Water Exchange Controls the Complex-Formation Mechanism of Water-Soluble Iron(III) Porphyrins: Conclusive Evidence for Dissociative Water Exchange from a High-Pressure17O NMR Study

Schneppensieper, Thorsten; Zahl, Achim; Eldik, Rudi van

doi:10.1002/1521-3773(20010504)40:9<1678::aid-anie16780>3.0.co;2-a

Cited by 66 publications

(31 citation statements)

References 27 publications

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“…This labilization can be nicely studied by O 17 -NMR as shown schematically for three different porphyrins in Scheme 5 [11]. From the temperature dependence of the NMR line broadening, the water exchange rate constant and the activation enthalpy and entropy values can be determined.…”

Section: Fe Porphyrinssupporting

confidence: 62%

“…7. The calculated volumes of activation are all significantly positive and further underline the operation of a dissociative interchange (I d ) or even a limiting dissociative (D) mechanism in the case of the TMPS complex [11]. Further investigations on the [Fe III (TMPS 4− )(H 2 O) 2 ] complex indicated that it exhibits a pK a value of 6.9 and undergoes a change in spin-state from a spin admixed (S = 5/2, 3/2) state at pH 5 to a high-spin (S = 5/2) state at pH 9.…”

Section: Fe Porphyrinsmentioning

confidence: 99%

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Fascinating inorganic/bioinorganic reaction mechanisms

Eldik

2007

Coordination Chemistry Reviews

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Section: Fe Porphyrinssupporting

confidence: 62%

Section: Fe Porphyrinsmentioning

confidence: 99%

Fascinating inorganic/bioinorganic reaction mechanisms

Eldik

2007

Coordination Chemistry Reviews

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“…In the case of iron-porphyrin complexes, the rates and the mechanism of water exchange were satisfactorily elucidated. 19 Fe III TSPP 3-as anionic, Fe III TM-4-PyP 5+ (Fe(III) meso-tetrakis(Nmethylpyridinium-4-yl)porphyrin) as cationic and Fe III TMPS n-(Fe(III) meso-tetrakis(sulfonatomesithyl)porphyrin) as sterically shielded anionic complexes were studied. For all three complexes a dissociative mode of activation was suggested on the basis of positive activation entropy and activation volume.…”

Section: Introductionmentioning

confidence: 99%

“…Since 1980 a value of 1.4 ¥ 10 7 s -1 was cited for the water exchange rate constants of Fe III TSPP 3-, 32 but it was later redetermined as 2 ¥ 10 6 s -1 . 19 From these values the average residence time is calculated as 100-500 ns for the iron complex; the higher limit seems to be more reliable. In spite of this remarkable progress in describing magnetic aspects of anomalous relaxivity of Mn III TSPP 3-another important factor, i.e.…”

Section: Introductionmentioning

confidence: 99%

Water exchange rates of water-soluble manganese(iii) porphyrins of therapeutical potential

et al. 2010

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The activation parameters and the rate constants of the water-exchange reactions of Mn III TE-2-PyP 5+ (meso-tetrakis(N-ethylpyridinium-2-yl)porphyrin) as cationic, Mn III TnHex-2-PyP 5+ (meso-tetrakis(N-n-hexylpyridinium-2-yl)porphyrin) as sterically shielded cationic, and Mn III TSPP 3-(meso-tetrakis(4-sulfonatophenyl)porphyrin) as anionic manganese(III) porphyrins were determined from the temperature dependence of 17 O NMR relaxation rates. The rate constants at 298 K were obtained as 4.12 ¥ 10 6 s -1 , 5.73 ¥ 10 6 s -1 , and 2.74 ¥ 10 7 s -1 , respectively. On the basis of the determined entropies of activation, an interchange-dissociative mechanism (I d ) was proposed for the cationic complexes (DS ‡ =~0 J mol -1 K -1 ) whereas a limiting dissociative mechanism (D) was proposed for Mn III TSPP 3-complex (DS ‡ = +79 J mol -1 K -1 ). A magnitude of the obtained water-exchange rate constants further confirms the suggested inner sphere electron transfer mechanism for the reactions of the two positively charged Mn(III) porphyrins with the various biologically important oxygen and nitrogen reactive species. Due to the high biological and clinical relevance of the reactions that occur at the metal site of the studied Mn(III) porphyrins, the determination of water exchange rates advanced our insight into their efficacy and mechanism of action, and in turn should impact their further development for both diagnostic (imaging) and therapeutic purposes.

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“…104,105 Finally, for this section, it is appropriate to reiterate that prediction of limits for DV ‡ ex from Equation 8.15 as in Figure 8.3 is applicable only to water exchange reactions of homoleptic metal aqua ions or their conjugate bases, although the predictions may serve as a rough guide for other water exchange processes. For THE SIMPLEST LIGAND SUBSTITUTION REACTIONS: SOLVENT EXCHANGE example, DV ‡ ex for water exchange on the water-soluble iron(III) porphyrin Fe(TMPS)(H 2 O) 2 3À (TMPS ¼ meso-tetra(sulfonatomesityl)porphine) is þ12 cm 3 / mol, 106 which certainly indicates a strongly dissociative mechanism but not necessarily a limiting D process.…”

Section: Water Exchange Reactionsmentioning

confidence: 99%

Ligand Substitution Dynamics in Metal Complexes

Swaddle

2010

Physical Inorganic Chemistry

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On the base of our previous studies due to the presence of halides in our complexes there is strong probability for obtaining coordination polymers. Crystal engineering well-defined as the understanding of intermolecular interactions in the context of crystal packing and the utilization of such understanding in the design of new solids with desired physical and chemical properties. Owing to the fact that the small changes in the ligands may play a significant role in the complexes, the organic ligand (1-naphtyl pyridine-2-carboxylate) (L), was synthesized. In order make more steric repulsion around of the complexes resulted in the substitution effect around of the naphtyl moiety was hired in the design. Relocation in the position of functional group was fulfilled our expectations. Three new mercury (II) halide complexes, [Hg(L)2Cl2] (1), [Hg(L)2Br2] (2) and [Hg(L)2I2] (3) were synthesized. All of the compounds were fully characterized using FT-IR, TGA, DSC, mass spectrometry, CHNOS elemental analyses, PXRD, NMR and SCXRD. The results indicate that metal-ligand polymerization controlled by substitution effect. The coordination geometry around the Hg (II) ion is seesaw shape in distorted tetrahedral geometry for compounds (1), (2) and (3) with τ4 of 0.74, 0.76 and 0.78, respectively. Due to the replacement of the functional group (mentioned substitution effect), flexibility of coodinated ligand was decreased. In the previously reported structures, the angle between two planes of aromatic rings in the analogous ligand was 78.37o which changed to the 59.47o, 50.75o and 64.90o for mercury halide series complexes. In present study these angles are 89.09, 89.73 and 88.90 for titled complexes based on new designed ligand. Consequently, this study emphasize that the substitution effect can play the significant role through the flexibility of designed ligand to control the metal-ligand polymerization.

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Water Exchange Controls the Complex-Formation Mechanism of Water-Soluble Iron(III) Porphyrins: Conclusive Evidence for Dissociative Water Exchange from a High-Pressure17O NMR Study

Cited by 66 publications

References 27 publications

Fascinating inorganic/bioinorganic reaction mechanisms

Fascinating inorganic/bioinorganic reaction mechanisms

Water exchange rates of water-soluble manganese(iii) porphyrins of therapeutical potential

Ligand Substitution Dynamics in Metal Complexes

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