Nathalie Solladié

Organic solar cells. Supramolecular composites of porphyrins and fullerenes organized by polypeptide structures as light harvesters

We have constructed supramolecular solar cells composed of a series of porphyrin–peptide oligomers [porphyrin functionalized α-polypeptides, P(H2P)n or P(ZnP)n (n = 1, 2, 4, 8, 16)], and fullerenes assembled on a nanostructured SnO2 electrode using an electrophoretic deposition method. Remarkable enhancement in the photoelectrochemical performance as well as the broader photoresponse in the visible and near-infrared regions is seen with increasing the number of porphyrin units in α-polypeptide structures. Formation of supramolecular clusters of porphyrins and fullerenes prepared in acetonitrile–toluene = 3 : 1 has been confirmed by transmission electron micrographs (TEM) and the absorption spectra. The highly colored composite clusters of porphyrin–peptide oligomers and fullerenes have been assembled as three-dimensional arrays onto nanostructured SnO2 films using an electrophoretic deposition method. A high power conversion efficiency (η) of ∼1.6% and the maximum incident photon-to-photocurrent efficiency (IPCE = 56%) were attained using composite clusters of free base and zinc porphyrin–peptide hexadecamers [P(H2P)16 and P(ZnP)16] with fullerenes, respectively. Femtosecond transient absorption and fluorescence measurements of porphyrin–fullerene composite films confirm improved electron-transfer properties with increasing number of porphyrins in a polypeptide unit. The formation of molecular assemblies between porphyrins and fullerenes with a polypeptide structure controls the electron-transfer efficiency in the supramolecular complexes, meeting the criteria required for efficient light energy conversion.

A supramolecular cup-and-ball C60-porphyrin conjugate system

In addition to the ammonium-crown ether recognition, pi-stacking interactions between the C60 sphere and the porphyrin moiety have been evidenced in a supramolecular complex obtained from a porphyrin-crown ether conjugate and a fullerene derivative bearing an ammonium unit.

Synthesis and Characterization of Novel Pyrene-Dendronized Porphyrins Exhibiting Efficient Fluorescence Resonance Energy Transfer: Optical and Photophysical Properties

A novel series of pyrene dendronized porphyrins bearing two and four pyrenyl groups (Py(2)-TMEG1 and Py(4)-TMEG2) were successfully synthesized. First and second generation Fréchet type dendrons (Py(2)-G1OH and Py(4)-G2OH) were prepared from 1-pyrenylbutanol and 3,5-dihydroxybenzyl alcohol. These compounds were further linked to a trimesitylphenylporphyrin containing a butyric acid spacer via an esterification reaction to obtain the desired products. Dendrons and dendronized porphyrins were fully characterized by FTIR and (1)H NMR spectroscopy and their molecular weights were determined by matrix-assisted laser desorption ionization time of flight mass spectrometry. Their optical and photophysical properties were studied by absorption and fluorescence spectroscopies. The formation of dynamic excimers was detected in the pyrene-labeled dendrons, with more excimer being produced in the higher generation dendron. The fluorescence spectra of the pyrene dendronized porphyrins exhibited a significant decrease in the amount of pyrene monomer and excimer emission, jointly with the appearance of a new emission band at 661 nm characteristic of porphyrin emission, an indication that fluorescence resonance energy transfer (FRET) occurred from one of the excited pyrene species to the porphyrin. The FRET efficiency was found to be almost quantitative ranging between 97% and 99% depending on the construct. Model Free analysis of the fluorescence decays acquired with the pyrene monomer, excimer, and porphyrin core established that only residual pyrene excimer formation in the dendrons could occur before FRET from the excited pyrene monomer to the ground-state porphyrin core.

Synthesis of multiporphyrinic α-polypeptides: towards the study of the migration of an excited state for the mimicking of the natural light harvesting device

Abstract The synthesis of a porphyrin functionalized derivative of the l -lysine is reported. Three peptides, bearing, respectively, two, four and eight chromophores, have been synthesized using the new porphyrin functionalized amino-acid.

ROTAXANES AND OTHER TRANSITION METAL-ASSEMBLED PORPHYRIN ARRAYS FOR LONG-RANGE PHOTOINDUCED CHARGE SEPARATION

Abstract Bis-porphyrin conjugates have been synthesized for performing long-range photoinduced charge separation. The electron donor is a zinc(II) porphyrin in the excited state and the electron acceptor is a gold(III) porphyrin. These elements or their free-base analogs have been assembled following two different strategies. In a first approach, the porphyrinic subunits, separated by one or more 2,9-diphenyl-1,10-phenanthroline spacers, have been incorporated into rotaxane structures containing up to four threaded macrocycles by copper(I) templated synthesis. In a second approach, a triad having strictly controlled geometry has been prepared following a new gathering strategy. This triad, consisting of two porphyrinic moieties assembled via a central bis(phenyl-terpyridine)ruthenium(II) complex, uses coordination rather than covalent chemistry to interconnect the components.

Novel porphyrinic peptides with assigned sequence of metallated chromophores, a further step towards redox switches

This paper reports the synthesis and the characterization of peptides encompassing an assigned sequence of chromophores. The obtained pentaporphyrin is expected to be a good candidate for the elaboration of redox switches.

Supramolecular click chemistry for the self-assembly of a stable Zn(II)–porphyrin–C60 conjugate

Owing to the complementarity between a bis-Zn(II)-porphyrin receptor and a fullerene ligand bearing two pyridine substituents, the substrate can be clicked onto the ditopic receptor, thus leading to a stable non-covalent macrocyclic 1 ratio 1 complex.

Exploitation of an unexpectedin situ heteroaromatic bromination for the synthesis of a porphyrin functionalized nucleoside

Abstract A 2′-deoxyuridine derivative functionalized via an acetylenic junction with a Zn(II) tetraarylporphyrin has been prepared. Is also reported an unexpected in situ bromination of the uracil nucleic base at the C5 position, which occurs during the transformation of a dibromo-olefin into its corresponding acetylenic anion. Download full-size image

Large photoactive supramolecular ensembles prepared from C60–pyridine substrates and multi-Zn(II)–porphyrin receptors

Fullerene derivatives bearing a pyridine sub-unit have been prepared. Their ability to form self-assembled supramolecular structures with mono- and polytopic Zn(II)–porphyrin receptors has been first evidenced by UV-vis studies. These supramolecular complexes are multi-component photoactive devices, in which the emission of the porphyrinic receptor is dramatically quenched by the fullerene units. This new property, resulting from the association of the different molecular sub-units, also allowed us to investigate in detail the self-assembly process using fluorescence titrations. The binding studies revealed positive cooperative effects for the assembly of the C60–pyridine derivatives with polytopic receptors as a result of intramolecular C60–C60 interactions between the different guests assembled onto the multi-Zn(II)–porphyrin hosts.

Polypeptides with pendant porphyrins of defined sequence of chromophores: towards artificial photosynthetic systems

In this paper we now report our ongoing progress in the preparation of artificial photosynthetic systems through the preparation of light harvesting multi-porphyrins. A tetramer, constituted of a central dipeptide functionalized by two free-base porphyrins and surrounded by one amino-acid bearing a pendant Zn(II) porphyrin on each side, has been chosen. The optical and photophysical properties of this tetramer have been studied by absorption and fluorescence spectroscopy. In addition, the energy transfer phenomenon has been studied and monitored by femtosecond time-resolved fluorescence. Our results indicate that the excited state dynamics redounding in the excitation being localized in the inner free-base porphyrins takes place in the time scale of approximately 1 ps.