Electron transfer porphyrin-based models

The synthesis of a molecule consisting of two porphyrin rings (free base or Zn complex) rigidly held by a 1, 10-phenanthroline spacer is described. This new molecule in which distance and orientation of the two porphyrins are well-defined may be an interesting model for the understanding of photodriven electron transfer processes within a redox chain. In particular, oblique disposition and large centre-to-centre separation between the two porphyrins, will they favour the slowing down of recombination reactions ... 

The value of k may be estimated as 6.3 x 10 s from the 1.6-ns fluorescence lifetime of a model zinc porphyrin which cannot imdergo energy or electron transfer. Thus, by Eq. 5, k is 2.2 x 10 s . Because the 2.7-ns component has the spectrum of the free base porphyrin, it represents the decay of Pzn- Pp- This decay should include step 4 and the electron transfer step 5. The value of the rate constant for step 4 may be estimated as 1.2 x 10 s from the 8.5-ns the singlet excited state lifetime (tq) measured for a model porphyrin for Pp. The electron transfer rate constant from the free base porphyrin to yield Pzn -Pp , is 2.5 x 10 s from ... 

The anthraquinone-based bolaphile 7 or 8 could not form homogeneous membranes due to steric interactions (Scheme 3) however, they could be integrated into host membranes formed by dihexadecylphosphate and dime-thyldioctadecylammonium bromide. The bolaamphiphile fixed the quinone functionality in the center of the membrane and served as a model for pool quinones. [20] Electron transfer was further demonstrated by light-induced charge transfer between cationic porphyrins dissolved in water and membrane-bound anthraquinone bolaphiles. [27]... 

A special situation is encountered with metal-porphyrin or metal-phthalo-cyanine molecules that can be either deposited by sublimation under UHV conditions or in solution environments. For these macrocyclic compounds, free-base species exist, i.e., the metal centers are not required per se as a construction unit. The building of supramolecular structures that incorporate porphyrin subunits is of great interest to many research groups. The rich photochemistry and redox properties (e.g., photoinduced electron transfer, luminescence, and light harvesting) of porphyrins have driven this interest. Porphyrins or phtalocyanines have a rich coordination chemistry that allows the inclusion of many different metal centers at their macrocycle. They serve in many respects as a model system since this constitutes a low-coordination complex. Recent STM studies report on the organization of metal-coordinated or free-base porphyrins as well as phthalocyanines on... 

Construction of intramolecular systems whose photoactive molecules are linked with conducting and insulating molecular wires is an important objective towards the realization of molecular electronic or photonic devices. For such an objective, systematization of donor-photosensitizer-acceptor triad molecules into large molecular systems is one of the feasible approaches to realize a simple model. This is because the incorporation of a photoactive moiety and a suitable electron donor and/or acceptor into a conducting polymeric chain is useful for various molecular electronic systems based on photoinduced electron transfer (11). A symmetrical donor-acceptor-donor triad molecule was polymerized by normal electrochemical oxidation which led to one-dimensional donor-acceptor polymers with porphyrin moieties separated by an ordered oligothienyl molecular wire (ID porphyrin array) (12). 

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