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1.
Jinseok Kim Dr. Juwon Oh Dr. Takanori Soya Dr. Tomoki Yoneda Dr. Seongchul Park Prof. Dr. Manho Lim Prof. Dr. Atsuhiro Osuka Prof. Dr. Dongho Kim 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(13):5167-5172
Expanded porphyrins with appropriate metalation provide an excellent opportunity to study excited-state aromaticity. The coordinated metal allows the excited-state aromaticity in the triplet state to be detected through the heavy-atom effect, but other metalation effects on the excited-state aromaticity were ambiguous. Herein, the excited-state aromaticity of gold(III) hexaphyrins through the relaxation dynamics was revealed via electronic and vibrational spectroscopy. The SQ states of gold [26]- and [28]-hexaphyrins showed interconvertible absorption and IR spectra with those of counterparts in the ground-state, indicating aromaticity reversal. Furthermore, while the T1 states of gold [28]-hexaphyrins also exhibited reversed aromaticity according to Baird's rule, the ligand-to-metal charge-transfer state of gold [26]-hexaphyrins contributed by the gold metal showed non-aromatic features arising from the odd-number of π-electrons. 相似文献
2.
Dr. Mercedes Alonso Dr. Balazs Pinter Prof. Dr. Paul Geerlings Prof. Dr. Frank De Proft 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(49):17631-17638
The heretofore unpredictable behavior of [26] and [28]hexaphyrins upon metalation has been elucidated through quantum chemical calculations. It is demonstrated that the molecular topology of Group 10 and Group 11 metal complexes of hexaphyrins depends on sensitive interplay between the intrinsic ligand strain and the metal–ligand interaction strength. As such, the aromaticity of the ligand and effective charge of the metal are revealed as key factors determining the binding mode and the preference for Möbius or Hückel structures. These findings offer a new perspective to rationalize experimental observations for metalated hexaphyrins. More importantly, the proposed guidelines could be useful for designing novel complexes of hexaphyrins, such as a hitherto unknown Möbius [26]hexaphyrin complex. 相似文献
3.
A Description of Vibrational Modes in Hexaphyrins: Understanding the Aromaticity Reversal in the Lowest Triplet State 下载免费PDF全文
Dr. Young Mo Sung Juwon Oh Koji Naoda Dr. Taegon Lee Woojae Kim Prof. Dr. Manho Lim Prof. Dr. Atsuhiro Osuka Prof. Dr. Dongho Kim 《Angewandte Chemie (International ed. in English)》2016,55(39):11930-11934
Aromaticity reversal in the lowest triplet state, or Baird's rule, has been postulated for the past few decades. Despite numerous theoretical works on aromaticity reversal, experimental study is still at a rudimentary stage. Herein, we investigate the aromaticity reversal in the lowest excited triplet state using a comparable set of [26]‐ and [28]hexaphyrins by femtosecond time‐resolved infrared (IR) spectroscopy. Compared to the relatively simple IR spectra of [26]bis(rhodium) hexaphyrin ( R26H ), those of [28]bis(rhodium) hexaphyrin ( R28H ) show complex IR spectra the region for the stretching modes of conjugated rings. Whereas time‐resolved IR spectra of R26H in the excited triplet state are dominated by excited state IR absorption peaks, while those of R28H largely show ground state IR bleaching peaks, reflecting the aromaticity reversal in the lowest triplet state. These contrasting IR spectral features serve as new experimental aromaticity indices for Baird's rule. 相似文献
4.
Akito Nakai Tomoki Yoneda Shin‐ichiro Ishida Kenichi Kato Atsuhiro Osuka 《化学:亚洲杂志》2019,14(2):256-260
A peripherally strapped [28]hexaphyrin takes a rectangular conformation and exhibits antiaromatic character. A cyclophane‐type dimer consisting of such [28]hexaphyrins was synthesized from hexakis(pentafluorophenyl) [26]hexaphyrin via SNAr reaction with allyl alcohol, one‐pot intra‐ and intermolecular olefin metathesis under improved Hoveyda–Grubbs catalysis, and final reduction with NaBH4. The cyclophane‐type structures of [26]‐ and [28]hexaphyrin dimers have been revealed by X‐ray analysis. Studies on the structural, optical, and electronic properties have led to a conclusion that there is no favorable electronic interaction between the two [28]hexaphyrin segments and thus no indication of 3D aromaticity. 相似文献
5.
1‐(Triisopropylsilyl)‐3,4‐dichloropyrrole and 1‐(triisopropylsilyl)‐3,4‐difluoropyrrole were conveniently prepared from the corresponding 3,4‐dibromopyrrole by lithiation followed by halogenation. 2,3,17,18‐Tetrahalogeno [26]‐ and [28]hexaphyrins have been prepared by condensation of 3,4‐dihalopyrroles and a dipyrromethane‐dicarbinol. 2,3,17,18‐Tetrahalogenated hexaphyrins display variable structural and electronic properties depending upon the halogen atom and the number of π‐electrons. Tetrabromo[28]hexaphyrin and tetrachloro[28]hexaphyrin were further reduced with excess NaBH4 to furnish meso‐reduced hexaphyrins as the first example of phlorin‐type meso‐aryl‐substituted hexaphyrins. 相似文献
6.
Ahn TK Kwon JH Kim DY Cho DW Jeong DH Kim SK Suzuki M Shimizu S Osuka A Kim D 《Journal of the American Chemical Society》2005,127(37):12856-12861
We have explored the electronic natures of representative expanded porphyrins, [26]- and [28]hexaphyrins, to investigate the interplay between the aromaticity and antiaromaticity that is brought by two electron oxidation/reduction processes. The excited singlet and triplet states of [26]hexaphyrin in solution exhibit lifetimes of 125 ps and 1.8 mus, respectively, as revealed by various time-resolved spectroscopic measurements. On the other hand, [28]hexaphyrin shows faster singlet and triplet lifetimes than those of [26]hexaphyrin, which is largely in accordance with the perturbation of aromaticity due to the pi electron formulation of [4n] in [28]hexaphyrins. The two-photon absorption cross-section values at 1200 nm for [26]hexaphyrins show ca. 9890 GM which is >10(2) larger than those of porphyrins. The reduced TPA values of 2600 and 810 GM of [28]hexaphyrin and perfluorinated [28]hexaphyrin, respectively, match well with their relatively short excited-state lifetimes. Overall, the enhanced excited-state lifetimes for various hexaphyrins go in line with the increased TPA cross-section values and the ring planarity. 相似文献
7.
A Möbius Aromatic [28]Hexaphyrin Bearing a Diethylamine Group: A Rigid but Smooth Conjugation Circuit 下载免费PDF全文
Tomohiro Higashino Takanori Soya Woojae Kim Prof. Dr. Dongho Kim Prof. Dr. Atsuhiro Osuka 《Angewandte Chemie (International ed. in English)》2015,54(18):5456-5459
The reaction of [26]hexaphyrin with triethylamine in the presence of BF3?OEt2 and O2 furnished a diastereomeric mixture of a diethylamine‐bearing [28]hexaphyrin as a rare example of a Möbius aromatic metal‐free expanded porphyrin. The Möbius aromaticity of these molecules is large, as indicated by their large diatropic ring currents, which are even preserved at 100 °C, owing to their internally multiply bridged robust structure with a smooth conjugation network. These molecules were reduced with NaBH4 to give an antiaromatic [28]hexaphyrin, and were oxidized with MnO2 to give aromatic [26]hexaphyrins, both through a Möbius‐to‐Hückel topology switch induced by a C? N bond cleavage. 相似文献
8.
Won‐Young Cha Jong Min Lim Dr. Min‐Chul Yoon Young Mo Sung Byung Sun Lee Sho Katsumata Masaaki Suzuki Hirotaka Mori Prof. Dr. Yoshiya Ikawa Prof. Dr. Hiroyuki Furuta Prof. Dr. Atsuhiro Osuka Prof. Dr. Dongho Kim 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(49):15838-15844
meso‐Hexakis(pentafluorophenyl)‐substituted neutral hexaphyrin with a 26π‐electronic circuit can be regarded as a real homolog of porphyrin with an 18π‐electronic circuit with respect to a quite flat molecular structure and strong aromaticity. We have investigated additional aromaticity enhancement of meso‐hexakis(pentafluorophenyl)[26]hexaphyrin(1.1.1.1.1.1) by deprotonation of the inner N? H groups in the macrocyclic molecular cavity to try to induce further structural planarization. Deprotonated mono‐ and dianions of [26]hexaphyrin display sharp B‐like bands, remarkably strong fluorescence, and long‐lived singlet and triplet excited‐states, which indicate enhanced aromaticity. Structural, spectroscopic, and computational studies have revealed that deprotonation induces structural deformations, which lead to a change in the main conjugated π‐electronic circuit and cause enhanced aromaticity. 相似文献
9.
Akito Nakai Shin‐ichiro Ishida Takanori Soya Atsuhiro Osuka 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(24):8281-8284
Ruthenium(II) π‐coordination onto [28]hexaphyrins(1.1.1.1.1.1) has been accomplished. Reactions of bis‐AuIII and mono‐AuIII complexes of hexakis(pentafluorophenyl) [28]hexaphyrin with [RuCl2(p‐cymene)]2 in the presence of NaOAc gave the corresponding π‐ruthenium complexes, in which the [(p‐cymene)Ru]II fragment sat on the deprotonated side pyrrole. A similar reaction of the bis‐PdII [26]hexaphyrin complex afforded a triple‐decker complex, in which the two [(p‐cymene)Ru]II fragments sat on both sides of the center of the [26]hexaphyrin framework. 相似文献
10.
Dr. Mercedes Alonso Prof. Paul Geerlings Prof. Frank de Proft 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(35):10916-10928
Recently, hexaphyrins have emerged as a promising class of π‐conjugated molecules that display a range of interesting electronic, optical, and conformational properties, including the formation of stable Möbius aromatic systems. Besides the Möbius topology, hexaphyrins can adopt a variety of conformations with Hückel and twisted Hückel topologies, which can be interconverted under certain conditions. To determine the optimum conditions for viable Möbius topologies, the conformational preferences of [26]‐ and [28]hexaphyrins and the dynamic interconversion between the Möbius and Hückel topologies were investigated by density functional calculations. In the absence of meso substituents, [26]hexaphyrin prefers a planar dumbbell conformation, strongly aromatic and relatively strain free. The Möbius topology is highly improbable: the most stable tautomer is 33 kcal mol?1 higher in energy than the global minimum. On the other hand, the Möbius conformer of [28]hexaphyrin is only 6.5 kcal mol?1 higher in energy than the most stable dumbbell conformation. This marked difference is due to aromatic stabilization in the Möbius 4n electron macrocycle as opposed to antiaromatic destabilization in the 4n+2 electron system, as revealed by several energetic, magnetic, structural, and reactivity indices of aromaticity. For [28]hexaphyrins, the computed activation barrier for interconversion between the Möbius aromatic and Hückel antiaromatic conformers ranges from 7.2 to 10.2 kcal mol?1, in very good agreement with the available experimental data. The conformation of the hexaphyrin macrocycle is strongly dependent on oxidation state and solvent, and this feature creates a promising platform for the development of molecular switches. 相似文献
11.
Ikuo Kawashima Hiroaki Imoto Masatoshi Ishida Hiroyuki Furuta Shunsuke Yamamoto Masaya Mitsuishi Susumu Tanaka Toshiki Fujii Kensuke Naka 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(34):11812-11816
Dibenzo[b,f]arsepins possessing severely distorted cores compared to those of other heteropins were synthesized. These derivatives exhibited dual photoluminescence in the green‐to‐red region (500–700 nm) and the near‐ultraviolet region (<380 nm), which could be attributed to the planarization of the arsepin core in the lowest singlet excited (S1) state. The computational approach for the assessment of the aromatic indices revealed that the dibenzoarsepins studied show aromaticity (8π system) in the S1 states in line with Baird's rule. The lone pair electrons of the arsenic atoms play a crucial role in the aromaticity in the S1 states. 相似文献
12.
Takanori Soya Prof. Dr. Atsuhiro Osuka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(30):10639-10644
The metalation of meso‐tetrakis(pentafluorophenyl)‐substituted [26]rubyrin has been explored with Group 9 metal salts (RhI, CoII, IrIII), affording a Hückel aromatic [26]rubyrin–bis‐RhI complex with a highly curved gable‐like structure, a Hückel antiaromatic [24]rubyrin–bis‐CoII complex that displays intramolecular antiferromagnetic coupling between the two CoII ions (J=?4.5 cm?1), and two Cp*‐capped IrIII complexes; in one, the iridium metal sits on the [26]rubyrin frame with two Ir?N bonds, whereas the other has an additional Ir?C bond, although both IrIII complexes display moderate aromatic character. This work demonstrates characteristic metalation abilities of this [26]rubyrin toward Group 9 metals. 相似文献
13.
Discovery of species with adaptive aromaticity (being aromatic in both the lowest singlet and triplet states) is particularly challenging as cyclic species are generally aromatic either in the ground state or in the excited state only, according to Hückel's and Baird's rules. Inspired by the recent realization of cyclo[18]carbon, here we demonstrate that cyclo[10]carbon possesses adaptive aromaticity by screening cyclo[n]carbon (n=8?24), which is supported by nucleus‐independent chemical shift (NICS), anisotropy of the current‐induced density (ACID), π contribution of electron localization function (ELFπ) and electron density of delocalized bonds (EDDB) analyses. Further study reveals that the lowest triplet state of cyclo[10]carbon is formed by in‐plane ππ* excitation. Thus, the major contribution to the aromaticity from out‐of‐plane π molecular orbitals does not change significantly in the lowest singlet state. Our findings highlight a crucial role of out‐of‐plane π orbitals in maintaining aromaticity for both the lowest singlet and triplet states as well as the aromaticity dependence on the number of the carbon in cyclo[n]carbon. 相似文献
14.
A Stable Antiaromatic 5,20‐Dibenzoyl [28]Hexaphyrin(1.1.1.1.1.1): Core AuIII Metalation and Subsequent Peripheral BIII Metalation 下载免费PDF全文
Shin‐ichiro Ishida Takanori Soya Prof. Dr. Atsuhiro Osuka 《Angewandte Chemie (International ed. in English)》2018,57(41):13640-13643
5,20‐Dibenzoyl [28]hexaphyrin(1.1.1.1.1.1) was synthesized as the first hexaphyrin bearing meso‐aroyl substituents. The meso‐dibenzoyl substituents are hydrogen‐bonded with the pyrrolic protons to stabilize an antiaromatic dumbbell conformer. Core metalation of this hexaphyrin with AuIII afforded rectangular and aromatic [26]hexaphyrin bis‐AuIII complexes, the major isomer of which was reduced with NaBH4 to give its antiaromatic 28π bis‐AuIII complex. This complex allowed facile peripheral metalation with BIII owing to the peripheral benzoyl substituents. 相似文献
15.
Mickaël Mnand Matthieu Sollogoub Bernard Boitrel Stphane LeGac 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(1):305-309
Conformational control over the highly flexible π‐conjugated system of expanded porphyrins is a key step toward the fundamental understanding of aromaticity and for the development of molecular electronics. We have synthesized unprecedented hexaphyrin–cyclodextrin (HCD) capped hybrids in which the hexaphyrin part is constrained in a planar rectangular conformation in either a 26 or a 28 π‐electron oxidation state ( [26] / [28]HCD ). These structures display strong aromaticity and antiaromaticity, respectively, exhibit markedly different chiroptical properties, and are interconvertible upon the addition of DDQ or NaBH(OAc)3, thus affording a rare switchable aromatic–antiaromatic system with a free‐base expanded porphyrin. Conformational analysis revealed discrimination of the two coordination sites of the hexaphyrin, one of which was coupled to a confined asymmetric environment, and fluxional behavior consisting of apparent rotation of the hexaphyrin cap through a shape‐shifting mechanism. 相似文献
16.
Hexaphyrin–Cyclodextrin Hybrids: A Nest for Switchable Aromaticity,Asymmetric Confinement,and Isomorphic Fluxionality 下载免费PDF全文
Dr. Mickaël Ménand Prof. Matthieu Sollogoub Dr. Bernard Boitrel Dr. Stéphane Le Gac 《Angewandte Chemie (International ed. in English)》2016,55(1):297-301
Conformational control over the highly flexible π‐conjugated system of expanded porphyrins is a key step toward the fundamental understanding of aromaticity and for the development of molecular electronics. We have synthesized unprecedented hexaphyrin–cyclodextrin (HCD) capped hybrids in which the hexaphyrin part is constrained in a planar rectangular conformation in either a 26 or a 28 π‐electron oxidation state ( [26] / [28]HCD ). These structures display strong aromaticity and antiaromaticity, respectively, exhibit markedly different chiroptical properties, and are interconvertible upon the addition of DDQ or NaBH(OAc)3, thus affording a rare switchable aromatic–antiaromatic system with a free‐base expanded porphyrin. Conformational analysis revealed discrimination of the two coordination sites of the hexaphyrin, one of which was coupled to a confined asymmetric environment, and fluxional behavior consisting of apparent rotation of the hexaphyrin cap through a shape‐shifting mechanism. 相似文献
17.
An Unusually Small Singlet–Triplet Gap in a Quinoidal 1,6‐Methano[10]annulene Resulting from Baird’s 4n π‐Electron Triplet Stabilization 下载免费PDF全文
Dr. Benjamin C. Streifel Dr. José L. Zafra Guzmán L. Espejo Prof. Carlos J. Gómez‐García Prof. Juan Casado Prof. John D. Tovar 《Angewandte Chemie (International ed. in English)》2015,54(20):5888-5893
Within the continuum of π‐extended quinoidal electronic structures exist molecules that by design can support open‐shell diradical structures. The prevailing molecular design criteria for such structures involve proaromatic nature that evolves aromaticity in open‐shell diradical resonance structures. A new diradical species built upon a quinoidal methano[10]annulene unit is synthesized and spectroscopically evaluated. The requisite intersystem crossing in the open‐shell structure is accompanied by structural reorganization from a contorted Möbius aromatic‐like shape in S0 to a more planar shape in the Hückel aromatic‐like T1. This stability was attributed to Baird’s Rule which dictates the aromaticity of 4n π‐electron triplet excited states. 相似文献
18.
5,20‐Bis(ethoxycarbonyl)‐[28]hexaphyrin was synthesized by acid catalyzed cross‐condensation of meso‐diaryl‐substituted tripyrrane and ethyl 2‐oxoacetate followed by subsequent oxidation. This hexaphyrin was found to be a stable 28π‐antiaromatic compound with a dumbbell‐like conformation. Upon oxidization with PbO2, this [28]hexaphyrin was converted into an aromatic [26]hexaphyrin with a rectangular shape bearing two ester groups at the edge side. The [28]hexaphyrin can incorporate two NiII or CuII metals by using the ester carbonyl groups and three pyrrolic nitrogen atoms to give bis‐NiII and bis‐CuII complexes with essentially the same dumbbell‐like structure. The antiaromatic properties of the [28]hexaphyrin and its metal complexes have been well characterized. 相似文献
19.
Gokulnath S Toganoh M Yamaguchi K Mori S Uno H Furuta H 《Dalton transactions (Cambridge, England : 2003)》2012,41(20):6283-6290
Singly N-confused [26] and [28]hexaphyrins (4, 5) with planar and twisted structures, respectively, were prepared via the acid catalyzed [3 + 3] condensation of N-confused and regular tripyrrane precursors. Hückel aromaticity is observed for [26]hexaphyrin, while the [28]hexaphyrin and its mono-Pd(II) complex exhibit "nonaromaticity" in spite of their M?bius-type structures, judging from the spectroscopic features and theoretical calculations. 相似文献
20.
Stphanie Parra Olivier Vitse Vronique Bnzech Carine Deleuze‐Masqufa Guy Subra Jacques Bompart Roger Escale Jean P. Chapat Pierre A. Bonnet 《Journal of heterocyclic chemistry》2001,38(1):41-44
The n‐butyllithium and lithium 2,2,6,6‐tetramethylpiperidide metalation and the halogen‐metal exchange of imidazo[1,2‐a]quinoxaline derivatives followed by quenching with various electrophiles were studied. The reaction conditions have been optimized and various C1 substituted imidazo[1,2‐a]quinoxalines were obtained in high yields. 相似文献