Synthesis of a Porous [14]Annulene Graphene Nanoribbon and a Porous [30]Annulene Graphene Nanosheet on Metal Surfaces

The electrical and mechanical properties of graphene-based materials can be tuned by the introduction of nanopores, which are sensitively related to the size, morphology, density, and location of nanopores. The synthesis of low-dimensional graphene nanostructures containing well-defined nonplanar nanopores has been challenging due to the intrinsic steric hindrance. Herein, we report the selective synthesis of one-dimensional (1D) graphene nanoribbons (GNRs) containing periodic nonplanar [14]annulene pores on Ag(111) and two-dimensional (2D) porous graphene nanosheet containing periodic nonplanar [30]annulene pores on Au(111), starting from a same precursor. The formation of distinct products on the two substrates originates from the different thermodynamics and kinetics of coupling reactions. The reaction mechanisms were confirmed by a series of control experiments, and the appropriate thermodynamic and kinetic parameters for optimizing the reaction pathways were proposed. In addition, the combined scanning tunneling spectroscopy (STS) and density functional theory (DFT) calculations revealed the electronic structures of porous graphene structures, demonstrating the impact of nonplanar pores on the π-conjugation of molecules.     

An ortho-fused tetrakisdehydro[14]annuleno[14]annulene consisting of two different types of bisdehydro[14]annulenes

Tetrakisdehydro[14]annuleno[14]annulene consisting of ‘acetylene-cumulene’ bisdehydro[14]annulene and Sondheimer's bishydro[14]annulene has been synthesized. It was found that a strong diatropicity was observed in the ‘acetylene-cumulene’ bisdehydro[14]annulene moiety, whereas diatropicity of another bisdehydro[14]annulene moiety shows marked decrease comparable with that of napthobisdehydro[14]annulene synthesized by Sondheimer.     

Trisdehydro[14]annuleno[16]annulene

Trisdehydro[14]annuleno[16]annulene consisting of an aromatic bisdehydro[14]annulene and an antiaromatic bisdehydro[16]annulene has been synthesized. The strong paratropicity was observed in the [16]annulene moiety being comparable with that of extremely unstable parent bisdehydro[16]annulene.     

Dodecatwistarene Imides with Zigzag-Twisted Conformation for Organic Electronics

1D nonplanar graphene nanoribbons generally have three possible conformers: helical, zigzag, and mixed conformations. Now, a kind of 1D nonplanar graphene nanoribbon, namely dodecatwistarene imides featuring twelve linearly fused benzene rings, was obtained by bottom-up synthesis of palladium-catalyzed Stille coupling and C−H activation. Single-crystal X-ray diffraction analyses revealed that it displays a zigzag-twisted conformation caused by steric hindrance between imide groups and neighboring annulated benzene rings with the pendulum angle of 53°. This conformation is very stable and could not convert into other conformations even when heated up to 250 °C for 6 h. Despite of the highly twisted topology, organic field-effect transistor based on it exhibits electron mobility up to 1.5 cm² V⁻¹ s⁻¹ after annealing.     

Dodecatwistarene Imides with Zigzag‐Twisted Conformation for Organic Electronics

1D nonplanar graphene nanoribbons generally have three possible conformers: helical, zigzag, and mixed conformations. Now, a kind of 1D nonplanar graphene nanoribbon, namely dodecatwistarene imides featuring twelve linearly fused benzene rings, was obtained by bottom‐up synthesis of palladium‐catalyzed Stille coupling and C?H activation. Single‐crystal X‐ray diffraction analyses revealed that it displays a zigzag‐twisted conformation caused by steric hindrance between imide groups and neighboring annulated benzene rings with the pendulum angle of 53°. This conformation is very stable and could not convert into other conformations even when heated up to 250 °C for 6 h. Despite of the highly twisted topology, organic field‐effect transistor based on it exhibits electron mobility up to 1.5 cm² V^?1 s^?1 after annealing.     

Tetrakisdehydro[14]annuleno[20]annulene

Tetrakisdehydro[14]annuleno[20]annulene consisting of an aromatic bisdehydro[14]annulene and an antiaromatic trisdehydro[20]annulene has been synthesized. The ¹H NHR spectra clearly indicate the induction of para- and diamagnetic ring currents in each of the [4n]- and [4n+2]-rings, respectively.     

Syntheses of an isoannelated annulene,a bisdehydro[14]annuleno[c]furan and bisdehydro[14]annulene derivatives

A bisdehydro[14]annuleno[c]furan, an isoannelated diatropic annulene, has been synthesized. Cyclic glycol, a precursor of the annuleno[c]furan, could be converted into bisdehydro[14]annulene derivatives under mild acidic conditions.     

A new liquid crystalline derivative of dibenzotetraaza[14]annulene: synthesis, characterization and the preliminary evaluation of mesomorphic properties

A new dibenzotetraaza[14]annulene ligand has been synthesized that contains two 2-hydroxybenzoyl and four 3,7-dimethyloctyloxy peripheral substituents. Its mesomorphic textures were observed by means of a polarizing optical microscopy.     

Tetrakisdehydro[14]annuleno[16]annulene

Tetrakisdehydro[14]annuleno[16]annulene consisting of an aromatic bisdehydro[14]-annulene and an antiaromatic trisdehydro[16]annulene has been synthesized. The ¹H NMR parameters clearly indicate the strong paratropicity and diatropicity of the 16-membered and 14-membered rings, respectively.     

A naphtho-tri-t-butyltrisdehydro[16]annulene

Synthesis of a naphtho-tri-t-butyltrisdehydro[16]annulene has been described. Suppression of paratropicity of the 16-membered ring was observed. Comparison of ¹H NMR spectrum of the [16]annulene with that of naphtho-tri-t-butylbisdehydro[14]annulene suggests that the trans double bond adjacent to naphthalene in the [16]annulene is twisted out of the mean molecular plane.     

Tetrakisdehydro[16]annuleno[18]annulene

Tetrakisdehydro[16]annuleno consisting of trisdehydro[16]annulene and bisdehydro[18] annulene has been synthesized. Induction of para- and diamagnetic ring currents in 16- and 18-membered rings, respectively, was clearly recognized by the ¹H NMR spectroscopy. A marked suppresion of the diatropicity in the 18π moiety was observed in the same trend as observed in tetrakisdehydro[14]annuleno[16]annulene.     

Giant molecular spoked wheels in giant voids: two-dimensional molecular self-assembly goes big

We present here the formation of giant pores in surface-confined molecular networks of a triangular-shaped dehydrobenzo-[12]annulene derivative: the diameter of the pores reaches over 7 nm and the giant pores are used as templates to accommodate a giant molecular spoked wheel, which allows us to observe rotational and adsorption-desorption dynamics of single guest molecules.     

2.2]paracyclophane/dehydroannulene hybrids: probing the aromaticity of the dehydro[14]annulene framework

The synthesis of [2.2]paracyclophane/dehydro[14]annulene hybrids 1 and 2 is reported. Comparison of the proton NMR spectra of 1 and 2 with their open precursors and with related model compounds reveals the pronounced effect of macrocycle formation upon the cyclophane protons H15/H16, which lie above the shielding cone of the diatropic [14]annulene moiety. [structure: see text]     

Molecular clusters in two-dimensional surface-confined nanoporous molecular networks: structure, rigidity, and dynamics

The self-assembly of a series of hexadehydrotribenzo[12]annulene (DBA) derivatives has been investigated by scanning tunneling microscopy (STM) at the liquid/solid interface in the absence and presence of nanographene guests. In the absence of appropriate guest molecules, DBA derivatives with short alkoxy chains form two-dimensional (2D) porous honeycomb type patterns, whereas those with long alkoxy chains form predominantly dense-packed linear type patterns. Added nanographene molecules adsorb in the pores of the existing 2D porous honeycomb type patterns or, more interestingly, they even convert the guest-free dense-packed linear-type patterns into guest-containing 2D porous honeycomb type patterns. For the DBA derivative with the longest alkoxy chains (OC20H41), the pore size, which depends on the length of the alkoxy chains, reaches 5.4 nm. Up to a maximum of six nanographene molecules can be hosted in the same cavity for the DBA derivative with the OC20H41 chains. The host matrix changes its structure in order to accommodate the adsorption of the guest clusters. This flexibility arises from the weak intermolecular interactions between interdigitating alkoxy chains holding the honeycomb structure together. Diverse dynamic processes have been observed at the level of the host matrix and the coadsorbed guest molecules.     

Dinaphthotetraaza[14]annulene copper(II) complexes in the electrocatalytic reduction of carbon dioxide and bisulfite anion

A modified synthetic route for the complexes [Cu(II)5,7,12,14-tetramethyldinaphtho [b,i][1,4,8,11]tetraaza[14]annulene], [Cu(II)tmdnTAA], and [Cu(II) 5,7,12,14-tetramethyl-6,13-dichloro-dinaphtho[b,i][1,4,8,11]tetraaza[14]annulene], [Cu(II)dCltmdnTAA], is presented in this work. The electrochemical characterization of both complexes and their precursors, [bis(2,4-pentanedionato)copper(II)], [Cu(II)(acac)₂] and [bis(3-chloro-2,4-pentanedionato)copper(II)], [Cu(II)(3-Cl-acac)₂], respectively, under nitrogen and carbon dioxide is also presented. The voltammetric response of [Cu(II)(acac)₂] and [Cu(II)(3-Cl-acac)₂] are different compared to [Cu(II)tmdnTAA] and [Cu(II)dCltmdnTAA] under nitrogen. Precursors show the reduction of Cu(I) to Cu(0) and the tetraazadinaphtho[14]annulene complexes do not. The chlorine substituted complex has a lower reduction potential than the unsubstituted homologue under nitrogen atmosphere. However, the contrary response is obtained in the presence of carbon dioxide: the unsubstituted complex is more catalytic in terms of potential because the current discharge appears 270?mV shifted to the anodic region. These facts can be explained in terms of electronic and steric effects. The modified electrode obtained by oxidative electropolymerization of [Cu(II)tmdnTAA] over glassy carbon electrode presented a suitable amperometric response for the sulfite reduction in acidic medium (pH?=?2.7). A linear correlation was observed for the catalytic current and sulfite concentration between 0.6–6.0?mM range.     

Phane properties of [2.2]paracyclophane/dehydrobenzoannulene hybrids

A series of [2.2]paracyclophane/dehydrobenzo[14]annulene (PC/DBA) hybrids (hydrocarbons 5, 6, 9, 10 b, and 10 c), [2.2]paracyclophane/dehydro[14]annulene (PC/DA) hybrids (7 and 8) and suitable model systems (11, 12, and 33) has been synthesized. Comparison of the electronic absorption spectra in each series of compounds provides further insight into the global communication between the decks in the [2.2]paracyclophane unit.     

‘Oligomere' Kondensationsprodukte von (1E,3E,5E)‐1,6‐Di(2‐furyl)hexa‐1,3,5‐trien mit Acetaldehyd: Tetrahydro‐tetramethyl‐octaepoxy[60]annulen(6.1.6.1.6.1.6.1)

Oligomeric Condensation Products of (1 E ,3 E ,5 E )‐1,6‐Di(2‐furyl)hexa‐1,3,5‐triene with Acetaldehyde: Tetrahydro‐tetramethyl‐octaepoxy[60]annulene(6.1.6.1.6.1.6.1) The Ca(NO₃)₂‐induced condensation of (1E,3E,5E)‐1,6‐di(2‐furyl)hexa‐1,3,5‐triene ( 6 ) with acetaldehyde yields the linear ‘oligomers' 7 – 11 with 2–6 1,6‐di(2‐furyl)hexa‐1,3,5‐triene units and 1–4 acetaldehyde units, besides a cyclic condensation product 12 obtained from 4 equiv. of 6 with 4 equiv. of acetaldehyde. According to spectroscopic studies, 12 is the tetrahydro‐tetramethyl‐octaepoxy[60]annulene(6.1.6.1.6.1.6.1) as the most expanded annulene system known so far. While the dehydrogenation of 12 to give the tetramethyl‐octaepoxy[60]annulene(6.1.6.1.6.1.6.1) cannot be achieved, the oxidation of 12 with Br₂ yields a black, in all organic solvents nearly insoluble solid 14 , which possibly is the tetramethyl‐octaepoxy[58]annulene(6.1.6.1.6.1.6.1) dication. Because of the insolubility of 14 , unfortunately most of its spectroscopic data are not available. However, the λ_max values in the UV/VIS/NIR spectrum of 14 (Soret and Q bands) are in line with the values of the tetraepoxy[26]annulene(4.2.4.2) dication, the tetraepoxy[30]annulene(4.4.4.4) dication, and the tetraepoxy[34]annulene(6.4.6.4) dication.     

Radikalionen von überbrückten [14] Annulenen. Untersuchungen zum Frontorbitaleinfluss auf Reaktivität und Bindungszustand

Radical Ions of Bridged [14] Annulenes. Investigations on the Influence of Frontier Orbitals on Reactivity and Bonding The radical anions and the radical cations derived from trans-15, 16-dimethyl-1, 4:8,11-ethandiyliden[14]annulene ( 6 ), trans-15-methyl-1,4:8,11-ethandiyliden[14]annulene ( 7 ) and cis-15, 16-propano-1,4:8,11-ethandiyliden[14]annulene ( 8 ) are described. The hyperfine data of the radical anions 6, 7 and 8 resemble those of the structurally related radical anions of trans-10b, 10c-dimethyldihydropyrene ( 4 ) and trans-10b, 10c-dihydropyrene ( 5 ). This finding leads to the conclusion, that the change in the relative arragement of the saturated bridge within the fourteen-membered π-perimeter by passing from 4 (5) to 6 ( 7, 8 ) does not in fluence the energetic sequence of the lowest unoccupied molecular orbitals. The behavior of 6 and 7 towards oxidation parallels the photochemical reactivity of 4 . The hyperfine coupling constants of the radical cations derived from 6 and 7 indicate that the removal of an electron is accompanied by an isomerization of the molecular framework. The investigation of the electron transfer process gby cyclic voltammetry supports these findings. The radical cations prefer the cyclophane-like structures 6a and 7a , in which the central σ-bond (C(15)–C(16) bond) is broken.     

Synthesis and properties of trefoil-shaped tris(hexadehydrotribenzo[12]annulene) and tris(tetradehydrotribenzo[12]annulene)

[reaction: see text] Trefoil-shaped tris(hexadehydrotribenzo[12]annulene) possessing a substructure of the ultimate two-dimensional C(sp)-C(sp(2)) network, graphyne, and the related tris(tetradehydrotribenzo[12]annulene) were synthesized, and their ground- and excited-state properties were investigated.     

The second cyclopropannulene: cycloprop-[8]annulene

Reacting (at 0 degrees C) a mixture of CH2Cl2 and monobromo[8]annulene (C8H7Br) with potassium tert-butoxide in hexamethylphosphoramide (HMPA) and following with exposure to potassium metal led to the formation of the anion radical of an HMPA-[6.1.0]bicyclononatetraene condensation product, in which two HMPA fragments are geminal and attached to the number 9 carbon. When the reaction sequence is carried out in THF, the dianion of cycloprop[8]annulene is predominantly formed. Neutral cycloprop[8]annulene can be isolated via the I2 oxidation of the THF solution. The NMR analysis reveals that the eight-membered ring is nearly planar, and the three-membered ring is more like a dimethylenecyclopropane than it is like a cyclopropene. Further, the chemical shifts due to the protons on the eight-membered ring are nearly 2 ppm further upfield than are those for [8]annulene itself, suggesting a paratropic ring current.