Spectral Evidence and Kinetics for Formation of the Sitting-Atop Complex of Copper(II) Ion with 5,10,15,20-Tetraphenylporphyrin in Acetonitrile

Inada, Yuji; Sugimoto, Yumi; Nakano, Yuko; Funahashi, Shigenobu

doi:10.1246/cl.1996.881

Cited by 19 publications

(25 citation statements)

References 11 publications

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“…This complex has been much discussed. SAT complexes of porphyrins with Pt 2þ , Cu 2þ , and Rh þ have been reported [15][16][17] and kinetic evidence indicates that it exists for many other ions [18][19][20][21], but there is not yet any crystal structure of a SAT complex. However recently, SAT complexes of Cu 2þ with various porphyrins in acetonitrile have been characterised by kinetic measurements, extended X-ray absorption fine structure (EXAFS) and nuclear magnetic resonance (NMR) methods [3,22,23].…”

Section: Introductionmentioning

confidence: 99%

The structure of sitting-atop complexes of metalloporphyrins studied by theoretical methods

Shen

Ryde

2004

Journal of Inorganic Biochemistry

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Section: Introductionmentioning

confidence: 99%

The structure of sitting-atop complexes of metalloporphyrins studied by theoretical methods

Shen

Ryde

2004

Journal of Inorganic Biochemistry

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“…[34] This complex has been much discussed. [35][36][37][38][39][40] Recently, sitting-atop complexes of Cu 2 + with various porphyrins in acetonitrile have been characterised by kinetic measurements, extended Xray absorption fine structure (EXAFS) and nuclear magnetic resonance (NMR) methods. [10,41,42] The complex was suggested to be six-coordinate with three kinds of Cu-N interactions with bond lengths of 205, 198 and 232 pm for pyrrolenine nitrogen atoms of the porphyrin and for acetonitrile nitrogen atoms at equatorial and axial sites, respectively.…”

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confidence: 99%

Reaction Mechanism of Porphyrin Metallation Studied by Theoretical Methods

Shen

Ryde

2005

Chemistry A European J

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We have studied the reaction mechanism for the insertion of Mg2+ and Fe2+ into a porphyrin ring with density functional calculations with large basis set and including solvation, zero-point and thermal effects. We have followed the reaction from the outer-sphere complex, in which the metal is coordinated with six water molecules and the porphyrin is doubly protonated, until the metal ion is inserted into the deprotonated porphyrin ring with only one water ligand remaining. This reaction involves the stepwise displacement of five water molecules and the removal of two protons from the porphyrin ring. In addition, a step seems to be necessary in which a porphyrin pyrrolenine nitrogen atom changes its interaction from a hydrogen bond to a metal-bound solvent molecule to a direct coordination to the metal ion. If the protons are taken up by a neutral imidazole molecule, the deprotonation reactions are exothermic with minimal barriers. However, with a water molecule as an acceptor, they are endothermic. The ligand exchange reactions were approximately thermoneutral (+/-20 kJ mol(-1), with one exception) with barriers of up to 72 kJ mol(-1) for Mg and 51 kJ mol(-1) for Fe. For Mg, the highest barrier was found for the formation of the first bond to the porphyrin ring. For Fe, a higher barrier was found for the formation of the second bond to the porphyrin ring, but this barrier is probably lower in solution. No evidence was found for an initial pre-equilibrium between a planar and a distorted porphyrin ring. Instead, the porphyrin becomes more and more distorted as the number of metal-porphyrin bonds increase (by up to 191 kJ mol(-1)). This strain is released when the porphyrin becomes deprotonated and the metal moves into the ring plane. Implications of these findings for the chelatase enzymes are discussed.

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“…), where the deprotonation from porphyrin occurs [8,11,13]. The activation enthalpy for the formation of a sitting-atop complex of H 2 TPP with Cu(II) in acetonitrile is reported to be 56 kJ mol À1 by Funahashi and coworkers [18,19]. The large value is assumed to arise from the deformation of planar H 2 TPP.…”

Section: Kineticsmentioning

confidence: 99%

“…Recently, Funahashi and coworkers have found the sitting-atop complex of H 2 TPP with Cu(II) as an intermediate in the formation of Cu(TPP) in acetonitrile with a very weak basicity [18,19]. We have recently reported the photophysical properties of Nalkylmetalloporphyrins of Zn(II), Mg(II), Al(III) and Si(IV) in acetonitrile [20].…”

Section: Introductionmentioning

confidence: 95%

Kinetics and mechanisms of the formation of a sitting-atop complex of N-alkylporphyrin with Al(III) in moist acetonitrile

Tsukahara

Onoue

Fujiwara

2001

J. Porphyrins Phthalocyanines

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ABSTRACT:The formation of a sitting-atop complex of a N-alkylporphyrin, containing a 6-hydroxyhexyl group, with Al 3 was studied in moist acetonitrile by equilibrium and kinetic measurements. A sandwich type of metalloporphyrin, where a metal ion binds two N-alkylporphyrins, appears to be formed under the conditions that porphyrins exist in excess over a metal ion. When a large excess of metal ion was used, a 1:1 type of sitting-atop complex of Al(III) N-alkylporphyrin was produced through formation of the sandwich type of Al(III) Nalkylporphyrin.

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Spectral Evidence and Kinetics for Formation of the Sitting-Atop Complex of Copper(II) Ion with 5,10,15,20-Tetraphenylporphyrin in Acetonitrile

Cited by 19 publications

References 11 publications

The structure of sitting-atop complexes of metalloporphyrins studied by theoretical methods

The structure of sitting-atop complexes of metalloporphyrins studied by theoretical methods

Reaction Mechanism of Porphyrin Metallation Studied by Theoretical Methods

Kinetics and mechanisms of the formation of a sitting-atop complex of N-alkylporphyrin with Al(III) in moist acetonitrile

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