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All‐benzenoid polycyclic aromatic hydrocarbons or macrocycles usually display localized aromaticity. On the other hand, incorporation of quinoidal units into the skeleton could lead to effective electron delocalization and global (anti)aromaticity. In this work, fully π‐conjugated macrocycle 1 and bismacrocycle 2 containing both para‐quinodimethane and triphenylamine units are efficiently synthesized mainly through intermolecular Friedel–Crafts alkylation reaction. They can be considered as a tetraazasuperbenzene and a hexaazasupernaphthalene, respectively, due to their similar geometry and electronic structures to the benzene and naphthalene. X‐ray crystallographic analyses reveal a largely planar geometry for both 1 and 2 and variable‐temperature NMR measurements disclose slow dynamic processes owing to restricted ring flipping of the phenyl rings. 1 and 2 can be easily oxidized into higher‐oxidation‐state species. NMR and theoretical calculations indicate that 12+ and 14+ show global anti‐aromaticity and aromaticity, respectively, with a dominant 32π and 30π conjugation pathway, while for the bismacrocycle 2, its dication 22+, tetracation 24+ and hexacation 26+ exhibit global aromaticity, antiaromaticity, and aromaticity with a 54π, 52π and 50π conjugation pathway along the outermost backbone, respectively. [ABSTRACT FROM AUTHOR]

Strain-promoted azide–alkyne cycloaddition (SpAAC) is a powerful tool in the field of bioconjugation and materials research. We previously reported a regioselective double addition of organic azides to octadehydrodibenzo[12]annulene derivatives with electron-rich alkyloxy substituents. In order to increase the reaction rate, electron-withdrawing substituents were introduced into octadehydrodibenzo[12]annulene. In this report, the synthesis of new octadehydrodibenzo[12]annulene derivatives, regioselective double addition of organic azides, and an application to crosslinking polymers are described.

The appropriate arrangement of near‐infrared (NIR) chromophores allows for the modification of the peak wavelength in the NIR region and efficient use of NIR light. However, the preparation of novel NIR chromophores using simple procedures remains a formidable challenge. Herein, we report the synthesis of ball‐shaped ruthenium complex oligomers. The metal complexes can be synthesized in a single step and interact strongly with NIR light. Alkyne‐substituted low‐symmetry ball‐shaped ruthenium complexes were synthesized and subjected to Eglinton coupling to obtain dehydro[12] and [18]annulene‐fused dimers and trimers. Fine‐tuning of the reaction conditions led to the selective synthesis of the target oligomers. NMR spectroscopy confirmed that the 18π‐aromatic and 12π‐antiaromatic properties of the annulene influenced the ruthenium complex chromophore, and magnetic circular dichroism spectroscopy showed changes in the electronic structure of their excited state owing to molecular‐symmetry differences. The absorption coefficient in the NIR region of the absorption spectra of the oligomers increased significantly, supporting the efficient use of light by oligomerization. The formation of oligomers using ball‐shaped metal complexes is a simple and effective strategy for controlling NIR optical properties. [ABSTRACT FROM AUTHOR]

The exploration of annulene's conformation, electronic properties and aromaticity has generated enduring interest over the years, yet it continues to present formidable challenges for annulenes with more than ten carbon atoms. In this study, we present the synthesis of a stable [10]cyclo‐para‐phenylmethine derivative (1), which bears a resemblance to [10]annulene. 1 can be readily oxidized into its respective cations, wherein electrons are effectively delocalized along the backbone, resulting in different conformations and aromaticity. Both 1 and its tetracation (14+ ⋅ 4SbF6−) exhibit a nearly planar conformation with a rectangular shape, akin to the E,Z,E,Z,Z‐[10]annulene. In contrast, the radical cation (1⋅+ ⋅ SbCl6−) possesses a doubly twisted Hückel topology. Furthermore, the dication (12+ ⋅ 2SbCl6−) displays conformational flexibility in solution and crystalizes with the simultaneous presence of Möbius‐twisted (1a2+ ⋅ 2SbCl6−) and Hückel‐planar (1b2+ ⋅ 2SbCl6−) isomers in its unit cell. Detailed experimental measurements and theoretical calculations reveal that: (1) 1 demonstrates localized aromaticity with an alternating benzenoid/quinoid structure; (2) 1a2+ ⋅ 2SbCl6− and 1b2+ ⋅ 2SbCl6− with 48π electrons are weakly Möbius aromatic and Hückel antiaromatic, respectively; (3) 14+ ⋅ 4SbF6− exhibits Hückel aromaticity (46π) and open‐shell diradical character. [ABSTRACT FROM AUTHOR]

Aromatic metalla‐annulenes are important aromatic compounds, research into which has been mainly concentrated on metal‐benzenes and their lower homologues. Reports on their superior homologs are rare, and this has greatly limited the systematic study of their properties. In this work, a series of osma‐dehydro[11]annulenes with good air and thermal stability were prepared in high yields through a simple [10+1] strategy, by incorporating a metal fragment into conjugated ten‐carbon chains in a one‐pot reaction. They are the first monometallic aromatic metalla‐[n]annulenes with the ring size larger than 6, and their Craig‐Hückel hybrid aromaticity is supported by various physical and computational parameters. Besides, these complexes show versatile reactivities, not only giving further evidence for their aromaticity, but also demonstrating their physical and chemical properties can easily be regulated. This work enriches the metalla‐aromatic chemistry, and provides a new avenue for the synthesis of large metalla‐annulenes with different ring sizes. [ABSTRACT FROM AUTHOR]

Non‐alternant non‐benzenoid hydrocarbons exhibit very different optical and electronic properties than their well‐studied benzenoid analogues. However, preparing such structures with extended conjugation length, remains challenging. Herein, we report the synthesis and properties of azuleno[2,1,8‐ija]azulene derivatives using a two‐step sequence involving a four‐fold aldol condensation between aromatic dialdehydes and readily available tetrahydropentalene‐2,5‐(1H,3H)‐dione. Molecules with band gap values ranging from 1.69 to 2.14 eV and molar extinction coefficients (ϵ) of nearly 3×105 M−1 cm−1 have been prepared. These annulene‐like structures exhibit significant diatropic ring currents (aromatic), as supported by 1H NMR spectroscopy and DFT calculations. Field‐effect transistors (OFETs) using azuleno[2,1,8‐ija]azulene derivatives as semiconductors exhibit charge mobility values of up to 0.05 cm2 V−1 s−1. [ABSTRACT FROM AUTHOR]

The structure geometry, vibrational frequencies, electronic and optical properties of a series of donor-acceptor substituted dodecadehydrotribenzo [18] annulenes ([18] DBA) were investigated using the B3LYP method at a 6-31+G (d, p) basis set. After optimization of the structures, HOMO and LUMO energies, gap energy (Eg), global hardness (η), chemical potential (µ), electrophilicity index (ω), maximum charge transfer (ΔNmax), electronegativity (χ), Fermi level (EFL), wavelength (λ), oscillator power (f0), and participation percentage (% Con) for [18] DBA derivatives. A significant increase in the first hyperpolarizability was observed by substitution on [18] DBA. The results of this study may be used to design and construct materials with adjustable electrical properties. The results indicate that the NLO response of [18] DBA could be enhanced by functionalizing different substitutions. In general, the NLO response and electronic properties of the S1-10 are more excellent than others. [ABSTRACT FROM AUTHOR]

An [8]cyclo‐para‐phenylmethine derivative ([8]CPPM‐Mes) was synthesized. X‐ray analysis revealed a tub‐shaped geometry similar to the cyclooctatetraene, with alternating benzenoid/quinoid structure. Variable‐temperature NMR measurements disclosed a slow valence tautomerization process with an interconversion energy barrier of about 11.7 kcal mol−1 at coalescence temperature (273 K), and two more lower‐barrier dynamic processes involving flipping of the 1,4‐phenyl rings on the backbone and rotation of the mesityl substituents. Its dication ([8]CPPM‐Mes2+) adopts a bowl‐like geometry with a smaller depth of the cavity, and a slow bowl inversion process was observed by dynamic NMR. The bond lengths of the benzenoid/quinoid rings are more averaged via electron delocalization and the molecule shows global aromaticity, which was further validated by NMR and theoretical analysis. [8]CPPM‐Mes2+ exhibits open‐shell diradical character with a small singlet‐triplet energy gap (−1.8 kcal mol−1). [ABSTRACT FROM AUTHOR]

Strain-promoted azide-alkyne cycloaddition (SpAAC) is a powerful tool in the field of bioconjugation and materials research. We previously reported a regioselective double addition of organic azides to octadehydrodibenzo[12]annulene derivatives with electron-rich alkyloxy substituents. In order to increase the reaction rate, electron-withdrawing substituents were introduced into octadehydrodibenzo[12]annulene. In this report, the synthesis of new octadehydrodibenzo[12]annulene derivatives, regioselective double addition of organic azides, and an application to crosslinking polymers are described., (Copyright © 2024, Takeda et al.)

[Display omitted] • Understanding the linear and nonlinear SIS (solvent-induced shift) behaviour for [n]annulenes (n: 12, 18, and 30) as a function of solvent polarity. • The outer protons of all the [n]annulenes are deshielded to a lesser extent than the inner protons. • A direct fit is obtained between the simple Onsager reaction field formalism and the results computed using multiple DFT levels within the IEFPCM solvation. • Different degrees of nonlinear SIS behaviour are observed in the same [n]annulene. • [18]annulene is found to possess an anisotropic reaction field inside its ring cavity, which leads to a higher degree of nonlinearity in the SIS values of the inner protons. We computationally investigate the effect of solvent polarity on the 1H NMR chemical shifts of a few annulenes using multiple DFT levels within the IEFPCM solvation formalism. The solvent polarity is parametrized by defining a dielectric function that can efficiently quantify the solvent-induced shift (SIS). Both the linear and the nonlinear SIS behavior are observed. As the polarity of the solvent increases, the value of SIS decreases for both the inner and the outer protons of [12]- and [30]annulenes as well as for the outer protons of [18]annulene. For the inner protons of C 2 [18]annulene, the nonlinearity is primarily due to the anisotropic environment inside the annulenic ring cavity, i.e. due to the existence of an anisotropic reaction field. Interestingly, the SIS values computed using multiple DFT levels within the IEFPCM solvation directly fit into the relatively simple Onsager's reaction field model. [ABSTRACT FROM AUTHOR]

In this research, the annulene molecule was selected as pi electron skeleton and the electron donor and acceptor groups were attached to it and their energetic, electronic properties, and optical properties were calculated. It was shown that these molecules have exothermic formation reaction which is the evidence of their stability. It was demonstrated that these substituents lowers the Eg of annulene and significantly increased its dipole moment especially for CN-AN-OLi and CF3-AN-OLi molecules. The UV-visible absorption of annulene drastically increased by the existence of these donor and acceptor groups. Improved visible absorption achieved for CN-AN-NHLi which the annulene molecule sandwiched between two -NHLi as highly electron donor and other –CN electron acceptor substituents. [ABSTRACT FROM AUTHOR]

Replacing of Boron and nitrogen atoms in [8] annulene molecule help us for explaining the details of mentioned magnetic mechanism concerning the ring currents of the carbon disappearing in the isoelectronic azabora-hetero-cycles variants (Bn Nn C(8-2n) H82-,n=0,1,2,3 and4 The (4n+2) systems aromatic on variants of BnNnC(8-2n) H8 (n=0, 1 ,2,3 and 4) via the localized orbital by considering the current density induced have been studied. It has been predicted a four-electron dia-tropic (aromatic) ring current for (4n+2) aza-bora-hetero-cycles variants of BnNnC (8-2n) H8(n=0,1 ,2,4) and a two-electron para-tropic (anti-aromatic) current for (4n) . HOMO and LUMO energies and also HOMO/LUMO overlapping in whole space have been calculated. Two forms can be considered, first the HOMO–LUMO transition leads to a para-tropic contribution, and second HOMO–LUMO+1 transitions to the dia-tropic contributions. In addition, the NICS and SNICS values confirm the amounts of aromaticity and anti-aromaticity in those rings.

Planarity is a very important structural character of molecules, which is closely related to many molecular properties. Unfortunately, there is currently no simple, universal, and robust way to measure molecular planarity. In order to fill this evident gap, we propose two metrics of molecular planarity, namely molecular planarity parameter (MPP) and span of deviation from plane (SDP), to quantitatively characterize planarity of molecules. MPP reflects the overall degree of deviation of the structure from a plane, while SDP represents the span of the structural deviation relative to the fitting plane; respectively, they are complementary to each other. The examples in this article demonstrate that these metrics have strong rationality and practicality. They can not only be used to investigate the planarity of the entire molecule, but also measure the planarity of local structures, and they can even be employed to study variation of molecular planarity during a dynamic process. In addition, we also propose a new representation, namely coloring atoms according to their signed deviation distance to the fitting plane. This kind of map allows researchers to intuitively and quickly recognize position of the atoms in the system relative to the fitting plane. It can be seen from the examples that this representation is very useful in graphically exhibiting molecular planarity. The methods proposed in this work have been implemented in our open-source analysis code Multiwfn, which can be freely obtained via http://sobereva.com/multiwfn. The use is very simple and rich file formats are supported as input file. [ABSTRACT FROM AUTHOR]

The electron density distributions among a series of [8] annulene (both ions and molecules) and its azabora derivatives, including its ions [BnNnC(8–2n) H8 (n = 1, 2, 3, 4)], are investigated by NBO and NMR analyses. The (4n+2)π and 4nπ systems (Hückel′s Rule) in these compounds are discussed via the localized orbital localization and electron localized function. A diatropic ring current (aromatic) and paratropic current (anti-aromatic) are distinguished. The natural hybrid orbital (NHO) direction and bond bending deviations from the line of nuclear centers are exhibited for understanding the states of π and σ orbitals. For , , and NBO calculations reveal that these structures are the dominant Lewis structures. In this work, for each NAO functions (core, valence, or Rydberg) the orbital occupancy and the orbital energies are discussed. In addition, the nucleus-independent chemical shifts and statistical nucleus independent chemical shifts confirm the amounts of aromaticity and antiaromaticity in these rings. [ABSTRACT FROM AUTHOR]

Electrochemical CO oxidation catalyzed by Rh complexes of tetraaza[14]annulene was examined. Rh complexes on carbon black exhibit much higher CO oxidation activity than Rh porphyrins or conventional Pt alloy catalysts. The onset potential for CO oxidation is lower than 0 V vs. a reversible hydrogen electrode. As a result, a combination of electrochemical CO oxidation by Rh tetraaza[14]annulene and proton reduction by Pt catalysts generates slight electricity. The combined overall reaction is a water‐gas shift reaction (CO+H2O→CO2+H2). The co‐presence of Rh tetraaza[14]annulene catalyst and Pt catalyst promotes the water‐gas shift reaction. [ABSTRACT FROM AUTHOR]

Doping, through oxidation or reduction, is often used to modify the properties of π‐conjugated oligomers. In most cases, the resulting charge distribution is difficult to determine. If the oligomer is cyclic and doping establishes global aromaticity or antiaromaticity, then it is certain that the charge is fully delocalized over the entire perimeter of the ring. Herein we show that reduction of a six‐porphyrin nanoring using decamethylcobaltocene results in global aromaticity (in the 6− state; [90 π]) and antiaromaticity (in the 4− state; [88 π]), consistent with the Hückel rules. Aromaticity is assigned by NMR spectroscopy and density‐functional theory calculations. [ABSTRACT FROM AUTHOR]

The (4n+2)π aromatic systems are studied in variants of C8H8(n+2) (n = −6, −4, −2, 0) via the localized orbital localization (LOL) and the electron localized function (ELF) by considering the induced current density. In this work, a four-electron dia-tropic (aromatic) ring current for (4n+2)π variants of C8H8(n+2) (n = −6, −4, −2, 0) and a two-electron paratropic (anti-aromatic) current for (4n)π arepredicted. With the HOMO and LUMO energies and also the HOMO/LUMO overlap in the whole space, it is possible to predict the transition states from delocalized currents in carbocyclic compounds to nitrogen-localized currents in all heterocyclic compounds in viewpoint of aromaticity and antiaromaticity. In addition, NICS and SNICS values confirm the degree of aromaticity and antiaromaticity in these rings. [ABSTRACT FROM AUTHOR]

π‐Conjugated macrocycles containing all‐benzenoid rings usually show local aromaticity, but reported herein is the macrocycle CBQT, containing alternating para‐quinodimethane and triphenylamine units displaying annulene‐like anti‐aromaticity at low temperatures as a result of structural rigidity and participation of the bridging nitrogen atoms in π‐conjugation. It was easily synthesized by intermolecular Friedel–Crafts alkylation followed by oxidative dehydrogenation. X‐ray crystallographic structures of CBQT, as well as those of its dication, trication, and tetracation were obtained. The dication and tetracation exhibited global aromaticity and antiaromaticity, respectively, as confirmed by NMR measurements and theoretical calculations. Both the dication and tetracation possess open‐shell singlet ground states, with a small singlet–triplet gap. [ABSTRACT FROM AUTHOR]

The synthesis of the new dye 1,6-methano[10]annulenecyanine is described. For this purpose, the 3,4-dicyano-1,6-methano[10]annulene and 3,4-carboxyimide-1,6-methano[10]annulene buildings blocks were synthesized in six to eight steps. In both cases, these building blocks were then cyclotetramerized to furnish a new Zn(II)-1,6-methano[10]annulenecyanine which presents a strong red-shifted absorption band at 800 nm and high solubility in common organic solvents.

Graphical abstract Highlight • The effect of the push-pull system on [14] and [18] annulene for improving light absorption in the visible and IR region was explored. • As the results, it was shown that: 1. After the placement of the molecule in the push-pull system, the intensity of light absorption increases and substantial red shift to visible and IR region was observed. • 2. Furthermore, it was shown that as the result of the placement of molecules in the push-pull system, the ring current was enhanced and hence the value of aromatics increases. • 3. The results of this research may be useful in designing new materials applicable as photosensitizers and photodynamic therapy. Abstract In the present research, an electron donor-acceptor compound (called push-pull systems) were studied using DFT methods in the vacuum space. We used [14] annulene and [18] annulene as π conjugated system and connected methoxy diphenylamine group as an electron donor and cyanoacrylic acid as an electron acceptor group. It was shown that the donor and acceptor groups narrowed the E g of structure which is the result of hyperconjugation. Pristine annulenes had intensive light absorption in the ultraviolet region in electromagnetic radiation. After both molecules sandwiched between electron donor-acceptor groups, a significant redshift from the UV region to the visible and IR region was observed. Also in NMR calculation, it was observed the amount of aromaticity has increased after sandwiching. In all IR and Raman spectrum, it was shown the amount and intensity of light absorption increased after placing annulenes in electron donor-acceptor groups. The results of this research may be useful in designing new materials applicable as photosensitizers and photodynamic therapy. [ABSTRACT FROM AUTHOR]

The main topological characteristics of altan-benzenoids are established. In particular, it is shown that the perimeter of Kekuléan altan-benzenoids is of size 4k , having a destablizing (antiaromatic) energy effect, similar to (4k)-annulenes.

A new concept in anionic 10 π aromaticity is described by the embedding of a compensating charge within an aromatic cyclononatetraenide ring by the symmetric superposition of an alkyl ammonium bridge. This is accomplished by the methylation of azatriquinacene to give a quaternary ammonium salt, followed by oxidation to the tetraene and final deprotonation. The resulting zwitterion is a stable [9]annulene with strong aromaticity as shown by its degree of C−C bond equalization and a nucleus-independent chemical shift value lower than that of benzene. The solid-state structure shows an eclipsed stacking motif with the electron-poor ammonium methyl groups occupying the electron-rich cavity of the aromatic bowl. [ABSTRACT FROM AUTHOR]

Cyclopenta ring fused bisanthene and its charged species were synthesized. The neutral compound has an open-shell singlet ground state and displays global anti-aromaticity. The dication also exhibits singlet diradical character but has a unique [10]annulene-within-[18]annulene global aromatic structure. The dianion is closed-shell singlet in the ground state and shows global aromaticity with 22 π electrons delocalized on the periphery. These findings prrovide new insight into the design and properties of global aromatic/anti-aromatic systems based on π-conjugated polycyclic hydrocarbons. [ABSTRACT FROM AUTHOR]

The 12-membered-ring metallacycles [mer-Re{≡CCH=C(R)C≡C−}Cl(PMe2Ph)3)]2 (R=CMe3, 1-adamantyl), which are organometallic analogues of antiaromatic octadehydro[12]annulene, are prepared by heating the methyl carbyne complexes mer-Re{≡CCH=C(R)C≡CH}(CH3)Cl(PMe2Ph)3. An intermolecular σ-bond metathesis between the Re−CH3 bond and the acetylenic C−H bond is proposed for their formation. [ABSTRACT FROM AUTHOR]

In the search for tricarbaporphyrinoids, a three-component acid-catalyzed condensation of azulene, 2,5-bis[( p-tolyl)hydroxymethyl]thiophene, and an aryl aldehyde has been elaborated, affording the appropriate thiatriazuliporphyrinogens. The subsequent oxidation yielded a rare example of a macrocyclic organic tetracation, which can be readily and reversibly converted into macrocyclic tri- and dicarbocations by addition of one or two hydroxides bound at the meso position(s). Further insight into the influence of carbocation formation on the geometry, electronic structure, and magnetic manifestation in 1H NMR spectroscopy has been obtained by using density functional theory calculations. The charge distribution was evaluated by mapping electron density surfaces with electrostatic potential (ESP). [ABSTRACT FROM AUTHOR]

The first examples of air-stable 20π-electron 5,10,15,20-tetraaryl-5,15-diaza-5,15-dihydroporphyrins, their 18π-electron dications, and the 19π-electron radical cation were prepared through metal-templated annulation of nickel(II) bis(5-arylamino-3-chloro-8-mesityldipyrrin) complexes followed by oxidation. The neutral 20π-electron derivatives are antiaromatic and the cationic 18π-electron derivatives are aromatic in terms of the magnetic criterion of aromaticity. The meso N atoms in these diazaporphyrinoids give rise to characteristic redox and optical properties for the compounds that are not typical of isoelectronic 5,10,15,20-tetraarylporphyrins. [ABSTRACT FROM AUTHOR]

Amolecular graph, consisting of undirected edges, can be represented as a sum of two digraphs, consisting of oppositely oriented directed edges. In the case of annulenes, the eigenvalue spectrum of the molecular graph is equal to the sum of the eigenvalue spectra of the respective two molecular digraphs.

Amolecular graph, consisting of undirected edges, can be represented as a sum of two digraphs, consisting of oppositely oriented directed edges. In the case of annulenes, the eigenvalue spectrum of the molecular graph is equal to the sum of the eigenvalue spectra of the respective two molecular digraphs.

The cleavage of CC bonds in π-conjugated systems is an important method for controlling their shape and coplanarity. An efficient way for the cleavage of an aromatic CC bond in a typical buckybowl corannulene skeleton is reported. The reaction of 2-pyridylcorannulene with a catalytic amount of IrCl3⋅ n H2O in ethylene glycol at 250 °C resulted in a structural transformation from the curved corannulene skeleton to a strain-free flat benzo[ ghi]fluoranthene skeleton through a site-selective CC cleavage reaction. This cleavage reaction was found to be driven by both the coordination of the 2-pyridyl substituent to iridium and the relief of strain in the curved corannulene skeleton. This finding should facilitate the design of carbon nanomaterials based on CC bond cleavage reactions. [ABSTRACT FROM AUTHOR]

A C3-symmetric π-conjugated macrocycle combined with an appropriate hydrogen bonding module (phenylene triangle) allowed the construction of crystalline supramolecular frameworks with a cavity volume of up to 58 %. The frameworks were obtained through non-interpenetrated stacking of a hexagonal sheet possessing three kinds of pores with different sizes and shapes. The activated porous material absorbed CO2 up to 96 cm3 g−1 at 195 K under 1 atm. [ABSTRACT FROM AUTHOR]

We report computations of excitation energies, magnetizabilities, and current strengths for the dianion, tetraanion, and hexaanion of the previously introduced altan-corannulene, a molecule designed to hold a strong paratropic current. None of these ions has a fully diatropic or paratropic pattern: dianion and tetraanion both have a paratropic/diatropic/diatropic pattern, whereas the hexaanion has a diatropic/paratropic/diatropic pattern, which is the 'mirror-image' of that of the neutral species. The patterns have been interpreted according to the ipsocentric formulation of the current density. Magnetizability and excitation energy suggest that the hexaanion should be an aromatic molecule. The next homologue of altan-corannulene6-, altan-altan-corannulene6-, has also been studied. Its large diamagnetizability has been effectively used to model the magnetic response of C806- cages. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Licht an, Poren auf: Zweidimensionale Poren werden durch Selbstorganisation von Azobenzol ‐ funktionalisierten dreieckigen Bausteinen an der Fest ‐ flüssig ‐ Grenzfläche auf Graphit gebildet. Die Poren können selektiv Gastmoleküle aufnehmen. Die Porengröße – und damit auch die Zahl der adsorbierten Gastmoleküle – lässt sich mit Licht unterschiedlicher Wellenlängen reversibel verändern (siehe Schema). [ABSTRACT FROM AUTHOR]

Four molecules of the recently introduced class of altan-molecules have been studied. They are the altan homologues of naphtalene, pyrene, pyracylene, and kekulene. Their optimized geometries are bowl shaped. The smaller three have current density patterns with an outer paratropic current, as expected for isolated [4 n]annulenes, whereas the larger displays an outer weak diatropic circulation. Computed magnetizabilities are consistent with the current density pattern. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Binding modes of a dibenzotetraaza[14]annulene (DBTAA) derivative with synthetic nucleic acids 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 dominant 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. [ABSTRACT FROM AUTHOR]

Abstract: Vacataporphyrin, a porphyrin devoid of one nitrogen atom is an annulene–porphyrin hybrid. Naming it in a different manner—butadieneporphyrin as one pyrrole unit is replaced with butadiene moiety, accents its carbaporphyrinoid nature. The molecule acts as a macrocyclic ligand which accommodates the following metal ions: cadmium(II), zinc(II), nickel(II) and palladium(II). The tripyrrin pincer of vacataporphyrin holds the metal close to the flexible butadiene fragment which may acquire different configurations depending on presence of light, acid concentration or axial ligand identity. The butadiene moiety of vacataporphyrin may be involved in a π-interaction with metal ions. A single example a σ palladium(II)–carbon bond has also been identified. Intricate multi-step structural changes have been spectroscopically detected for palladium(II) vacataporphyrin. A peculiar reversible switch between vacataporphyrin conformers characterized by Hückel or Möbius topology has been accompanied by a change of electronic structure revealed respectively by aromaticity or antiaromaticity. [Copyright &y& Elsevier]

Abstract: A short series of dehydrobenzothieno- and dehydropyridothieno[15]annulene ([15]DBTA and [15]DPTA) hybrids were assembled from thiophene, acetylene, and benzene/pyridine components. The molecules were constructed in a convergent manner and their properties examined optically, electrochemically, and thermally. In addition to lowered energy of electronic transitions of the 15-membered macrocycles, their emissive properties are discussed. The observed trends correspond with previously reported [14]annulenes, and are further rationalized using DFT (B3LYP/6-311G∗∗) calculations. [Copyright &y& Elsevier]

Abstract: Titration of three electron donor-functionalized bis(dehydrobenzo[n]annuleno)benzenes and a corresponding acyclic 1,2,4,5-tetrakis(phenylethynyl)benzene derivative with trifluoroacetic acid in CH2Cl2 resulted in two-stage emission switching behavior in which initial acidification caused bathochromic shifts, followed by dramatic hypsochromic shifts upon further addition of acid. Differences in the various spectra are rationalized by structure and chromophore architecture. The results indicate independent manipulation of frontier molecular orbital energy levels by stepwise ion addition, therefore suggesting transient and tunable intramolecular charge transfer systems upon partial protonation. [Copyright &y& Elsevier]

Abstract: Syntheses of all-Z-tribenzo[12]annulenes (1a–c) and Z,Z-tribenzodidehydro[12]annulenes (2a–c) by the reduction of the corresponding tribenzohexadehydro[12]annulenes 3a–c were carried out using a low valent titanium complex generated from Ti(O-i-Pr)4 and i-PrMgCl. The unique structure of the first reduction products 2a–c as well as 1a–c was fully characterized. Complexation of these annulenes with silver(I) ions produces the corresponding silver complexes. Among them, the silver complexes of 2a–c exhibit interesting monomer–dimer equilibrium. [Copyright &y& Elsevier]

All-Z-hexabenzo[24]annulene was synthesized via a poly-cis-stilbene intermediate. The single crystal of the annulene has a chiral C3-symmetry with a central benzene trimer substructure. Although the compound is highly flexible in solution, the C3-symmetric structure is stabilized by three concurrent CH/π interactions. [Copyright &y& Elsevier]