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Hopf et al. reported the high-temperature 6π-electrocyclization of cis-hexa-1,3-diene-5-yne to benzene in 1969. Subsequent studies using this cyclization have been limited by its very high reaction barrier. Here, we show that the reaction barrier for two model systems, (E)-1,3,4,6-tetraphenyl-3-hexene-1,5-diyne (1a) and (E)-3,4-bis(4-iodophenyl)-1,6-diphenyl-3-hexene-1,5-diyne (1b), is decreased by nearly half on a Au(111) surface. We have used scanning tunneling microscopy (STM) and noncontact atomic force microscopy (nc-AFM) to monitor the Hopf cyclization of enediynes 1a,b on Au(111). Enediyne 1a undergoes two sequential, quantitative Hopf cyclizations, first to naphthalene derivative 2, and finally to chrysene 3. Density functional theory (DFT) calculations reveal that a gold atom from the Au(111) surface is involved in all steps of this reaction and that it is crucial to lowering the reaction barrier. Our findings have important implications for the synthesis of novel graphene nanoribbons. Ullmann-like coupling of enediyne 1b at 20 °C on Au(111), followed by a series of Hopf cyclizations and aromatization reactions at higher temperatures, produces nanoribbons 12 and 13. These results show for the first time that graphene nanoribbons can be synthesized on a Au(111) surface using the Hopf cyclization mechanism.

Vertically oriented nanostructures bring unparalleled high surface area, light trapping capability, and high device density to electronic, optoelectronic, and energy storage devices. However, general methods to prepare such structures remain sparse and are typically based on anodized metal oxide templates. Here, we demonstrate a new approach: using vertically oriented tetraaniline nanopillar arrays as templates for creating nanopillars and nanotubes of other materials. The tetraaniline templates are scalable and easy to prepare. Vertical arrays of a variety of materials can be created by directly coating them onto the tetraaniline nanopillars via vapor, solution, or electrodeposition. Since the tetraaniline template is encased within the target material, it does not require post-deposition removal, thus enabling vertical structure formation of sensitive materials. Conversely, removal of the encased tetraaniline template provides vertically oriented nanotube arrays in a lost-wax-type operation. The resulting vertical structures exhibit a high degree of orientation and height uniformity, with tunable feature size, spacing, and array density. Furthermore, the deposition location and shape of the vertical arrays can be patterned at a resolution of 3 μm. Collectively, these attributes should broaden the material repertoire for vertically oriented structures, and lead to advancements in energy storage, electronics, and optoelectronics.

The synthesis of graphene nanoribbons (GNRs) that contain site-specifically substituted backbone heteroatoms is one of the essential goals that must be achieved in order to control the electronic properties of these next generation organic materials. We have exploited our recently reported solid-state topochemical polymerization/cyclization-aromatization strategy to convert the simple 1,4-bis(3-pyridyl)butadiynes 3a,b into the fjord-edge nitrogen-doped graphene nanoribbon structures 1a,b (fjord-edge N2[8]GNRs). Structural assignments are confirmed by CP/MAS 13C NMR, Raman, and XPS spectroscopy. The fjord-edge N2[8]GNRs 1a,b are promising precursors for the novel backbone nitrogen-substituted N2[8]AGNRs 2a,b. Geometry and band calculations on N2[8]AGNR 2c indicate that this class of nanoribbons should have unusual bonding topology and metallicity.

The efficiency of biological photosynthesis results from the exquisite organization of photoactive elements that promote rapid movement of charge carriers out of a critical recombination range. If synthetic organic photovoltaic materials could mimic this assembly, charge separation and collection could be markedly enhanced. We show that micelle-forming cationic semiconducting polymers can coassemble in water with cationic fullerene derivatives to create photoinduced electron-transfer cascades that lead to exceptionally long-lived polarons. The stability of the polarons depends on the organization of the polymer-fullerene assembly. Properly designed assemblies can produce separated polaronic charges that are stable for days or weeks in aqueous solution.

Our program on capacitive energy storage is a comprehensive one that combines experimental and computational components to achieve a fundamental understanding of charge storage processes in redox-based materials, specifically transition metal oxides. Some of the highlights of this program are the identification of intercalation pseudocapacitance in Nb2O 5, which enables high energy density to be achieved at high rates, and the development of a new route for synthesizing mesoporous films in which preformed nanocrystal building blocks are used in combination with polymer templating. The resulting material architectures have large surface areas and enable electrolyte access to the redox active pore walls, while the interconnected mesoporous film provides good electronic conductivity. Select first-principles density-functional theory studies of prototypical pseudocapacitor materials are reviewed, providing insight into the key physical and chemical features involved in charge transfer and ion diffusion. Rigorous multiscale physical models and numerical tools have been developed and used to reproduce electrochemical properties of carbon-based electrochemical capacitors with the ultimate objective of facilitating the optimization of electrode design. For the organic photovoltaic (OPV) program, our focus has been ongoing beyond the trial-and-error Edisonian approaches that have been responsible for the increase in power conversion efficiency of blend-cast (BC) bulk heterojunction blends of polymers and fullerenes. Our first approach has been to use molecular self-assembly to create the ideal nanometer-scale architecture using thermodynamics rather than relying on the kinetics of spontaneous phase segregation. We have created fullerenes that self-assemble into one-dimensional stacks and have shown that use of these self-assembled fullerenes lead to dramatically enhanced OPV performance relative to fullerenes that do not assemble. We also have created self-assembling conjugated polymers that form gels based on electrically continuous cross-linked micelles in solution, opening the possibility for water-processable "green" production of OPVs based on these materials. Our second approach has been to avoid kinetic control over phase separation by using a sequential processing (SqP) technique to deposit the polymer and fullerene materials in separate deposition steps. The polymer layer is deposited first, using solvents and deposition conditions that optimize the polymer crystallinity for swelling and hole mobility. The fullerene layer is then deposited in a second step from a solvent that swells the polymer but does not dissolve it, allowing the fullerene to penetrate into the polymer underlayer to the desired degree. Careful comparison of composition- and thickness-matched BC and SqP devices shows that SqP not only produces more efficient devices but also leads to devices that behave more consistently. © 2014 American Chemical Society.

The efficiency of bulk heterojunction (BHJ) organic photovoltaics is sensitive to the morphology of the fullerene network that transports electrons through the device. This sensitivity makes it difficult to distinguish the contrasting roles of local electron mobility (how easily electrons can transfer between neighboring fullerene molecules) and macroscopic electron mobility (how well-connected is the fullerene network on device length scales) in solar cell performance. In this work, a combination of density functional theory (DFT) calculations, flash-photolysis time-resolved microwave conductivity (TRMC) experiments, and space-charge-limit current (SCLC) mobility estimates are used to examine the roles of local and macroscopic electron mobility in conjugated polymer/fullerene BHJ photovoltaics. The local mobility of different pentaaryl fullerene derivatives (so-called 'shuttlecock' molecules) is similar, so that differences in solar cell efficiency and SCLC mobilities result directly from the different propensities of these molecules to self-assemble on macroscopic length scales. These experiments and calculations also demonstrate that the local mobility of phenyl-C60 butyl methyl ester (PCBM) is an order of magnitude higher than that of other fullerene derivatives, explaining why PCBM has been the acceptor of choice for conjugated polymer BHJ devices even though it does not form an optimal macroscopic network. The DFT calculations indicate that PCBM's superior local mobility comes from the near-spherical nature of its molecular orbitals, which allow strong electronic coupling between adjacent molecules. In combination, DFT and TRMC techniques provide a tool for screening new fullerene derivatives for good local mobility when designing new molecules that can improve on the macroscopic electron mobility offered by PCBM. The roles of local and macroscopic electron mobility in conjugated polymer/fullerene BHJ photovoltaics are examined via a combination of density functional theory, flash-photolysis time-resolved microwave conductivity, and space-charge-limit current (SCLC) mobility estimates. The local mobility of different fullerene derivatives ('shuttlecock' molecules) is similar, so differences in solar cell efficiency and SCLC mobilities result directly from the different propensities of these molecules to self-assemble on macroscopic length scales. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A study was conducted to investigate the double Diels-Alder cycloaddition of two tethered isobenzofurans to the fullerene [C.sub.60]. The method helps to easily perform the saturation of two of the three C=C double bonds within a six-membered ring of [C.sub.60] and provides the means of saturating the remaining double bond of a six-membered ring of [C.sub.60] via the side chains of the isobenzofurans with suitably reactive functional groups.

A conjugated amphiphilic polyelectrolyte, a poly(phenylene ethylene) (PPE), and the structurally analogous neutral polymer are synthesized. It is concluded on the basis of a combination of absorption and photoluminescence spectroscopy and dynamic light scattering that the solution-phase aggregation of the uncharged PPE could be reversibly controlled by varying the solvent polarity and concentration.

The 2-azaphenalenyl radical 2 is synthesized and characterized by ESR spectroscopy. Variable-temperature ESR measurements were carried out on both the phenalenyl and the 2-azaphenalenyl radicals.

Experiments were conducted where asymmetries were observed across a monolayer of dimethylanilinoaza(C(sub 60))fullerene, (DMA-NC(sub 60), 1) sandwiched between gold electrodes of relatively large size (0.265 mm(super 2)). The result showed a sigmoidal and slightly asymmetric behavior bespeaking of a moderate unimolecular rectification, and a high increase in the current to 0.3 to 1 A.

Research has been conducted on the diastereomeric tetrakisfulleroids. The synthesis of these compounds carried out via the use of trans-1 bis-Diels-Alder adduct is described.

The link between fullerene structure and triplet properties was examined.

The formation of several 1,2-bisketenes by the photolysis of cyclobutenediones has been studied, and time-resolved infrared spectroscopy has been used to observe the species. UV spectroscopy was used to measure the rates of thermal conversion of 1,2-bisketenes back to cyclobutenediones, including ketenes with CN,super6, Br,super7 alkynyl,super8 thio,super9 and alkoxysuper10 substituents.

C60 unit undergoes Diels-Alder reaction with 1,3-dienes to form the ball-and-chain system having C60 and donor-substituted aryl chromophores linked through a rigid saturated polynorbornane-bicyclo(2.2.0)hexane hydrocarbon bridge. A similar reaction of bis(diene) forms soluble dumb-bell system having two C60 chromophores. The norbornylogous bridge transfers electrons and energy by a strong through-bond coupling mechanism. Ab initio, semi-empirical, and molecular mechanics show that activation barriers between folded and extended conformers have a consistent value.

The special symmetry properties of fullerene pi-system allow strong electron coupling with the tetraalkyl-p-phenylenediamine donor hydrocarbon bridge to allow photoinduced electron transfer. Photoexcitation in (C60(3)TMPD) system results in a complete intramolecular charge separation and is independent of solvent polarity. The charge separated states are not detected due to fast charge recombination. In (C60(11)DMA), the photoinduced charge separation occurs only in polar solvents like benzonitrile and the dipolar state can be detected because of the slow rate of charge recombination.

The synthesis of nanosized molecular allotropes of carbon and rigid fullerene-rich polymers is made possible by utilizing fullerenes with solubilizing fragments which are easily withdrawn. The transformation of t-BOC to C60 includes the in situ production of diene which suffer (4+2) cycloaddition with dimethyl acetylenedicarboxylate giving the bicyclic complex, which on fast cycloreversion lead to C60 and dimethyl phthalate.

The lithium salt of a specific hydrazone was reacted with C60 to yield diethynylmethanobuckministerfullerene, which was subjected to desilylation. CI-TQMS, IR, UV-vis and NMR spectroscopies were used to characterize this compound. Buckministerfullerene produced single oxygen to inhibit HIV-1 protease and promote DNA cleavage. The diethynyl compound was found in macrocyclic and polymeric carbon allotropes.

The Diels-Alder functionalization and the verification of alcohol with alpha-benzyl N-(tert-butoxycarbonyl)-L- glutamate, and N-(benzyloxycarbonyl)-L-alamine were used to prepare the first alpha amino acid derivatives of C60. The reduction of ketone, obtained in good yield by the Diels Alder reaction of 2-(trimethylsiyl)oxy-1,3-butadiene with C60, results in the formation of 1, 9-(4-hydroxycyclohexano) buckminster fullerene.

A molecular approach is described to the control of both the length-scale of polymer/fullerene phase segregation and the electron mobility in the fullerene network. Bulk heterojunction solar cells are studied in order to understand how molecular control over fullerene-fullerene interactions might translate into a favorable BHJ morphology and thus improve electron mobility and photovoltaic device performance.

The set of remarkable systems for exploring atomic interactions and molecular dynamics are provided by trapping the atoms and molecules inside the fullenrene cages. The H NMR measurements on the endohederal H2@AOCF in solid state is described.

Fullerenes are unparalleled among carbon-based molecules in their combination of structural, topological, and electronic features. The methodology is described which allows a straightforward insertion of a C(sub 2) unit onto the framework of C(sub 60) giving stable C(sub 62) derivatives in a one-pot synthesis.

The photophysical properties of two novel C60 derivatives are examined and these compounds consist of a ring-opened C60 and its dihydro precursor, both, which include an orifice. The triplet-state photophysical properties of a unique pair of fullerene derivatives containing an orifice in the carbon cage are studied.