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Chirality in two dimensions (2D) has attracted increasing attention with regard to interesting fundamental aspects as well as potential applications. This article reports several aspects of supramolecular chirality control as exemplified by self-assembled monolayer networks (SAMNs) formed by a class of chiral building blocks consisting of a triangular conjugated core and alkoxy chains on the periphery. It highlights 2D chirality induction phenomena through a classic "sergeants-and-soldiers" mechanism, in which the inducer is incorporated into a network component, as well as through a "supramolecular host-guest" mechanism, in which the inducer is entrapped in the porous space, leading to counterintuitive chirality reversal. Stereochemical control can be extended to three dimensions too, based on interlayer hydrogen bonding of the same class of building blocks bearing hydroxy groups, exhibiting diastereospecific bilayer formation at both single molecule level and supramolecular level arising from orientation between the top and bottom layers. Finally, we showcase that homochiral SAMNs can also be used as templates for the grafting of in situ generated aryl radicals, by covalent bond formation to the basal graphitic surface, thereby yielding topologically chiral functionalized graphite, and thus extending the potential of chiral SAMNs.

We herein report a unique example of on-surface adaptive self-assembly. A pentagon-shaped macrocycle, cyclic [5]meta-phenyleneacetylene [5]CMPA, is trapped by the adaptive supramolecular network formed by an isosceles triangular molecule, alkoxy substituted dehydrobenzo[14]annulene [14]ISODBA at the liquid/graphite interface, leading to a highly ordered and large-area bicomponent self-assembled molecular network (SAMN), as revealed by scanning tunneling microscopy (STM).

The dianion and dication of tetramesityl-substituted tetracyclopentatetraphenylene, a circulene consisting of alternating five- and six-membered rings, have been generated by reduction with alkali metals and oxidation with antimony(V) halides, respectively. They are theoretically predicted to adopt double annulenoid structures called annulene-within-an-annulene models in which the outer and inner conjugation circuits are significantly decoupled. The theoretical structures were experimentally proven by X-ray crystallographic analyses and the electronic configurations were supported by MCD spectra. Based on the

Self-sorting of multiple building blocks for correctly positioning molecules through orthogonal recognition is a promising strategy for construction of a hierarchical self-assembled molecular network (SAMN) on a surface. Herein we report that a trigonal molecule, dehydrobenzo[12]annulene (DBA) derivative having three tetradecyloxy chains and three hydroxy groups in an alternating manner, forms hierarchical triangular clusters of different sizes ranging from 2.4 to 16.4 nm, consisting of 3 to 78 molecules, respectively, at the liquid/graphite interface. The key is the dynamic combination of three different conformational states, which is solvent and concentration dependent. The present knowledge extends design strategies for production of sophisticated hierarchical SAMNs using a single component at the liquid/solid interface., Self-sorting of multiple building blocks for correctly positioning molecules through orthogonal recognition is a promising strategy for construction of a hierarchical self-assembled molecular network (SAMN) on a surface.

Chiral structures created through the adsorption of molecules onto achiral surfaces play pivotal roles in many fields of science and engineering. Here, we present a systematic study of a novel chiral phenomenon on a surface in terms of organizational chirality, that is, meso-isomerism, through coverage-driven hierarchical polymorphic transitions of supramolecular assemblies of highly symmetric π-conjugated molecules. Four coverage-dependent phases of dehydrobenzo[12]annulene were uniformly fabricated on Ag(111), exhibiting unique chiral characteristics from the single-molecule level to two-dimensional supramolecular assemblies. All coverage-driven phase transitions stem from adsorption-induced pseudo-diastereomerism, and our observation of a lemniscate-type (∞) supramolecular configuration clearly reveals a drastic chiral phase transition from an enantiomeric chiral domain to a meso-isomeric achiral domain. These findings provide new insights into controlling two-dimensional chiral architectures on surfaces.

Scanning tunnelling microscope observations at the 1-phenyloctane/graphite interface reveal how chiral structural information at the molecular level is transferred and expressed structurally at the 2D supramolecular level for a porous system. The chirality of self-assembled molecular networks formed by chiral dehydrobenzo[12]annulene (cDBA) derivatives having three chiral chains and three achiral chains, alternatingly, is compared with those of cDBAs having six chiral chains reported previously. While for all cDBAs homochiral surfaces are formed, their handedness is not simply a reflection of the absolute configuration of the stereogenic centres. Both the number of stereogenic centres as well as the length of the achiral chains determine the supramolecular handedness, providing a deep insight into the supramolecular chirality induction mechanisms at play. Moreover, these cDBAs act to induce chirality in porous networks formed by achiral DBAs. ispartof: ANGEWANDTE CHEMIE-INTERNATIONAL EDITION vol:58 issue:23 pages:7733-7738 ispartof: location:Germany status: published

By using a novel protocol to spatially confine molecules in well-defined small 2D areas, the so-called nanocorrals, we show using scanning tunneling microscopy (STM) how this kind of confinement affects self-assembled molecular network (SAMN) formation at a liquid-solid interface. The 2D lateral confinement, imposed by the size of the nanocorrals, has a clear impact on the phase selectivity of a molecule that can form both low-density and high-density SAMNs, the high-density phase being promoted by the confinement. ispartof: CHEMICAL COMMUNICATIONS vol:55 issue:15 pages:2226-2229 ispartof: location:England status: published

Stereocontrolled multilayer growth of supramolecular porous networks at the interface between graphite and a solution was investigated. For this study, we designed a chiral dehydrobenzo[12]annulene (DBA) building block bearing alkoxy chains substituted at the 2 position with hydroxy groups, which enable van der Waals stabilization in a layer and potential hydrogen-bonding interactions between the layers. Bias voltage-dependent scanning tunneling microscopy (STM) experiments revealed the diastereospecificity of the bilayer with respect to both the intrinsic chirality of the building blocks and the supramolecular chirality of the self-assembled networks. Top and bottom layers within the same crystalline domain were composed of the same enantiomers but displayed opposite supramolecular chiralities.

Controlled covalent functionalization of graphitic surfaces with molecular scale precision is crucial for tailored modulation of the chemical and physical properties of carbon materials. We herein present that porous self-assembled molecular networks (SAMNs) act as nanometer scale template for the covalent electrochemical functionalization of graphite using an aryldiazonium salt. Hexagonally aligned achiral grafted species with lateral periodicity of 2.3, 2.7, and 3.0 nm were achieved utilizing SAMNs having different pore-to-pore distances. The unit cell vectors of the grafted pattern match those of the SAMN. After the covalent grafting, the template SAMNs can be removed by simple washing with a common organic solvent. We briefly discuss the mechanism of the observed pattern transfer. The unit cell vectors of the grafted pattern align along nonsymmetry axes of graphite, leading to mirror image grafted domains, in accordance with the domain-specific chirality of the template. In the case in which a homochiral building block is used for SAMN formation, one of the 2D mirror image grafted patterns is canceled. This is the first example of a nearly crystalline one-sided or supratopic covalent chemical functionalization. In addition, the positional control imposed by the SAMN renders the functionalized surface (homo)chiral reaching a novel level of control for the functionalization of carbon surfaces, including surface-supported graphene. ispartof: JOURNAL OF THE AMERICAN CHEMICAL SOCIETY vol:142 issue:16 pages:7699-7708 ispartof: location:United States status: published

Amazing aromaticity: ChemPlusChem is pleased to present its special issue on novel aromatic compounds, guest-edited by Nazario Martin and Yoshito Tobe. This project was initiated following the 2015 ISNA-16 meeting held in Madrid and the issue features top-quality contributions covering synthesis, properties and applications of acenes, annulenes, azulenes, fullerenes, oligo(thiophene)s, and porphyrin/phthalocyanines.

A dehydrobenzo[12]annulene attached by three platinum catecholate units is oxidized chemically or electrochemically to generate mono-, di-, and trications. Similarly, a platinum catecholate complex with a dibenzo[8]annulene framework also generates mono- and dications upon oxidation. On the basis of theoretical and spectroscopic studies with respect to energetic, structural, and magnetic criteria, these dications are deduced to be aromatic, thus demonstrating a new method for stabilizing aromatic dications.

Reductive coupling of 2,7-bis(bromomethyl)naphthalene using phenyllithium gave anti-[22](2,7)naphthalenophane, [23](2,7)naphthalenophane, and [24](2,7)naphthalenophane, the distribution of which was dependent on the reaction conditions. The structure of the first compound was established by X-ray crystallographic analysis. On the basis of the similarity between the NMR and UV spectra of [23](2,7)naphthalenophane with those reported for syn-[22](2,7)naphthalenophane, we conclude that the compound originally assigned to be syn-4 was in fact 6.

A rotaxane composed of a ring molecule having a metaphenylene unit, which swings as a pendulum, and a dianthrylethane unit, which undergoes isomerization in response to external stimuli, and an axle molecule with two different stopper units was synthesized. The rates of the rocking motion, which were switched reversibly, changed substantially by changing the size of the ring component in response to photo- and thermal-stimuli.

The synthesis of a new triaminoguanidinium‐based ligand with three tris‐chelating [NNO]‐binding pockets and C 3 symmetry is described. The reaction of tris‐(2‐pyridinylene‐N‐oxide)triaminoguanidinium salts with zinc(II) formate leads to the formation of cyclic supramolecular coordination compounds which in solution bind fullerenes in their spherical cavities. The rapid encapsulation of C60 can be observed by NMR spectroscopy and single‐crystal X‐ray diffraction and is verified using computation., Cage bound: Synthesis of a new triaminoguanidinium‐based ligand with three tris‐chelating [NNO] binding pockets and C 3‐symmetry is described. Reaction with zinc(II) formate leads to the formation of cyclic supramolecular coordination compounds that in solution are able to bind fullerenes in their spherical cavities. The rapid encapsulation of C60 is observed by NMR spectroscopy and X‐ray diffraction and is validated by DFT.

Three isomers of quinodimethanes (QDMs) adopt different electronic configurations and geometries, generating their own characteristic physical properties. Incorporation of QDMs into non-benzenoid aromatic or antiaromatic frameworks not only planarizes the whole π system optimizing conjugation, but also changes the electronic properties inherent to QDMs, sometimes drastically, due to the topology of the π system, through interaction with the remaining part of the molecules. In non-benzenoid systems, molecular orbital levels and orbital distribution are uneven compared to benzenoid systems, thereby polarizing the ground state and leading to unique behavior in excited states. In antiaromatic systems, open-shell, diradical character, which is inherent to QDMs, may be enhanced due to small HOMO-LUMO energy gap. In this chapter, effects of incorporating QDMs into non-benzenoid aromatic or antiaromatic frameworks are discussed focusing on the open-shell, diradical character with respect to their molecular structures, antiaromaticity, and physical properties related to the open-shell character and molecular orbital levels and materials applications, as well as covering historical works to the current state-of-the-art achievements.

A tetramesityl derivative of hitherto unknown tetracyclopenta[def,jkl,pqr,vwx]tetraphenylene (TCPTP), which is a potential tetraradicaloid hydrocarbon, was synthesized. Theoretical calculations based on spin-flip time-dependent density functional theory predict that the closed-shell D2h form of TCPTP is more stable than the open-shell D4h form with its slightly tetraradical character. The tetramesityl derivative (Mes)4 -TCPTP exhibits remarkable antiaromaticity as a result of the peripheral 20-π-electron circuit, which causes an absorption maximum at a long wavelength and a small HOMO-LUMO gap. In solution, (Mes)4 -TCPTP most likely adopts rapidly equilibrating D2h structures that interconvert via the D4h transition state. X-ray crystallographic analysis showed (Mes)4 -TCPTP as an approximate D2h structure.

We demonstrate the effective confinement of surface electrons in the pores of molecular networks formed by dehydrobenzo[12]annulene (DBA) molecules with butoxy groups (DBA-OC4) on Au(111). Investigation of the network formation starting from single molecules reveals a considerable interaction of the molecules with the substrate, which is at the origin of the observed confinement.

The 9,10-bis(3-aryl-2-naphthyl)anthracenes 3 were prepared by the benzannulation reaction of 2-(phenylethynyl)benzaldehyde (1) and the corresponding 9,10-bis(arylethynyl)anthracenes 2 in the presen...

We report on the design and fabrication of a four-component supramolecular network using the ‘core–shell’ approach. Each ‘core’ component templates the formation of an outer ‘shell’ leading to formation of three concentric ‘shells’ around the central guest. The ‘shells’ are formed only in presence of guests thus demonstrating remarkable selectivity in molecular recognition. crosscheck: This document is CrossCheck deposited related_data: Supplementary Information identifier: Kunal S. Mali (ORCID) identifier: Yoshito Tobe (ORCID) identifier: Steven De Feyter (ORCID) copyright_licence: The Royal Society of Chemistry has an exclusive publication licence for this journal copyright_licence: This article is freely available. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence (CC BY 3.0) history: Received 17 November 2016; Accepted 20 December 2016; Advance Article published 5 January 2017; Version of Record published 17 January 2017 ispartof: Chemical Communications vol:53 issue:6 pages:1108-1111 ispartof: location:England status: published

Multicomponent network formation by using a shape-persistent macrocycle (MC6) at the interface between an organic liquid and Au(111) surface is demonstrated. MC6 serves as a versatile building block that can be coadsorbed with a variety of organic molecules based on different types of noncovalent interactions at the liquid–solid interface. Scanning tunneling microscopy (STM) reveals the formation of crystalline bicomponent networks upon codeposition of MC6 with aromatic molecules, such as fullerene (C60) and coronene. Tetracyanoquinodimethane, on the other hand, was found to induce disorder into the MC6 networks by adsorbing on the rim of the macrocycle. Immobilization of MC6 itself was studied in two different noncovalently assembled host networks. MC6 assumed a rather passive role as a guest and simply occupied the host cavities in one network, whereas it induced a structural transition in the other. Finally, the central cavity of MC6 was used to capture C60 in a complex three-component system. Precise immobilization of organic molecules at discrete locations within multicomponent networks, as demonstrated here, constitutes an important step towards bottom-up fabrication of functional surface-based nanostructures. ispartof: Chemistry - a European Journal vol:21 issue:4 pages:1652-1659 ispartof: location:Germany status: published

The development of the chemistry of non-alternant non-benzenoid hydrocarbons is reviewed in connection with the International Symposium on Novel Aromatic Compounds (ISNA) and the author's personal anecdotes. Past molecules include the classics of this class of compounds, pentalene, azulene, and heptalene, and the structurally integrated congeners such as indacenes formed by benzannelation and benzinterposition, which were extensively studied during the last century. Indenofluorene isomers constructed by benzannelation to indacenes represent present molecules, which have attracted much interest in recent years in view of their potential in optoelectronic applications. The unusual properties of the most exotic isomer, indeno[2,1-b]fluorene, are specifically described to demonstrate that the benzannelation is not simply a modification for stabilization. Finally, as future molecules, those consisting of linear and cyclic arrays of indenofluorene motifs formed by further extension are proposed.

Singlet biradicaloids are certainly one of the most frequently discussed topics at ISNA-15. In this review our own work on the synthesis, molecular structures, and physical properties relevant to biradical character of indenofluorene isomers are described. These include indeno[2,1-a]fluorene with an o-quinodimethane substructure, benz[c]indeno[2,1-a]fluorene which is the first 2,3-naphthoquinodimethane derivative isolated, and indeno[2,1-b]fluorene with an m-quinodimethane (m-xylylene) subunit. The observed physical properties are explained in terms of the theoretically derived biradical factors (y), HOMO-LUMO energy gaps, and singlet-triplet energy gaps in the ground state electronic configurations. In addition, we discuss here two perspectives in the biradicaloid chemistry, (i) two- and three-dimensional indenofluorene congeners arranged in a macrocyclic form and (ii) macrocyclic indenofluorenes having multiple radical characters.

Multifunctional π-expanded macrocyclic oligothiophene 6-mer 1, as well as 9- (2) and 12-mers (3), was synthesized using a McMurry coupling reaction as the key step. The 6-mer 1 was converted to cyclo[6](2,5-thienylene-ethynylene) (4) by using a bromination-dehydrobromination procedure. From X-ray analysis, the crystal structures of nonplanar 1 and round-shaped 2 and 4 were elucidated. STM showed that 4 formed a self-assembled monolayer at the liquid/solid interface to produce a hexagonal porous network. Chemical oxidation of 1, 2, and 4 with 1 and 2 equiv of Fe(ClO4)3 produced 1(•+) and 1(2+), 2(•+) and 2(2+), and 4(•+) and 4(2+), respectively. Although oligothiophene radical cations containing β,β-disubstituted thiophenes usually do not form π-dimers, 4(•+) clearly formed a π-dimer owing to its planar, round shape. As for the dications of 1, 2, and 4, 1(2+), which has 34π-electrons, exhibited a large diatropic ring current effect, whereas 34π dication 4(2+) only showed a medium diatropic ring current effect. In contrast to 1(2+) and 4(2+), 52π dication 2(2+) had biradical cationic character instead of Hückel-type cyclic conjugation. Interestingly, 6-mer 1 showed polymorphism and unusual melting point behavior due to the number of stable conformations in the solid state. Single crystals of 1 melted at 176 °C, whereas an amorphous film of 1 crystallized in the temperature range of 80-83 °C to form a lamellarly stacked microcrystalline film, which melted at 139 °C. The polymorphism of 1 was applied to either fluorescence switching or switching of field effect transistor (FET) activity and electrical conductivity.

A highly efficient recognition phenomenon was observed between alkoxylated arylene-ethynylene macrocycles bearing identical side chains but different core size, which is based on van der Waals interactions between alkoxy chains. The ratio of both molecules and the environment of each molecule have been statistically analyzed to quantify the recognition efficiency.

Synthesis of 13,14-dimesitylbenz[c]indeno[2,1-a]fluorene (9b), a 2,3-naphthoquinodimethane derivative isolated for the first time, was achieved. The X-ray crystallographic structure and spectroscopic and electrochemical properties of 9b indicate substantial singlet biradical character which is higher than that of 11,12-dimesitylindeno[2,1-a]fluorene (8b), in accord with the quantum chemical study. Cycloadditions with oxygen and dichlorodicyano-p-benzoquinone took place at the inner naphthalene carbons rather than the most reactive exocyclic carbons because of the effective steric protection by the mesityl groups at the latter positions. [4 + 2] Cyclodimerization also took place at the inner naphthalene position as a 4π component and at the outer naphthalene ring as a 2π component.

Two-dimensional (2D) supramolecular self-assembly at liquid-solid interfaces is a thermodynamically complex process producing a variety of structures. The formation of multiple network morphologies from the same molecular building blocks is a common occurrence. We use scanning tunnelling microscopy (STM) to investigate a structural phase transition between a densely packed and a porous phase of an alkylated dehydrobenzo[12]annulene (DBA) derivative physisorbed at a solvent-graphite interface. The influence of temperature and concentration are studied and the results combined using a thermodynamic model to measure enthalpy and entropy changes associated with the transition. These experimental results are compared to corresponding values obtained from simulations and theoretical calculations. This comparison highlights the importance of considering the solvent when modeling porous self-assembled networks. The results also demonstrate the power of using structural phase transitions to study the thermodynamics of these systems and will have implications for the development of predictive models for 2D self-assembly.

We present herein the synthesis and properties of the largest hitherto unknown graphyne fragment, namely trigonally expanded tetrakis(dehydrobenzo[12]annulene)s (tetrakis-DBAs). Intramolecular three-fold alkyne metathesis reactions of hexakis(arylethynyl)DBAs 9 a and 9 b using Fürstner's Mo catalyst furnished tetrakis-DBAs 8 a and 8 b substituted with tert-butyl or branched alkyl ester groups in moderate and fair yields, respectively, demonstrating that the metathesis reaction of this protocol is a powerful tool for the construction of graphyne fragment backbones. For comparison, hexakis(arylethynyl)DBAs 9 c-g have also been prepared. The one-photon absorption spectrum of tetrakis-DBA 8 a bearing tert-butyl groups revealed a remarkable bathochromic shift of the absorption cut-off (λcutoff ) compared with those of previously reported graphyne fragments due to extended π-conjugation. Moreover, in the two-photon absorption spectrum, 8 a showed a large cross-section for a pure hydrocarbon because of the planar para-phenylene-ethynylene conjugation pathways. Hexakis(arylethynyl)-DBAs 9 c-e and 9 g and tetrakis-DBA 8 b bearing electron-withdrawing groups aggregated in chloroform solutions. Comparison between the free energies of 9 e and 8 b bearing the same substituents revealed the more favorable association of the latter due to stronger π-π interactions between the extended π-cores. Polarized optical microscopy observations, DSC, and XRD measurements showed that 8 b and 9 e with branched alkyl ester groups displayed columnar rectangular mesophases. By the time-resolved microwave conductivity method, the columnar rectangular phase of 8 b was shown to exhibit a moderate charge-carrier mobility of 0.12 cm(2) V(-1) s(-1) . These results indicate that large graphyne fragments can serve as good organic semiconductors.

Smaller can be better: The first example of meta-quinodimethane embedded in an indenofluorene framework has been synthesized. 10,12-Dimesitylindeno[2,1-b]fluorene exhibits extremely low-energy light absorption, despite the small conjugation space of the molecule, which consists of only 20 π electrons.

On-surface chemical reactions hold the potential for manufacturing nanoscale structures directly onto surfaces by linking carbon atoms in a single-step reaction. To fabricate more complex and functionalized structures, the control of the on-surface chemical reactions must be developed significantly. Here, we present a thermally controlled sequential three-step chemical transformation of a hydrocarbon molecule on a Cu(111) surface. With a combination of high-resolution atomic force microscopy and first-principles computations, we investigate the transformation process in step-by-step detail from the initial structure to the final product via two intermediate states. The results demonstrate that surfaces can be used as catalysing templates to obtain compounds, which cannot easily be synthesized by solution chemistry., On-surface chemical reactions provide an attractive route for making tailored nanostructures. Here the authors present a thermally-controlled sequential on-surface transformation of a hydrocarbon molecule, characterized via high-resolution atomic force microscopy and density functional theory calculations.

Supramolecular self-assembly in two-dimensional (2D) spaces on solid surfaces is the subject of intense current interest because of perspectives for various applications in nanoscience and nanotechnology. At the liquid/graphite interface, we found by means of scanning tunneling microscopy molecules with a rigid triangular core, a twelve-membered phenylene-ethynylene macrocycle called dehydrobenzo[12]-annulene (DBA), substituted by six flexible alkoxy chains selfassembled to form hexagonal porous 2D molecular networks via van der Waals interactions between interdigitated alkyl chains as the directional intermolecular linkages. Factors that affect the formation of the porous 2D molecular networks including alkyl chain length, solvent, solute concentration, and temperature were elucidated through a systematic study. Because DBA molecules are versatile for chemical modification, they turned out to be highly adaptive for on-surface supramolecular chemistry with respect to (i) pore size control by changing the chain length, (ii) study of parity effect due to even or odd number chains, (iii) generation of supramolecular chirality on surfaces by introducing stereocenters, (iv) chemical modification of the pore interior for selective co-adsorption of guest molecules by introducing functional groups. Additionally, formation of superlattice structures on surfaces was incidentally observed by mixing DBAs of different alkoxy chain parity or by addition of guest molecules via an induced-fit mechanism. These results made significant contribution to advancement of supramolecular chemistry in 2D space. ispartof: Bulletin of the Chemical Society of Japan vol:89 issue:11 pages:1277-1306 status: published

Cyclic arrays consisting of six zinc-porphyrin units are constructed by the supramolecular self-assembly of a dehydrobenzo[12]-annulene derivative having three zinc porphyrin units at the liquid/graphite interface. Binding with C60 furnishes cyclic hexameric arrays of the complexes on the surface. crosscheck: This document is CrossCheck deposited related_data: Supplementary Information identifier: Keiji Hirose (ResearcherID) identifier: Steven De Feyter (ORCID) identifier: Yoshito Tobe (ORCID) copyright_licence: The Royal Society of Chemistry has an exclusive publication licence for this journal history: Received 31 August 2016; Accepted 24 November 2016; Accepted Manuscript published 24 November 2016; Advance Article published 30 November 2016; Version of Record published 13 December 2016 ispartof: Chemical Communications vol:52 issue:100 pages:14419-14422 ispartof: location:England status: published

© 2016 The Chemical Society of Japan. A self-assembled monolayer of a mixture of radical 2,3,7,8,12,13,17,18-octaethylporphyrin (OEP)TbIII doubledecker (TbIII(OEP)2) single-molecule magnets and alkoxylated dehydrobenzo[12]annulene (DBA) at the 1-phenyloctane/highly oriented pyrolytic graphite interface was investigated using scanning tunneling microscopy. The observations revealed that single TbIII(OEP)2 molecules were incorporated in the 2D pores of the honeycomb structure formed by a DBA derivative containing octyloxy chains. The number of TbIII(OEP)2 molecules coadsorbed in the porous DBA networks increased with increasing concentration of the TbIII(OEP)2 radical solution. ispartof: Chemistry Letters vol:45 issue:3 pages:286-288 status: published

Treatment of octadehydrotribenzo[14]annulene ([14]DBA) with bromine or iodine gave the corresponding tetrahalo-substituted benzodiindenocyclooctatetraenes selectively via tandem twofold transannula...

Tris-(2-hydroxybenzylidene)triaminoguanidinium salts having six alkyl chains with proper spacing served as new molecular building blocks for the formation of porous honeycomb networks by van der Waals interaction between interdigitated alkyl chains at the liquid/graphite interfaces.

Self-assembled monolayers of a series of tetraalkoxy-substituted octadehydrodibenzo[12]annulene (DBA) derivatives 1c-g possessing butadiyne linkages were studied at the 1,2,4-trichlorobenzene (TCB) or 1-phenyloctane/graphite interface by scanning tunneling microscopy (STM). The purpose of this research is not only to investigate the structural variation of two-dimensional (2D) monolayers, but also to assess a possibility for peri-benzopolyacene formation by two-dimensionally controlled polymerization on a surface. As a result, the formation of three structures, porous, linear, and lamella structures, were observed by changing the alkyl chain length and the solute concentration. The formation of multilayers of the lamella structure was often observed for all compounds. The selection of molecular networks is basically ascribed to intermolecular and molecule-substrate interactions per unit area and network density. The selective appearance of the linear structure of 1d is attributed to favorable epitaxial registry matching between the substrate lattice and the overlayer lattice. Even though the closest interatomic distance between the diacetylenic units of the DBAs in the lamella structure (approximately 0.6 nm) is slightly larger compared to the typical distances necessary for topochemical polymerization, the reactivity toward external stimuli (electronic-pulse irradiation from an STM tip and UV irradiation) was investigated. Unfortunately, no evidence for polymerization of the DBAs on the surface was observed. The present results indicate the necessity for further designing a suitable system for the on-surface construction of structurally novel conjugated polymers, which are otherwise difficult to prepare.

To develop a synthetic method of thiophene-based polycyclic aromatic compounds, we investigated the tandem cyclization of 1,6-dithienyl-1,5-hexadien-3-ynes under flash vacuum pyrolysis (FVP) conditions at high temperatures (850 or 1050 °C). As a result, several isomeric naphthodithiophene derivatives were obtained as mixtures, from which a few isomers were isolated. The structural assignments of the products were performed on the basis of combination of the experimental and calculated 1 H NMR chemical shifts of either purified products or mixtures of them. Plausible mechanisms for the formation of the products are proposed.

We have designed and synthesized rotaxanes whose rates of rocking motion (pendular motion) were switched reversibly through changes to the size of the ring component in response to external stimuli. The ring molecules of the rotaxanes incorporate a metaphenylene unit, which swings like a pendulum, and a dianthrylethane unit, which undergoes reversible isomerization in response to photo- and thermal stimuli and changes the size of the ring component. The rocking rates were estimated quantitatively by variable-temperature (VT) NMR spectroscopy and saturation transfer experiments, which revealed substantial changes in the rates between the open and closed forms, particularly in the case of rotaxanes with an isopropoxy group attached to a phenylene unit.

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.

Design, synthesis, and demonstration of a prototype of a shuttling molecular machine with a reversible brake function are reported. It is a photochemically and thermally reactive rotaxane composed of a dianthrylethane-based macrocycle as the ring component and a dumbbell shaped molecular unit with two, secondary ammonium stations separated by a phenylene spacer as the axle component. The rate of shuttling motion was shown to be reduced to less than 1 % (from 340 to

A concept and demonstration of a switching in frequencies of molecular motions are described using a pseudorotaxane system. The setup consists of dibenzylammonium hexafluorophosphate and a photochromic dianthrylethane-based [24]crown-8-type macrocycle, which we designed as a key ring component for the pseudorotaxane system having photocontrollable threading functionality by changing the size of ring component due to the action of light.

A 2-nitrated 3-oxoester reacted with amines or alcohols to afford unsymmetrical malonic acid derivatives as a result of nucleophilic substitution accompanying C–C bond cleavage. The 2-nitrated 3-ox...

A dominant theme within the research on two-dimensional chirality is the sergeant–soldiers principle, wherein a small fraction of chiral molecules (sergeants) is used to skew the handedness of achiral molecules (soldiers) to generate a homochiral surface. Here, we have combined the sergeant–soldiers principle with temperature-dependent molecular self-assembly to unravel a peculiar chiral amplification mechanism at the solution–solid interface in which, depending on the concentration of a sergeant–soldiers solution, the majority handedness of the system can either be amplified or entirely reversed after an annealing step, furnishing a homochiral surface. Two discrete pathways that affect different stages of two-dimensional crystal growth are invoked for rationalizing this phenomenon and we present a set of experiments where the access to each pathway can be precisely controlled. These results demonstrate that a detailed understanding of subtle intermolecular and interfacial interactions can be used to induce drastic changes in the handedness of a supramolecular network. The formation of homochiral supramolecular networks at solution–solid interfaces typically relies on the soldier-and-sergeant approach, in which a small amount of chiral modifier defines the handedness of the network. Now, judicious choice of the sergeant, solvent, temperature and concentration has enabled chiral induction pathways to be controlled so that a homochiral surface of either handedness can be assembled from the same system.

“Kekulene” is a doughnut-like shaped polycyclic aromatic hydrocarbon consisting of cyclically arrayed benzene rings. It has attracted a great deal of theoretical interest because it is regarded as an ideal model to study conjugation circuits of π electrons, i.e. whether they delocalize locally in benzene rings or globally throughout the molecule. Though kekulene was synthesized in 1978, it was the only known compound of this class of compounds for a long time. Recently, new kekulene-related molecules, septulene, which is a non-alternant benzenoid hydrocarbon, and a tetracyclopentatetraphenylene (TCPTP) derivative belonging to non-alternant non-benzenoid hydrocarbons, were synthesized. This article presents theoretical and experimental aspects of kekulene-related molecules focusing on the viewpoint of conjugation circuits by classifying them into three types: benzenoid kekulenes including kekulene itself and septulene, yet unknown anti-kekulene and non-alternant non-benzenoid kekulenes represented by TCPTP.