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Two isomers of 9,10-dihydro- as-indacenodithiophenes (DIDTs) and the corresponding diketones having an as-indacene core were synthesized. Their thermal, photophysical, and electrochemical properties were investigated, revealing that they depend on the direction of the fusion of the thiophene rings. For the DIDTs, the effect of the mode of ring fusion on the physical properties is discussed by comparison with the previously reported derivatives of DIDT isomers with an s-indacene core. The observed difference between the highest occupied molecular orbital (HOMO)/lowest unoccupied molecular orbital (LUMO) levels of the DIDT isomers is ascribed to the efficiency of π-conjugation, which depends on α- or β-linkage between the terminal thiophenes with the central benzene ring. In addition, the effect of the peripheral aromatic ring (thiophene or benzene) is elucidated by comparison with indeno[2,1- a]fluorene (DIF) bearing an as-indacene core. The HOMO levels of DIDTs are significantly raised compared to that of structurally related DIF because of electron-donating character of the thiophene rings. For the DIDT diketones, structural effect due to the proximate carbonyl groups is discussed by comparison with the isomers with remote carbonyl groups. In diketones bearing proximate carbonyl groups, the LUMO levels are destabilized owing to antibonding interaction between the carbonyl oxygen atoms, resulting in approach of the LUMO and LUMO+1 energy levels.

© 2018 American Chemical Society. Chemical and structural defects in otherwise pristine materials can result in either an improved or degraded material performance. Unfortunately, little is known about the role of these defects in complex hierarchical processes, such as self-assembly. Here, the influence of defective surfaces on physisorbed self-assembly occurring at liquid/solid interfaces is investigated. Covalently bound defects on graphite surfaces are generated by electrochemically activating diazonium cations. After creating the defective substrates, a solution containing self-assembling molecules was deposited on the surface. Subsequent scanning probe investigations expose how the chemisorbed molecular units can either be incorporated within a porous hexagonal network, or generate local perturbations in the form of partial or full desorption of the physisorbed molecules. Overall, the chemisorbed molecules alter the local energy landscape for self-assembly to isolate new molecular packing arrangements. With a single-molecule perspective, this work outlines how chemical defects contribute to the formation of metastable assemblies and their evolutionary pathways toward higher-symmetry networks. ispartof: JOURNAL OF PHYSICAL CHEMISTRY C vol:122 issue:42 pages:24046-24054 status: published

We investigated the self-assembled monolayers of octadehydrodibenzo[12]annulene (DBA) derivatives to see the effect of multiple intermolecular interactions on the formation of face-on vs edge-on configurations of planar compounds having weak core to core interactions at the liquid/graphite interfaces by means of scanning tunneling microscopy (STM). A DBA derivative having an N-dodecylamide chain at each end of the π-core formed face-on mode self-assemblies at the interfaces of both 1-phenyloctane (PO) and 1-octanoic acid (OA) and graphite. On the other hand, another DBA having both N-dodecylamide chains and methoxymethyl groups formed an edge-on mode self-assembly at the PO/graphite interface. However, at the OA/graphite interface, it formed a face-on mode self-assembly due to the solvent–molecule hydrogen bonds which suppress the intermolecular interactions. These results indicate that by multiple interactions between substituents the edge-on mode of self-assembly can be stabilized, rendering the otherwi...

To demonstrate key roles of multiple interactions between multiple components and multiple phases in the formation of an uncommon self-assembling pattern, we present here the construction of a porous hexagonal star (h-star) structure using a trigonal molecular building block at the liquid/ solid interface. For this purpose, self-assembly of hexaalkoxysubstituted dehydrobenzo[12]annulene derivatives DBA-OCns was investigated at the tetradecane/graphite interface by means of scanning tunneling microscopy (STM). Monolayer structures were significantly influenced by coadsorbed tetradecane molecules depending on the alkyl chains length (C13−C16) of DBA-OCn. However, none of DBA-OCn molecules formed the expected trigonal complexes, indicating that an additional driving force is necessary for the formation of the trigonal complex and its assembly into the h-star structure. As a first approach, we employed the “guest induced structural change” for the formation of the h-star structure. In the presence of two guest molecules, nonsubstituted DBA and hexakis(phenylethynyl)benzene which fit the respective pores, an h-star structure was formed by DBAOC15 at the tetradecane/graphite interface. Moreover, a tetradecane molecule was coadsorbed between a pair of alkyl chains of DBA-OC15, thereby blocking the interdigitation of the alkyl chain pairs. Therefore, the h-star structure results from the selfassembly of the four molecular components including the solvent molecule. The second approach is based on aggregation of perfluoroalkyl chains via fluorophilicity of DBA-F, in which the perfluoroalkyl groups are substituted at the end of three alkyl chains of DBA-OCn via p-phenylene linkers. A trigonal complex consisting of DBA-F and three tetradecane molecules formed an h-star structure, in which the perfluoroalkyl groups that orient into the alkane solution phase aggregated at the hexagonal pore via fluorophilicity. The present result provides useful insight into the design and control of complex molecular self-assembly at the liquid/solid interface. ispartof: Langmuir vol:31 issue:25 pages:7032-7040 ispartof: location:United States status: published

Biphenylophane 1 bridged by acetylene and diacetylene linkages was synthesized. X-ray analysis revealed its highly deformed diacetylene unit with a bond angle of 160°. Enantiomers of 1 resolved by chiral HPLC underwent facile racemization with an activation energy of 90.6 kJ mol(-1). Transannular cyclization of 1 was induced by heating to generate benzyne intermediate 8, which was intercepted by furan to give 9, and by treatment with bromine to give dibromodibenzopicene (10).

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.

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.

Using alkoxylated derivatives of triangular dehydrobenzo[12]annulene (DBA) as building blocks, we demonstrate control of a formation of 2D molecular networks on Au(111). The tunability of intermolecular interactions by substituting alkoxy groups can improve the homogeneity of the 2D molecular network by restricting the number of polymorphs, and it can induce domain-specific chirality. The π-conjugated triangular core of each alkoxylated DBA derivative is locked on a specific site on the Au(111) surface by the interaction between the oxygen atoms of the molecule and the gold (Au) surface atoms, and the relative importance of intermolecular hydrogen bonding versus van der Waals interactions depends on the length of the alkoxy groups. Such tunable intermolecular interactions balanced with surface–molecule interaction may eventually enable control of the formation of 2D molecular networks. These results could lead to potential applications in tailoring 2D molecular networks or allow the use of these networks ...

We present a systematic scanning tunneling microscopic study on the mixing behavior of molecules (DBAs) with different alkyl substituents at the solid-liquid interface to reveal the phase behavior of complex systems. The phase behavior of binary mixtures of alkylated DBAs at the solid-liquid interface can be predicted by the 2D isomorphism coefficient. In addition, we also investigated the influence of coadsorption of template molecules on the phase behavior of DBA mixtures. Coadsorption of these molecules significantly promotes mixing of DBAs, possibly by affecting the recognition between alkyl chains. Monte Carlo simulations prove that the 2D isomorphism coefficient can predict the phase behavior at the interface. These results are helpful for the understanding of phase behavior of complex assembling systems and also for the design of programmable porous networks and hierarchical architectures at the solid-liquid interface.

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.

A highly rotaxane-selective synthesis via aminolysis of prerotaxanes, which were composed of a phenolic pseudo-crown ether as a ring component and a bulky stopper unit, was developed. The best result was obtained in the case of aminolysis of 3b with 3,5-dimethylbenzylamine which proceeded quantitatively with ca. 100% rotaxane selectivity forming the corresponding rotaxane 5b. The rotaxanes were formed by kinetically controlled attack of the amine from the backside of the ring component of the prerotaxanes.

The self-assembly of a series of hexadehydrotribenzo[12]annulene (DBA) derivatives has been scrutinized by scanning tunneling microscopy (STM) at the liquid-solid interface. First, the influence of core symmetry on the network structure was investigated by comparing the two-dimensional (2D) ordering of rhombic bisDBA 1a and triangular DBA 2a (Figure 1). BisDBA 1a forms a Kagomé network upon physisorption from 1,2,4-trichlorobenzene (TCB) onto highly oriented pyrolytic graphite (HOPG). Under similar experimental conditions, DBA 2a shows the formation of a honeycomb network. The core symmetry and location of alkyl substituents determine the network structure. The most remarkable feature of the DBA networks is the interdigitation of the nonpolar alkyl chains: they connect the pi-conjugated cores and direct their orientation. As a result, 2D open networks with voids are formed. Second, the effect of alkyl chain length on the structure of DBA patterns was investigated. Upon increasing the length of the alkyl chains (DBAs 3c-e) a transition from honeycomb networks to linear networks was observed in TCB, an observation attributed to stronger molecule-substrate interactions. Third, the effect of solvent on the structure of the nonpolar DBA networks was investigated in four different solvents: TCB as a polar aromatic solvent, 1-phenyloctane as a solvent having both aromatic and aliphatic moieties, n-tetradecane as an aliphatic solvent, and octanoic acid as a polar alkylated solvent. The solvent dramatically changes the structure of the DBA networks. The solvent effects are discussed in terms of factors that influence the mobility of molecules at the liquid-solid interface such as solvation.

[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.

[structures: see text] A hexagonal diethynylbenzene macrocycle having exterior octyloxymethyl groups undergoes spontaneous polymerization at room temperature to form hardly soluble materials, in contrast to the corresponding dehydrotetramer and dehydrooctamer, which are stable enough to show their melting points at higher than 140 degrees C.

[6n]Paracyclophenediynes 2a-d (n = 3-6) having [4.3.2]propellatriene units were prepared as precursors of the corresponding [6n]paracyclophynes. Laser irradiation of 2a-d produced the negative ions of [6n]paracyclophynes 1a-d (n = 3-6) by extrusion of the indan fragments, which were detected by time-of-flight mass spectrometry.

To generate dibenzotetrakisdehydro[12]- and dibenzopentakisdehydro[14]annulenes ([12]- and [14]DBAs) having a highly deformed triyne moiety, [4.3.2]propellatriene-anneleted dehydro[12]- and dehydro[14]annulenes were prepared as their precursors. UV irradiation of the precursors resulted in the photochemical [2 + 2] cycloreversion to generate the strained [12]- and [14]DBAs, respectively. The [12]DBA was not detected by 1H NMR spectroscopy, but it was intercepted as Diels-Alder adducts in solution, suggesting its intermediacy. Its spectroscopic characterization was successfully carried out by UV-vis spectroscopy in a 2-methyltetrahydrofuran (MTHF) glass matrix at 77 K and by FT-IR spectroscopy in an argon matrix at 20 K. On the other hand, the [14]DBA was stable enough for observation by 1H and 13C NMR spectra in solution, though it was not isolated because of the low efficiency of the cycloreversion. The [14]DBA was also characterized by interception as Diels-Alder adducts in solution and by UV-vis spectroscopy in a MTHF glass matrix at 77 K. The kinetic stabilities of the DBAs are compared with the related dehydrobenzoannulenes with respect to the topology of the pi-systems. In addition, the tropicity of the [14]DBA is discussed based on its experimental and theoretical 1H NMR chemical shifts.

m-Diethynylbenzene macrocycles (DBMs), buta-1,3-diyne-bridged [4(n)]metacyclophanes, have been synthesized and their self-association behaviors in solution were investigated. Cyclic tetramers, hexamers, and octamers of DBMs having exo-annular octyl, hexadecyl, and 3,6,9-trioxadecyl ester groups were prepared by intermolecular oxidative coupling of dimer units or intramolecular cyclization of the corresponding open-chain oligomers. The aggregation properties were investigated by two methods, the (1)H NMR spectra and the vapor pressure osmometry (VPO). Although some discrepancies were observed between the association constants obtained from the two methods, the qualitative view was consistent with each other. The analysis of self-aggregation by VPO revealed unique aggregation behavior of DBMs in acetone and toluene, which was not elucidated by the NMR method. Namely, the association constants for infinite association are several times larger than the dimerization constant, suggesting that the aggregation is enhanced by the formation of dimers (a nucleation mechanism). In polar solvents, DBMs aggregate more strongly than in chloroform due to the solvophobic interactions between the macrocyclic framework and the solvents. Moreover, DBMs self-associate in aromatic solvents such as toluene and o-xylene more readily than in chloroform. In particular, the hexameric DBM having a large macrocyclic cavity exhibits extremely large association constants in aromatic solvents. By comparing the aggregation properties of DBMs with the corresponding acyclic oligomers, the effect of the macrocyclic structure on the aggregation propensity was clarified. Finally, it turned out that DBMs tend to aggregate more readily than the corresponding phenylacetylene macrocycles, acetylene-bridged [2(n)]metacyclophanes, owing to the withdrawal of the electron density from the aromatic rings by the butadiyne linkages which facilitates pi-pi stacking interactions.

Butadiyne-bridged [4(4)](2,6)pyridinophane and [4(6)](2, 6)pyridinophane derivatives were synthesized, and their heteroassociations with the corresponding metacyclophanes and complexations with organic cations were investigated.

As a method to generate all-carbon molecules having highly reactive polyyne units from stable precursors, the [2 + 2] cycloreversion of [4.3.2]propella-1,3,11-triene derivatives was developed. To test the efficiency of this method, the reaction was first applied to simple diethynyl- and dibutadiynyl-substituted propellatrienes, which produced upon UV-irradiation linear hexatriyne and decapentayne derivatives, respectively. Next, dehydro[12]-, [16]-, [18]-, [20]-, and [24]annulene derivatives annelated by the [4.3.2]propellatriene units were prepared as precursors to the corresponding cyclo[n]carbons, a monocyclic form of carbon clusters. Laser-desorption mass spectra of the dehydroannulenes exhibited, in the negative mode, peaks due to the corresponding cyclo[n]carbon anions (n = 12, 16, 18, 20, and 24) formed by successive losses of aromatic indane fragments. Solution photolysis of the dehydro[16]annulene and dehydro[18]annulene derivatives formed reactive polyyne intermediates by [2 + 2] cycloreversion ...

The synthesis and structural characterization of hitherto unknown tetradehydrodinaphtho[10]annulene, a hydrocarbon whose synthesis had been attempted four decades ago, was achieved for the first time. Moreover, the dinaphtho[10]annulene was transformed smoothly into stable zethrene derivatives substituted at its 7,14-positions, showing that it serves as a good reservoir of zethrene derivatives. Optical and electrochemical properties of a disubstituted zethrene derivative are also presented.

The first clear differentiation on deslipping rates affected by the difference in the diastereomeric stereocenters of rotaxanes up to 8.4 times and unexpectedly large steric kinetic isotope effect on the deslipping reaction (ca. 20%) were observed. On the basis of the kinetic parameters, steric kinetic isotope effect, and (1)H NMR spectra of the nondeuteriated and deuteriated rotaxanes, we propose a deslipping mechanism involving pre-equilibrium.

[6](9,10)Anthracenophane (1a) was synthesized by the benzoannelation method starting from dibromo[6]paracyclophane 6 via diepoxyanthracenophanes 3a and 4a. In a similar fashion, peri-substituted de...

Highly Li + -selective ionophores based on 14-crown-4 derivatives were designed and synthesized, and the relationship of their molecular structures and ion selectivities was investigated in order to obtain a highly Li + -selective electrode. The ion selectivities were examined with 11 kinds of 14-crown-4 derivatives, which were prepared a ccording to the proposed two types of Li + ionophore models. Excellent Li + -selective ionophores were obtained by introducing a bulky «block» subunit into the ethano-bridge section of the base crown ring, which effectively prevents the formation of a 2:1 or 3:1 sandwich-type complex consisting of the crown ether and cations larger than Li +

Sterically congested cyclam derivatives 2, 3s, 3a, 4, 5c, and 5t and their Ni(II) complexes have been synthesized. Magnetic susceptibility measurements of the complexes in the solid state and in water solution indicate that the less congested complexes Ni(1) 2+ and Ni(5t) 2+ are high-spin species in the solid state and Ni(1) 2+ , Ni(5c) 2+ , and Ni(5t) 2+ and low-spin species in solution

Irradiation of [6](1,4)-anthracenophane (5) through a solution filter (λ>350 nm) gave five kinds of cyclobutane dimers conjoined at the C1 and C2 of the anthracene core. Neither valence isomerization to the Dewar isomer nor [4+4] dimerization at C9 and C10 was observed. The absence of remarkable effect of concentration or solvent polarity on the product distribution suggests that the dimerization of 9 proceeds through an excited triplet state

The first total syntheses and structural studies of [6] (1,4) naphthalenophane (4) and [6] (1,4) anthracenophane (5), the smallest-bridged isolable cyclophanes with bent acene nuclei, are disclosed. The acenophanes 4 and 5 were successfully synthesized by the oxidative decarboxylation of benzo- and naphtho-fused propellenecarboxylic acids: the bridgehead olefins followed by subsequent treatment with potassium tert-butoxide

We present here the formation of a modular 2D molecular network composed of two different types of square-shaped butadiyne-bridged macrocycles, having intrinsic molecular voids, aligned alternately at the solid-liquid interface. Site-selective inclusion of a guest cation took place at every other molecular void in the molecular network with two different recognition sites.

We present here the formation of a molecular Kagomé network within a two-dimensional (2D) crystal on a surface. This system provides a clear example of how, by design, molecular geometry can be expressed at the level of the 2D crystal lattice, leading to the formation of open networks. Key elements to control molecular network formation are core symmetry, location and orientation of interacting and connecting substituents, as well as symmetry matching between the networks and the surface.

We report here the generation of tetrakisdehydro[12]annulene possessing a highly deformed triyne component from the [4.3.2]propellatriene-annelated precursor by its photolysis extruding indan and the characterization of the highly reactive annulene by chemical and spectroscopic methods. In addition to the chemical evidence for the formation of the title compound in solution such as interception as a Diels-Alder adduct, we succeeded in its characterization by UV-vis and FTIR spectra in an argon matrix at 20 K. The experimental IR spectrum agreed well with the theoretical one calculated by the DFT method.

Extremely air- and acid-sensitive [6](9,10)anthracenophane (1), the smallest-9,10-bridged anthracene, has been synthesized by reductive deoxygenation of diepoxyanthracenophane (4) with a low-valent titanium reagent, and it was characterized by its NMR and electronic spectrum

Photolysis of trienediynes (1a) and (1b) and trienetetrayne (1c) having a [4.3.2]propellane framework yielded the respective lines polyynes (2a-c) in good efficiency through [2+2] cycloreversion, extruding indan (3)