Porphyrins fullerene complexation

The most recent report of -coordination to a ruthenium porphyrin fragment details the reaction of [Ru(OEP)j2 with C o in benzene/THF (100 1) solution. The UV-visible spectrum of the complex showed a new band at 780 nm, not observed in the spectrum of either Ru(OEP) 2 or C(,o, and H and C NMR data also indicated the presence of a new complex. This has been formulated on the basis of the spectroscopic data as the fullerene complex Ru(OEP)(... 

Fullerenes are spontaneously attracted to porphyrins and metalloporphyrins. The palladium-linked m-pyridyl dimer (shown in Figure 42) has a high binding constant in solution. Addition of C60 or C70 to solutions of these palladium-linked bis-porphyrins gave complexes that were chromatographically distinct from their individual components. This indication of tight binding was also seen in MALDI mass spectra.517... 

Reaction of 217 with Cjq leads to the amino-protected porphyrin-fulleropyrroli-dine, which can easily be deprotected to the corresponding amine [229, 277]. By further functionalization via amide coupling an easy access to extended donor-acceptor systems is possible. A carotene-porphyrin-fullerene triad was prepared by reaction of the amine with the appropriate carotene acid chloride. The motivation for the synthesis of all these donor-acceptor systems is the attempt to understand and imitate the photosynthetic process. On that score, a model for an artificial photosynthetic antenna-reaction center complex has been achieved by attaching five porphyrin cores in a dendrimer-like fashion to the fullerene [242]. 

Fig. 6.51 Dendritically linked porphyrin/zinc complexes with fullerene at the focal point (according to Aida et al.)...

FIGURE 2.2 Supramolecular nanostructures for light driven energy and electron transfer. This research is focused on rational design and study of self-assembled porphyrin, fullerene, and carbon nanotube bearing supramolecular complexes and nanostructures. 

Both simple porphyrin-fullerene dyads and more complex systems may be very useful in artificial photosynthetic or molecular-scale electronie applications, due espeeially to the low reorganization energy of fullerenes and their low sensitivity to solvent parameters. 

Fig. 4 Schematic drawing of the inclusion adduct of fullerene inside the jaw-like bis-porphyrin Pd complex (see [60])...

Sun D, Tham FS, Reed CA, Chaker L, Boyd PD (2002) Supramolecular fullerene-porphyrin chemistry, fullerene complexation by metalated Jaws Porphyrin Hosts. J Am Chem Soc 124(23) 6604-6612... 

Various tripod systems have been synthesized with the goal of fullerene complexation (Fignre 9). One such scaffold involves a tripod with rigid linkers this system is proposed to make a supramolecnlar network wherein the net stoichiometry is expected to be 1 2 (tripod to fullerene). On the basis of an experimental analysis, it was conclnded that each fnllerene is always held by two porphyrins. These two porphyrins can be oriented snch that a U-shaped arrangement is defined between two porphyrins contained within the same molecule, 8. Or, the two porphyrins can from two separate tripods. In aU cases, the distances between the snrface of Ceo and the porphyrin plane were fonnd to range from 2.52 to 2.92 A, as wonld be expected for a system in which n-n interactions persist. 

Efficiency of the fullerene complexation is governed by the length of the linker between the porphyrin molecules and gold nanoparticle. The optimal linker was found to be... 

A methanofullerene derivative possessing an ammonium subunit has been prepared and subsequently shown to form a supramolecular complex with a porphyrin-crown ether conjugate <06T1979>. The synthesis and study of these fullerene-containing supramolecular photoactive devices have also been reported <06CRC1022>. 

Redox molecules are particularly interesting for an electrochemical approach, because they offer addressable (functional) energy states in an electrochemically accessible potential window, which can be tuned upon polarization between oxidized and reduced states. The difference in the junction conductance of the oxidized and the reduced forms of redox molecules may span several orders of magnitude. Examples of functional molecules used in these studies include porphyrins [31,153], viologens [33, 34,110,114,154,155], aniline and thiophene oligomers [113, 146, 156, 157], metal-organic terpyridine complexes [46, 158-163], carotenes [164], nitro derivatives of OPE (OPV) [165, 166], ferrocene [150, 167, 168], perylene tetracarboxylic bisimide [141, 169, 170], tetrathia-fulvalenes [155], fullerene derivatives [171], redox-active proteins [109, 172-174], and hydroxyquinones [175]. 

Other examples have shown that pristine fullerenes serve as electron shuttles in liquid-based electrolytes [100,101], In this context, clusters of pristine fullerenes were deposited on top of Ti02 electrodes that were modified with ruthenium (II) complex, porphyrins, and fluorescein. All of these examples featured overall enhancements of... 

Reaction of 175 with Cgg yields a hydroxy-functionalized fullerene that can be further derivatized. This hydroxy-fullerene was coupled with a porphyrine unit via a polyethyleneglycol-Hnker. This linker can be arranged similarly to a crown-ether to complex metal cations. Complexation is used to tune the distance between the porphyrin imit and the Cgg-moiety and thus tune the donor-acceptor properties of this porphyrin-fuUerene hybrid [177]. 

The conjugation in the molecular wire may be disrupted or modulated to create systems with different properties. For example, a porphyrin Ceo donor-acceptor system linked with a conjugated binaphthyl unit, has a preference for the atropi-somer where the fullerene unit is closer to the porphyrin system, thus increasing the through space interactions [82]. The charge transfer process on a dyad containing a crown ether in the linker structure can be modulated by complexation/ decomplexation of sodium cations [83] but even more interesting is the construction of supramolecular systems where the donor and acceptor moieties are... 

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