One-Pot Divergent Synthesis of a 13-Ring Triquinone and its Facile Conversion to a [4.4.4]Tridecastarphene.

Acenes are notable for their optoelectronic properties and applications in organic electronics. Starphenes are structurally related molecules possessing three acene arms that radiate linearly from a central benzene ring (i. e.

Syntheses, characterizations and reactions of acene-2,3-dicarbaldehydes.

Here, we report improved syntheses, detailed characterizations and reactions of a series of acene-2,3-dicarbaldehydes including tetracene-2,3-dicarbaldehyde. DFT calculations corroborate and complement the experimental results. Tetracene-2,3-dicarbaldehyde and the benchmark organic semiconductor pentacene have isoelectronic π-systems and similar HOMO-LUMO gaps.

Kinetically stabilized 1,3-diarylisobenzofurans and the possibility of preparing large, persistent isoacenofurans with unusually small HOMO-LUMO gaps.

DFT calculations demonstrate that an isoacenofuran of any size possesses a smaller HOMO-LUMO gap than the corresponding acene bearing an isoelectronic π-system (i.e., the same total number of rings).

Interfacial shear stress between single-walled carbon nanotubes and gold surfaces with and without an alkanethiol monolayer.

A novel and effective technique is developed to make the first determination of shear stress between dielectrophoretically assembled single-walled carbon nanotubes (SWNTs) and surfaces. The results demonstrate that we can vary the shear stress by a factor of 20 by functionalizing a gold surface with different alkanethiols. The interfacial shear stress between a small bundle of SWNTs and a gold surface with and without self-assembled monolayers of alkanethiol (2-phenylethanethiol or 2-aminoethanethiol) is determined.

An improved synthesis of pentacene: rapid access to a benchmark organic semiconductor.

Pentacene is an organic semiconductor used in a variety of thin-film organic electronic devices. Although at least six separate syntheses of pentacene are known (two from dihydropentacenes, two from 6,13-pentacenedione and two from 6,13-dihydro-6,13-dihydroxypentacene), none is ideal and several utilize elevated temperatures that may facilitate the oxidation of pentacene as it is produced. Here, we present a fast (-2 min of reaction time), simple, high-yielding (≥ 90%), low temperature synthesis of pentacene from readily available 6,13-dihydro-6,13-dihydroxypentacene.

Probing intramolecular CH-π interactions in o-quinodimethane adducts of [60]fullerene using variable temperature NMR.

Several o-quinodimethane adducts of [60]fullerene were synthesized and their intramolecular aryl CH-fullerene π interactions were studied using variable temperature-NMR (VT-NMR). Evaluation of the rate constants associated with the first-order transition states for cyclohexene boat-to-boat inversions enables quantification of ΔG(‡) values for each inversion. A comparison between two constitutional isomers, only one of which is capable of intramolecular CH-π interactions, provides a lower limit of 0.

Open-shell singlet character of stable derivatives of nonacene, hexacene and teranthene.

The electronic ground states of the recently synthesized stable nonacene derivatives (J. Am. Chem.

Design, synthesis, and characterization of a persistent nonacene derivative.

A significant technical barrier (i.e., facile oxidative degradation) that has prevented the preparation of large acenes has now been breached.

Field-assisted nanopatterning of metals, metal oxides and metal salts.

The tip-based nanofabrication method called field-assisted nanopatterning or FAN has now been extended to the transfer of metals, metal oxides and metal salts onto various receiving substrates including highly ordered pyrolytic graphite, passivated gold and indium-tin oxide. Standard atomic force microscope tips were first dip-coated using suspensions of inorganic compounds in solvent. The films prepared in this manner were non-uniform and contained inorganic nanoparticles.

Molecular self-assembly of functionalized fullerenes on a metal surface.

We present a combined experimental and theoretical study of the self-assembly of C60 molecules functionalized with long alkane chains on the (111) surface of silver. We find that the conformation of the functionalized C60 changes upon adsorption on Ag(111) and that the unit cell size in the self-assembled monolayer is determined by the interactions between the functional groups. We show that C60 molecules can be assembled in ordered 2D arrays with intermolecular distances much larger than those in compact C60 layers, and propose a novel way to control the surface pattern by appropriate chemical functionalization.

Exploiting substituent effects for the synthesis of a photooxidatively resistant heptacene derivative.

Substituent effects have been exploited to produce an unusually persistent heptacene derivative. In total, four new heptacene derivatives with varying levels of photooxidative resistance (1 < 2 < 3 < 4) have been synthesized. A combination of p-(t-butyl)thiophenyl substituents at positions 7 and 16 (i.

1,2-Dimethyl-4,5-diphenyl-benzene determined on a Bruker SMART X2S benchtop crystallographic system.

The title compound, C(20)H(18), has two crystallographically independent mol-ecules in the asymmetric unit. The phenyl substituents of mol-ecule A are twisted away from the plane defined by the central benzene ring by 131.8 (2) and -52.

2,3-Bis(bromo-meth-yl)-1,4-diphenyl-benzene.

In the title compound, C(20)H(16)Br(2), the terminal phenyl groups are twisted away from the central ring by approximately 55 and -125° (average of four dihedral angles each), respectively. The crystal structure is stabilized by a combination of inter-molecular and intra-molecular inter-actions including inter-molecular π-π stacking inter-actions [C atoms of closest contact = 3.423 (5) Å].

2,5-Dichloro-thio-phene 1,1-dioxide.

The complete mol-ecule of the title compound, C(4)H(2)Cl(2)O(2)S, is generated by crystallographic twofold symmetry, with the S atom lying on the rotation axis. In the crystal, the molecules are linked by C-H⋯O hydrogen bonds..

Substituent effects in pentacenes: gaining control over HOMO-LUMO gaps and photooxidative resistances.

A combined experimental and computational study of a series of substituted pentacenes including halogenated, phenylated, silylethynylated and thiolated derivatives is presented. Experimental studies include the synthesis and characterization of six new and six known pentacene derivatives and a kinetic study of each derivative under identical photooxidative conditions. Structures, HOMO-LUMO energies and associated gaps were calculated at the B3LYP/6-311+G**//PM3 level while optical and electrochemical HOMO-LUMO gaps were measured experimentally.

Self-assembly of long chain alkanes and their derivatives on graphite.

We combine scanning tunneling microscopy (STM) measurements with ab initio calculations to study the self-assembly of long chain alkanes and related alcohol and carboxylic acid molecules on graphite. For each system, we identify the optimum adsorption geometry and explain the energetic origin of the domain formation observed in the STM images. Our results for the hierarchy of adsorbate-adsorbate and adsorbate-substrate interactions provide a quantitative basis to understand the ordering of long chain alkanes in self-assembled monolayers and ways to modify it using alcohol and acid functional groups.

Hydrogenation of single-wall carbon nanotubes using polyamine reagents: combined experimental and theoretical study.

We combine experimental observations with ab initio calculations to study the reversible hydrogenation of single-wall carbon nanotubes using high boiling polyamines as hydrogenation reagents. Our calculations characterize the nature of the adsorption bond and identify preferential adsorption geometries at different coverages. We find the barrier for sigmatropic rearrangement of chemisorbed hydrogen atoms to be approximately 1 eV, thus facilitating surface diffusion and formation of energetically favored, axially aligned adsorbate chains.

Thermal, sonochemical, and mechanical behaviors of single crystal [60]fullerene nanotubes.

Although related to conventional carbon nanotubes in both shape and construction, fullerene nanowhiskers and fullerene nanotubes have received far less attention. A modified liquid-liquid interfacial precipitation technique is described to produce relatively uniform batches of [60]fullerene nanotubes in high yield. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) reveal that the tubes possess approximately 100-nm inside diameters and 300-nm outside diameters.

4,7-diphenylisobenzofuran: a useful intermediate for the construction of phenyl-substituted acenes.

The formation and subsequent reactivity of previously unknown 4,7-diphenylisobenzofuran, 5, is reported. The Diels-Alder reaction between 5 and p-benzoquinone in boiling glacial acetic acid yields an unprecedented exo,exo anti dual cycloaddition product, 16b, in excellent yield and with 100% diastereoselectivity. Differences between the reactivities of 5 and the more common 1,3-diphenylisobenzofuran are highlighted.

Toward uniform nanotubular compounds: synthetic approach and ab initio calculations.

We propose to synthesize a new class of single-walled nanotubular compounds (SWNCs) and investigate the interplay between their structural and electronic properties using ab initio density functional calculations. SWNCs are composed of cyclacenes of variable diameter interconnected by various linker compounds. Cyclacenes map directly onto and can be viewed as the shortest segments of (n,0) zigzag carbon nanotubes.

Facile, scalable, regioselective synthesis of C3v C60H18 using organic polyamines.

[chemical structure: see text]. Organic polyamines are efficient reagents for the regioselective hydrogenation of [60]fullerene. When [60]fullerene is heated in diethylenetriamine, a known C60H18 isomer with C3v symmetry is produced and isolated in good purity without the need for chromatographic separation.

Fullerene-acene chemistry: diastereoselective synthesis of a cis,cis-tris[60]fullerene adduct of 6,8,15,17-tetraphenylheptacene.

[structure: see text]. A one-pot, diastereoselective synthesis of a cis,cis-tris[60]fullerene adduct of 6,8,15,17-tetraphenylheptacene has been demonstrated starting from [60]fullerene and 5,7,9,14,16,18-hexahydro-6,8,15,17-tetraphenylheptacene.

Fullerene-acene chemistry: single-crystal X-ray structures for a [60]fullerene-pentacene monoadduct and a cis-bis[60]fullerene adduct of 6,13-diphenylpentacene.

[structure: see text]. Crystal structures of the cis-bis[60]fullerene adduct of 6,13-diphenylpentacene (with the closest carbon atoms on adjacent fullerenes only 3.065(8) angstroms apart) and the [60]fullerene-pentacene monoadduct are in remarkably close agreement with the MM2 calculated structures.