Annulene Derivatives Research Articles

Synthesis, electronic spectroscopy, electrochemistry and catalytic activity of a new Co (II) complex of 1,4,8,11-tetraaza[14]annulene derivative

A new Co (II) complex of 6,13-disubstituted 1,4,8,11-tetraaza[14]annulene derivative has been synthesized by template condensation reaction of 2-(1-quinolinium-1-yl) trimethinium salt (B) with 1,2-diaminopyridine in the presence of Co (II) acetate in DMF. The electrochemical behavior of the metal complex showed a CoII/CoI redox couple at about −0.99V vs. Ag/Ag+ in DMF solvent. Axial ligation of N-donor ligands such as pyridine and imidazole was found to shift the reduction potential of CoII/CoI to more negative potential. The binding of N-donor axial ligands to the metal complex was monitored by measuring changes at about 458nm (maximun absorption of the metal complex) and shifts in the CoII/CoI redox couple potential upon addition of various concentrations of the N-donor axial ligand. Results showed that the number of axial ligand molecules bound to the metal complex is ≈1 and the oxidized state of cobalt (CoII) is more stabilized than the reduced state (CoI) in the presence of the axial ligand. The metal complex also showed catalytic activity toward hydrogen peroxide decomposition in the presence of the N-donor axial ligand.

Self-Assembled Air-Stable Supramolecular Porous Networks on Graphene

Functionalization and modification of graphene at the nanometer scale is desirable for many applications. Supramolecular assembly offers an attractive approach in this regard, as many organic molecules form well-defined patterns on surfaces such as graphite via physisorption. Here we show that ordered porous supramolecular networks with different pore sizes can be readily fabricated on different graphene substrates via self-assembly of dehydrobenzo[12]annulene (DBA) derivatives at the interface between graphene and an organic liquid. Molecular resolution scanning tunneling microscopy (STM) and atomic force microscopy (AFM) investigations reveal that the extended honeycomb networks are highly flexible and that they follow the topological features of the graphene surface without any discontinuity, irrespective of the step-edges present in the substrate underneath. We also demonstrate the stability of these networks under liquid as well as ambient air conditions. The robust yet flexible DBA network adsorbed on graphene surface is a unique platform for further functionalization and modification of graphene. Identical network formation irrespective of the substrate supporting the graphene layer and the level of surface roughness illustrates the versatility of these building blocks.

ChemInform Abstract: Synthesis of New Dibenzo‐tetraaza and Dibenzo‐dioxadiaza[14]annulene Derivatives Using 3‐Bromo‐Substituted Vinamidinium Salt.

AbstractSix new dibenzotetraaza‐ and dibenzodioxadiaza[14]annulene derivatives such as (III) and (V) are synthesized via a twofold condensation reaction of bromo‐substituted vinamidinium salt (I) with aromatic diamines and aminophenols.

Hexadecadehydrodibenzo[20]-, Tetracosadehydrotribenzo[30]-, and Dotriacontadehydrotetrabenzo[40]annulenes: Syntheses, Characterizations, Electronic Properties, and Self-Associations

Hexadecadehydrodibenzo[20]-, tetracosadehydrotribenzo[30]-, and dotriacontadehydrotetrabenzo[40]annulene derivatives ([20]-, [30]-, and [40]DBAs) possessing tetrayne linkages were synthesized. X-ray diffraction analysis demonstrated that the molecules of [30]DBA and p-xylene form a 2D sheetlike structure. Planar [20]- and [30]DBAs show significantly weak or almost no tropicity. The extension of the acetylenic linkages from a diyne to a tetrayne unit narrows HOMO-LUMO gaps. The self-association behavior of [30]DBA in solution resulting from effective π-π stacking interactions was observed.

Synthesis of New Metal-Free 1,4,8,11-Tetraaza[14]annulene Derivatives Using 2-Heteroaryl-substituted Trimethinium Salts

The reaction of 2-heteroaryl-substituted trimethinium salts (A, B, and C) with aromatic 1,2-diamines (a, b, c, d, and e) in acetonitrile/acetic acid leads to 6,13-disubstituted 1,4,8,11-tetraaza[14]annulene derivatives (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14). The UV–vis spectral behavior of these compounds was examined in acetonitrile. Elemental analysis, IR, 1H-NMR, 13C-NMR, and mass spectra confirm the molecular structure of the newly synthesized compounds.

Thiophene-Fused Bisdehydro[12]annulene That Undergoes Transannular Alkyne Cycloaddition by Either Light or Heat

A new bisdehydro[12]annulene derivative having a thiophene-fused structure has been synthesized. This highly twisted π-conjugated macrocycle with two acetylene moieties in close proximity produces a [2+2]-type alkyne cycloadduct by either photoirradiation or mild heating without any transition metals. Theoretical calculations reveal that the thermal reaction proceeds through successive 8π and 4π electrocyclic reactions, while the photochemical reaction is an asynchronous concerted [2+2] cycloaddition. The fused structure with the less-aromatic thiophene ring is crucial for achieving this reaction. The cycloadduct, thiophene-fused biphenylene, has significant potential as a new polycyclic π-scaffold for electronic applications.

Guest-dependent Structural Transformation of Dehydrobenzoannulene Inclusion Crystals Composed of π-Stacked Parallelogram Columnar Motifs

Abstract Octadehydrotribenzo[14]annulene (DBA) derivative 1 gave inclusion crystals with thirteen kinds of aromatic guest molecules. Heat-induced guest release of the inclusion crystals resulted in the formation of guest-free polymorphs, Forms I and III, which depended on the guest species.

Role of Substrate in Directing the Self-Assembly of Multicomponent Supramolecular Networks at the Liquid–Solid Interface

The self-assembly of multicomponent networks at the liquid-solid interface between Au(111) or highly oriented pyrolytic graphite (HOPG) and organic solvents was investigated using scanning tunneling microscopy. Alkoxylated dehydrobenzo[12]annulene (DBA) derivatives form hexagonal nanoporous networks, which trap either single molecules of coronene (COR) or small clusters of COR and isophthalic acid to form multicomponent networks. The pattern of interdigitation between alkyl chains from DBA molecules produces hexagonal pores that are either chiral or achiral. On Au(111) substrates multicomponent networks display an ordered superlattice arrangement of chiral and achiral pores. In comparison, similar networks on HOPG display only chiral pores. The unique superlattice structure observed on Au(111) is related to a lower energetic preference for chiral pores than on HOPG and increased diffusion barriers for guest molecules. The increased diffusion barriers for guests allow them to act as nucleation sites for the formation of achiral pores. Following the initial nucleation of an achiral pore, restrictions imposed by the accommodation of guests within the porous network mean that subsequent growth naturally leads to the formation of the superlattice structure.

デヒドロベンゾ[12]アヌレン誘導体による一次元包接空間を有する超構造の構築

デヒドロベンゾ[12]アヌレン誘導体による一次元包接空間を有する超構造の構築

固液界面におけるアルコキシ基により置換されたデヒドロベンゾ[12]アヌレン誘導体の混合挙動

固液界面におけるアルコキシ基により置換されたデヒドロベンゾ[12]アヌレン誘導体の混合挙動

Surface-enhanced Raman Scattering Study of the Binding Modes of a Dibenzotetraaza[14]annulene Derivative with DNA/RNA Polynucleotides

Binding modes of a dibenzotetraaza14annulene (DBTAA) derivative with synthetic nucleic ac- ids were studied using surface-enhanced Raman spectroscopy (SERS). Changes in SERS intensity and appearance of new bands in spectra were attributed to different complexes formed between the DBTAA molecules and DNA/RNA polynucleotides. A decrease in intensity pointed to intercalation as the domi- nant binding mode of the annulene derivative with poly dGdC-poly dGdC and poly rA-poly rU, whereas new bands in the spectra at 735 cm −1 and 1345 cm −1 revealed binding within the minor groove of poly dAdT-poly dAdT. When all the dominant binding sites were occupied, SERS spectra implied that small molecules bind on the outside of the DNA analogues, while exist mainly as free molecules in equimolar ratio with the synthetic RNA polynucleotide, thereby indicating higher affinity for DNA than for RNA.(doi: 10.5562/cca2106)

Construction of 1D π‐Stacked Superstructures with Inclusion Channels through Symmetry‐Decreasing Crystallization of Discotic Molecules of C3 Symmetry

Supramolecular architectures that possess both 1D π-stacked columns and inclusion channels were constructed by symmetry-decreasing crystallization of dehydrobenzo[12]annulene (DBA) derivatives with naphthyl arms and C(3) symmetry. The crystallization can be interpreted as i) formation of a two-fold column, ii) layer formation, and iii) lamination of the layer accompanied by guest inclusion.

Self‐Assembled Monolayers of Alkoxy‐Substituted Octadehydrodibenzo[12]annulenes on a Graphite Surface: Attempts at peri‐Benzopolyacene Formation by On‐Surface Polymerization

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.

Conductance of Single Triangular Dehydrobenzo[12]annulene Derivative Bridged between Au Electrodes

Abstract A triangular dehydrobenzo[12]annulene (DBA) molecule bridged between Au electrodes was investigated by scanning tunneling microscopy break junction technique. The conductance of the single DBA molecule was determined to be 2.5 × 10−5 G0 (G0 = 2e2/h). Though the DBA has three anchor units which can bind to metal electrodes, the conductance measurement revealed that two of three anchor units per molecule are most likely to bind to the Au electrodes to form a single molecular junction.

Cationic side-chains control DNA/RNA binding properties and antiproliferative activity of dicationic dibenzotetraaza[14]annulene derivatives

Studied dicationic dibenzotetraaza[14]annulene derivatives intercalate into synthetic double stranded DNA and RNA, while their positively charged side-chains additionally interact within the minor groove of polynucleotides, contributing to the overall affinity of compounds and controlling pronounced A–T(U) over G–C sequence preference as well as stronger thermal stabilization of ds-DNA than ds-RNA. Furthermore, all compounds showed moderate to high antiproliferative activity against five human tumour cell lines, whereby clear correlation between the structure of the side-chain and cytotoxic activity was observed.

Specific Interaction between Chloroform and the Pockets of Triangular Annulene Derivatives Providing Symmetry Carry‐Over Crystallization

What's it got in its pockets? Symmetry carry-over crystallization of hexadehydrotribenzo[12]annulene derivatives was provided by specific complexation between the annulene and the chloroform molecule through mainly dispersion forces (see picture). In the complex, a hydrogen atom of the chloroform fits into the annulene's “pocket” surrounded by π electrons.

Conformational Polymorphism of Octadehydrodibenzo[12]annulene with Dimethyl Phthalate Moieties

In this study, we found that an octadehydrodibenzo[12]annulene derivative with two dimethyl phthalate moieties yielded three polymorphic crystals I, II, and III, in which the annulene core arranges in herringbone, parallel-π-stacked, and zigzag-π-stacked fashion, respectively. This is the first example for dehydroannulenes to show polymorphic crystal structures. These polymorphs are brought from varied conformations of the dimethyl phthalate moieties because the direction of the carbonyl oxygen atoms in the phthalate affects the manner of CH/O interaction abundantly observed in the present systems. It is also revealed that the decomposition temperature of the polymorphic crystals varied over a wide range of values (112−163 °C), even though the crystals are composed of an identical molecule. This indicates that the molecular arrangement might have significant influence on the thermal stability and/or intermolecular reactivity of the annulene.

Optical and electric properties depending on molecular arrangement of dehydro[12]annulene derivative

Optical and electric properties depending on molecular arrangement of dehydro[12]annulene derivative

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.

Cover Picture: Superstructure-Dependent Optical and Electrical Properties of an Unusual Face-to-Face, π-Stacked, One-Dimensional Assembly of Dehydrobenzo[12]annulene in the Crystalline State (Chem. Eur. J. 14/2008)

A face-to-face π-stacked one-dimensional (1D) assembly of π-conjugated discotic molecules is a promising superstructure for organic semiconductor materials. In their article, I. Hisaki, M. Miyata et al. on page 4178 ff. describe the construction and the optical and electrical properties of a π-stacked 1D assembly composed of a dehydrobenzo[12]annulene derivative in the crystalline state. Compared with the herringbone-like assembly of the parent annulene, the 1D assembly revealed significantly-anisotropic charge mobility (Σμ=1.5×10−1 cm2 V−1 s−1) along the columnar axis.