Photogeneration porphyrins

Immoos CE, Di Bilio AJ, Cohen MS, van Der Veer W, Gray HB, Farmer PJ. Electron-transfer chemistry of Ru-linker(heme)-modified myoglobin rapid intraprotein reduction of photogenerated porphyrin cation radical. Inorg Chem 2004 43 3593-6. 

Harima et al. (1989) measured the photogeneration efficiencies of 5,10,15,20-tetraphenylporphyrin (TPP) and its Zn complex (ZnTPP) doped with tetracyano-quinodimethane (TCNQ), o-chloranil (Chi), phenothiazine (Pz), and I. TCNQ, Chi, and I are electron acceptors while Pz is a donor. The porphyrins were selected on the basis of differences in exciton diffusion lengths (Tanimura et al., 1980 Yamashita et al., 1987) and oxidation potentials (Felton, 1978). The photogeneration of I doped ZnTPP was described by a direct ionization process via a singlet state of ZnTPP and ascribed to a reduction of the electron-hole recombination rate in the depletion layer. For TPP doped with Chi, Pz, or I, the results were explained by exciplex dissociation (Loutfy and Menzel, 1980). For... 

Presented experimental data reveal that for CdSe/ZnS quantum dots with two ZnS monolayers values follow a monotonous function drastically decaying with the QD core diameter. From the physico-chemical point of view, we conjecture that upon interaction of P with QD surface, the electron wave function may be locally modified (via inductive and/or mesomeric effects [9]) forming a surface local state capable to trap the electron of the photogenerated exciton (Fig. 2A). Thus, we will consider the behaviour of the electron wave function at the interface to the functional pyridyl group of the attached porphyrin. The single-carrier envelope wave functions y/a in a spherical core/shell QD are determined by the Schrodinger equation... 

Under circumstances where the sensitizer is efficiently reduced by the donor in the excited state, then one can obtain photoreduction of MV2+ via a reductive cycle. Proflavine and other acridine dyes sensitized reduction of MV2+ as well as Zn-Porphyrin sensitized reduction under high donor concentrations have been shown111,319 to follow such a mechanism. In both cases, the photogenerated sensitizer anion-radicals being good reductants themselves, also can play the role of the acceptor (relay) molecules. With efficient Pt-PVA catalysts, it has been shown118,333 to be the case for proflavine and Ru(bipy)3. 

The electron-donor aspect of molecules such as porphyrins can be used to induce charge-transfer photogeneration in surfaces. -... 

The phthalocyanines are still of some interest, and Ayers has interpreted the photoelectrochemistry of copper phthalocyanine in terms of the band-model for semiconductors. Menzel et alf have studied the photoconductivity and electrical field-induced fluorescence quenching in metal-free phthalocyanine films. Doping of the film increases charge-carrier photogeneration, and it seems likely that the mechanism is extrinsic, involving field-assisted exciplex dissociation. These are complicated materials, which are difficult to purify, and the mechanisms of carrier generation in polycrystalline and amorphous films are still obscure. The porphyrins and monolayer assemblies of chlorophyll on SnOj electrodes 2 72,273 ijggjj studied. 

The upper lim cone conformed calix[4]arene-zinc porphyrin (ZP) conjugate 180 derivatized at ZP with a p5u-omellitimide (PI) electron acceptor at the distal position on calixarene with a carotenoid unit was designed and S5mthesized for stud5ung the electric field effect of photogenerated ion pair on an adjacent chromophore. The photoinduced charge separation within a ZP-PI electron donor-acceptor pair having an 8.4 A center-center distance in a linear orientation has been found to... 

Schaafsma, T.J., T.J. Savenije, R.B.M. Koehorst, RJ. Vergeldt, and J. Wienke (1997). Luminescent properties and photogeneration of charge carriers in porphyrin dimers and molecular photo-diodes. J. Lumin. 72-74, 81-82. 

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