Electron transfer reactions between copper(ii) porphyrin complexes and various oxidizing reagents in acetonitrileElectronic supplementary information (ESI) available: Figures reporting the UV-visible absorption spectra of [Cu(OEP)] and the product of the reaction of [Cu(OEP)] with Cu(ii) triflate in acetonitrile, the dependence of the absorbance on the ratio of the total concentrations of Cu(ii) ion and [Cu(OEP)] for the reaction of [Cu(OEP)] and Cu(ii) triflate, and the dependence of the pseudo-first-orde

Abstract

Homogeneous electron transfer reactions of the Cu(II) complexes of 5,10,15,20-tetraphenylporphyrin (TPP) and 2,3,7,8,12,13,17,18-octaethylporphyrin (OEP) with various oxidizing reagents were spectrophotometrically investigated in acetonitrile. The reaction products were confirmed to be the pi-cation radicals of the corresponding Cu(II)-porphyrin complexes on the basis of the electronic spectra and the redox potentials of the complexes. The rate of the electron transfer reaction between the Cu(II)-porphyrin complex and solvated Cu(2+) was determined as a function of the water concentration under the pseudo first-order conditions where Cu(2+) is in large excess over the Cu(II)-porphyrin complex. The decrease in the pseudo first-order rate constant with increasing the water concentration was attributed to the stepwise displacement of acetonitrile in [Cu(AN)(6)](2+)(AN = acetonitrile) by water, and it was concluded that only the Cu(2+) species fully solvated by acetonitrile, [Cu(AN)(6)](2+), possesses sufficiently high redox potential for the oxidation of Cu(ii)-OEP and Cu(ii)-TPP. The reactions of the Cu(II)-porphyrin complexes with other oxidizing reagents such as [Ni(tacn)(2)](3+)(tacn = 1,4,7-triazacyclononane) and [Ru(bpy)(3)](3+)(bpy = 2,2'-bipyridine) were too fast to be followed by a conventional stopped-flow technique. Marcus cross relation for the outer-sphere electron transfer reaction was used to estimate the rate constants of the electron self-exchange reaction between Cu(II)-porphyrin and its pi-cation radical: log(k/M(-1) s(-1))= 9.5 +/- 0.5 for TPP and log(k/M(-1) s(-1))= 11.1 +/- 0.5 for OEP at 25.0 degrees C. Such large electron self-exchange rate constants are typical for the porphyrin-centered redox reactions for which very small inner- and outer-sphere reorganization energies are required.

Valence Tautomerization of High-Valent Manganese(V)-Oxo Corrole Induced by Protonation of the Oxo Ligand

“…The rate constant for the intermolecular ET rate constant ( k ET ) was evaluated using the Marcus cross relationship (eq ): k 11 and k 22 are the rate constants for self-exchange reactions, K 12 is the ET equilibrium constant, and f is a frequency factor close to unity . According to the Marcus cross relationship (eq ), the rate constant of intermolecular ET was estimated to be in the range of 3 × 10 9 –3 × 10 10 M –1 s –1 using k 11 of 5.3 × 10 6 M –1 s –1 for Me 2 Fc/Me 2 Fc + , k 22 value of 1 × 10 9 –1 × 10 11 M –1 s –1 , based on values for porphyrin species, and a K 12 value (calculated from E 1/2 of the cyclic voltammetry of (tpfc +• )­Mn IV (OH), Figure S2) of 1.9 × 10 3 . The estimated rate constant is consistent with the experimental measurements that k ET > 10 7 M –1 s –1 .…”

A colorimetric molecular probe for Cu(ii) ions based on the redox properties of Ru(ii) phthalocyanines

“…species by: (1) solvating the copper(II) ions, giving rise to [Cu(II)(CH 3 CN) 6 ] 2+ , with enhanced redox potential, able to oxidize the phthalocyanine 1 14 and (2) stabilizing the copper(I) ions through the formation of [Cu(I)(CH 3 CN) 4 ] + , which is known as one of the most stable copper(I) species. 14,15 Finally, once the selective chemical sensing of Cu(II) was determined we focused on the reversibility of the process. In order to examine this, we carried out a series of experiments employing different anions, which have been previously described as excellent Cu(II)/Cu(I) coordinating agents.…”

Hexanuclear Gold(I) Phosphide Complexes as Platforms for Multiple Redox‐Active Ferrocenyl Units

“…[19] In the presence of a chemical oxidant, Cu(OTf) 2 (E o [Cu 2+/+ ] = ca. 0.66 V vs. Fc + /0 ), [20] the ferrocene-containing complexes 1-7, display noticeable spectroscopic changes in the electronic absorption spectra. The UV/Vis absorption spectral changes of 4 (1.5 10 À5 m) in acetonitrile (0.1 m nBu 4 N(OTf)) upon addition of Cu(OTf) 2 (0-4 mm) are illustrated in Figure 2 as an example.…”