Blending through-space and through-bond π-π-coupling in [2,2']-paracyclophane-oligophenylenevinylene molecular wires.

A series of ZnP-pCp-oPPV-C60 conjugates covalently connected through [2,2']-paracyclophane-oligophenylenevinylene (pCp-oPPV) bridges containing one, two, and three [2,2']-paracyclophanes (pCps) has been prepared in multistep synthetic procedures involving Horner-Wadsworth-Emmons olefination reactions and/or Heck type Pd-catalyzed reactions. Molecular modeling suggests that charge transfer is effectively mediated by the pCp-oPPVs through a predominant hole-transfer mechanism. Photophysical investigation supports molecular modeling and reveals two major trends.

Dendritic metalloporphyrin-fullerene conjugates: changing the microenvironment around redox-active centers and its impact on charge-transfer reactions.

Photophysical investigations on a series of (2,4,6)-tris-substituted metalloporphyrin-fullerene conjugates revealed the effects of an electron-rich microenvironment surrounding the electron-donating porphyrin as a function of the metal center. On one hand, for all conjugates-water-soluble and non-water-soluble-ultrafast charge separation was observed upon photoexcitation. On the other hand, when examining the charge recombination dynamics for the non-water-soluble conjugates it becomes obvious that the (2,4,6)-tris-substitution stabilizes the radical-ion-pair state relative to the mono-substitution in the ortho-, meta-, and para-position.

Dendronized fullerene-porphyrin conjugates in ortho, meta, and para positions: a charge-transfer assay.

The physicochemical characterization, that is, ground and excited state, of a new series of dendronized porphyrin/fullerene electron donor-acceptor conjugates in nonaqueous and aqueous environments is reported. In contrast to previous work, we detail the charge-separation and charge-recombination dynamics in zinc and copper metalloporphyrins as a function of first- and second-generation dendrons as well as a function of ortho, meta, and para substitution. Both have an appreciable impact on the microenvironments of the redox-active constituents, namely the porphyrins and the fullerenes.

A charge-transfer challenge: combining fullerenes and metalloporphyrins in aqueous environments.

A series of truly water-soluble C(60)/porphyrin electron donor-acceptor conjugates has been synthesized to serve as powerful mimics of photosynthetic reaction centers. To this end, the overall water-solubility of the conjugates was achieved by adding hydrophilic dendrimers of different generations to the porphyrin moiety. An important variable is the metal center of the porphyrin; we examined zinc(II), copper(II), cobalt(II), nickel(II), iron(III), and manganese(III).

Efficient utilization of higher-lying excited states to trigger charge-transfer events.

Several new fullerene-heptamethine conjugates, which absorb as far as into the infrared spectrum as 800 nm, have been synthesized and fully characterized by physicochemical means. In terms of optical and electrochemical characteristics, appreciable electronic coupling between both electroactive species is deduced. The latter also reflect the excited-state features.