28265-17-0Relevant articles and documents
Synthesis and properties of a new (octaethylporphyrinato)-manganese(III)–pyridinyl-substituted pyrrolidinofullerene dyad
Ovchenkova,Bichan,Lomova
, p. 1503 - 1508 (2016/11/29)
The formation of a porphyrin–fullerene dyad from 2′-(pyridin-4-yl)-5′-(pyridin-2-yl)-1′-(pyridin-3-ylmethyl)-2′,5′-dihydro-1′H-pyrrolo[3′,4′: 1,9](C60-Ih)[5,6]fullerene and (2,3,7,8,12,13,17,18-octaethylporphyrinato) manganese(III) with axial chloride ligand has been studied on a quantitative level with the goal of obtaining supramolecules possessing biological activity. Preliminarily, the reaction of manganese(III) porphyrin with pyridine has been studied. The donor–acceptor dyads are formed either instantaneously and reversibly (pyridine) or slowly and irreversibly (substituted fullerene). In both cases, the reaction is a one-step process for which thermodynamic and kinetic parameters have been determined. The results can be used to optimize conditions for the synthesis of porphyrin–fullerene dyads. The obtained dyads have been characterized by spectral data and stability constants.
Thermodynamic and kinetic aspects of two- and three-electron redox processes mediated by nitrogen atom transfer
Keith Woo,Goll, James G.,Czapla, Donald J.,Alan Hays
, p. 8478 - 8484 (2007/10/02)
Treatment of (meso-tetra-p-tolylporphyrinato)manganese(V) nitride, (TTP)Mn≡N, with (octaethylporphyrinato)manganese(II), Mn(OEP), in toluene leads to the reversible transfer of the nitrido ligand between the two metal complexes to form (OEP)Mn≡N and Mn(TTP). The net result is a formal three-electron reduction of (TTP)MnvN to (TTP)MnII This occurs with a second-order rate constant of (5.6 ± 1.2) × 103 M-1 s-1 to form an equilibrium mixture with Koq 1.2 ± 0.5 at 20°C. The thermodynamic and activation parameters for this process are ΔH° = 2.0 ± 0.2 kcal/mol, ΔS° = 7.1 ± 0.6 cal/mol·K, ΔH? = 9.4 ± 0.7 kcal/mol, and ΔS? = -10 ± 2 cal/mol·K. In THF at 20°C, the equilibrium constant is 1.8 ± 0.2 and the rate constant drops to 2.3 ± 0.3 M-1 s-1. When a manganese(III) porphyrin complex is used as a reductant, reversible nitrogen atom transfer still occurs but mediates a formal two-electron process. At 22°C, the exchange process between (TTP)MnCl and (OEP)Mn≡N produces (TTP)Mn≡N and (OEP)MnCl with a second-order rate constant of 0.010 ± 0.007 M-1 s-1 (ΔH? = 19 ± 2 kcal/mol and ΔS? = -3 ± 6 cal/mol·K) and forms an equilibrium mixture with Keq = 24.3 ± 3.3 (ΔH° = -7.0 ± 0.6 kcal/mol and ΔS° = -17 ± 2 cal/mol-K). Evidence for the formation of a binuclear μ-nitrido intermediate is presented for both processes. For the two-electron redox reaction, kinetic studies and mechanistic probes support a pathway which involves an initial chloride dissociation from the Mn(III) complex. Nitrogen atom transfer subsequently occurs between the Mn≡N complex and the four-coordinate Mn(III) cationic species.
