The nature and characteristics of the CH/π interaction are discussed by comparison with other weak molecular forces such as the CH/O and OH/π interaction. The CH/π interaction is a kind of hydrogen bond operating between a soft acid CH and a soft base π-system (double and triple bonds, C6 and C5 aromatic rings, heteroaromatics, convex surfaces of fullerenes and nanotubes). The consequences of CH/π hydrogen bonds in supramolecular chemistry are reviewed on grounds of recent crystallographic findings and database analyses. The topics include intramolecular interactions, crystal packing (organic and organometallic compounds), host/guest complexes (cavity-type inclusion compounds of cyclodextrins and synthetic macrocyclic hosts such as calixarenes, catenanes, rotaxanes and pseudorotaxanes), lattice-inclusion type clathrates (including liquid crystals, porphyrin derivatives, cyclopentadienyl compounds and C60 fullerenes), enantioselective clathrate formation, catalytic enantioface discriminating reactions and solid-state photoreaction. The implications of the CH/π concept for crystal engineering and drug design are evident.

CH/π hydrogen bonds in crystals

In the last three decades, zero-dimensional, one-dimensional, and two-dimensional carbon nanomaterials (i.e., fullerenes, carbon nanotubes, and graphene, respectively) have attracted significant attention from the scientific community due to their unique electronic, optical, thermal, mechanical, and chemical properties. While early work showed that these properties could enable high performance in selected applications, issues surrounding structural inhomogeneity and imprecise assembly have impeded robust and reliable implementation of carbon nanomaterials in widespread technologies. However, with recent advances in synthesis, sorting, and assembly techniques, carbon nanomaterials are experiencing renewed interest as the basis of numerous scalable technologies. Here, we present an extensive review of carbon nanomaterials in electronic, optoelectronic, photovoltaic, and sensing devices with a particular focus on the latest examples based on the highest purity samples. Specific attention is devoted to each class of carbon nanomaterial, thereby allowing comparative analysis of the suitability of fullerenes, carbon nanotubes, and graphene for each application area. In this manner, this article will provide guidance to future application developers and also articulate the remaining research challenges confronting this field.

Carbon nanomaterials for electronics, optoelectronics, photovoltaics, and sensing

Fullerenes and porphyrins are molecular architectures ideally suited for devising integrated, multicomponent model systems to transmit and process solar energy. Implementation of C60 as a 3-dimensional electron acceptor holds great expectations on account of their small reorganization energy in electron transfer reactions and has exerted a noteworthy impact on the improvement of light-induced charge-separation. This article describes how the specific compositions of porphyrin chromophores linked to C60—yielding artificial light harvesting antenna and reaction center mimics—have been elegantly utilized to tune the electronic couplings between donor and acceptor sites and the total reorganization energy. Specifically, the effects that these parameters have on the rate, yield and lifetime of the energetic charge-separated states are considered.

Fullerene–porphyrin architectures; photosynthetic antenna and reaction center models

Polymer solar cells (PSCs) are composed of a blend film of a conjugated polymer donor and a soluble fullerene derivative acceptor sandwiched between a PEDOT : PSS coated ITO positive electrode and a low workfunction metal negative electrode. The conjugated polymer donor and the fullerene derivative acceptor are the key photovoltaic materials for high performance PSCs. For the acceptors, although [6,6]-phenyl-C61-butyric acid methyl ester (PC60BM) and its corresponding C70 derivative PC70BM are dominantly used as the acceptors in PSC at present, several series of new fullerene derivatives with higher-lying LUMO energy level and better solubility were reported in recent years for further improving the power conversion efficiency of the PSCs. In this perspective paper, we reviewed the recent research progress on the new fullerene derivative acceptors, including various PC60BM-like C60 derivatives, PC60BM bisadduct, PC70BM bisadduct, indene-C60 bisadduct and indene-C70 bisadduct, trimetallic nitride endohedral fullerenes and other C60 derivatives with multi side chains. The synthesis and physicochemical properties of PC60BM and PC70BM were also introduced considering the importance of the two fullerene acceptors.

Fullerene derivative acceptors for high performance polymer solar cells

The idea1 that fullerenes might be able to encapsulate atoms and molecules has been verified by the successful synthesis of a range of endohedral fullerenes, in which metallic or non-metallic species are trapped inside the carbon cage2,3,4,5,6,7,8,9,10,11,12,13. Metal-containing endohedral fullerenes have attracted particular interest as they might exhibit unusual material properties associated with charge transfer from the metal to the carbon shell. However, current synthesis methods have typical yields of less than 0.5%, and produce multiple endohedral fullerene isomers, which makes it difficult to perform detailed studies of their properties. Here we show that the introduction of small amounts of nitrogen into an electric-arc reactor allows for the efficient production of a new family of stable endohedral fullerenes encapsulating trimetallic nitride clusters, ErxSc3-xN@C80 (x = 0–3). This ‘trimetallic nitride template’ process generates milligram quantities of product containing 3–5% Sc3N@C80, which allows us to isolate the material and determine its crystal structure, and its optical and electronic properties. We find that the Sc3N moiety is encapsulated in a highly symmetric, icosahedral C80 cage, which is stabilized as a result of charge transfer between the nitride cluster and the fullerene cage. We expect that our method will provide access to a range of small-bandgap fullerene materials, whose electronic properties can be tuned by encapsulating nitride clusters containing different metals and metal mixtures.

Small-bandgap endohedral metallofullerenes in high yield and purity

Solutions of C60, C60O, or C70 and metal complexes of octaethylporphyrin (OEPH2) yield crystals that contain both the fullerene and the porphyrin. The structures of C60·2CoII(OEP)·CHCl3, C60·2ZnII(OEP)·CHCl3, and C60O·2CoII(OEP)·CHCl3 are isomorphous and contain an ordered C60 cage surrounded by two MII(OEP) units. Although there is no covalent bond between the fullerene and porphyrin components, the separation between these units is shorter than normal van der Waals contact. Crystals of C70·CoII(OEP)·C6H6·CHCl3, C70·NiII(OEP)·C6H6·CHCl3, and C70·CuII(OEP)·C6H6·CHCl3 are also isomorphous with an ordered fullerene, but have only one porphyrin/fullerene contact. Crystalline C60·ClFeIII(OEP)·CHCl3 lacks the close face-to-face porphyrin/porphyrin contact that is common to all of the other structures reported here but retains the intimate contact between the porphyrin and the fullerene. In (C120O)·CoII(OEP)·0.6C6H6·0.4CHCl3 the fullerene dimer is enclosed by two CoII(OEP) moieties. Unfortunately disorder in th...

Interaction of Curved and Flat Molecular Surfaces. The Structures of Crystalline Compounds Composed of Fullerene (C60, C60O, C70, and C120O) and Metal Octaethylporphyrin Units

Formation of a Curved Silver Nitrate Network That Conforms to the Shape of C60 and Encapsulates the Fullerene—Structural Characterization of C60{Ag(NO3)}5

Nature 401, 55–57; 1999 In the second paragraph on page 55, the third sentence is misleading and should read “The yields even exceed those of the empty-cage C84” (without the erroneously inserted text “…the usually most abundant species…”).

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Erratum: Small-bandgap endohedral metallofullerenes in high yield and purity

Pentamethylcyclopentadienylruthenium(II) half-sandwich complexes containing the alkenyl phosphine ligand allyldiphenylphosphine (ADPP) are described. ADPP reacts with [(η5-C5Me5)RuCl2]2 to give the...

Hemilabile Properties of the η3-Allyldiphenylphosphine (ADPP) Homophosphaallyl Ligand: Synthesis and Reactions of [(η5-C5Me5)Ru(η3-ADPP)(η1-ADPP)][PF6]

Kalyani Maitra

Papers

Small-bandgap endohedral metallofullerenes in high yield and purity

Interaction of Curved and Flat Molecular Surfaces. The Structures of Crystalline Compounds Composed of Fullerene (C60, C60O, C70, and C120O) and Metal Octaethylporphyrin Units

Formation of a Curved Silver Nitrate Network That Conforms to the Shape of C60 and Encapsulates the Fullerene—Structural Characterization of C60{Ag(NO3)}5

Erratum: Small-bandgap endohedral metallofullerenes in high yield and purity

Hemilabile Properties of the η3-Allyldiphenylphosphine (ADPP) Homophosphaallyl Ligand: Synthesis and Reactions of [(η5-C5Me5)Ru(η3-ADPP)(η1-ADPP)][PF6]