to their selective removal. This fraction has been shown to associate/aggregate significantly in most (if not all) solvents. Recent work on the nature and possible mechanisms of the molecular association of asphaltenes in solution can be extended to help elucidate the molecular interactions occurring between asphaltenes and metalloporphyrins, and hence the nature of the inclusion of metalloporphyrins within the asphaltene fraction. Many different solvent systems including aromatics, chloro-carbons, alcohols, ketones, as well as other polar solvents have been used to extract the metalloporphyrins from the asphaltene fraction with limited success. In most cases, the effect of asphaltene solubility and aggregation in the given solvent were not considered. The selective separation of metalloporphyrins is clearly hampered by gaps in the basic understanding of the metalloporphyrin properties and behavior in solution.

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Homo- and heterodimer formation in metalloporphyrins

Cited by 15 publications

References 1 publication

Electrochemistry of nonplanar copper(ii) tetrabutano- and tetrabenzotetraarylporphyrins in nonaqueous media

Electrochemistry of nonplanar copper(ii) tetrabutano- and tetrabenzotetraarylporphyrins in nonaqueous media

The Chemistry and Biochemistry of Vanadium and the Biological Activities Exerted by Vanadium Compounds

Chemistry and Association of Vanadium Compounds in Heavy Oil and Bitumen, and Implications for Their Selective Removal

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