Search

openaire: EC/FP7/610446/EU//PAMS According to Hückel theory, an anti-aromatic molecule possessing (4n)π-electrons becomes unstable. Although the stabilization has been demonstrated by radialene-type structures - fusing aromatic rings to anti-aromatic rings - in solution, such molecules have never been studied at a single molecular level. Here, we synthesize a cyclobutadiene derivative, dibenzo[b,h]biphenylene, by an on-surface intramolecular reaction. With a combination of high-resolution atomic force microscopy and density functional theory calculations, we found that a radialene structure significantly reduces the anti-aromaticity of the cyclobutadiene core, extracting π-electrons, while the small four-membered cyclic structure keeps a high density of the total charge.

Although aromaticity is a key concept in chemistry that is frequently used to explain the structure and reactivity of organic compounds, it remains challenging to actually measure this property. Proper probes allow for an experimental quantification of aromaticity using nuclear magnetic resonance (NMR) spectroscopy and in this study 15,16-dimethyl-15,16-dihydropyrene (DHP) is demonstrated to be particularly well suited for this purpose. DHP has two internal methyl groups, which are positioned within the π cloud of this bridged, planar, and rigid [14]annulene, and are therefore shifted to higher field in proton NMR spectra owing to ring-current effects. A specific DHP derivative bearing strongly electron-donating dimethylamino and strongly electron-accepting nitro groups in a relative pseudo-para orientation has been synthesized and characterized with respect to its quinoid character. Solvatochromism as well as a reduced ring current show that the partial quinoid character in this push-pull DHP derivative is about 12 %. This study extends the scope of DHP as an aromaticity probe and aids in the better understanding of the phenomenon of aromaticity.

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.

Internally 1,3-phenylene- and 2,5-thienylene-bridged [46]decaphyrins 2 and 3 have been synthesized. While 2 shows modest aromatic character derived from the global 46π-conjugated circuit, 3 displays larger aromatic character owing to the contribution of an (annuleno)annulene-type network consisting of two twisted Möbius aromatic thia[28]hexaphyrin segments in addition to the global 46π-network. Upon protonation, these [46]decaphyrins underwent large structural changes to acquire strong aromaticity. Protonated 3 has been revealed to take on a planar structure composed of fused two triangular thia[28]hexaphyrin segments.

We have studied the self-assembly structure of meso-diphenyltetrathia [22]-annulene [2,1,2,1] (DPTTA) on highly oriented pyrolytic graphite (HOPG), Au(111), and single-layer graphene (SLG) modified Au(111) substrates. High resolution scanning tunneling microscopy (STM) reveals that DPTTA molecules pack into one dimensionally ordered row structure on graphene and HOPG surfaces, while assemble into two dimensional close-packed structure on Au(111) surface. We ascribe this difference to the effect of the substrate. The addition of C60 molecules on these DPTTA modified substrates further reveals that the structural difference in DPTTA adlayer can affect its ability to form donor-acceptor (D-A) hierarchical structure with C60 molecules. The results provide an example of substrate effect in self-assemblies of functional molecules, which is significant for the design of molecular based devices.

We previously reported a novel Au-catalyzed sequential activation of two different propargyl carboxylates to 6-methylene-6H-benzo[7]annulene-5,8-diyl dicarboxylates. This reaction has been extended to syntheses of highly functionalized 2,2′-bibenzo[7]annulenes with four biphenyls bearing two sets of different propargyl carboxylates.

C26H41NO5, orthorhombic, P212121 (no. 19), a = 9.6178(8) Å, b = 13.3335(11) Å, c = 19.0758(16) Å, V = 2446.3(4) Å3, Z = 4, R gt(F) = 0.0389, wRref (F2 ) = 0.0888, T = 296(2) K.

In this issue of Chem, Jishan Wu and colleagues provide the first examples of annulene-within-an-annulene (AWA) structures in which the inner and outer conjugated circuits are formally fully decoupled. Existing models of AWA aromaticity might need to be revised to account for the exceptional behavior of these novel structures.

Searching new antioxidants compounds to prevent or reduce the impact of oxidative stress on cells, we designed and synthesized several N-acylhydrazone derivatives with dibenzo[a,d][7]annulene moiety. In this work, a series of previously synthesized N-acylhydrazone derivatives bearing 5H-dibenzo[a,d][7]annulene moiety 7a-g were evaluated for antioxidant activity effect, using the DPPH method. The highest antioxidant activity was exhibited by the compound 7f containing in his molecule 4-hydroxy-3-methoxyphenyl fragment.

We present a general extension of the metadynamics allowing for an automatic sampling of quantum property manifolds (ASQPM) giving rise to functional landscapes that are analogous to the potential energy surfaces in the frame of the Born-Oppenheimer approximation. For this purpose, we employ generalized electronic collective variables to carry out biased molecular dynamics simulations in the framework of quantum chemical methods that explore the desired property manifold. We illustrate our method on the example of the "biradicality landscapes", which we explore by introducing the natural orbital occupation numbers (NOONs) as the electronic collective variable driving the dynamics. We demonstrate the applicability of the method on the simulation of \textit{p}-xylylene and [8]annulene allowing to automatically extract the biradical geometries. In the case of [8]annulene the ASQPM metadynamics leads to the prediction of biradical scaffolds that can be stabilized by a suitable chemical substitution, leading to the design of novel functional molecules exhibiting biradical functionality.

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., Negative isn't always bad: Reduction of a porphyrin nanoring by the addition of 4 or 6 electrons was found to result in global (anti)aromaticity (see picture), as revealed by 1H NMR spectroscopy and DFT calculations. Thus, the Hückel rules apply to huge macrocyclic anions, and the charge in these anions is fully delocalized.

Synthesis of a triporous nanographene with 102 sp2 carbon atoms by combining solution and surface chemistry., The synthesis of porous nanographenes is a challenging task for solution chemistry, and thus, on-surface synthesis provides an alternative approach. Here, we report the synthesis of a triporous nanographene with 102 sp2 carbon atoms by combining solution and surface chemistry. The carbon skeleton was obtained by Pd-catalyzed cyclotrimerization of arynes in solution, while planarization of the molecule was achieved through two hierarchically organized on-surface cyclodehydrogenation reactions, intra- and inter-blade. Remarkably, the three non-planar [14]annulene pores of this nanographene further evolved at higher temperatures showing interesting intra-porous on-surface reactivity.

In this article, the topological resonance energy (TRE) method was used to investigate the global aromaticity of a set of [18]annulene-derived compounds which were obtained by replacing either two, four, or all six of the inner hydrogen atoms of [18]annulene with bridges (oxygen, imino-, sulfur, or combinations of the three). Our TRE results show that all the mono-bridged, di-bridged, and tri-bridged [18]annulenes are globally aromatic systems with positive TREs and show relatively larger aromaticity in comparison with the [18]annulene. The aromaticity of each compound was explained using the topological charge stabilization (TCS) rule. The bond resonance energy (BRE) and circuit resonance energy (CRE) methods were used to evaluate local aromaticity. Our BRE and CRE results show that incorporation of five-membered heterocyclic rings changes the main conjugation pathway of the bridged [18]-annulenes. The local aromaticities arising from the five-membered heterocyclic rings (6π) contribute strongly to global aromaticity. However, the ring current (RC), which arises from the 18π annulene-like pathway structures, is the primary determinant of the magnetic properties of the molecule. Our RC results are in good agreement with available 1H-NMR chemical shift data.

Aggregation-induced emission (AIE) is a photophysical phenomenon correlated closely with the excited-state intramolecular motions. Although AIE has attracted increasing attention due to the significant applications in biomedical and optoelectronics, an in-depth understanding of the excited-state intramolecular motion has yet to be fully developed. Here we found the non-aromatic annulene derivative of cyclooctatetrathiophene shows typical AIE phenomenon in spite of its rotor-free structure. The underlying mechanism is investigated through photoluminescence spectra, time-resolved absorption spectra, theoretical calculations, circular dichroism as well as by pressure-dependent fluorescent spectra etc., which indicate that the aromaticity reversal from ground state to the excited state serves as a driving force for inducing the excited-state intramolecular vibration, leading to the AIE phenomenon. Therefore, aromaticity reversal is demonstrated as a reliable strategy to develop vibrational AIE systems. This work also provides a new viewpoint to understand the excited-state intramolecular motion behavior of lumiongens., Molecular systems displaying aggregation-induced emission (AIE) have important biomedical and optoelectronic applications. Here the authors report a further mechanism for AIE, through aromaticity reversal from the ground state to the excited state, in the non-aromatic annulene derivative of cyclooctatetrathiophene.

The involvement of NMDA receptors containing the GluN2B subunit in neurodegenerative disorders including Alzheimer's and Parkinson's disease renders this NMDA receptor subtype an interesting pharmacological target. The aim of this study was the bioisosteric replacement of benzene, methoxybenzene and aniline moieties of known potent GluN2B selective NMDA receptor antagonists by a thiophene ring. In a nine-step synthesis starting from commercially available propionic acid 9 the thiophene derivative 7a was obtained as a bioisostere of the potent GluN2B ligands cis-3 and trans-3. [7]Annuleno[b]thiophene 8a without a benzylic OH moiety was prepared in a six-step synthesis starting from carboxylic acid 18. 8a represents a bioisostere of potent GluN2B ligands 4 and 5. [7]Annulenothiophene 8a without a benzylic OH moiety reveals approx. 8-fold higher GluN2B affinity (K(i) = 26 nM) than the analogous thiophene derivative 7a with a benzylic OH moiety (K(i) = 204 nM). Both thiophene bioisosteres show a slight preference for GluN2B receptors over both σ receptors. The data indicate that the bioisosteric replacement of benzene or substituted benzene rings by a thiophene ring is well tolerated by the NMDA receptor. Furthermore, the benzylic OH moiety seems not to be essential for high GluN2B affinity.

An iridium-catalyzed tandem olefin migration/Cope rearrangement of alkenyl ω-ene cyclopropanes is reported. By this means, a variety of complex annulenes are obtained as single diastereomers starting from cyclopropyl ester derived from simple 1,ω-dienes and alkenyldiazo compounds. Long-range olefin migration over up to 10 positions could be realized and coupled with an efficient Cope rearrangement to yield valuable scaffolds. Various functional groups are well-tolerated, giving rise to densely functionalized products. Furthermore, the present methodology could be successfully extended to yield bicyclic cycloheptenones starting from readily available alkenyl cyclopropanols via a Kulinkovich reaction.

International audience; A number of singly (180°) twisted, largely single-stranded and thus conformationally rather fragile, Möbius molecules have been synthesized within the last 15 years, which are aromatic with 4n electrons, thus violating the Hückel rule. Annulenes with significantly higher twist (e.g. 540°) that retain a full cyclic conjugation path have been elusive, mainly because of the high strain and loss of orbital overlap. Recently, a topological strategy was devised to project the “twist” into “writhe”, thus reducing the strain. However, orbital overlap was still severely reduced within the flexible building blocks. We now present a single and a triple twisted annulene with fully conjugated peripheries. They are unique in their pronounced band shape and conformational robustness as they are made up of three fully kata-condensed [5]helicene fragments. The triple twisted molecule exhibits a strong diatropic ring current in the outer periphery, even though the π system includes 4n electrons. The diatropic current is counterbalanced by a paratropic current in the σ system, resulting in no net manifestation of macrocyclic aromaticity. The key step of the synthesis of both Möbius compounds is a Perkin condensation of complementary bifunctional bismaleates leading to a flexible macrocycle containing alternating benzene and biphenyl fragments. Subsequent photocyclization yields a separable mixture of rigid diastereomeric tris-helicene macrocycles of the above topologies.

Treatment of the SiMe3 -protected dichloro-rhenium carbyne complexes Re{≡CCH=C(R)C≡CSiMe3 }Cl2 (PMe2 Ph)3 (R = CMe3 , 1-adamantyl) with CsF in methanol directly afforded the 12-membered metallacycles {ReCl(PMe2 Ph)3 }2 {≡CCH=C(R)C≡C-}2 . The electronic structure of the metallacycle was investigated by density functional calculations. The UV-vis spectrum of the metallacycle shows a red-shifted band compared to that of the starting dichlorocarbyne complex. Treatment of {ReCl(PMe2 Ph)3 }2 {≡CCH=C(CMe3 )C≡C-}2 with HCl produced the dichloro-rhenium carbyne complex Re{≡CCH=C(CMe3 )C≡CH}Cl2 (PMe2 Ph)3 , which is consistent with the electronic structure of the 12-membered metallacycles.

In this study, the carbonylative sonogashira coupling reaction was performed in the presence of CO (2 MPa) and Nitmtaa@DFNS as NPs. Nickel(II)dibenzotetramethyltetraaza[14]annulene complex (Nitmtaa) prepared and immobilized on amino-fucntionnalized DFNS (N-DFNS) via Ni N (NH2) bond to obtain a stable and reusable new nanocatalyst named as Nitmtaa@DFNS. Good to superb performance products were provided deploying Nitmtaa@DFNS nanocatalyst. In addition, the anatomy of Nitmtaa@DFNS has been distinguished by various methods, including XRD, VSM, FT-IR, SEM, EDX, TEM, and TGA. In addition, the hot filtration test provided complete insight into the heterogeneity of the catalyst. The reuse and recycling of the catalyst were repeatedly investigated for coupling reactions. In addition, the mechanism of the coupling reactions was thoroughly studied.

A practical method was developed for the gain of potentially biologically active 4-aryl-5,8-epiminobenzo[7]annulenes using tropinone as starting material with an azabicyclo[3.2.1]octan skeleton. In an effort to improve product yield, reaction process conditions were optimized and the cascade Michael/cyclization reaction went most smoothly using tetrahydrofuran as solvent in the presence of DBU at 60and#176;C for 10 hours. More diverse 4-aryl-5,8-epiminobenzo[7]annulenes were synthesized in good yields and structurally identified by NMR, FTIR and mass spectrometry analysis. The assembly of the heterocyclic core proceeds by a cascade Knoevenagel condensation, Michael addition and cyclocondensation sequence with a broad substrate applicability and good functional group tolerance.

An order of magnitude difference in photo-reactivity between bis- (photo-DIBOD, 1) and mono-cyclopropenone - caged dibenzocyclooctadiynes (MC-DIBOD, 5) allows for selective mono-decarbonylation of 1. Alternatively, 5 is prepared by selective mono-cyclopropanation of dibenzo[a, e]cyclooctadiyne. MC-DIBOD (5) permits efficient sequential SPAAC cross-linking of azide-derivatized substrates. Cycloaddition to 5 converts an azide moiety into a photo-caged form of triazole-fused dibenzo[a, e]cyclooctyne (3). While azide reactivity MC-DIBOD (5) and dibenzo[a, e] cyclooctadiyne (DIBOD, 2) is similar to other cyclooctynes, fusion of triazole to dibenzocyclooctyne system in 3 results in three orders of magnitude enhancement in SPAAC rates. In methanol, 3 reacts with butyl azide at an astonishing rate of 34 M−1s−1, thus representing the most reactive cyclooctyne analog reported so far. MC-DIBOD (5) was utilized in the preparation of mixed bis-triazoles and derivatization of the protein (BSA) with fluorescent dye and polyethylene glycol.

Macrocyclic compound (E)-Nidmdbdptaa (1) has been synthesized from (E)-Nidmdptaa, a derivative of macrocyclic ligand tetramethyldibenzotetraaza[14]annulene (tmtaa) and benzoyl chloride by the grafting reaction on 6, 13 positions of (E)-Nidmdptaa. The demetallation of 1 leads to its free base, (E)-H2dmdbdptaa (2). The monobenzoyl substituted macrocyclic analogues of 1 and 2, (E)-Nidmmbdptaa (3) and (E)-H2dmmbdptaa (4) are also synthesized and characterized, respectively. As well as 2, the introduction of benzoyl groups to nonplanar saddle-shaped (E)-Nidmdptaa changes the awkward shape of 1, forming a supramolecular host for aromatic ring. The single crystal X-ray diffraction analyses show that 1 includes a benzo ring of the adjacent 1 molecule, and 2 clamps a solvent molecule, toluene, by supramolecular weak interactions of van der Waals forces and crystal close packing.

The structural, electronic, and nonlinear optical (NLO) properties of pristine dodecadehydrotribenzo[18]annulene ([18]DBA) functionalizing with the alkali metal atom (Li and Na), NH2 and NO2 functi...

Cyclization of the ether enyne 1 catalyzed by [Ru]NCCH3(+) ([Ru] = Cp(PPh3)2Ru) in CHCl3 generates a diastereomeric mixture of the substituted tetrahydropyran 11. Presumably, formation of an allenylidene complex is followed by a cyclization by nucleophilic addition of the olefinic group to Cγ of the ligand giving a boat-like six-membered ring. The diastereoselectivity is controlled by the 1,3-diaxial interaction. The vinylidene complex 7, a precursor of 11, is obtained from 1 and [Ru]Cl. In a mixture of MeOH/CHCl3, the domino cyclization of 1 further affords 14a, a chromene product catalytically. The second cyclization proceeds via nucleophilic addition of the resulting olefinic unit to Cα of 7. But the ether enyne 3 with a cyclopentyl ring on the olefinic unit undergoes only single cyclization due to steric effect. The propargyl alcohol and the two terminal methyl groups on the olefinic unit shape the cyclization. Thus, similar all-carbon 1,n-enynes (n = 7, 8, 9) 4-6 each with an aromatic linker undergo direct domino cyclization catalyzed by [Ru]NCCH3(+), to give derivatives of tricyclic fluorene, phenanthrene and dibenzo[7]annulene, respectively, with no intermediate observed.

The 12-membered-ring metallacycles [mer-Re{≡CCH=C(R)C≡C-}Cl(PMe2 Ph)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(PMe2 Ph)3 . An intermolecular σ-bond metathesis between the Re-CH3 bond and the acetylenic C-H bond is proposed for their formation.

altan-molecules are formed from parent molecules with outgoing C–H bonds by substituting the C–H bonds with C–C bonds to alternating carbon atoms of an annulene. If the outgoing C–H bonds are even, which happens for totally fused aromatic hydrocarbons, the altan-molecule has a 4n perimeter expected to hold a paratropic circulation, in consideration of its poor coupling with the inner part of the molecule. This qualitative expectation is borne out in many systems by ab initio and tight-binding calculations, but it breaks down when the perimeters of the parent molecule and its altan derivative are of close dimensions. The theoretical design of these molecules is reviewed. The possible importance of their anions and their open-shell singlet ground states is also briefly discussed. Copyright © 2016 John Wiley & Sons, Ltd.

The structures of a series of polycyclic derivatives of [n]annulenes (n = 8, 10, 12, 14) functionalized with peripheral cyclobutadiene rings were studied using the DFT B3LYP/6-311+G(3df,2p) and M062X/6-311+G(3df,2p) methods. The compounds with n = 8 and 10 have the planar and those with n = 12, 14 saddle-shaped conformations of the central rings. Stabilization of non-standard planar forms of the hydrocarbons with central 12- and 14-membered conjugated rings may be achieved through π-complexation of C=C bonds of the cyclobutadiene fragments with beryllium atoms to afford the sandwich-like complexes with circular arrangement of beryllium centers around the perimeter of a ligand.

Iron-promoted cyclization of 1-benzyl-2-alkynylbenzenes with diorganyl diselenides led to the synthesis of 9-(organoselanyl)-5H-benzo[7]annulenes whereby the mutual action between diorganyl diselenides and iron(III) chloride in a 0.5:1.0 mol ratio was essential in order to achieve the maximal yields of the products. The cyclization reaction tolerated a variety of functional groups, such as trifluoromethyl, chloro, fluoro and methoxy, in both the 1-benzyl-2-alkynylbenzenes and the diorganyl diselenides, giving the seven-membered heterocyclic products exclusively via a 7-endo-dig cyclization process.

Introduction of rigid aryl substituents into the periphery of a π-conjugated molecule changes its assembly manner from that of the parent compound, resulting in drastic changes of optical and electrical properties of the assembly. In this study, we revealed that ortho-thienyl substituted octadehydrodibenzo[12]annulene derivative 2 yielded two types of crystal structures with zigzag and one-dimensionally (1D) π-stacked motifs. Their thermal, optical, and electrical properties were investigated. Furthermore, we demonstrate that although the phenyl- and thienyl-substituted derivative (1 and 2, respectively) yielded closely resembled 1D π-stacked columns in their crystals (1-column and 2-II, respectively), arrangements of the columns are completely different due to subtle differences of the substituents. Such differences in the arrangements drastically affect the lifetime of charge carrier generated in crystals, although the intensity of the photoconductivity is almost the same in both crystals. These results...

Comprehensive investigations of crystal structures, electrical transport properties and theoretical simulations have been performed over a series of sulfur-bridged annulene-based donor-acceptor complexes with an alternate stacking motif. A remarkably high mobility, up to 1.57 cm(2) V(-1) s(-1) for holes and 0.47 cm(2) V(-1) s(-1) for electrons, was obtained using organic single crystal field-effect transistor devices, demonstrating the efficient ambipolar transport properties. These ambipolar properties arise from the fact that the electronic couplings for both holes and electrons have the same super-exchange nature along the alternate stacking direction. The magnitude of super-exchange coupling depends not only on the intermolecular stacking distance and pattern, but also the energy level alignments between the adjacent donor-acceptor moieties. The concluded transport mechanism and structure-property relationship from this research will provide an important guideline for the future design of organic semiconductors based on donor-acceptor complexes.

The present work aims to study solvent effects on the polarizability (α), static first hyperpolarizability (β) and one- and two-photon absorption (OPA and TPA) properties of a new class of molecules viz. triply twisted Möbius annulenes, recently studied by us in vacuum phase [Kundi et al., Phys. Chem. Chem. Phys., 2015, 17, 6827]. We have employed linear and quadratic response theories within the framework of time-dependent density functional theory with the CAM-B3LYP functional and a cc-pVDZ basis set to calculate different parameters. The microscopic details of the said properties have been studied using a two-state model (2SM) approach, which performs very well in the case of β and TPA of the first excited state of all the systems. However for the second excited state, the 2SM results are far from those of response theory. In fact, in comparison to response theory, 2SM predicts an opposite trend for the TP activity of some of the model systems, indicating a significant contribution from the other higher excited states. The anomaly between the 2SM approach and response theory has been resolved by incorporating three states in the calculations.

The charge transport properties of tetrathia[22]annulene-[2,1,2,1] derivatives (DPTTA, $$\hbox {DPTTACH}_{3}$$ and DPTTACl) were investigated by the density functional theory coupled with incoherent charge-hopping model at the molecular and crystal levels to shed light on the relationship between the charger carrier mobility and substitution effects. It is found that that the low-lying and delocalized LUMOs and larger adiabatic electron affinities of these compounds are beneficial to their stability when acting as n-type organic semiconductors. The reorganization energy and transfer integral can significantly influence the charge carrier mobility. The $$\hbox {DPTTACH}_{3}$$ has large electron mobility ( $$0.177\hbox { cm}^{2}\cdot \hbox { V}^{-1}\cdot \hbox { s}^{-1}$$ ) owing to the small reorganization energy and larger transfer integral originating from the face-to-face $$\uppi $$ – $$\uppi $$ stacking among the three compounds. From the viewpoint of transfer integral, the transfer integral among the dominant hopping pathways indicates that the charge transport occurs in the parallel dimers with $$\uppi $$ – $$\uppi $$ interaction. On the basis of the angular resolution anisotropic mobility investigation, the $$\hbox {DPTTACH}_{3}$$ exhibit remarkable anisotropic behavior. We hope that our work can help the experimenters understand how to tune charge transport through a small molecular modification.

The quantum charge transport calculations at metal–molecule–metal junctions lead to various electronic properties suitable in the field of miniaturization. Finite bias-dependent conductivity is calculated through porphyrin, hexaphyrin, and hexathia[26π]annulene molecular junction devices connected to the metallic or semiconducting electrode using non-equilibrium Green's function technique based on the density functional theory method. The ( I − V) characteristic curves calculated for various donor–insulator–acceptor (D–σ–A) devices show a Ohmic, diode, or rectifier-like nature depending on the donor acceptor substitution effect in the above molecules connected to the electrode. The rectification ratio R ( I + / I − or I − / I +) calculated for such devices varies from 2 to 70, and maximum R is calculated for the D–A-substituted porphyrin molecular junction. The I − V characteristics, rectification, and negative differential resistance effect found in such devices are well analyzed by projected density of states and molecular-projected self-consistent Hamiltonian eigenstate, local density of state calculations. Molecular conductivity calculations in D–σ–A devices using porphyrin, hexaphyrin, and hexathia[26π]annulene show promise in the field of molecular electronics and memory storage devices.

The idea of replacing traditional silicon-based electronic components with the ones assembled by organic molecules to further scale down the electric circuits has been attracting extensive research focuses. Among the molecularly assembled components, the design of molecular logic gates with simple structure and high Boolean computing speed remains a great challenge. Here, by using the state-of-the-art nonequilibrium Green’s function theory in conjugation with first-principles method, the spin transport properties of single-molecule junctions comprised of two serially connected transition metal dibenzotetraaza[14]annulenes (TM(DBTAA), TM = Fe, Co) sandwiched between two single-walled carbon nanotube electrodes are theoretically investigated. The numerical results show a close dependence of the spin-resolved current-voltage characteristics on spin configurations between the left and right molecular kernels and the kind of TM atom in TM(DBTAA) molecule. By taking advantage of spin degree of freedom of electrons, NOR or XNOR Boolean logic gates can be realized in Fe(DBTAA) and Co(DBTAA) junctions depending on the definitions of input and output signals. This work proposes a new kind of molecular logic gates and hence is helpful for further miniaturization of the electric circuits.

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.

In this study, the adsorption characteristics together with the modified thermomechanical properties of stable BxCyNz heteronanotubes, i.e. BC2N, BC3, and NC3, in ambient conditions have been explored under the adsorption of NiTMTAA molecules (NiTMTAA/heteronanotube). Employing molecular dynamics study, it is observed that π-π stacking interaction plays a major role in the adsorption of NiTMTAA. The radius of gyration and circumferential distribution along the axis of NTs demonstrate the higher agglomeration of molecules near the wall of CNT and BC3 than that of other NTs. Moreover, it is observed that CNT and BNNT possess the highest Young’s modulus and thermal conductivity than those of heteronanotubes. According to the results, the adsorption of NiTMTAA molecules reduces thermal conductivity. Unlikely, Young’s modulus of NiTMTAA/heteronanotubes for small weight percentage of NiTMTAA molecules (

Herein, we report a general, efficient and solvent-free method for the one-pot synthesis of allylic esters via dehydrogenation of unactivated alkanes and subsequent oxidative cross coupling with different substituted carboxylic acids. A simple, well defined and air stable Cu(II)-complex, [Cu(MeTAA)], featuring a tetraaza-macrocyclic ligand (tetramethyltetraaza[14]annulene (MeTAA)) is used as the catalyst. A wide variety of substituted allylic esters were synthesized in high yields starting from readily available starting materials. Control reactions were carried out to understand the reaction sequence and the plausible mechanism.

It is shown, on the example of the monocyclic cyclononatetraenyl cation, C 9 H 9 + , that the fully-variational optimization of modern ab initio wavefunctions based on spin-coupled generalized valence bond (SCGVB) theory vindicates, in a surprising level of detail, essential features of Heilbronner's ideas for the electronic structure of Mobius annulenes such as the arrangement of overlapping carbon 2p atomic orbitals along a Mobius strip, leading to a phase inversion between the first and last orbitals. In the SCGVB description, the aromaticity of this Mobius system with eight π electrons follows from the extensive resonance between VB structures.

A novel (Z)-2,8-dibromo-9-(bromomethylene)-3,5,5-trimethyl-6,7,8,9-tetrahydro-5H-benzo [7] annulene was synthesized by bromination with N-Bromosuccinimide (NBS) of Aryl-Himachalene. The product of this reaction was characterized by 13C NMR, 1H NMR, FT-IR spectroscopy and single crystal X-ray diffraction. In the solid state, the molecules are associated by Br⋯Br halogen bonds, C–H···π interactions and C–H⋯Br hydrogen bonds. The optimized structure parameters of the studied molecule was determined theoretically using density functional theory (DFT/B3LYP) method 6-31 + G(d, p) basis set, and compared with previously reported experimental findings. Calculated chemical shift values and vibrational wavenumbers showed good agreement with the experimental data. The electronic properties, such as HOMO and LUMO energies, and molecular electrostatic potential (MEP) are also performed.

In this study, the impact of one or two hydroxy moieties at the benzo[7]annulene scaffold on the GluN2B affinity and cytoprotective activity was analyzed. The key intermediate for the synthesis of OH-substituted benzo[7]annulenamines 11–13 and 17 was the epoxyketone 8. Reductive epoxide opening of 8 resulted with high regioselectivity in the 5-hydroxyketone 9 (Pd(OAc)2, HCO2H, phosphane ligand) or the 6-hydroxyketone 10 (H2, Pd/C), whereas hydrolysis in aqueous dioxane led to the dihydroxyketone 14. Reductive amination of these ketones with primary amines and NaBH(OAc)3 afforded the benzo[7]annulenamines 11–13 and 17. In receptor binding studies 5-OH derivatives 11 and 12 showed higher GluN2B affinity than 6-OH derivatives 13, which in turn were more active than 5,6-di-OH derivative 17a. The same order was found for the cytoprotective activity of the ligands. The tertiary amine 12a with one OH moiety in 5-position represents the most promising GluN2B negative allosteric modulator with a binding affinity of Ki = 49 nM and a cytoprotective activity of IC50 = 580 nM. In the binding pocket 12a shows a crucial H-bond between the benzylic OH moiety and the backbone carbonyl O-atom of Ser132 (GluN1b). It was concluded that a 5-OH moiety is essential for the inhibition of the NMDA receptor associated ion channel, whereas a OH moiety in 6-position is detrimental for binding and inhibition. An OH or CH2OH moiety at 2-position results in binding at the ifenprodil binding site, but very weak ion channel inhibition.

The 4-benzylpiperidine moiety is a central structural element of potent N-methyl-d-aspartate (NMDA) receptor antagonists containing the GluN2B subunit. To obtain novel GluN2B ligands suitable for positron emission tomography, the benzylpiperidine moiety was replaced with fluorinated ω-phenylalkylamino groups. For this purpose three primary propyl- and butylamines 7 a-c and one butyraldehyde 7 d bearing a fluorine atom and an ω-phenyl moiety were prepared in 3- to 7-step syntheses. Compounds 7 a-d were attached to various scaffolds of potent GluN2B antagonists (scaffold hopping) instead of the original 4-benzylpiperidine moiety. Although benzoxazol-2-ones and indoles with a benzylpiperidine moiety show high GluN2B affinity, the corresponding fluorophenylalkylamine derivatives did not result in high Glu2B affinity. Moderate GluN2B affinity was observed for a 3-(fluoroalkyl)-substituted tetrahydro-1H-3-benzazepine (Ki =239 nm). However, high GluN2B affinity was obtained for the tetrahydro-5H-benzo[7]annulen-7-amines 12 a-c (Ki =17-30 nm). Docking studies resulted in the same binding pose for 12 a as for the lead compound Ro 25-6981. It can be concluded that some GluN2B ligands (benzoxazolones, indoles) do not tolerate replacement of the 4-benzylpiperidine moiety with flexible fluorinated phenylalkyl side chains, but other scaffolds such as tetrahydro-3-benzazepines and -benzo[7]annulenes retain interaction with NMDA receptors containing the GluN2B subunit.