Tetrabenzo[8]circulene: Aromatic Saddles from Negatively Curved Graphene

An aromatic saddle was designed from the hypothetical three-dimensional graphene with the negative Gaussian curvature (Schwarzite P192). Two aromatic saddles, tetrabenzo[8]­circulene (<b>TB8C</b>) and its octamethyl derivative <b>OM-TB8C</b>, were synthesized by the Scholl reaction of cyclic octaphenylene precursors. The structure of <b>TB8C</b> greatly deviates from planarity, and the deep saddle shape was confirmed by single-crystal X-ray crystallography. There are two conformers with the <i>S</i>₄ symmetry, which are twisted compared to the DFT structure (<i>D</i>_2<i>d</i>). The theoretical studies propose that the interconversion of <b>TB8C</b> via the planar transition state (125 kcal mol^–1) is not possible. However, the pseudorotation leads to a low-energy tub-to-tub inversion via the nonplanar transition state (7.3 kcal mol^–1). The ground-state structure of <b>TB8C</b> in solution is quite different from the X-ray structure because of the crystal-packing force and low-energy pseudorotation. <b>OM-TB8C</b> is a good electron donor and works as the p-type semiconductor

Tetrabenzo[8]circulene: Aromatic Saddles from Negatively Curved Graphene

An aromatic saddle was designed from the hypothetical three-dimensional graphene with the negative Gaussian curvature (Schwarzite P192). Two aromatic saddles, tetrabenzo[8]­circulene (<b>TB8C</b>) and its octamethyl derivative <b>OM-TB8C</b>, were synthesized by the Scholl reaction of cyclic octaphenylene precursors. The structure of <b>TB8C</b> greatly deviates from planarity, and the deep saddle shape was confirmed by single-crystal X-ray crystallography. There are two conformers with the <i>S</i>₄ symmetry, which are twisted compared to the DFT structure (<i>D</i>_2<i>d</i>). The theoretical studies propose that the interconversion of <b>TB8C</b> via the planar transition state (125 kcal mol^–1) is not possible. However, the pseudorotation leads to a low-energy tub-to-tub inversion via the nonplanar transition state (7.3 kcal mol^–1). The ground-state structure of <b>TB8C</b> in solution is quite different from the X-ray structure because of the crystal-packing force and low-energy pseudorotation. <b>OM-TB8C</b> is a good electron donor and works as the p-type semiconductor

Tetrabenzo[8]circulene: Aromatic Saddles from Negatively Curved Graphene

An aromatic saddle was designed from the hypothetical three-dimensional graphene with the negative Gaussian curvature (Schwarzite P192). Two aromatic saddles, tetrabenzo[8]­circulene (<b>TB8C</b>) and its octamethyl derivative <b>OM-TB8C</b>, were synthesized by the Scholl reaction of cyclic octaphenylene precursors. The structure of <b>TB8C</b> greatly deviates from planarity, and the deep saddle shape was confirmed by single-crystal X-ray crystallography. There are two conformers with the <i>S</i>₄ symmetry, which are twisted compared to the DFT structure (<i>D</i>_2<i>d</i>). The theoretical studies propose that the interconversion of <b>TB8C</b> via the planar transition state (125 kcal mol^–1) is not possible. However, the pseudorotation leads to a low-energy tub-to-tub inversion via the nonplanar transition state (7.3 kcal mol^–1). The ground-state structure of <b>TB8C</b> in solution is quite different from the X-ray structure because of the crystal-packing force and low-energy pseudorotation. <b>OM-TB8C</b> is a good electron donor and works as the p-type semiconductor

Tetradecafluorosexithiophene: The First Perfluorinated Oligothiophene

Tetradecafluorosexithiophene:  The First Perfluorinated Oligothiophen

Tetradecafluorosexithiophene: The First Perfluorinated Oligothiophene

Tetradecafluorosexithiophene:  The First Perfluorinated Oligothiophen

Dynamic Assembly of Coordination Boxes from (en)Pd(II) Unit and a Rectangular Panel-Like Ligand: NMR, CSI-MS, and X-ray Studies

Dynamic Assembly of Coordination Boxes from (en)Pd(II) Unit and a Rectangular Panel-Like Ligand:  NMR, CSI-MS, and X-ray Studie

Tetracyclo(2,7-carbazole)s: Diatropicity and Paratropicity of Inner Regions of Nanohoops

Three N-substituted tetracyclo­(2,7-carbazole)­s were synthesized to investigate the inner regions of nanohoops. One compound has a 5,5-dimethylnonane bridge between two neighboring <i>anti</i>-carbazoles, which can be used as covalently bonded “methane probes”. These probes near the ring center are strongly shielded by local ring currents and exhibit a singlet at δ = −2.70 ppm in ¹H NMR. To visualize local and macrocyclic ring currents separately, we drew nucleus-independent chemical shift contour maps of tetracyclo­(9-methyl-2,7-carbazole) and [<i>n</i>]­cycloparaphenylenes (CPPs). Local ring currents make the interior diatropic, and paratropic regions exist only outside the ring. Macrocyclic ring currents in [5]­CPP to [7]­CPP generate deshielding cones, which are typical of antiaromatic [4<i>n</i>]­annulenes

Selective and Random Syntheses of [<i>n</i>]Cycloparaphenylenes (<i>n</i> = 8–13) and Size Dependence of Their Electronic Properties

[n]Cycloparaphenylenes (n = 8–13, CPPs) were synthesized, and their physical properties were systematically investigated. [8] and [12]CPPs were selectively prepared from the reaction of 4,4′-bis(trimethylstannyl)biphenyl and 4,4′′-bis(trimethylstannyl)terphenyl, respectively, with Pt(cod)Cl2 (cod = 1,5-cyclooctadiene) through square-shaped tetranuclear platinum intermediates. A mixture of [8]–[13]CPPs was prepared in good combined yields by mixing biphenyl and terphenyl precursors with platinum sources. Products were easily separated and purified by using gel permeation chromatography. In 1H NMR spectra, the proton of the CPPs shifts to a lower field as n increased due to an anisotropic effect from the nearby PP moieties. Although the UV–vis spectra were rather insensitive to the size of the CPPs, the fluorescence spectra changed significantly in relation to their size. A larger Stokes shift was observed for the smaller CPPs. Redox properties of the CPPs were measured for the first time by using cyclic voltammetry, and the smaller CPPs had lower oxidation potentials. The results are consistent with the HOMO energies of CPPs, of which the smaller CPPs had higher energies

Synthesis, Characterization, and Electron-Transport Property of Perfluorinated Phenylene Dendrimers

Synthesis, Characterization, and Electron-Transport Property of Perfluorinated Phenylene Dendrimer

Tetracyclo(2,7-carbazole)s: Diatropicity and Paratropicity of Inner Regions of Nanohoops

Three N-substituted tetracyclo­(2,7-carbazole)­s were synthesized to investigate the inner regions of nanohoops. One compound has a 5,5-dimethylnonane bridge between two neighboring <i>anti</i>-carbazoles, which can be used as covalently bonded “methane probes”. These probes near the ring center are strongly shielded by local ring currents and exhibit a singlet at δ = −2.70 ppm in ¹H NMR. To visualize local and macrocyclic ring currents separately, we drew nucleus-independent chemical shift contour maps of tetracyclo­(9-methyl-2,7-carbazole) and [<i>n</i>]­cycloparaphenylenes (CPPs). Local ring currents make the interior diatropic, and paratropic regions exist only outside the ring. Macrocyclic ring currents in [5]­CPP to [7]­CPP generate deshielding cones, which are typical of antiaromatic [4<i>n</i>]­annulenes