2,491 results on '"Annulene"'
Search Results
2. Parts‐per‐Million‐Level, Catalytic [3+2]‐Annulations for the Asymmetric Synthesis of Methanobenzo[7]annulenes
- Author
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Guguloth Thirupathi, Dhevalapally B. Ramachary, A. Suresh Kumar, and Etikala Ashok
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Molecular Structure ,Tandem ,Organic Chemistry ,Thiourea ,Enantioselective synthesis ,Parts-per notation ,Stereoisomerism ,General Chemistry ,Annulene ,Medicinal chemistry ,Catalysis ,Lawsone ,chemistry.chemical_compound ,chemistry ,Molecule ,Ton - Abstract
3-Alkyl-lawsones selectively reacted with α-alkyl-nitroethylenes under 500 parts-per-million (ppm) quinine-NH-thiourea-catalysis to furnish the chiral methanobenzo[7]annulenes in up to >99 % ee with >20 : 1 dr and TON up to 1820 through tandem Michael/Henry [3+2]-annulations. These asymmetric ppm-level, catalytic tandem [3+2]-annulations would be highly inspirational for the design of many more ppm-level organocatalytic reactions, and at the same time these final molecules are basic skeletons of antibiotics.
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- 2021
3. Organocatalytic Enantioselective Michael‐Aldol[3+2] Annulation for the Synthesis of Nitro‐Methanobenzo[7] annulenes
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Jin-Yu Liu, Yang Zhang, and Xiao-Hai Zhang
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Annulation ,Aldol reaction ,Chemistry ,Organocatalysis ,Organic Chemistry ,Nitro ,Enantioselective synthesis ,Organic chemistry ,Physical and Theoretical Chemistry ,Annulene - Published
- 2021
4. Benzo‐fused Tri[8]annulenes as Molecular Models of Cubic Graphite
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Uwe H. F. Bunz, Jan Freudenberg, Barbara Ejlli, Frank Rominger, Pascal Nußbaum, and Klaus Müllen
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chemistry.chemical_classification ,Communication ,molecular cup ,Polycyclic aromatic hydrocarbon ,General Chemistry ,Crystal structure ,Annulene ,Phenanthrene ,cyclooctatetraene ,Ring (chemistry) ,Communications ,Catalysis ,chemistry.chemical_compound ,Cyclooctatetraene ,Crystallography ,chemistry ,Cubic Graphite ,carbon allotrope ,Benzene ,cyclotrimerization - Abstract
Cyclotrimerization of 9,10‐dibromo‐9,10‐dihydrodibenzo[3,4:7,8]cycloocta[1,2‐l]phenanthrene with potassium tert‐butoxide in the presence of a transition‐metal catalyst afforded two polycyclic aromatic hydrocarbon stereoisomers consisting of three cyclooctatetraene (COT) moieties connected via a central benzene ring. Both isomeric tri[8]annulenes were obtained selectively through the choice of the catalyst: The α,α,α‐form (Ru catalyst) displayed a threefold symmetrywith the COT subunits forming the side walls of a (chiral) molecular cup. In the thermodynamically more stable α,α,β‐isomer (Pd catalyst), one of the three boat‐shaped COTs was flipped over and faced the opposite molecular hemisphere with respect to the central benzene ring as evidenced by crystal structure analysis. Both title compounds are small segments of “cubic graphite”, an elusive carbon allotrope., Two benzo‐fused tri[8]annulenes were synthesized via cyclotrimerization reactions, introducing two valid model compounds of the yet elusive carbon allotrope cubic graphite. Both conformers do not interconvert via temperature‐ or light‐induced stimuli.
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- 2021
5. Synthesis of Dibenzo[a,e]cyclooctene-5,11(6H,12H)-diones via the Elusive Benzocyclobutenone Anion
- Author
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Yu Liu, Jun Chen, Yingchao Huang, and Ping Lu
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chemistry.chemical_compound ,chemistry ,Cyclooctene ,Organic Chemistry ,Annulene ,Base (exponentiation) ,Medicinal chemistry ,Catalysis ,Ion ,Carbanion - Abstract
We reported here a facile synthesis of dibenzo[a,e]cyclooctene-5,11(6H,12H)-diones via dimerization of benzocyclobutenones in the presence of simple base via the elusive benzocyclobutenone anion. The temperature effect played a crucial role in the dimerization reaction. Further synthesis of 5,11-disubstituted dibenzo[a,e]cyclooctenes (dibenzo[a,e][8]annulenes) from dibenzo[a,e]cyclooctene-5,11(6H,12H)-diones was also explored.
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- 2021
6. Synthesis, Characterization, Electrochemical and Antimicrobial Studies of Iron(II) and Nickel(II) Macrocyclic Complexes
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Prashant Tevatia, Deepak Kumar Das, Anuj Kumar, and Vinod Kumar Vashistha
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Metal ions in aqueous solution ,chemistry.chemical_element ,02 engineering and technology ,Annulene ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,Medicinal chemistry ,0104 chemical sciences ,chemistry.chemical_compound ,Nickel ,Transition metal ,chemistry ,Oxidation state ,Pyridine ,Octahedral molecular geometry ,0210 nano-technology - Abstract
Herein, we synthesized [12] membered pyridine based transition metal macrocyclic complexes [MIILCl2] (M = Fe(II) and Ni(II), L = 6,12,5,11-tetraphenyl di(2-pyridyl)[b,h][1,4,7,10]-N4[12]annulene). The synthesized macrocycles were characterized by using microanalysis (C, H, and N), DTA/TGA and other spectroscopic techniques. A nonplanar saddle-shaped octahedral geometry was assigned to the macrocycles. The TGA results indicated the higher stability of these macrocycles over 250°C temperature. Cyclic volumetric studies showed the abnormal quasi-reversible behavior for these complexes, which further indicates the unusual oxidation state on metal ions. In addition, these macrocyclic complexes possess good antimicrobial activities against E. coli, P. aeruginosa, B. cereus, S. aureus and antifungal against C. albicans when compared with Gentamycin.
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- 2021
7. Palladium-Catalyzed [4 + 3] or [2 + 2 + 3] Annulation via C–H Activation and Subsequent Decarboxylation: Access to Heptagon-Embedded Polycyclic Aromatic Hydrocarbons
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Xiahong Chen, Xiumei Yang, Yuan Yang, Guobo Deng, Yun Liang, Minghao Zhang, and Yankun Xu
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chemistry.chemical_classification ,Annulation ,010405 organic chemistry ,Decarboxylation ,Organic Chemistry ,chemistry.chemical_element ,Polycyclic aromatic hydrocarbon ,Annulene ,010402 general chemistry ,Ring (chemistry) ,01 natural sciences ,Biochemistry ,Combinatorial chemistry ,0104 chemical sciences ,Catalysis ,chemistry ,Heptagon ,Physical and Theoretical Chemistry ,Palladium - Abstract
The construction of a seven-membered ring in the polycyclic aromatic hydrocarbon skeleton remains a notoriously difficult but attractive challenge. Herein a novel palladium-catalyzed [4 + 3] decarboxylative annulation of 2-iodobiphenyls with 2-(2-halophenyl)acrylic acids is reported, which provides an efficient approach for assembling various tribenzo[7]annulenes via a C-H activation and decarboxylation process. Moreover, tribenzo[7]annulenes can be also synthesized via a [2 + 2 + 3] decarboxylative annulation strategy by employing readily available 1,2-halobenzenes, phenylboronic acids, and 2-(2-halophenyl)acrylic acids.
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- 2021
8. Experimental and Theoretical Evidence for Aromatic Stabilization Energy in Large Macrocycles
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Lara Tejerina, Michael Jirásek, Michel Rickhaus, and Harry L. Anderson
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Isodesmic reaction ,010405 organic chemistry ,Chemistry ,Aromaticity ,General Chemistry ,Annulene ,010402 general chemistry ,Ring (chemistry) ,01 natural sciences ,Biochemistry ,Porphyrin ,Catalysis ,0104 chemical sciences ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Computational chemistry ,Molecule ,Density functional theory ,Antiaromaticity - Abstract
Enhanced thermodynamic stability is a fundamental characteristic of aromatic molecules, yet most previous studies of aromatic stabilization energy (ASE) have been limited to small rings with up to 18 π-electrons. Here we demonstrate that ASE can be detected experimentally in π-conjugated porphyrin nanorings with Hückel circuits of 76-108 π-electrons. This conclusion is supported by analyzing redox potentials to calculate the energy change for isodesmic reactions that convert an aromatic ring to an antiaromatic ring or vice versa. It is also supported by analyzing the energy barriers to conformational equilibria that disrupt aromaticity in the transition state. Both types of experiment indicate that cationic porphyrin nanorings display ASEs of 1-5 kJ mol-1. Density functional theory calculations reproduce the results for both types of experiment and predict ASEs in the range of 1-16 kJ mol-1. The experimental ASEs in porphyrin nanorings are compared with an experimental ASE of [18]annulene of ∼11 kJ mol-1, deduced from analysis of the energy barriers to conformational equilibria in [16], [18], and [20]annulene. Calculated energies of isodesmic reactions give an ASE of ∼37 kJ mol-1 in [18]annulene. This work contributes to a fundamental understanding of aromaticity in large macrocycles.
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- 2021
9. Synthesis of Carbonyl‐substituted Tetracyanodihydrotetraaza[14]annulenes
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W. Fabiola Sanjuan-Szklarz, Konrad Pawluczyk, Jarosław Kowalski, and Krzysztof Woźniak
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Inorganic Chemistry ,Chemistry ,Computational chemistry ,Annulene - Published
- 2021
10. Synthesis of new <scp>metal‐free</scp> 1,2,4,5,9,10,12, <scp>13‐octaaza</scp> [16]annulene derivatives using the reaction of vinamidinium salts with thiocarbohydrazide
- Author
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A. M. Mehranpour and Askar Sabet
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Thiocarbohydrazide ,chemistry.chemical_compound ,Metal free ,Chemistry ,Organic Chemistry ,Polymer chemistry ,Annulene - Published
- 2021
11. Synthesis, bonding properties and ether activation reactivity of cyclobutadienyl-ligated hybrid uranocenes
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Akseli Mansikkamäki, Richard A. Layfield, and Nikolaos Tsoureas
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Trimethylsilyl ,Silylation ,010405 organic chemistry ,Chemistry ,Ligand ,Ether ,General Chemistry ,Annulene ,010402 general chemistry ,01 natural sciences ,Medicinal chemistry ,3. Good health ,0104 chemical sciences ,chemistry.chemical_compound ,Uranocene ,Reactivity (chemistry) ,Diethyl ether - Abstract
A series of hybrid uranocenes consisting of uranium(iv) sandwiched between cyclobutadienyl (Cb) and cyclo-octatetraenyl (COT) ligands has been synthesized, structurally characterized and studied computationally. The dimetallic species [(η4-Cb′′′′)(η8-COT)U(μ:η2:η8-COT)U(THF)(η4-Cb′′′′)] (1) forms concomitantly with, and can be separated from, monometallic [(η4-Cb′′′′)U(THF)(η8-COT)] (2) (Cb′′′′ = 1,2,3,4-tetrakis(trimethylsilyl)cyclobutadienyl, COT = cyclo-octatetraenyl). In toluene solution at room temperature, 1 dissociates into 2 and the unsolvated uranocene [(η4-Cb′′′′)U(η8-COT)] (3). By applying a high vacuum, both 1 and 2 can be converted directly into 3. Using bulky silyl substituents on the COT ligand allowed isolation of base-free [(η4-Cb′′′′)U{η8-1,4-(iPr3Si)2C8H6}] (4), with compounds 3 and 4 being new members of the bis(annulene) family of actinocenes and the first to contain a cyclobutadienyl ligand. Computational studies show that the bonding in the hybrid uranocenes 3 and 4 has non-negligible covalency. New insight into actinocene bonding is provided by the complementary interactions of the different ligands with uranium, whereby the 6d orbitals interact most strongly with the cyclobutadienyl ligand and the 5f orbitals do so with the COT ligands. The redox-neutral activation of diethyl ether by [(η4-Cb′′′′)U(η8-C8H8)] is also described and represents a uranium-cyclobutadienyl cooperative process, potentially forming the basis of further small-molecule activation chemistry., The synthesis, structure and bonding in a series of hybrid uranocenes consisting of cyclobutadienyl and cyclo-octatetraenyl ligands is described.
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- 2021
12. Fluorescent molecular glass based on hexadehydrotribenzo[12]annulene
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Tomoyuki Akutagawa, Ichiro Hisaki, Takashi Takeda, and Yotaro Kasahara
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Materials science ,Liquid crystalline ,Intermolecular force ,Metals and Alloys ,General Chemistry ,Annulene ,Fluorescence ,Catalysis ,Glass material ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Crystallography ,Planar ,Materials Chemistry ,Ceramics and Composites ,Dielectric anomaly - Abstract
We prepared octylbenzoate-substituted [12]DBA (C8[12]DBA) as an organic molecular glass material. Even with a central large, planar π unit of [12]DBA, which is generally advantageous for the formation of a crystalline/liquid crystalline state, this compound formed a thermally stable glass state due to its small intermolecular π contact between [12]DBA units and twisted geometries around the terminal benzoate units. C8[12]DBA showed a unique dielectric anomaly and isolated fluorescence properties in the glass state.
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- 2021
13. Multi-functional photocatalytic activity of transition-metal tetraaza[14]annulene frameworks
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Wenqing Zhang, Hongxia Bu, Juan Wang, Mingwen Zhao, Lanling Zhao, and Yuanyuan Qu
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Materials science ,Renewable Energy, Sustainability and the Environment ,Oxygen evolution ,02 engineering and technology ,General Chemistry ,Reaction intermediate ,Annulene ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,01 natural sciences ,0104 chemical sciences ,Catalysis ,Transition metal ,Photocatalysis ,Water splitting ,General Materials Science ,Metal-organic framework ,0210 nano-technology - Abstract
Multi-functional catalysts for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) are highly desired in the development of renewable energy conversion and storage technologies. Using first-principles calculations, we demonstrated the recently-synthesized two-dimensional (2D) metal organic frameworks (MOFs) of transition metals (TM = Cr–Zn, Ru–Ag, Ir, and Pt) atoms and tetraaza[14]annulene (TAA) can deem as multi-functional photocatalysts. Fe-TAA and Rh-TAA MOFs show the bi-functional catalytic activity towards ORR/OER and HER/OER, respectively, while Ir-TAA MOF is a promising tri-functional catalyst for HER/OER/ORR. The catalytic activity of TM-TAA MOFs was revealed to be governed by the binding strength between the TM atom and reaction intermediates, which can be correlated to the d-band center of the TM atoms. Remarkably, the electronic band structures and the photocatalytic activity of Ir-TAA and Rh-TAA MOFs fulfil the requirements of overall water splitting under visible light irradiation. Our findings proposed a new family of 2D MOFs as efficient catalysts for the OER, ORR, and HER in clean energy technologies, offering a promising perspective in catalyst design.
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- 2021
14. Chalice‐Type Tridentate Silicon Lewis Acids of C 3 Symmetry in a Single Step Starting from Hexadehydrotribenzo[12]annulene
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Anna Schwartzen, Norbert W. Mitzel, Beate Neumann, Jan-Henrik Weddeling, Hans-Georg Stammler, and Jana Langosch
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Hydrosilylation ,Sonogashira coupling ,Alkyne ,Crystal structure ,010402 general chemistry ,01 natural sciences ,Catalysis ,Coupling reaction ,chemistry.chemical_compound ,Polymer chemistry ,Molecule ,tridentate Lewis acids ,Lewis acids and bases ,chemistry.chemical_classification ,Full Paper ,010405 organic chemistry ,Chemistry ,Organic Chemistry ,chalice structure ,General Chemistry ,Full Papers ,Annulene ,0104 chemical sciences ,solid-state structures ,annulenes - Abstract
Tridentate Lewis acids with aligned functions were synthesized based on the rigid framework hexadehydrotribenzo[12]annulene. The backbone and its fluorinated analogue were synthesised in one‐pot syntheses, with alkyne deprotection and Sonogashira cross coupling reaction being carried out in one step. Hydrosilylation of the annulene with chlorohydrosilanes proceeded highly selectively and afforded rigid poly‐Lewis acids with three SiCl3 or SiCl2Me substituents perfectly oriented to one side of the molecule in a single step. The progress of hydrosilylation was investigated by time‐correlated NMR spectroscopic studies. The crystal structures show that the framework is symmetrically functionalised and the silyl substituents are aligned in one direction. To increase the acidity of the Lewis acids the chlorosilyl substituents were fluorinated with SbF3. Further investigation of hydrometallation reactions (M=B, Al, Ga, Sn) did not lead to corresponding structures., A single‐step one‐pot synthesis, the hydrosilylation of the planar hydrocarbon hexadehydrotribenzo[12]annulene, provides access to chalice‐like trifunctional Lewis acids of C 3 symmetry with all functions oriented to the same side of the molecule. The synthesis of such poly‐functionalized donor‐free hydrocarbon derivatives is important for the development of new poly‐Lewis acids.
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- 2020
15. ANALYSIS OF LOCALIZED ORBITALS IN AZABORA DERIVATIVES OF [8] ANNULENE: IN THE VIEWPOINT OF AROMATICITY AND INDUCED RING CURRENTS
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Majid Monajjemi
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Inorganic Chemistry ,Physics ,Crystallography ,Valence (chemistry) ,Atomic orbital ,Chemical shift ,Materials Chemistry ,Molecule ,Aromaticity ,Physical and Theoretical Chemistry ,Annulene ,Antiaromaticity ,Natural bond orbital - Abstract
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 (Huckel′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 $${{\text{B}}_{2}}{{\text{N}}_{\text{2}}}{{\text{C}}_{4}}\text{H}_{8}^{2-}$$ , $${{\text{B}}_{\text{4}}}{{\text{N}}_{\text{4}}}\text{H}_{8}^{2-}$$ , and $${{\text{B}}_{\text{4}}}{{\text{N}}_{\text{4}}}\text{H}_{8}^{2+}$$ 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.
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- 2020
16. Spectroscopic and theoretical optical properties of indoleninyl‐substituted dibenzotetraaza[14]annulenes
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Abdul Kariem Arof, Mehmet Taşer, Wan Jefrey Basirun, Mustafa Karakaya, Nurhidayatullaili Muhd Julkapli, Aysun Gozutok, Chee Chin Fei, Asli Karakas, and Abdul Qaiyum Ramle
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Chemistry ,Computational chemistry ,Organic Chemistry ,Annulene - Published
- 2020
17. Electrochemical CO oxidation by a Rh tetraaza[14]annulene‐based catalyst
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Shin-ichi Yamazaki, Masafumi Asahi, Zyun Siroma, and Tsutomu Ioroi
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Organic Chemistry ,Inorganic chemistry ,chemistry.chemical_element ,Annulene ,Electrochemistry ,Electrocatalyst ,Catalysis ,Water-gas shift reaction ,Rhodium ,Inorganic Chemistry ,chemistry ,Fuel cells ,Physical and Theoretical Chemistry - Published
- 2020
18. <scp> N ‐Hydroxy </scp> ‐1,6‐methano[10]annulene‐3,4‐dicarboximide/Co( <scp>OAc</scp> ) 2 : A novel catalytic system for the aerobic oxidation of alkylarenes
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Ang Zuo, Jianjun Liu, and Shengli Zuo
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Chemistry ,Organic Chemistry ,Annulene ,Medicinal chemistry ,Catalysis - Published
- 2020
19. Observation of Möbius Aromatic Planar Metallaborocycles
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Joseph Czekner, G. Stephen Kocheril, Ling Fung Cheung, and Lai-Sheng Wang
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Chemistry ,Aromaticity ,General Chemistry ,Annulene ,010402 general chemistry ,Ring (chemistry) ,01 natural sciences ,Biochemistry ,Molecular physics ,Catalysis ,0104 chemical sciences ,Delocalized electron ,Colloid and Surface Chemistry ,Ab initio quantum chemistry methods ,Möbius aromaticity ,Electron counting ,Topology (chemistry) - Abstract
Mobius aromaticity was developed for twisted annulenes with electron counting rules opposite to those of Huckel aromaticity. The introduction of transition metals makes it possible for planar cyclic systems to exhibit Mobius aromaticity. Here we report the first planar monocyclic metallaboron systems with Mobius aromaticity. The structures and bonding of two rhenium-boride clusters are studied by high-resolution photoelectron imaging and ab initio calculations. The ReB3- cluster is shown to have a near-pyramidal structure, while ReB4- is found to be a planar pentagonal ring. Chemical bonding analyses show that both ReB4- and ReB4 possess four delocalized π-electrons, including two π-electrons in an orbital of Mobius topology. NICS calculations reveal strong aromatic characters in ReB4- and ReB4, consistent with the 4n electron counting rule for Mobius aromaticity.
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- 2020
20. Molecular Structural Properties of [n]-Annulene (n = 8, 10, 12, 14) and its Boron Nitride Derivatives: Analysis of NMR, NBO, ELF and PDI
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Majid Monajjemi and F. Mollaamin
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Inorganic Chemistry ,Crystallography ,Valence (chemistry) ,Atomic orbital ,Chemistry ,Chemical shift ,Materials Chemistry ,Molecule ,Aromaticity ,Physical and Theoretical Chemistry ,Annulene ,Ion ,Natural bond orbital - Abstract
Due to the importance of structural properties of annulene in physical and inorganic chemistry, the trajectory of the NBO to MO evolution can be written as natural atomic orbitals (NAO) → natural hybrid orbital (NHO) → natural bond orbital (NBO) → natural semi-localized MO (NLMO) → MO. The electron density distribution in this [n]-annulene series (both ions and molecules) (n = 8, 10, 12, 14) is investigated by NMR, NBO, ELF, FLU, and PDI analyses. The (4n+2)π and also 4nπ systems (Huckel’s rule) on variants of those compounds via the localized orbital localization (LOL) and electron localized function (ELF) are discussed, and a diatropic ring current (aromatic) is also distinguished for some other paratropic currents (anti-aromatic). The NHO direction and bond bending deviations from the line of nuclear centers are exhibited for understanding the situation of π and σ orbitals. In this work, for each NAO function, core, valence, or Rydberg, the orbital occupancy and the orbital energies are discussed. In addition, nucleus independent chemical shifts (NICSs) and statistical nucleus chemical shifts (S-NICSs) confirm the aromaticity and anti-aromaticity amounts in those rings.
- Published
- 2020
21. Targeted synthesis of meso-aryl substituted aromatic trans-doubly N-confused dithia/diselena [18] porphyrins (1.1.1.1) with NIR absorption: spectroscopic and theoretical characterization
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Dandamudi Usharani, Mohandas Sangeetha, Sumit Sahoo, Harapriya Rath, and Soumita Bera
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Solution state ,Aryl ,Organic Chemistry ,Aromaticity ,Annulene ,Biochemistry ,Characterization (materials science) ,chemistry.chemical_compound ,Crystallography ,chemistry ,Yield (chemistry) ,Physical and Theoretical Chemistry ,Absorption (chemistry) ,Conformational isomerism - Abstract
High yield synthesis and spectroscopic isolation of two hitherto unknown highly stable single conformers of meso-aryl substituted dithia/diselena trans-doubly N-confused porphyrins with fully π-conjugated [18] annulene structures are reported. In-depth solution state spectroscopic measurements and DFT level theoretical calculations strongly show the distinct aromaticity with strong NIR absorption of these new macrocycles.
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- 2020
22. Biliazine: a ring open phthalocyanine analog with amesohydrogen bond
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Christopher J. Ziegler, Briana R. Schrage, and Victor N. Nemykin
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Hydrogen bond ,Metals and Alloys ,Aromaticity ,General Chemistry ,Annulene ,Ring (chemistry) ,Catalysis ,Spectral line ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Metal ,chemistry.chemical_compound ,Crystallography ,chemistry ,visual_art ,Materials Chemistry ,Ceramics and Composites ,visual_art.visual_art_medium ,Phthalocyanine ,Chelation - Abstract
The hemiporphyrazine type chelate and phthalocyaninine analog biliazine (H2BlzH) and its metal complexes can be synthesized in one-step from a monosubstituted diiminisoindoline (DII). This singly substituted precursor is produced from the reaction of unsubstituted DII and 2-aminopyrazole. The biliazine macrocycle is a tetradentate chelate where the ring is closed via a strong hydrogen bond at the meso position. Although the hydrogen bond closes the ring, there is little evidence for 18-electron type annulene aromaticity across the macrocycle, as seen in the UV-visible and MCD spectra and supported by DFT calculations.
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- 2020
23. Theoretical study on aromatic and open-shell characteristics of carbon nanobelts composed of indeno[1,2-b]fluorene units: dependence on the number of units and charge states
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Ryohei Kishi, Masayoshi Nakano, Masaki Yamane, Wataru Yoshida, Yosuke Shimizu, and Ryosuke Sugiura
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Materials science ,General Chemical Engineering ,chemistry.chemical_element ,Charge (physics) ,General Chemistry ,Conjugated system ,Fluorene ,Annulene ,chemistry.chemical_compound ,Crystallography ,Delocalized electron ,chemistry ,Organic synthesis ,Open shell ,Carbon - Abstract
In this study, we theoretically investigate the aromatic and open-shell characteristics of carbon nanobelts (CNBs) composed of five- and six-membered rings. We have designed nanobelts composed of indeno[1,2-b]fluorene ([1,2-b]IF) units, which are referred to as [N]IF-CNB (N: the number of five-membered rings). The number of π-electrons, nπ, in neutral [N]IF-CNB is 7N, and thus depending on N and charge states, nπ can be 4n + 2 and 4n. Quantum chemical calculations on neutral [6]IF-CNB and [8]IF-CNB and dicationic [8]IF-CNB2+ have revealed that they are expected to exhibit unique aromatic and open-shell characteristics depending on nπ, there are several analogies of the electronic structures in [N]IF-CNB to those in [N]annulene. Delocalized and intermediate open-shell electronic structures of [N]IF-CNB are also useful to drastically change the third-order nonlinear optical properties. These results suggest that theoretically designed [N]IF-CNB can be attractive and challenging targets of organic synthesis for realizing novel open-shell functional conjugated macrocycles.
- Published
- 2020
24. Design of annulene-within-an-annulene systems by the altanisation approach. A study of altan-[n]annulenes
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Riccardo Zanasi, Guglielmo Monaco, Patrick W. Fowler, Matteo Piccardo, and Alessandro Soncini
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Physics ,010304 chemical physics ,Analytical expressions ,General Physics and Astronomy ,Annulene ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,symbols.namesake ,Quantum mechanics ,0103 physical sciences ,symbols ,Molecule ,Molecular orbital ,Singlet state ,Physical and Theoretical Chemistry ,Hamiltonian (quantum mechanics) ,Eigenvalues and eigenvectors - Abstract
The altanisation strategy, devised to design molecules with large and paratropic perimeter circulations, is applied to the family of [n]annulenes to give, altan-[n]annulenes, i.e. [n,5]coronenes. Analytical expressions are obtained for the eigenvalues of the Hückel Hamiltonian for altan-[n]annulenes, and used in conjunction with selection rules derived from the ipsocentric approach to predict patterns of global ring current in these systems. Density-functional calculations performed on seven altan-[n]annulenes, three neutral and four charged, give current-density maps in essential agreement with the predictions obtained at the unperturbed Hückel level. All but one of the systems show patterns with the tropicities expected for isolated annulenes, in line with the altanisation concept. The apparent exception is altan-[11]annulene−, the only singlet system with a well defined open-shell character in the studied set. The key role of open-shell character can be accommodated by appropriate choice of the occupation numbers of the initial Hückel molecular orbitals, where the anion altan-[11]annulene− is considered as an [11]annulene inside the [22]annulene anion.
- Published
- 2020
25. Understanding the structures and aromaticity of heteroporphyrins with computations
- Author
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Yun-Fang Yang, Qunmin Wang, Yuanbin She, Xiaoli Fang, and Xiahe Chen
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Hydrogen ,Chemical shift ,Organic Chemistry ,Heteroatom ,chemistry.chemical_element ,Aromaticity ,Annulene ,Ring (chemistry) ,Biochemistry ,Porphyrin ,Crystallography ,chemistry.chemical_compound ,chemistry ,Moiety ,Physical and Theoretical Chemistry - Abstract
Heteroporphyrins are porphyrin derivatives with replacement of the pyrrolic NH moiety by other heteroatom-containing groups, such as PH, AsH, SiH2, O, S, etc. For all studied heteroporphyrins, the macrocycle structure is distorted due to the presence of large heteroatoms. The HOMO-LUMO gap of heteroporphyrins is generally decreased compared to regular porphyrins. Both nucleus independent chemical shifts values and visualized anisotropy of induced current density were computed to describe the aromaticity of heteroporphyrins. The plots of anisotropy of induced current density suggest that the ring current diverged into an outer and an inner pathway at each ring. The current mainly passes through the outer path at the pyrrolic rings with inner hydrogen and through the inner path at the pyrrolic rings without inner hydrogen. In both regular porphyrin and O-substituted heteroporphyrins, the aromatic pathway is mainly contributed by the 22π-electron aromatic route model. Heteroatoms such as PH, AsH, S, Se and Te have little contribution to the aromaticity of heteroporphyrins. In addition, the π conjugation is also interrupted at the CH2 and SiH2 moiety, and the ring current mainly passes through the outer path of the heteroporphyrins with CH2 and SiH2 replacing the pyrrolic NH moiety. Therefore the 18π-[18]annulene model is dominated in PH-, AsH-, S-, Se-, Te-, CH2- and SiH2-substituted heteroporphyrins. These computational studies shed new light on the aromatic characters of heteroporphyrins, and will facilitate the further development of various novel heteroporphyrins.
- Published
- 2020
26. Unraveling the kinetics and molecular mechanism of gas phase pyrolysis of cubane to [8]annulene
- Author
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Temer S. Ahmadi, Ehsan Zahedi, Luis R. Domingo, Ahmad Seif, and Elham Mazarei
- Subjects
RRKM theory ,Exergonic reaction ,chemistry.chemical_classification ,Electron density ,Materials science ,010304 chemical physics ,Double bond ,General Chemical Engineering ,General Chemistry ,Annulene ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,Reaction rate constant ,chemistry ,Cubane ,0103 physical sciences ,Physical chemistry ,Single bond - Abstract
The kinetic and electron density flows are studied theoretically for the gas phase pyrolysis of cubane via its cage opening to reach bicyclooctatriene and then thermal rearrangement of bicyclooctatriene to produce [8]annulene which is the experimentally observed major product. The observed kinetic data at the MN15-L/maug-cc-pVTZ level of theory were in good agreement with the experimental results as compared to the CBS-QB3 method. The cage opening and the thermal rearrangement steps at the experimentally employed temperature of 520 K were exergonic and exothermic. The atmospheric rate constants calculated by means of the RRKM theory show that the cage opening is the rate-determining step. The temperature dependence of the rate constant for the cage opening step at the MN15-L level can be expressed as log(k/s−1)1barMN15-L = (15.63) − (48.99 kcal mol−1)/RT ln 10. The molecular mechanism of the reactions has been investigated by means of the bonding evolution theory (BET) at the B3LYP/6-311G (d,p) level of theory. The cage opening course is described topologically by cleaving of C1–C2, C4–C8, and C5–C6 single bonds and electron saturation of the C1–C4, C2–C6, and C5–C8 bonds, while the rearrangement of bicyclooctatriene is described by C3–C7 bond rupture, depopulation of C1–C4 and C5–C8 double bonds, and electron saturation of C1–C5, C3–C4, and C7–C8 bonds. Electron density rearrangement along the two successive steps are asynchronous and the sequence of catastrophes can be represented as: η-1-13-C†C†FFFC†C†FFFC†C†-2-6-[C]2C†[F]2[C†]2C†-0.
- Published
- 2020
27. Modelling aromatisation of (BN)nH2n azabora-annulenes
- Author
-
Cate S. Anstöter, Patrick W. Fowler, and Christopher M. Gibson
- Subjects
Physics ,010405 organic chemistry ,General Physics and Astronomy ,Electron ,Annulene ,010402 general chemistry ,Ring (chemistry) ,01 natural sciences ,Molecular physics ,Planarity testing ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Ab initio quantum chemistry methods ,Borazine ,Potential energy surface ,Physical and Theoretical Chemistry ,Ring current - Abstract
Despite a long tradition of descriptions of borazine as an ‘inorganic benzene’, this molecule is a non-aromatic species according to the magnetic (ring-current) criterion. Borazine, borazocine, and the larger neutral (BN)nH2n azabora-annulene heterocycles in planar conformations, although π-isoelectronic with [2n]annulenes, support only localized induced currents in perpendicular magnetic fields. The π-current maps of these systems comprise superpositions of separate ‘lone-pair’ circulations on all nitrogen centres. For the systems with n > 4, planarity must be enforced by a constraint. Qualitative orbital analysis based on the ipsocentric approach to calculation of induced current density suggests that global induced currents could be produced through strategic changes to the π electron count. In ab initio calculations, azabora-annulenes with rings of size [8]- and larger were indeed found to support global diatropic ring currents in both anionic and cationic forms with (4N + 2) π electron counts. The planar conformation of the charged ring typically occupies a stationary point of higher order on the potential energy surface, rather than a minimum. However, the borazocine dianion, [B4N4H8]2−, occupies a planar minimum, supports a diatropic ring current of strength comparable to that in benzene, and is predicted to participate in sandwich compounds; it is therefore a good candidate for an aromatised azabora-annulene.
- Published
- 2020
28. Induced magnetic field in sp-hybridized carbon rings: analysis of double aromaticity and antiaromaticity in cyclo[2N]carbon allotropes
- Author
-
Nickolas D. Charistos and Alvaro Muñoz-Castro
- Subjects
Materials science ,General Physics and Astronomy ,Aromaticity ,02 engineering and technology ,Annulene ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Molecular physics ,0104 chemical sciences ,Magnetic field ,Bond length ,Ring size ,Molecular geometry ,Physical and Theoretical Chemistry ,0210 nano-technology ,Ground state ,Antiaromaticity - Abstract
The induced magnetic field of C2N (N = 3-14) carbon rings was dissected to contributions from out-of-plane and in-plane π orbitals revealing two concurrent long range shielding or deshielding cones as a manifestation of the dual aromatic and antiaromatic character of C4n+2 and of C4n rings respectively. Aromaticity based on the magnetic criterion was evaluated with regard to the bonding pattern and geometrical characteristics that elucidate the influence of bond length and bond angle alteration on out-of-plane and in-plane magnetic responses. Ground state polyynic geometries of C4n+2 rings exhibit comparable shielding cones to annulenes, decreasing the magnetic response with regard to the ring size and similar πout and πin diatropicity. Transition state cumulenic rings display increased aromaticity expressed by a very strong constant magnetic response and augmented πout diatropicity with regard to πin. The variations of the induced magnetic field are explained on the basis of frontier orbital interactions through rotational excitations, which enable further rationalization of the aromatic/antiaromatic behavior.
- Published
- 2020
29. Trapping a pentagonal molecule in a self-assembled molecular network: an alkoxylated isosceles triangular molecule does the job
- Author
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Steven De Feyter, Masaru Anzai, Yoshito Tobe, Kazukuni Tahara, and Masahiko Iyoda
- Subjects
Materials science ,Metals and Alloys ,Supramolecular chemistry ,General Chemistry ,Trapping ,Annulene ,Catalysis ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,Crystallography ,law ,Isosceles triangle ,Materials Chemistry ,Ceramics and Composites ,Alkoxy group ,Molecule ,Graphite ,Scanning tunneling microscope - Abstract
We herein report a unique example of on-surface adaptive self-assembly. A pentagon-shaped macrocycle, cyclic [5]meta-phenyleneacetylene [5]CMPA, is trapped by the adaptive supramolecular network formed by an isosceles triangular molecule, alkoxy substituted dehydrobenzo[14]annulene [14]ISODBA at the liquid/graphite interface, leading to a highly ordered and large-area bicomponent self-assembled molecular network (SAMN), as revealed by scanning tunneling microscopy (STM).
- Published
- 2020
30. A flexible expanded heterocorrole: Tellura[22]porphyrin(6.1.1.0)
- Author
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Sandra Hojniak-Thyssen, Ewa Pacholska-Dudziak, Michał Szczepaniak, and Lechosław Latos-Grażyński
- Subjects
010405 organic chemistry ,chemistry.chemical_element ,General Chemistry ,Annulene ,010402 general chemistry ,01 natural sciences ,Porphyrin ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Polymer chemistry ,Moiety ,Reaction path ,Tellurium - Abstract
An expanded heterocorrole, meso-tetraaryl-tellura[22]porphyrin(6.1.1.0), containing a bipyrrole moiety and a six-carbon long link, has been synthesized. The reaction path proceeds through a controlled acid-promoted extrusion of one tellurium atom from meso-aryl-26,28-ditellurasapphyrin, leading to a structure where one tellurophene ring of the substrate is replaced by a bridging acyclic four-carbon unit. This aromatic porphyrin-annulene hybrid is conformationally flexible in solution, on account of the C4 unit adopting two different configurations: trans–cis–trans or all-trans. Studies of the dynamic behavior of tellura[22]porphyrin(6.1.1.0) in solution were performed by means of 1H and 125Te NMR spectroscopy. The X-ray structure of the all-trans form with trapezoid macrocyclic skeleton is also presented.
- Published
- 2019
31. An Investigation into the Stephens-Castro Synthesis of Dehydrotriaryl[12]annulenes: Factors Influencing the Cyclotrimerization
- Author
-
Jean-Marc Strub, Alexandre Varnek, Paul N. W. Baxter, Abdelaziz Al Ouahabi, Lydia Karmazin, and Sarah Cianférani
- Subjects
010405 organic chemistry ,Computational chemistry ,Chemistry ,Organic Chemistry ,Chimie/Autre ,Physical and Theoretical Chemistry ,Annulene ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences - Published
- 2019
32. Calculations Predict That Heavy-Atom Tunneling Dominates Möbius Bond Shifting in [12]- and [16]Annulene
- Author
-
Claire Castro, Cameron S. Michel, William L. Karney, and Jessica K. Arbitman
- Subjects
Tunneling rate ,010405 organic chemistry ,Chemistry ,Organic Chemistry ,Atom ,Physical and Theoretical Chemistry ,Annulene ,Atomic physics ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Quantum tunnelling ,0104 chemical sciences - Abstract
The contribution of heavy-atom tunneling to reactions of [12]- and [16]annulene was probed using small-curvature tunneling rate calculations. At the CCSD(T)/cc-pVDZ//M06-2X/cc-pVDZ level, tunneling is predicted to account for more than 50% of the rate for Möbius bond shifting and ca. 35% of the rate for electrocyclization in [12]annulene, and over 80% of the rate for Möbius bond shifting in [16]annulene, at temperatures at which these reactions have been observed experimentally.
- Published
- 2019
33. Partial Oxidation-Induced Electrical Conductivity and Paramagnetism in a Ni(II) Tetraaza[14]annulene-Linked Metal Organic Framework
- Author
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Inseon Oh, Jung-Woo Yoo, Ming Huang, Sang Kyu Kwak, Onur Buyukcakir, Se Hun Joo, Won Kyung Seong, Yi Jiang, Xiong Chen, Sun Hwa Lee, and Rodney S. Ruoff
- Subjects
Chemistry ,Inorganic chemistry ,General Chemistry ,Conjugated system ,Annulene ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,Metal ,Paramagnetism ,Colloid and Surface Chemistry ,Electrical resistivity and conductivity ,visual_art ,visual_art.visual_art_medium ,Metal-organic framework ,Partial oxidation - Abstract
We report the synthesis and characterization of a two-dimensional (2D) conjugated Ni(II) tetraaza[14]annulene-linked metal organic framework (NiTAA-MOF) where NiTAA is a macrocyclic MN4 (M = metal,...
- Published
- 2019
34. A Highly Strained Al-Al σ-Bond in Dianionic Aluminum Analog of Oxirane for Molecule Activation
- Author
-
Rei Kinjo, Kota Koshino, and School of Physical and Mathematical Sciences
- Subjects
Pericyclic reaction ,Isocyanide ,Spectroscopic Analysis ,Aluminum Alloys ,General Chemistry ,Annulene ,Biphenylene ,Sigmatropic reaction ,Biochemistry ,Catalysis ,Coupling reaction ,Benzonitrile ,chemistry.chemical_compound ,Crystallography ,Colloid and Surface Chemistry ,chemistry ,Chemistry [Science] ,Stepwise reaction - Abstract
Since aluminum is the most electropositive element among the p-block elements, the construction of molecules bearing a dianionic Al-Al σ-bond is inherently highly challenging. Herein, we report the first synthesis of a dianionic dialane(6) 2 based on the Al2O three-membered ring scaffold, namely, an aluminum analog of oxirane. The structure of 2 has been unambiguously ascertained by spectroscopic analysis as well as X-ray crystallography, and computational studies revealed that 2 bears a highly strained Al-Al σ-bond. 2 readily reacts with the unsaturated substrates such as isocyanide, ethylene, and ketone, concomitant with the cleavage of the Al-Al σ-bond under mild conditions, leading to the four- and five-membered heterocycles 3-5. Furthermore, the reaction of 2 with two molecules of benzonitrile (PhCN) furnishes a seven-membered heterocycle 6, resulting from the C-C coupling reaction of PhCN. We further delineate that 2 selectively activates an arene ring C-C bond of biphenylene, rendering a di-Al-substituted benzo[8]annulene derivative 7. Preliminary computational studies propose that the stepwise reaction mechanism involves the Al-Al σ-bond cleavage, dearomative Al-C bond formation, subsequent sigmatropic [1,3]shifts, and a pericyclic reaction. Ministry of Education (MOE) Nanyang Technological University Submitted/Accepted version We are grateful to Nanyang Technological University (NTU) and the Singapore Ministry of Education (MOE2018-T2-2-048(S)) for financial support.
- Published
- 2021
35. Nickel catalyzed sustainable synthesis of benzazoles and purines via acceptorless dehydrogenative coupling and borrowing hydrogen approach
- Author
-
Nanda D. Paul, Rakesh Mondal, Amit Kumar Guin, and Gargi Chakraborty
- Subjects
Benzimidazole ,Reaction mechanism ,Organic Chemistry ,Borrowing hydrogen ,Annulene ,Benzoxazole ,Biochemistry ,Combinatorial chemistry ,Catalysis ,chemistry.chemical_compound ,chemistry ,Benzothiazole ,Macrocyclic ligand ,Physical and Theoretical Chemistry - Abstract
Herein we report nickel-catalyzed sustainable synthesis of a few chosen five-membered fused nitrogen heterocycles such as benzimidazole, purine, benzothiazole, and benzoxazole via acceptorless dehydrogenative functionalization of alcohols. Using a bench stable, easy to prepare, and inexpensive Ni(II)-catalyst, [Ni(MeTAA)] (1a), featuring a tetraaza macrocyclic ligand (tetramethyltetraaza[14]annulene (MeTAA)), a wide variety of polysubstituted benzimidazole, purine, benzothiazole, and benzoxazole derivatives were prepared via dehydrogenative coupling of alcohols with 1,2-diaminobenzene, 4,5-diaminopyrimidine, 2-aminothiphenol, and 2-aminophenol, respectively. A wide array of benzimidazoles were also prepared via a borrowing hydrogen approach involving alcohols as hydrogen donors and 2-nitroanilines as hydrogen acceptors. A few control experiments were performed to understand the reaction mechanism.
- Published
- 2021
36. Revisiting Dehydrothiopheno[12]annulenes: Synthesis, Electronic Properties, and Aromaticity
- Author
-
Tatsuru Kuroiwa, Ken Ishiwata, Kazukuni Tahara, Yasuhiro Ohtomo, and Shingo Hashimoto
- Subjects
chemistry.chemical_compound ,Crystallography ,Diene ,chemistry ,Organic Chemistry ,Thiophene ,Aromaticity ,Nuclear magnetic resonance spectroscopy ,Annulene ,Ring (chemistry) ,Electronic properties ,Antiaromaticity - Abstract
The aromaticity and electronic properties of acetylene-bridged hexadehydrotristhiopheno[12]annulenes (HDTAs) were revisited using a combined experimental and theoretical approach. Moreover, we attempted the synthesis of the butadiyne-bridged octadehydrobisthiopheno[12]annulenes (ODTAs). While the formation of ODTAs was indicated by NMR spectroscopy, mass spectrometry, and UV-vis absorption measurements, our attempts to isolate ODTAs were unsuccessful on account of its instability. Instead, their structure and energetic properties were predicted using DFT calculations. HDTA isomers in which the position where the thiophene rings are fused to the 12-membered ring differs (b- vs c-position) show distinct differences in their HOMO-LUMO energy gaps (EGap). ODTAs also show large EGap differences depending on the fusion position of the thiophene rings. The diene character of the thiophene ring significantly changes the electronic properties; i.e., EGap differences of >1 eV were observed between the isomers of both HDTAs and ODTAs. A theoretical evaluation of HDTAs and ODTAs revealed significant variation in the local aromaticity/antiaromaticity between the b- and c-isomers. The antiaromatic character of the 12-membered ring is attenuated for the b-isomers, whereas it is decreased substantially for the c-isomers. The results of this study are useful for a detailed understanding of the fundamental aspects of dehydrothiopheno[12]annulenes.
- Published
- 2021
37. Hierarchical two-dimensional molecular assembly through dynamic combination of conformational states at the liquid/solid interface
- Author
-
Kazukuni Tahara, Matsuhiro Maeda, Ruri Nakayama, Steven De Feyter, and Yoshito Tobe
- Subjects
Materials science ,Nanostructure ,SURFACE ,Interface (Java) ,Chemistry, Multidisciplinary ,TRIMESIC ACID ,NANOSTRUCTURES ,law.invention ,chemistry.chemical_compound ,law ,SOLID INTERFACE ,Molecule ,STRATEGY ,Graphite ,Crystallization ,Science & Technology ,General Chemistry ,Annulene ,SUPRAMOLECULAR NETWORKS ,Chemistry ,chemistry ,Chemical physics ,Physical Sciences ,Trimesic acid ,CRYSTALLIZATION ,Derivative (chemistry) - Abstract
Self-sorting of multiple building blocks for correctly positioning molecules through orthogonal recognition is a promising strategy for construction of a hierarchical self-assembled molecular network (SAMN) on a surface. Herein we report that a trigonal molecule, dehydrobenzo[12]annulene (DBA) derivative having three tetradecyloxy chains and three hydroxy groups in an alternating manner, forms hierarchical triangular clusters of different sizes ranging from 2.4 to 16.4 nm, consisting of 3 to 78 molecules, respectively, at the liquid/graphite interface. The key is the dynamic combination of three different conformational states, which is solvent and concentration dependent. The present knowledge extends design strategies for production of sophisticated hierarchical SAMNs using a single component at the liquid/solid interface., Self-sorting of multiple building blocks for correctly positioning molecules through orthogonal recognition is a promising strategy for construction of a hierarchical self-assembled molecular network (SAMN) on a surface.
- Published
- 2021
38. Catalytic Asymmetric Synthesis of Benzobicyclo[3.2.1]octanes
- Author
-
Swamy Peraka, Dhevalapally B. Ramachary, and Mohammed Anif Pasha
- Subjects
Molecular Structure ,010405 organic chemistry ,Chemistry ,Stereochemistry ,Organic Chemistry ,Thiourea ,Enantioselective synthesis ,Stereoisomerism ,General Chemistry ,Annulene ,Octanes ,010402 general chemistry ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Lawsone ,chemistry.chemical_compound ,Aldol reaction ,Organocatalysis ,Intramolecular force ,Wittig reaction - Abstract
Lawsone aldehydes were directly transformed into the biologically important, unique carbon skeleton of chiral methanobenzo[f]azulenes/methanodibenzo[a,d][7]annulenes in high dr and ee and in very good yields by using quinine-thiourea-catalyzed tandem Wittig/intramolecular Michael/intramolecular aldol reactions. This asymmetric catalytic tandem protocol will be highly useful because these final molecules are basic skeletons of important antibiotics.
- Published
- 2021
39. Monocyclic and Dicyclic Dehydro[20]annulenes Integrated with Perylene Diimide
- Author
-
Zhaohui Wang, Shouke Yan, Yujian Liu, Ning Xue, Cheng Zeng, and Wei Jiang
- Subjects
Electron mobility ,Chemistry ,Supramolecular chemistry ,Regioselectivity ,General Chemistry ,General Medicine ,Annulene ,Chromophore ,Catalysis ,chemistry.chemical_compound ,Crystallography ,Diimide ,HOMO/LUMO ,Perylene - Abstract
A novel kind of monocyclic and dicyclic dehydro[20]annulenes exhibiting specific sizes and topologies from regioselective unilateral ortho-diethynyl PDI, is developed by Cu-catalyzed Glaser-Hay homo-coupling and cross-coupling. Through the integration of electron-deficient PDI chromophores into the dehydroannulene scaffolding, these macrocycles exhibit intense and characteristic absorption properties and the degenerated LUMO levels. The single-crystal X-ray diffraction analysis unambiguously revealed unique porous supramolecular structures, which display micropore characteristics with surface area of 120.74 m2 g-1 . A moderate electron mobility of 0.05 cm2 V-1 s-1 for chlorine-free dehydro[20]annulene based on micrometer-sized single-crystalline transistors was witnessed. The porous and yet semiconducting features signify the prospects of PDI-integrated dehydroannulenes in organic optoelectronics.
- Published
- 2021
40. Delocalization Effects and Tunable Emission in a Class of Charged Cyclazines with Nitrogen on the Periphery
- Author
-
Jais Kurian, M Muraleedharan Kannoth, Lakshmi Chakkumkumarath, Kanneth S. Shurooque, and Venkatachalam Ramkumar
- Subjects
Diffraction ,Structure analysis ,010405 organic chemistry ,Chemistry ,Organic Chemistry ,chemistry.chemical_element ,Charge (physics) ,Annulene ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Nitrogen ,Aromatic ring current ,0104 chemical sciences ,Delocalized electron ,Chemical physics ,Physical and Theoretical Chemistry ,Carbon - Abstract
A new class of cyclazine analogues with periphery reminiscent of an aza[10]annulene framework, tethered internally by an sp3 carbon, is presented. In depth structure analysis based on NMR and X-ray diffraction data gave a deeper insight into the effect of electron delocalization on their structure and properties. A characteristic change in chemical shift positions suggested an aromatic ring current in these systems. Attractive emission properties in solid and solution states involving charge transfer is another highlight.
- Published
- 2021
41. Synthesis of a Highly Aromatic and Planar [10]Annulene
- Author
-
Blaquiere Cs, Gengler S, Gravel M, Parmar K, and Lukan B
- Subjects
Ring size ,chemistry.chemical_compound ,Crystallography ,Materials science ,chemistry ,Diradical ,Aromaticity ,Ideal (ring theory) ,Annulene ,Planarity testing ,Cyclopropane ,Ring strain - Abstract
As the next neutral structure following Hückels rule, a planar and aromatic [10]annulene is ideal to study the link between ring size and aromaticity. However, the puckered geometry of the parent [10]annulene suggests that the aromatic stabilization energy is not sufficient to overcome the ring strain that exists when the system is forced into planarity. It has been shown computationally that this ring strain can be alleviated through the addition of two or more cyclopropane rings to the periphery, thereby creating theoretically aromatic structures. An alternative strategy to eliminating the issue of ring strain was demonstrated experimentally with the successful preparation of the highly aromatic 1,6-didehydro[10]annulene. However, the system rapidly cyclizes at -40°C to a naphthalene diradical due to the close proximity of the in-plane p-orbitals present in the system. Here we show that cyclopropanating one side of the unstable annulene successfully prevents the destabilizing cross-ring interaction while maintaining a highly aromatic structure. Remarkably, the formed [10]annulene is bench stable and can be stored for extended periods of time.
- Published
- 2021
42. Metalla-aromatics: Planar, Nonplanar, and Spiro
- Author
-
Wen-Xiong Zhang, Shengfa Ye, Zhe Huang, Yongliang Zhang, Chao Yu, Junnian Wei, and Zhenfeng Xi
- Subjects
Materials science ,010405 organic chemistry ,Aromaticity ,General Medicine ,General Chemistry ,Annulene ,010402 general chemistry ,01 natural sciences ,Planarity testing ,0104 chemical sciences ,Crystallography ,Delocalized electron ,chemistry.chemical_compound ,Atomic orbital ,Ferrocene ,chemistry ,Chemical bond ,Atom - Abstract
ConspectusThe concept of aromaticity is one of the most fundamental principles in chemistry. It is generally accepted that planarity is a prerequisite for aromaticity, and typically the more planar the geometry of an aromatic compound is, the stronger aromatic it is. However, it is not always the case, particularly when transition metals are involved in conjugation and electron delocalization of aromatic systems, i.e., metalla-aromatics. Because of the intrinsic nature of transition-metal orbitals, besides planar geometries, the most stable molecular structures of metalla-aromatic compounds could take nonplanar and even spiro geometries. In this Account, we outline several unprecedented types of metalla-aromatics developed recently in our research group.Around seven years ago, we found that 1,4-dilithio-1,3-butadienes, dilithio reagents with π-conjugation, could function as non-innocent ligands and react with low-valent transition-metal complexes, generating monocyclic metalla-aromatic compounds. Later on, by taking advantage of the unique behavior of dilithio reagents and the intrinsic nature of different transition metals, we have synthesized a series of metalla-aromatic compounds, of which four types are discussed here, and each of them represents the first of its kind. First, nearly planar aromatic dicupra[10]annulenes, a 10 π-electron aromatic system with two bridging Cu atoms participating in the orbital conjugation and electron delocalization, are synthesized by annulating two dilithio reagents with two Cu(I) complexes.Second, four kinds of spiro metalla-aromatics, featuring planar (with Pd, Pt, or Rh as the spiro atom) geometry with a whole 10π aromatic system, octahedral (tris-spiro metalla-aromatics with V as the spiro atom) geometry with an entire 40π Craig-Mobius aromatic system, tetrahedral (with Mn as the spiro atom) geometry having two independent and perpendicular 6π planar aromatic rings, and tetrahedral (with Mn as the spiro atom) geometry with one planar and one nonplanar 6π aromatic rings, respectively, are generated. In sharp contrast to spiroaromaticity with carbon acting as the spiro atom described in Organic Chemistry, the metal spiro atom herein takes part in orbital conjugation and electron delocalization.Third, nonplanar aromatic butadienyl diiron complexes are realized. Different from planar aromatic systems featuring delocalized π-type overlap, this nonplanar metalla-aromaticity is achieved by the novel σ-type overlap between the two Fe 3dxz orbitals and the butadienyl π orbital, forming a 6π aromatic system. Fourth, dinickelaferrocene, a ferrocene analogue with two aromatic nickeloles, is synthesized from our monocyclic aromatic dilithionickelole and FeBr2. The aromaticity of dinickelaferrocene and its nickelole ligands is realized by electron back-donation from the Fe 3d orbital to the π* orbital of nickeloles, which also deepens our understanding of the origin of aromaticity.The search for unprecedented and exciting aromatic systems, particularly with transition metals being involved, will continue to drive this intriguing research field forward. Given the synthetic strategies and various types of metalla-aromatics developed and described, diversified metalla-aromatics of interesting structures and reaction chemistry, novel chemical bonding modes, and useful functions can be expected.
- Published
- 2021
43. Expanded Porphyrin Contraction: From [22]Triphyrin(6.6.0) to [22]Triphyrin(6.5.0)
- Author
-
Ewa Pacholska-Dudziak, Sandra Hojniak-Thyssen, and Lechosław Latos-Grażyński
- Subjects
chemistry.chemical_classification ,010405 organic chemistry ,Organic Chemistry ,Protonation ,General Chemistry ,Annulene ,010402 general chemistry ,01 natural sciences ,Porphyrin ,Catalysis ,0104 chemical sciences ,chemistry.chemical_compound ,Crystallography ,Column chromatography ,Hydrocarbon ,chemistry ,Moiety ,Anion binding ,Pyrrole - Abstract
An expanded triphyrin containing a bipyrrole moiety and annulene links, namely tetraphenyl-[22]triphyrin(6.5.0), 2, has been synthesized. The synthesis proceeded by a postsynthetic transformation of tetraphenyl-[22]triphyrin(6.6.0), 1, in a metal-free unexpected and unprecedented ring contraction during column chromatography on alumina. The observed transformation, located at the hydrocarbon chain linking the pyrrole units, formally corresponds to a subtraction of one carbon atom from an annulene circuit. In contrast to the flexible substrate 1, the product 2 is conformationally rigid, and capable of chloride anion binding in its protonated form.
- Published
- 2019
44. Cyclobis(7,8‐( para ‐quinodimethane)‐4,4′‐triphenylamine) and Its Cationic Species Showing Annulene‐Like Global (Anti)Aromaticity
- Author
-
Shaoqiang Dong, Chunyan Chi, Tullimilli Y. Gopalakrishna, and Yi Han
- Subjects
010405 organic chemistry ,Intermolecular force ,Aromaticity ,General Chemistry ,General Medicine ,Annulene ,Alkylation ,010402 general chemistry ,Triphenylamine ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Dication ,chemistry.chemical_compound ,Crystallography ,chemistry ,Singlet state ,Antiaromaticity - Abstract
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.
- Published
- 2019
45. Global Aromaticity in Macrocyclic Polyradicaloids: Hückel’s Rule or Baird’s Rule?
- Author
-
Chunchen Liu, Yong Ni, Jishan Wu, Guangwu Li, and Xuefeng Lu
- Subjects
Physics ,Valence (chemistry) ,Chemical physics ,Diradical ,Excited state ,Hückel's rule ,Aromaticity ,General Medicine ,General Chemistry ,Annulene ,Ground state ,Antiaromaticity - Abstract
Aromaticity is one of the most important concepts in organic chemistry to understand the electronic properties of cyclic π-conjugated molecules. Over a century, different aromaticity rules have been developed and validated. For planar monocyclic conjugated polyenes (also known as [n]annulenes), they will be aromatic if they contain [4N + 2] π electrons according to Huckel's rule, or antiaromatic if they have [4N] π electrons. Topological change from a planar to a half-twisted Mobius strip will lead to [4N] ([4N + 2]) aromaticity (antiaromaticity), which is just inverse to Huckel's rule. When the molecules are excited into the first triplet excited state, the Huckel (anti)aromaticity observed in the ground state will become reversed according to Baird's rule. Strictly speaking, these basic rules are only applicable for monocyclic conjugated systems, but some polycyclic systems such as porphyrinoids may also follow these rules if there is a dominant [n]annulene-like conjugation pathway. On the other hand, all-benzenoid polycyclic aromatic hydrocarbons usually display local aromaticity with π electrons predominantly localized at certain benzene rings according to Clar's aromatic sextet rule. In recent years, some proaromatic and antiaromatic molecules with even number of paired electrons have been found to exhibit open-shell diradical character and unique optical, electronic, and magnetic activities. One of the major driving forces is their intrinsic tendency to become aromatic in the open-shell diradical/polyradical forms. A number of stable diradicaloids and linear polyradicaloids have been successfully synthesized by using thermodynamic and kinetic stabilizing strategies. Herein, our particular interest is a type of macrocyclic polyradicaloid in which multiple frontier π-electrons are antiferromagnetically coupled with each other in a cyclic mode. Formally, these free electrons may behave like normal π-electrons in the [n]annulenes, and thus, it raises questions about their possible global aromaticity and which rule they will follow. In the past 5 years, our group has synthesized a series of macrocyclic polyradicaloids and systematically investigated their global aromaticity and electronic properties. Some important findings include: (1) global (anti)aromaticity is generally observed, but there is a balance between local aromaticity and global aromaticity; (2) most of these molecules follow Huckel's rule in the singlet state and display respective (anti)aromatic characteristics; (3) in some special cases, both Huckel's rule and Baird's rule can be applicable, and a unique annulene-within-an-annulene super-ring structure was demonstrated for the first time; (4) global antiaromaticity in the transition state is also important and a slow valence tautomerization process was observed in a supercyclobutadiene tetraradicaloid. These studies demonstrate how these open-shell macrocyclic polyradicaloids adapt their geometry and spin state to reach the lowest-energy state (aromatic). In this Account, we will mainly discuss their synthesis, global aromaticity, and the fundamental structure-radical character-aromaticity-properties relationships. Various experimental methods (e.g., NMR, X-ray crystallographic analysis, and electronic absorption spectroscopy) and theoretical calculations (e.g., anisotropy of the induced current density, nucleus independent chemical shift, and isochemical shielding surface) have been used to elaborate their (anti)aromatic character. At the end, a perspective on the possible three-dimensional global aromaticity in fully conjugated cagelike diradicaloids or polyradicaloids will be also discussed.
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46. Reversible Two-Electron Redox Reactions Involving Tetralithio/Dilithio Palladole, Platinacycle, and Dicupra[10]annulene
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Wen-Xiong Zhang, Yongliang Zhang, Zhenfeng Xi, and Zhe Huang
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Inorganic Chemistry ,010405 organic chemistry ,Computational chemistry ,Chemistry ,Organic Chemistry ,Electron ,Physical and Theoretical Chemistry ,Annulene ,010402 general chemistry ,01 natural sciences ,Redox ,0104 chemical sciences - Abstract
The reaction chemistry of metalla-aromatics is fundamentally interesting. In this work, we find that tetralithio spiroaromatic palladole and platinacycle complexes 1 undergo selective two-electron ...
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- 2019
47. On‐Surface Evolution of meso ‐Isomerism in Two‐Dimensional Supramolecular Assemblies
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Jaehoon Jung, Juyeon Park, Sunmi Bak, Maki Kawai, Yoshito Tobe, Yousoo Kim, Kazukuni Tahara, and Ju Hyung Kim
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Phase transition ,Nanostructure ,Materials science ,High Energy Physics::Lattice ,Supramolecular chemistry ,General Chemistry ,Annulene ,Catalysis ,Condensed Matter::Soft Condensed Matter ,Chemical physics ,Molecule ,Self-assembly ,Physics::Chemical Physics ,Enantiomer ,Chirality (chemistry) - Abstract
Chiral structures created through the adsorption of molecules onto achiral surfaces play pivotal roles in many fields of science and engineering. Here, we present a systematic study of a novel chiral phenomenon on a surface in terms of organizational chirality, that is, meso-isomerism, through coverage-driven hierarchical polymorphic transitions of supramolecular assemblies of highly symmetric π-conjugated molecules. Four coverage-dependent phases of dehydrobenzo[12]annulene were uniformly fabricated on Ag(111), exhibiting unique chiral characteristics from the single-molecule level to two-dimensional supramolecular assemblies. All coverage-driven phase transitions stem from adsorption-induced pseudo-diastereomerism, and our observation of a lemniscate-type (∞) supramolecular configuration clearly reveals a drastic chiral phase transition from an enantiomeric chiral domain to a meso-isomeric achiral domain. These findings provide new insights into controlling two-dimensional chiral architectures on surfaces.
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- 2019
48. Unconventional Aromaticity in Organometallics: The Power of Transition Metals
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Jun Zhu, Qiong Xie, and Dandan Chen
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010405 organic chemistry ,Aromaticity ,General Medicine ,General Chemistry ,Annulene ,010402 general chemistry ,Ring (chemistry) ,Hyperconjugation ,01 natural sciences ,0104 chemical sciences ,Delocalized electron ,chemistry.chemical_compound ,chemistry ,Möbius aromaticity ,Computational chemistry ,Organometallic chemistry ,Antiaromaticity - Abstract
Aromaticity, one of the most fundamental concepts in chemistry, has attracted considerable attention from both theoreticians and experimentalists. Much effort on aromaticity in organometallics has been devoted to metallabenzene and derivatives. In comparison, aromaticity in other organometallics is less developed. This Account describes how our group has performed quantum chemical calculations to examine aromaticity in recently synthesized novel organometallic complexes. By collaborations with experimentalists, we have extended several aromaticity concepts into organometallics to highlight the power of transition metals. In general, the transition metal could participate in delocalization either out of rings or in the rings. We examined the former by probing the possibility of transition metal substituents in hyperconjugative aromaticity, where the metal is out of the rings. Calculations on tetraaurated heteroaryl complexes reveal that incorporation of the aurated substituents at the nitrogen atom can convert nonaromaticity in the parent indolium into aromaticity in the aurated one due to hyperconjugation, thus extending the concept of hyperconjugative aromaticity to heterocycles with transition metal substituents. More importantly, further analysis indicates that the aurated substituents can perform better than traditional main-group substituents. Recently, we also probed the strongest aromatic cyclopentadiene and pyrrolium rings by hyperconjugation of transition metal substituents. Moreover, theoretical calculations suggest that one electropositive substituent is able to induce aromaticity; whereas one electronegative substituent prompts nonaromaticity rather than antiaromaticity. We also probed the possibility of Craig-type Möbius aromaticity in organometallic chemistry, where the position of the transition metals is in the rings. According to the electron count and topology, aromaticity can be classified as Hückel-type and Möbius-type. In comparison with numerous Hückel aromatics containing 4 n+2 π-electrons, Möbius aromatics with 4 n π-electrons, especially the Craig-type species, are particularly limited. We first examined aromaticity in osmapentalynes. Theoretical calculations reveal that incorporation of the osmium center not only reduces the ring strain of the parent pentalyne, but also converts Hückel antiaromaticity in the parent pentalyne into Craig-type Möbius aromaticity in metallapentalynes. Further studies show that the transition metal fragments can also make both 16e and 18e osmapentalenes aromatic, indicating that the Craig-type Möbius aromaticity in osmapentalyne is rooted in osmapentalenes. In addition, Möbius aromaticity is also possible in dimetalla[10]annulenes, where the lithium atoms are not spectator cations but play an important role due to their bonding interaction with the diene moieties. We then examined the possibility of σ-aromaticity in an unsaturated ring. Traditional π-aromaticity is used to describe the π-conjugation in fully unsaturated rings; whereas σ-aromaticity may stabilize fully saturated rings with delocalization caused by σ-electron conjugation. We found that the unsaturated three-membered ring in cyclopropaosmapentalene is σ-aromatic. Very recently, we extended σ-aromaticity into in a fully unsaturated ring. The concepts and examples presented here show the importance of interplay and union between experiment and theory in developing novel aromatic systems and, especially, the indispensable role of computational study in rationalization of unconventional aromaticity. All these findings highlight the strong power of transition metals originating from participation of d orbitals in aromaticity, opening an avenue to the design of unique metalla-aromatics.
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49. Ab Initio Molecular Orbital Study of the First Four Si/C Alternately Substituted Annulenes
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Michael W. Schmidt, Nikita Matsunaga, and Takako Kudo
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Crystallography ,Chemistry ,Excited state ,Ab initio ,Molecular orbital ,Physical and Theoretical Chemistry ,Annulene - Abstract
The ground and low-lying excited states of four alternating Si/C annulenes, HnSin/2Cn/2 with n = 4, 6, 8, and 10, have been investigated by ab initio molecular orbital methods and compared to those...
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- 2019
50. Reversing the Handedness of Self‐Assembled Porous Molecular Networks through the Number of Identical Chiral Centres
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Yoshito Tobe, Ruri Nakayama, Kazukuni Tahara, Steven De Feyter, Aya Noguchi, and Elke Ghijsens
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Supramolecular chirality ,Materials science ,Chemistry, Multidisciplinary ,Supramolecular chemistry ,chirality ,010402 general chemistry ,01 natural sciences ,Catalysis ,Stereocenter ,liquid ,SUPRAMOLECULAR CHIRALITY ,Porosity ,dehydrobenzo[12]annulene ,Science & Technology ,010405 organic chemistry ,INDUCTION ,RECOGNITION ,Absolute configuration ,scanning tunnelling microscopy ,self-assembly ,General Chemistry ,General Medicine ,Annulene ,0104 chemical sciences ,Chemistry ,Crystallography ,RESOLUTION ,Physical Sciences ,solid interfaces ,Self-assembly ,Chirality (chemistry) ,INTERFACES - Abstract
Scanning tunnelling microscope observations at the 1-phenyloctane/graphite interface reveal how chiral structural information at the molecular level is transferred and expressed structurally at the 2D supramolecular level for a porous system. The chirality of self-assembled molecular networks formed by chiral dehydrobenzo[12]annulene (cDBA) derivatives having three chiral chains and three achiral chains, alternatingly, is compared with those of cDBAs having six chiral chains reported previously. While for all cDBAs homochiral surfaces are formed, their handedness is not simply a reflection of the absolute configuration of the stereogenic centres. Both the number of stereogenic centres as well as the length of the achiral chains determine the supramolecular handedness, providing a deep insight into the supramolecular chirality induction mechanisms at play. Moreover, these cDBAs act to induce chirality in porous networks formed by achiral DBAs. ispartof: ANGEWANDTE CHEMIE-INTERNATIONAL EDITION vol:58 issue:23 pages:7733-7738 ispartof: location:Germany status: published
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- 2019
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