(5,15-Dianthracen-9-yl-10,20-dihexyl­porphyrinato)nickel(II): a planar nickel(II) porphyrin

The title compound, [Ni(C60H52N4)], is an example of a meso tetra­substituted nickel(II) porphyrin with both meso aryl and alkyl residues. The mol­ecule exhibits a planar macrocycle with an average deviation of the 24 macrocycle atoms from their least-squares plane (Δ24) of 0.01 Å and an average Ni—N bond length of 1.960 (2) Å. The NiII atom lies on a center of inversion. The structure presents a rare example for a planar nickel(II) porphyrin, as meso-substituted nickel(II) porphyrins with either only meso-aryl or with meso-alkyl residues typically exhibit a ruffled conformation

Clay-fulleropyrrolidine nanocomposites

In this work, we describe the insertion of a water-soluble bisadduct fulleropyrrolidine derivative into the interlayer space of three layered smectite clays. The composites were characterized by a combination of powder X-ray diffraction, transmission electron microscopy, X-ray photoemission and FTIR spectroscopies, and laser flash photolysis measurements. The experiments, complemented by computer simulations, give insight into the formation process, structural details, and properties of the fullerene/clay nanocomposites. The reported composite materials constitute a new hybrid system, where C-60 differs from its crystals or its solutions, and open new perspectives for the design and construction of novel C-60-based organic/clay hybrid materials.</p

Self-assembly of chiral-at-end diketopyrrolopyrroles: symmetry dependent solution and film optical activity and photovoltaic performanace

Chiral thiophene-diketopyrrolopyrrole derivatives have been synthesised to investigate the potential of stereochemistry and symmetry as a means of modulating properties by influencing self-assembly of these purely organic materials. In particular, derivatives of diketopyrrolopyrrole were employed because of their proven interest as dyes, especially for organic solar cells. The natural product myrtenal was used as the source of stereochemistry, introduced through a Kröhnke reaction of a thiophenebearing pyridinium salt and diketopyrrolopyrroles were prepared through Suzuki coupling with this chiral moiety at one end only as well as at both ends. Absorption spectroscopy and electrochemistry confirmed the potential suitability of the compounds for photovoltaic devices. The nanostructures formed by the compounds have been probed with circular dichroism spectroscopy in solution and in films. It is shown that a chiral C2 symmetric molecule assembles in solution giving a strong circular dichroic signal while as a film this optical activity is nulled, whereas an asymmetric homologue is most optically active as a thin film. The X-ray crystal structure of the asymmetric compound shows a polar order of the molecules that might explain this observation. The lack of optical activity in solution is very likely a result of the high solubility of the compound. The results reaffirm the sensitivity of circular dichroism spectroscopy to inter-chromophore organisation, whereas absorption spectroscopy in the visible region reveals only slight changes to the bands. The differing order in the compounds also affects their performance in bulk heterojunction photovoltaic devices. Atomic force microscopy of the blended thin films with the fullerene derivative usually employed (PC61BM) showed that smooth and well mixed films were achieved, with the conditions required during spin coating depending greatly on the derivative, because of their differing solubility. The apparently better performance of the symmetrical compound (although with very low efficiency) is probably a result of the alignment of the molecules inferred by the circular dichroism experiments, whereas the asymmetric compound presumably adopts a twisted supramolecular organisation

X-ray photoemission spectroscopy study on the effects of functionalization in fulleropyrrolidine and pyrrolidine derivatives

Fulleropyrrolidine and pyrrolidine derivatives were studied using X-ray photoemission spectroscopy in order to determine the effects of the C60-cage on the pyrrolidine nitrogen, as well as the influence of further derivatisation. Charge transfer from the carbon pyrrolidine ring to the C60-cages is observed and this charge redistribution influences not only the carbon atoms but also the nitrogen. The major influence of different functionalization groups on the pyrrolidine nitrogen is whether or not they lead to quaternisation while no differences could be detected for different groups (methyl group or alkyl chain) producing one or the other configuration. However, the type of counter ion is important for the stability of the pyrrolidinium nitrogen: demethylated nitrogen, always found to be present in iodide counter balanced compounds, disappears in compounds counter balanced with BF4- anion.

Dendrimer-Functionalized Single-Wall Carbon Nanotubes: Synthesis, Characterization, and Photoinduced Electron Transfer

We describe the synthesis and characterization of a series of single-wall carbon nanotubes (SWNTs) functionalized with polyamidoamine dendrimers. Importantly, the dendrimers are linked directly to the SWNT surface using a divergent methodology. This approach allows the number of functional groups on the nanotubes to be increased without provoking significant damage to the conjugated p-system of the SWNTs

Nucleosides as organizing agents

International audienceIn the present review, we discuss the results of the research we have done over the last decade on multiporphyrinic architectures bearing a nucleotidic backbone, compare all the data, offer a novel overview, and emphasize common capabilities of nucleosides appearing in various systems, providing a new insight on the preorganizing capabilities of nucleosidic backbones. The efficiency of nucleosides as preorganizing agents was investigated through the synthesis and study of various bisporphyrins bearing nucleosidic linkers, as well as through the investigation of the conformation of linear and arborescent multiporphyrins constructed on a nucleosidic backbone. The capacity of these molecules to complex guests with a high association constant was used as a tool to evaluate their degree of preorganization, as well as the investigation of the electronic coupling existing between their chromophores and their photo chemical capacities. Such an overview of one decade of scientific investigations documents the fact that rigid linkers between chromophores are not necessary for their spatial preorganization, opening new routes to the faster synthesis of flexible highly preorganized molecular architectures avoiding the long and tedious synthesis of rigid tweezers, especially for the preparation of rigid linkers which may bring solubility and stability problems