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Orthogonal and twisted dimers of pyrrole-fused pentaazapolycyclic hydrocarbons (pentaazacoronene analogs) were synthesized, linked either directly or by phenylenes. Although the dimers and the reference monomer did not have any substituents at the [Formula: see text]-positions of the terminal pyrroles, two reversible oxidation waves were observed in the cyclic voltammograms. ESR measurements of the chemically generated dications of the dimers showed typical radical cation signals, indicating successful accumulation of the redox activity of the pentaazacoronene analog.

Cyclo[8]pyrrole–phosphonate complexes were synthesized via the anion exchange method from cyclo[8]pyrrole sulfate. The molecular structures were determined by X-ray diffraction studies.

During the preparative investigation of [Formula: see text]-expanded porphyrinoids based on the retro-Diels-Alder reaction of bicyclo[2.2.2]octadiene(BCOD)-fused precursors for benzo- and benzo[[Formula: see text]]fluorantho[9,10]-[[Formula: see text]]porphyrins by the [3+1] porphyrin synthesis using tripyrrane-1,14-dicarbaldehyde and BCOD-fused pyrroles, serendipitous formation of the corresponding corroles was observed. After elucidation of the reaction conditions, the [3+1] reaction afforded 21,31-dihydro-21,31-ethanobenzo[[Formula: see text]]fluorantho[9,10-[Formula: see text]]corrole in 23% yield as well as a trace amount of the corresponding porphyrin. In the sapphyrin synthesis by the [3+2] approach using the tripyrrane-1,14-dicarbaldehyde and a bipyrrole, the similar reaction conditions resulted in the formation of 5-pyrrolylcorrole in a 38% yield as well as isosmaragdyrin and the originally targeted sapphyrin.

Bicyclo[2.2.2]octadiene(BCOD)-fused 5,15-diazaporphyrins were synthesized via a metal-template aza-annulation of dipyrrin-metal complexes as a soluble precursor of tetrabenzodiazaporphyrin. 10-Azacorrole copper complex with a meso-imine bridge was serendipitously obtained via the same reaction using dimethylBCOD-fused dipyrrin-copper complex.

[Formula: see text]-Extended azacoronene has been synthesized via an S[Formula: see text]Ar reaction using acenaphthopyrrole and octafluoronaphthalene utilizing successive Scholl reactions. Although the chiral conformers could not be isolated, the new azacoronene analog exhibited longer-wavelength absorption and reversible oxidation properties, which are characteristic of pyrrole-fused azacoronenes. When combined with the results of our DFT calculations, the experimental results indicate weaker global aromaticity than that of previously reported azacoronenes.

π-Expanded homoHPHACs with thiocarbonyl and carbonyl bridges change their global aromaticity in response to external stimuli as observed in tropothione and tropone.

A "3+3" condensation reaction of 1,3-di(2-pyrrolyl)azulene with aryl aldehyde followed by an oxidative aromatization afforded diazuliamethyrin, [24]diazulihexaphyrin(0.1.0.0.1.0). X-ray diffraction analysis revealed a relatively planar structure of diprotonated diazuliamethyrin with a mean plane deviation of 0.37 Å. A 24π non- or antiaromatic character was confirmed by

Bicyclo[2.2.2]octadiene(BCOD)-fused dithiaamethyrin 4 was synthesized via a “3+3” condensation method. Thermal conversion of the BCOD moieties afforded tetrabenzodithiaamethyrin 5. The highly planar structures of 4 and 5 were confirmed by X-ray diffraction studies. The 1H NMR, absorption and MCD spectra, together with TD-DFT calculations revealed that both BCOD-fused and [Formula: see text]-extended dithiaamethyrins have a 24[Formula: see text] antiaromatic character.

Introduction of functional groups on a [Formula: see text]-conjugated system is one of the most promissing methods to modulate their chemical and physical properties. Here, dinitrohexapyrrolohexaazacoronene (dinitroHPHAC) was synthesized, in which two nitro groups are introduced at the same pyrrole ring. The dinitroHPHAC possesses a large dipole moment ([Formula: see text] = 11.7 D at B3LYP/6-31G(d,p)) and showed solvatochromism with decreased HOMO-LUMO energy gap. Interestingly, the colour of the solid is black to the naked eye. The global aromaticity of the dication state is decreased compared with those of pristine HPHAC and mononitroHPHAC.

Cyclo[9]pyrrole, a ring-expanded porphyrin without meso-bridges and having an odd number of pyrroles, was synthesized via the oxidative coupling of 2,2':5',2″-terpyrrole. X-ray crystallography showed a C2-like symmetry with a large root-mean-square deviation. The optical properties and electronic structures were analyzed using magnetic circular dichroism spectroscopy and time-dependent density functional theory calculations.

Here we report a highly stable 16π-electron antiaromatic system based on the ligand-oxidized Cu(ii)-tetrabenzocorrole. The antiaromaticity of the monocationic corrole complex was elucidated with the unique bond length alternation pattern of the crystal structure and the spectral diagnostic features. The NICS and GIMIC calculations clearly depicted its inner 15-membered-ring main pathway with a strong paratropic ring current.

Performing bottom-up synthesis by using molecules adsorbed on a surface is an effective method to yield functional polycyclic aromatic hydrocarbons (PAHs) and nanocarbon materials. The intramolecular cyclodehydrogenation of hydrocarbons is a critical process in this synthesis; however, thus far, its elementary steps have not been elucidated thoroughly. In this study, we utilize the metal tip of a low-temperature noncontact atomic force microscope as a manipulable metal surface to locally activate dehydrogenation for PAH-forming cyclodehydrogenation. This method leads to the dissociation of a H atom of an intermediate to yield the cyclodehydrogenated product in a target-selective and reproducible manner. We demonstrate the metal-tip-catalyzed dehydrogenation for both benzenoid and nonbenzonoid PAHs, suggesting its universal applicability as a catalyst for nanographene synthesis.

Symmetrical octaphenyltetrabenzoporphyrins 3 were synthesized via cyclotetramerization from bicyclo[2.2.2]octadiene (BCOD)-fused pyrrole, followed by a thermal conversion based on retro Diels–Alder...

A rigid wing-shaped bicyclo[2.2.2]octadiene-fused bis-hexapyrrolohexaazacoronene (HPHAC) is synthesized, and subsequent chemical oxidation affords a stable biradical dication and an aromatic tetracation. The physicochemical properties and single-crystal structures in various oxidation states are characterized. The face-to-face π-stacked dimeric structures are observed in the neutral and dicationic states. The HPHAC flakes can act as aromatic walls in a tetracation state, producing enlarged induced magnetic shielding space through the superimposition effect.

A ring-contracted carbaporphyrin, azulitriphyrin(2.1.1), was synthesized via intramolecular McMurry coupling reaction. Absorption, NMR spectra and NICS calculations of protonated azulitriphyrin(2.1.1) revealed its Hückel aromatic character as a 14[Formula: see text] porphyrinoid.

A helicene compound called AIBTh, wherein two azulene units are fused with isobenzothiophene, has been prepared and characterized by spectroscopic and crystallographic methods. The enantiomers of A...

Novel thermally convertible precursors of tetrabenzoporphyrin (TBP) were synthesized by tetramerization of the corresponding bicyclo[2.2.2]octadiene(BCOD)-fused pyrroles. These precursors showed hi...

Di(acenaphtho)-fused BODIPYs with four electron-withdrawing N,N-dimethylcarbamoyl groups were obtained by complexation of the corresponding dipyrrins, which were also proven to be a stable deep-red...

1,3-Dihydrothieno[3,4-a]- and 1,3,8,10-tetrahydrodithieno[3,4-a;3′4′-m]-HPHACs were prepared by the successive SNAr reactions of hexafluorobenzene with 1,3-dihydrothieno[3,4-c]pyrrole and 3,4-dihex...

Bis(bicyclic) molecules dimethanochrysene and diethanochrysene were prepared by Diels-Alder reaction of the naphthodiyne equivalent with cyclopentadiene and 1,3-cyclohexadiene, respectively. Reaction of dimethanochrysene and 7,9-diphenyl-8H-cyclopent[a]acenaphthylen-8-one resulted in the generation of a fluorescent hydrocarbon in unexpected multistep pericyclic reactions. Syn-oriented diethanochrysene-connected bisporphyrin tweezers was prepared from the reaction of chrysene-bridged syn-dipyrrole with tripyrranedicarbaldehyde. The structure of the receptor and its 1 : 1 complex with C60 or C70 was determined by X-ray diffraction analysis. The dihedral angles of the bicyclo[2.2.2]octadiene moieties were narrowed by complexation of the receptor with the fullerenes. The binding affinities of the tweezers with C60 and C70 were calculated to be 2.7(4)×104 and 8.01(7)×104 M-1 , respectively by UV-vis and fluorescence spectroscopy.

A hexapyrrolohexaazacoronene (HPHAC) with 12 less-bulky peripheral ethyl groups than its aryl-containing HPHAC counterpart was synthesized to investigate the innate character of HPHAC. X-ray diffraction analysis revealed that HPHAC had a planar structure and close packing because of CH-π interactions between the alkyl groups and the HPHAC core. Compared to the previously reported HPHAC decorated with 12 peripheral aryl groups, this electron-rich π-system exhibited reversible multistep oxidations at low potentials and easily formed mono- and dicationic salts and charge-transfer (CT) complexes with 7,7,8,8-tetracyano-p-quinodimethane. These oxidized species exhibited clear changes in the bond-length alternation of the pyrrole units in the crystal state, indicating charge and spin delocalization. The distinct upfield shift of the central carbon signal of the dication in the 13C NMR spectrum affirms the global aromaticity from the viewpoint of a magnetic criterion. In the UV-vis/NIR spectra, broad absorption in the NIR region was observed only for HPHAC2+ and not the structurally similar cyclo[6]pyrrole. Magnetic circular dichroism measurements and time-dependent density functional theory calculations revealed that the broad absorption was assigned to the CT transition from the central benzene ring to the outer pyrrole rings.

Radially π-extended hexapyrrolohexaazacoronene (HPHAC 2) was synthesized in two steps with 2,5-di-tert-butyl-acenaphtho[1,2-c]pyrrole and hexafluorobenzene. Like its parent HPHAC 1a, 2 exhibited re...

New types of macrocyclic compounds, deltaarenes, are prepared. The compounds were readily synthesized in three steps from an arenedithiol and benzoquinone, and the yields of the macrocyclization reaction reached up to 40% under high dilution conditions. X-ray crystallographic analysis revealed that the macrocycle has a relatively rigid trimeric structure with a unique triangular hole, the size of which was approximately 11 A along each side. NMR data suggests that the ring has a C3-symmetric structure. The X-ray analysis showed that the hole is large enough to capture one molecule of chlorobenzene. Use of a variety of dithiols allowed the synthesis of different types of deltaarene derivatives. MO calculations showed that the hole size depends on the dithiol unit. Deprotection of the twelve methoxyl groups was easily achieved by treatment with BBr3 and yielded the free-OH deltaarene derivative.

A core-expanded, pyrrole-fused azacoronene analogue containing two unusual N-doped heptagons was obtained from commercially available octafluoronaphthalene and 3,4-diethylpyrrole in two steps as a heteroatom-doped nonplanar nanographene. Full fusion with the formation of the tetraazadipleiadiene framework and the longitudinally twisted structure was unambiguously confirmed by single-crystal X-ray diffraction analysis. The edge-to-edge dihedral angle along the acene moiety was 63°. This electron-rich π-system showed four reversible oxidation peaks. Despite the nonplanar structure, the Hückel aromaticity owing to a peripheral π-conjugation in the dicationic state was concluded from the bond-length alternation and nucleus-independent chemical shift (NICS) and anisotropy of the induced current density (ACID) calculations.

The adsorption configurations of heptahelicene ([7]H) molecules on Cu(001) are investigated with noncontact atomic force microscopy (ncAFM) and scanning tunneling microscopy (STM). Because of the suppression of thermal diffusion at 5 K, racemic [7]H molecules exist as monomers, dimers, trimers, and tetramers on the surface. The terminal naphthaleno part of the molecule is attached horizontally to the substrate so that the two benzene ring centers are located at the hollow sites, whereas the other terminal is protruded toward a vacuum. A procedure for picking a [7]H molecule up from the surface (vertical manipulation) enables us to functionalize the tip apex to enhance the spatial resolution of ncAFM. The ncAFM images with the helicene tip clarify that whereas the tetramers are homochiral, the dimers and trimers are heterochiral. In contrast, homochiral dimers and trimers are unobservable probably because of the rapid formation of the stable homochiral tetramers. Thus, ncAFM imaging can identify the geomet...

Benzene-fused bis(acenaphthoBODIPY)s prepared by retro-Diels–Alder reaction of bicyclo[2.2.2]octadiene-fused precursors showed strong absorption bands in the near-infrared region and very weak absorptions in the visible region.

In this study, a benzene-fused bis(thiaporphyrin) was synthesized by the retro-Diels–Alder reaction of a bicyclo[2.2.2]octadiene (BCOD)-fused bis(thiaporphyrin) precursor. This precursor was prepared by the double [3+1] porphyrin synthesis of the BCOD-fused dipyrrole with thiatripyrrane. The ultraviolet–visible (UV–vis) spectrum of benzene-fused bis(thiaporphyrin) in dichloromethane was extremely different from that of the corresponding benzene-fused bis(porphyrin). In contrast, extremely similar spectra were obtained in the presence of trifluoroacetic acid. The similar electronic structures in the protonated states were supported by X-ray analysis and time-dependent density-functional theory (TD-DFT) calculations.

Chiral 2,3- trans -substituted piperidines were readily prepared in three steps from β-amino-α-methylene esters, which were prepared by the Michael/Mannich domino reaction of chiral sulfinimines. Hydrogenation of the N -tosyl-2-aryl-1,2,5,6-tetrahydropyridine intermediates took place smoothly in the presence of a Pd/C catalyst to give trans -2,3-disubstituted piperidines in good yields and in a highly stereoselective manner. The total synthesis of optically active ( 2S,3R )-( − )- epi- CP-99,994 was achieved in six-steps from an unsaturated piperidine.

Controlling the structural deformation of organic molecules can drive unique reactions that cannot be induced only by thermal, optical or electrochemical procedures. However, in conventional organic synthesis, including mechanochemical procedures, it is difficult to control skeletal rearrangement in polycyclic aromatic hydrocarbons (PAHs). Here, we demonstrate a reaction scheme for the skeletal rearrangement of PAHs on a metal surface using high-resolution noncontact atomic force microscopy. By a combination of organic synthesis and on-surface cyclodehydrogenation, we produce a well-designed PAH—diazuleno[1, 2, 3-cd:1′, 2′, 3′-fg]pyrene—adsorbed flatly onto Cu(001), in which two azuleno moieties are highly strained by their mutual proximity. This local strain drives the rearrangement of one of the azuleno moieties into a fulvaleno moiety, which has never been reported so far. Our proposed thermally driven, strain-induced synthesis on surfaces will pave the way for the production of a new class of nanocarbon materials that conventional synthetic techniques cannot attain., 金属表面で分子を曲げて骨格を変える新・有機合成法を開発 --原子間力顕微鏡を用いて炭素骨格変換の可視化に成功--. 京都大学プレスリリース. 2017-07-24.

A bicyclo[2.2.2]octadiene(BCOD)-fused bis(dipyrromethane) derivative was reacted with methylal in the presence of trifluoroacetic acid followed by oxidation with chloranil to give a doubly N-confused phlorin derivative, which did not undergo the retro-Diels-Alder reaction extruding an ethylene molecule on heating. In contrast, a 7-tert-butoxybicyclo[2.2.1]heptadiene(7-BuOBCHD)-fused bis(dipyrromethane) yielded benzene-ring-fused doubly N-confused porphyrins by following similar reaction sequences.

An antiaromatic cation of the expanded hexapyrrolohexaazacoronene (HPHAC) 1+ was synthesized by a Vilsmeier-type reaction of the partially unfused HPHAC 2. X-ray diffraction analysis revealed the formation of a seven-membered ring with a methyne linkage between the pyrrole moieties. Although 1+ is a monocation, upfield shifts of the peripheral ethyl protons were clearly observed in the 1H NMR spectra, indicating 24π antiaromaticity. Global antiaromaticity was also supported by nucleus-independent chemical shift and anisotropy of the induced current density calculations. Cation 1+ displayed two reversible oxidations and one irreversible reduction in the cyclic voltammetry measurements. Treatment of 1+ with NOSbF6 gave aromatic trication 13+ with 22π-electron conjugation.

The protonation behavior of bicyclo[2.2.2]octadiene (BCOD)-fused thiaporphyrin and thiabenzoporphyrin was examined by titration with trifluoroacetic acid. Neutral, monorotonated, and diprotonated species of thiaporphyrins were easily detected by UV–vis spectral measurement. The first (K1) and second (K2) equilibrium constants were found to be K1 = 520 and K2 ≈ 7.1 for BCOD-fused thiaporphyrin and K1 = 1.4 × 104 and K2 ≈ 1.4 for thiabenzoporphyrin. The difference between K1 and K2 values of thiaporphyrins is larger than that observed for porphyrins (N4-porphyrins). The main contributing conjugation pathways for thiaporphyrins in both protonated species were investigated by NICS and AICD quantum calculations using their atomic geometries obtained by X-ray structural analysis. The 18π-conjugation pathways of the neutral, monoprotonated, and diprotonated species thiaporphyrins were found to contain 18, 19, and 20 atoms, respectively. Results of 1H NMR studies also support the major contributing pathways.

Parikh–Doering oxidation of diethyl 9-hydroxy-2,6-dimethyl-4,8-dihydro-4,8-methanopyrrol[3,4-f]isoindole-1,7-dicarboxylate produced diethyl 9-oxo-2,6-dimethyl-4,8-dihydro-4,8-methanopyrrol[3,4-f]isoindole-1,7-dicarboxylate. This carbonyl derivative spontaneously underwent cheletropic extrusion of carbon monoxide, producing diethyl 2,6-dimethylpyrrol[3,4-f]isoindole-1,7-dicarboxylate, which showed 14π-electronic aromaticity on the whole five-six-five ring system.

The tetramethylammonium salts of diplatinum(II) complexes composed of mono-lacunary Keggin-type silico and germanotungstates, [(CH3)4N]4[α-SiW11O39{cis-Pt(NH3)2}2]·13H2O (TMA-Si-Pt) and [(CH3)4N]4[α-GeW11O39{cis-Pt(NH3)2}2]·11H2O (TMA-Ge-Pt), were synthesized and crystallized. Single crystals of a tetramethylammonium salt of Keggin-type diplatinum(II)-coordinated phosphotungstate [(CH3)4N]3[α-PW11O39{cis-Pt(NH3)2}2]×10H2O (TMA-P-Pt) were also obtained. The X-ray structural analyses revealed that the two cis-platinum(II) moieties, [cis-Pt(NH3)2]2+, were each coordinated to two oxygen atoms in a mono-vacant site of [XW11O39](12-n)- (Xn+ = Si4+, Ge4+, P5+). FTIR spectra of TMA-Si-Pt and TMA-Ge-Pt also suggested that the two platinum(II) moieties were coordinated to the vacant site of [SiW11O39]8- and [GeW11O39]8-. The 1H NMR spectra in DMSO-d6 of TMA-Si-Pt and TMA-Ge-Pt showed signals assigned to the two sets of NH3 ligands coordinated to the platinum sites. These three platinum compounds showed hydrogen evolution from aqueous triethanolamine solution under visible light irradiation (λ ≥ 400 nm) in the presence of eosin Y, α-Keggin mono-aluminum-substituted silicotungstate, and titanium dioxide. The catalytic activities were influenced by the central atoms, and TMA-P-Pt showed the highest activities among the three platinum compounds.

The organozirconium complex with α-Keggin-type mono-aluminum-substituted silicotungstate, [(n-C4H9)4N]6[α-SiW11Al(OH)2O38ZrCp2]2·2H2O (TBA–Si–Al–Zr) was synthesized by the reaction of Cp2Zr(OTf)2·THF (or Cp2ZrCl2) with [(n-C4H9)4N]4K0.5H0.5[α-SiW11{Al(OH2)}O39]·H2O in acetonitrile. This compound showed high catalytic activities for Meerwein–Ponndorf–Verley reduction of ketones with 2-propanol in both homogeneous and heterogeneous system.

We report covalently interchain-linked graphene nanoribbons fabricated on Au(111) by a stepwise growth process via two-zone chemical vapor deposition. Prepolymer arrays were grown by surface-assist...

Synthesis of an azacoronene, in which both pyrrole and azulene moieties are circularly fused, was achieved just in three steps. This new azacoronene exhibited multistep reversible oxidations under electrochemical and chemical conditions. Formation of an aromatic 22π-electron conjugation and a tropylium cation (6π-electron conjugation) in the dicationic state was revealed by the single-crystal X-ray crystallographic analysis as well as the nucleus-independent chemical shift (NICS) and anisotropy of the induced current density (ACID) calculations.

Three 2-fluoroacetonylbenzoxazole ligands 1a-c and their new Zn(II) complexes 2a-c have been synthesized. In addition, syntheses of new metal [Mg(II), Ni(II), Cu(II), Pd(II), and Ag(I)] complexes from 1a have been also described. The molecular and crystal structures of six metal complexes 2b and 2d-h were determined by single-crystal X-ray diffraction analyses. Their antibacterial activities against six Gram-positive and six Gram-negative bacteria were evaluated by minimum inhibitory concentrations (MIC), which were compared with those of appropriate antibiotics and silver nitrate. The results indicate that some metal compounds have more antibacterial effects in comparison with free ligands and have preferred antibacterial activities that may have potential pharmaceutical applications. Noticeably, the Ag(I) complex 2h exhibited low MIC value of 0.7 µM against Pseudomonas aeruginosa, which was even superior to the reference drug, Norfloxacin with that of 1.5 µM. Against P. aeruginosa, 2h is bacteriostatic, exerts the cell surface damage observed by scanning electron microscopy (SEM) and is less likely to develop resistance. The new 2h has been found to display effective antimicrobial activity against a series of bacteria.

Unsymmetrically substituted 8-methoxy-2-hydroxy-3,7-diarylthiodibenzofurans were readily prepared by the intramolecular oxidative condensation reaction of hydroquinone dimers in good yields.

Iron salt-catalyzed Friedel-Crafts alkylation of chiral α-aryl alcohols with a trimethylsilyl group was found to proceed with retention of the configuration of the hydroxyl group as a leaving group. The memory of chirality of this system stems from the β-silyl effect of the trimethylsilyl group on the carbocation intermediate.

In this study, hexagonal shape-persistent cyclophane with D2h symmetry and rigid dihedral angles was obtained through the key SNAr reaction of perfluorobenzene moieties and dipyrroles. The X-ray analysis of the compound thus obtained revealed a hexagonal macrocyclic structure with D2h symmetry due to the dihedral angles of 120° and double 120° for bicyclo[2.2.2]octadiene-fused dipyrrole and syn-diethanotetrahydroanthracene-fused dipyrrole, respectively.