Iron(II) and magnesium(II) porphyrin acid solvolysis reactions

Valiotti, A. B.; Adeyemo, Adegboye; Hambright, Peter

doi:10.1016/0020-1650(81)80004-9

Cited by 9 publications

(4 citation statements)

References 8 publications

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“…This difference is consistent with the behavior of Mg"TAP and MgnTSPP, where the value of k2Ku is 10 times lower for the positively charged porphyrin. 21 Reductive demetallation took place at pH < 4 with CunTSPP, at pH < 3 with CunTAP, and at pH < 1.5 with CunTMPyP. These results are in line with the relative acid solvolysis rate constants of a variety (Zn11, Mg11, Pb11, Cd11, Hg11) of metalloporphyrins,18,25 which are in the order of their respective free base proton basicities, -TSPP > -TAP » -TMPyP.…”

Section: W[h+][ac"] Vs [H+]2/[h+][supporting

confidence: 58%

One-electron reduction and demetallation of copper porphyrins

Kumar¹,

Neta²,

Sutter³

et al. 1992

J. Phys. Chem.

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Section: W[h+][ac"] Vs [H+]2/[h+][supporting

confidence: 58%

One-electron reduction and demetallation of copper porphyrins

Kumar¹,

Neta²,

Sutter³

et al. 1992

J. Phys. Chem.

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“…5), and the border-line cases, e.g., zinc(II) and magnesium(II) porphyrins, in which the metal center is in the plane but with ionic character in bonding, therefore it can be easily exchanged. This categorization of metalloporphyrins based on the metal exchange reactions was confirmed by the investigation of the acid solvolysis reactions: the reaction rate constants proved to be correlated with the lability of complexes: Cd 2+ >Mg 2+ >Mn 2+ >Fe 2+ >Zn 2+ >> Co 2+ >Cu 2+ >Ni 2+ [27]. We complemented this categorization aspect with the experiences from distortion that also in metalloporphyrins the planarity or nonplanarity of the macrocycle is basically responsible for spectral characteristics; the electronic structure of metal ions is secondary, mainly in the in-plane complexes.…”

Section: A) B)mentioning

confidence: 69%

Application of the electronic spectra of porphyrins for analytical purposes: The effects of metal ions and structural distortions

Valicsek

Horváth

2013

Microchemical Journal

122

118

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We investigated the UV-Vis absorption, singlet-1 and singlet-2 fluorescence, as well as the formation of several metalloporphyrins from equilibrial and kinetic aspects in aqueous solution. Among these complexes were numerous typical out-of-plane and several in-plane metalloporphyrins, and between the two categories, a few border-line cases. On the basis of our results, we have complemented the categorization introduced by Barnes and Dorough for the metalloporphyrins. According to our observations, also in metalloporphyrins, the distortion, i.e., the planarity or nonplanarity of the macrocycle, is basically responsible for the spectral characteristics, while the electronic structure of metal center is a secondary factor, with a considerable importance mainly in the in-plane complexes. The type of complexes can be spectrophotometrically determined on the basis of their UV-Vis absorption and fluorescence spectra. Beside the spectral and photophysical effects of metalation, also those of the structural distortions were studied, which can originate also from metalation, protonation or overcrowded peripheral substitution of the free-base porphyrins, as well as from the axial ligation of metalloporphyrins. Our observation may be useful for different spectrophotometric analytical detection and determination methods, e.g. size-selective metal detection using free-base porphyrins (or other ringed chelate ligands), as well as the determination of Lewis bases as potential axial ligands, using metalloporphyrins.

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“…The same two-proton rate law that we find for the trivalent lanthanides has been demonstrated before for acid solvolysis reactions of water soluble ZnII,8,11 CdII,9 Pb11,lO FeII,12 MnII,13 and MgII (ref. 12) porphyrins. The divalent derivatives also give a log k vs. Ro correlation,l2 and the porphyrin nucleus deformations postulated for metal ion removal have been discussed.14 At high [H+] {where kobs, 0~ [H+]}, PrIILTMPyP reacts about l o 7 times faster than does the LuIII complex, and a 0.1 8, increase in the ionic radius of the co-ordinated metal ion leads to a remarkable 32000 fold increase in the rate parameters.…”

mentioning

confidence: 99%

Acid solvolysis kinetics of lanthanide porphyrins

Haye¹,

Hambright²

1988

J. Chem. Soc., Chem. Commun.

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The kinetics of the acid solvolysis reactions of twelve water-soluble lanthanide tetrakis(N-methyl-4-pyridy1)porphyrins (Ln-P) follow rate = k, [Ln-PI [H+12/{(k-1/k2) + [H+l} at 25 O C, I = 0.8 M (LiN03/HN03) indicating that two rotons are required for solvolysis, and since log (k1k2/kP1) = 45.0R0 -39.4(Ro is the ionic radius in A), a 0.1 1 change in radius has a 32000 fold rate effect.The tumour-localizing ability of certain porphyrin molecules complexed with paramagnetic metal ions' makes watersoluble lanthanide porphyrins attractive candidates as in vivo magnetic resonance imaging agents for malignant tissues.2 Since nothing is quantitatively known about the in vitro stability of lanthanide porphyrins in aqueous solution, we report the kinetics of the acid solvolysis reactions of twelve lanthanide tetrakis-(N-methyl-4-pyridyl)porphyrins (M-fi At pH 8, with 10 ~L M M-P and 25 mM edta, the Ni", MnIII 7 , Cu" RhIII, InIIr, ZnII, VOIV, FeIII, A P , CrIII, Pd", and SnIV porphyrins were unchanged after 25 h in the dark.

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Iron(II) and magnesium(II) porphyrin acid solvolysis reactions

Cited by 9 publications

References 8 publications

One-electron reduction and demetallation of copper porphyrins

One-electron reduction and demetallation of copper porphyrins

Application of the electronic spectra of porphyrins for analytical purposes: The effects of metal ions and structural distortions

Acid solvolysis kinetics of lanthanide porphyrins

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