ZnTPP cation radical

Phenylmethylphenacylsulfonium p-toluenesulfonate (PMPS), an onium salt, is known as a self-destructive electron acceptor which decomposes rapidly into phenylmethylsulfide and a phenacyl rachcal upon accepting an electron (59). When PMPS is added to an aqueous solution of ZnTPP-functionalized unimer micelles, the electron acceptor is localized on the anionic surface of the unimer micelle. The election transfer from the 2HnTPP triplet to PMPS produces a ZnTPP cation radical (ZnTPP ) and a phenacyl radical as transient species (Scheme 1), but reaction between these two transient species, which usually follows the photoinduced forward election transfer in homogeneous solutions, is prevented in the unimer micelle system because the ZnTPP " and phenacyl radical species are separated. Thus, the porphyrin cation radicals can be accumulated in the unimer micelle. 

Analysis of the absorption amd MOD spectra of ZnTPP and MgOEP. The opticad absorption and MOD spectra of ZnTPP" " and HgOEP " , shown in Figures 2 and 3, are representative of the A2u suid Aj q ground states, respectively, that are found for porphyrin tr-cation radical species. Results from deconvolution cadculations carried out for both the absorption amd MCD spectrad envelopes of these tt-cation radicad spectra are adso shown in Figures 2 and 3, plotted as the individuad component bamds that are... 

Bienvenue et al. [96] used the expression similar to Eq. (40) to describe quantitatively the dependence of the photocurrent through the planar BLM upon the applied photo voltage AU in the System 40 of Table 1. Photocurrent was caused by the the transfer through membrane of ZnTPP+ radical cations. Note that in this case the potential difference affecting the motion of ZnTPP+ cation is equal to only 60% of the external voltage apparently due to the location of ZnTPP+ sufficiently deep below the surface of the membrane. 

Zn OEP undergoes a fully reversible one-electron oxidation at 525 mV [Fuhrhop (78)] and ZnTPP at 710 mV [.Felton (59)]. The visible spectra of the resulting cr-cation radicals consist of one broad band covering the whole visible range. Zn OEP+ forms a stable n-n dimer, which produces a very strong, broad absorption band with a maximum around 930 nm [Fuhrhop (79)]. This diamagnetic dimer has exactly the same redox behavior as the monomer and is also formed when the monomeric radical is crystallized. 

The decay of the ESR signal caused by the porphyrin cation radical in the poly(A/Cd/ZnTPP) system is much slower than that in the poly(A/La/ ZnTPP) system. A detectable amount of porphyrin cation radicals persisted more than 1 day in the poly(A/Cd/ZnTPP) system. In the terpolymer sys-... 

The porphyrin skeletal mode frequencies are all slightly lower both for the triplet and for the ground state. Table II lists the triplet downshifts, l-7cm , along with the shifts observed for radical cations (13a) and anions (13b) for MgTPP and ZnTPP reported by Itoh and coworkers. Since the triplet excited states are formed by... 

The mechanism for substitution of a nucleophile at a P-position of the ZnTPP macrocycle is a little different, since an EiCNmesoE2CNpCB process occurs in this case with two different successive nucleophilic attacks [110]. After electrogeneration of the porphyrin radical cation (ZnTPP step Ei), a first nucleophilic attack takes place at a wieso-position (step CNmeso)- This is kinetically more favorable because there is a larger charge density on the mesocarbons as compared to that on the P-carbons [123,124]. However, there is no proton that can be removed from the substituted me o-position after the second oxidation step (step E2) in this case, and a second nucleophilic attack takes place at the P-position (step Cnp) which simultaneously leads to the loss of the pyridinium attached to the /new-position. Then, the spare proton at the P-position can be removed in a last step in order to recover the aromaticity of the macrocycle (step Cb). As before, the global reaction can be written as shown in Eq. 2 ... 

Excitation of the metallo-porphyrin occurs by transfer of an electron to the ZnTPP radical cation, yielding a-tetralone and water as the other products. The reaction of ZnTPP with other peroxides known to generate excited carbonyl products by other mechanisms has also been examined [8]. Chemiluminescence is inefficient in all these other cases confirming the special features claimed for direct formation of excited states from secondary peroxides. 

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