Mercury(II) reactions with water-soluble porphyrins

Robinson, Louis R.; Hambright, Peter

doi:10.1021/ic00030a024

Cited by 29 publications

(16 citation statements)

References 5 publications

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“…For Zn 2 + /Cd(II)-OEP, the rate constant was 124 ± 2 L mol -1 s -1 , while the Cd(II)-TBP gave (4.9 ± 0.10) ϫ 10 -1 L mol -1 s -1 . The OEP exchange is approximately 250 times faster than that of TBP, in accord with other porphyrins, where the most basic porphyrin exchange is the fastest [31,32].…”

Section: Metal Ion Exchange and Acid Solvolysis Reactionssupporting

confidence: 61%

Tetrabenzoporphyrins: Metal Incorporation and Exchange Kinetics, Ligational Equilibria and Pulse Radiolysis Studies

Cromer

Hambright

Grodkowski

et al. 1997

J. Porphyrins Phthalocyanines

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The solution chemistry of tetrabenzoporphyrin ( TBP ) and several of its metal derivatives were compared with that of the corresponding octaethylporphyrins. Kinetic studies were done on zinc and cadmium ion incorporation and the exchange reactions of cadmium porphyrins with zinc. Formation constants of Cd (II), Cu (II), VO (IV), Ni (II), Zn (II) and Mg (II) porphyrins with pyridine were determined for both compounds. The spectra of the radical cations of Ni (II), Mg (II) and H 2- TBP were obtained, as well as that of the radical anion of Mg (II)- TBP . Aside from the new Ni (I)- TBP , no long-lived intermediates, as noted with other porphyrins, were observed upon reduction of the tetrabenzoporphyrins. The low basicity and rigidity of the tetrabenzoporphyrin nucleus may explain many of its relative reactivity properties.

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Section: Metal Ion Exchange and Acid Solvolysis Reactionssupporting

confidence: 61%

Tetrabenzoporphyrins: Metal Incorporation and Exchange Kinetics, Ligational Equilibria and Pulse Radiolysis Studies

Cromer

Hambright

Grodkowski

et al. 1997

J. Porphyrins Phthalocyanines

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“…The 62,63 According to the kinetic investigation for the Cu(II) ion incorporation into TPPS in the presence of the Hg(II) ion in water, the heterodinuclear porphyrin complex, in which two different metal ions simultaneously bind to tpps 6- …”

Section: Metalloporphyrin Formation Catalyzed By Large Metal Ionsmentioning

confidence: 99%

Dynamic Study of Metal-Ion Incorporation into Porphyrins Based on the Dynamic Characterization of Metal Ions and on Sitting-Atop Complex Formation

2001

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The metalloporphyrin formation reaction is one of the important processes from both analytical and bioinorganic points of view.The large molar absorption coefficient and very high stability of the metalloporphyrins are very useful for the highly sensitive analysis of trace amounts of metal ions, and the size selectivity of the porphyrins is valuable for the separation of various kinds of metal ions. 1-7 A variety of metalloporphyrin formation rates are also applicable for the kinetic analysis of metal ions. We succeeded in the detection of the sitting-atop (SAT) copper(II) complex of TPP (5,10,15,20-tetraphenylporphyrin) in acetonitrile (AN) as a solvent with a very low Brønsted basicity, where two pyrrolenine nitrogens in the Cu(II)-SAT complex coordinate to the metal ion and two protons still remain on the pyrrole nitrogens. The structure parameters around the copper(II) ion in the Cu(II)-SAT complex, as determined by a fluorescent EXAFS method, suggest an axially elongated and equatorially distorted six-coordinate geometry. We measured the rates of the formation reaction of the SAT complexes for a series of transition metal(II) ions in AN using the stopped-flow technique. We propose the mechanism where there is a rapid deformation equilibrium of the porphyrin ring prior to the rate-determining step of the bond rupture of a coordinated solvent molecule on the metal(II) ion. Furthermore, we measured the rates of the deprotonation reaction of the Cu(II)-SAT complex by some Brønsted bases and indicated that the rate-determining step is the attack of the base on the proton of the pyrrole nitrogen in the SAT complex. Finally, a unified mechanism relevant to the porphyrin metalation mechanism has been proposed.

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“…Larger metal ions such as Cd 2+ , Hg 2+ , or Pb 2+ , however, can catalyse the formation of normal 40 metalloporphyrins via generation of SAT complex intermediates. [13][14][15][16][17][18] In these species the distortion caused by the outof-plane location of the larger metal center makes two diagonal pyrrolic nitrogens more accessible to another metal ion on the other side of the porphyrin ligand. 19 45 Deviating from the coplanar metalloporphyrins, the OOP complexes, on account of their distorted structure and kinetic lability, display special photochemical properties, such as photoinduced charge transfer from the porphyrin ligand to the metal center, leading to irreversible ring opening of the ligand and 50 dissociation on excitation at both the Soret-and the Q-bands.…”

Section: Introductionmentioning

confidence: 99%

Equilibrium, photophysical and photochemical examination of anionic lanthanum(iii) mono- and bisporphyrins: the effects of the out-of-plane structure

2012

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Lanthanum(III) ion forms kinetically labile complexes with the 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin anion (H2TSPP 4-), the compositions and formation constants of which significantly depend on the presence of potential axial ligands (at 0.01 M). Deviating from the chloride ion, acetate coordinating to the metal center hinders the formation of bisporphyrin complex. In these 10 lanthanum(III) complexes, the metal center, due to its large ionic radius (103.2 pm), is located out of the ligand plane, distorting it. Accordingly, the absorption and fluorescence spectra of these coordination compounds display special properties characteristic of the so-called sitting-atop (SAT) or out-of-plane (OOP) porphyrin complexes. Metalation significantly decreases the quantum yield of the fluorescence from the S1 excited state. Quantum chemical calculations (DFT) confirm the considerable OOP 15 displacement of the La(III) center (about 120 pm in the monoporphyrin complexes). The monoporphyrins display efficient fluorescence (0.03), while the bisporphyrin does not emit. Differing from the normal (in-plane) metalloporphyrins, excitation of these lanthanum(III) porphyrins leads to an irreversible ligandto-metal charge transfer (LMCT) followed by the opening of the porphyrin ring, which is also typical of OOP complexes. Dissociation releasing free-base porphyrin can also be observed upon irradiation of the 20 monoporphyrin in acetate solution, while in the presence of chloride ions interconversions of the monoand bisporphyrins may also take place beside the irreversible photoredox reaction.

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Mercury(II) reactions with water-soluble porphyrins

Cited by 29 publications

References 5 publications

Tetrabenzoporphyrins: Metal Incorporation and Exchange Kinetics, Ligational Equilibria and Pulse Radiolysis Studies

Tetrabenzoporphyrins: Metal Incorporation and Exchange Kinetics, Ligational Equilibria and Pulse Radiolysis Studies

Dynamic Study of Metal-Ion Incorporation into Porphyrins Based on the Dynamic Characterization of Metal Ions and on Sitting-Atop Complex Formation

Equilibrium, photophysical and photochemical examination of anionic lanthanum(iii) mono- and bisporphyrins: the effects of the out-of-plane structure

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