A new armchair carbon nanobelt synthesized by tuning the regioselectivity of the Scholl reaction of quinquephenyl.

A new armchair carbon nanobelt is successfully synthesized by tuning the regioselectivity of the Scholl reaction of 1,1':2',1'':4'',1''':2''',1''''-quinquephenyl. This nanobelt exhibits a preferential binding affinity towards C70 over C60 as found from photoluminescence titration experiments.

Synthesis, aromatization and cavitates of an oxanorbornene-fused dibenzo[de,qr]tetracene nanobox.

Oxanorbornene-fused double-stranded macrocycles, represented by kohnkene, are not only synthetic precursors toward short segments of zigzag carbon nanotubes but also typical cavitands processing an intrinsic cavity. However, their capability to bind guest molecules in solution remained unexplored. Herein we report a new member of oxanorbornene-fused double-stranded macrocycles, which is named a nanobox herein because of its shape. Reductive aromatization of this oxanorbornene-fused nanobox leads to observation of a new zigzag carbon nanobelt by high resolution mass spectroscopy. The fluorescence titration and NMR experiments indicate that this nanobox encapsulates C70 in solution with a binding constant of (3.2 ± 0.1) × 106 M-1 in toluene and a high selectivity against C60 and its derivatives. As found from the X-ray crystallographic analysis, this nanobox changes the shape of its cross-section from a rhombus to nearly a square upon accommodating C60.

Synthesis of Zigzag Carbon Nanobelts through Scholl Reactions.

Zigzag carbon nanobelts are a long-sought-after target for organic synthesis. Herein we report new strategies for designing and synthesizing unprecedented zigzag carbon nanobelts, which present a wave-like arrangement of hexagons in the unrolled lattice of (n,0) single wall carbon nanotubes (n=16 or 24). The precursors of these zigzag carbon nanobelts are hybrid cyclic arylene oligomers consisting of meta-phenylene and 2,6-naphthalenylene as well as para-phenylene units. The Scholl reactions of these cyclic arylene oligomers form multiple carbon-carbon bonds selectively at the α-positions of naphthalene units resulting in the corresponding zigzag carbon nanobelts. As monitored with fluorescence spectroscopy, one of these nanobelts binds C60 with an association constant as high as (6.6±1.1)×106  M-1 in the solution in toluene. Computational studies combining linear regression analysis and hypothetical homodesmotic reactions reveal that these zigzag nanobelts have strain in the range of 67.5 to 69.6 kcal mol-1 , and the ladderization step through Scholl reactions is accompanied by increase of strain as large as 69.6 kcal mol-1 . The successful synthesis of these nanobelts demonstrates the powerfulness and efficiency of Scholl reactions in synthesizing strained polycyclic aromatics.

A Nitrogen-Doped Hexapole [7]Helicene versus Its All-Carbon Analogue.

Two synthetic nanographenes (NGs), N-H7H and C-H7H, were prepared. N-H7H is doped with nitrogen, and C-H7H is the all-carbon analogue. Both are hexapole [7]helicenes (H7Hs), and their structures were identified by single-crystal X-ray diffraction. Sharp contrasts in absorption (abs λmax , 683 vs. 593 nm), emission (em λmax , 894 vs. 777 nm), and electrochemical behavior (ox E1 , 0.28 vs. 0.53 V) were observed between N-H7H and C-H7H, and the origin of these differences was rationalized by theoretical calculations. Studies on N-H7H and C-H7H set a clear example to elucidate the remarkable effects of N-doping on the physical properties of NGs.

Synthesis and Characterization of Hexapole [7]Helicene, A Circularly Twisted Chiral Nanographene.

We report the synthesis and characterization of two hexapole [7]helicenes (H7Hs). Single crystal X-ray diffraction unambiguously confirms the molecular structure. H7H absorbs light, with distinct Cotton effect, from ultraviolet to the near-infrared (λmax = 618 nm). Cyclic voltammetry reveals nine reversible redox states, consecutively from -2 to +6. These chiroptical and electronic properties of H7H are inaccessible from helicene's small homologues.

A julolidine-fused anthracene derivative: synthesis, photophysical properties, and oxidative dimerization.

We describe the synthesis and characterization of a julolidine-fused anthracene derivative J-A, which exhibits a maximum absorption of 450 nm and a maximum emission of 518 nm. The fluorescent quantum yield was determined to be 0.55 in toluene. J-A dimerizes in solution via oxidative coupling. Structure of the dimer was characterized using single crystal X-ray diffraction.

Janusarene: A Homoditopic Molecular Host.

A homoditopic molecular host, janusarene, is presented that has two back-to-back compactly arranged nanocavities for guest complexation. The unique two-face structural feature of janusarene allows it to bind and align various guest compounds concurrently, which include spherical pristine fullerene C60 and planar polycyclic aromatic hydrocarbons (PAHs), such as pyrene, perylene, and 9,10-dimethylanthracene. The host-guest interactions were characterized by single-crystal X-ray diffraction. A pairwise encapsulation of the PAH guests by janusarene enables PAH dimers to be obtained that deliver spectroscopic properties distinct from those of PAHs dissolved in solution, or in the bulk state. A monotopic control host was also synthesized and used to characterize the host-guest complexing behavior in solution.