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Ken Tanaka - One of the best experts on this subject based on the ideXlab platform.
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rhodium catalyzed highly diastereo and enantioselective synthesis of a configurationally stable s shaped double Helicene like molecule
Angewandte Chemie, 2020Co-Authors: Suzuka Kinoshita, Ryota Yamano, Yu Shibata, Yusuke Tanaka, Kyoichi Hanada, Takashi Matsumoto, Kazunori Miyamoto, Atsuya Muranaka, Masanobu Uchiyama, Ken TanakaAbstract:An S-shaped double Helicene-like molecule (>99 % ee), possessing stable helical chirality, has been synthesized by the rhodium(I)/difluorphos complex-catalyzed highly diastereo- and enantioselective intramolecular double [2+2+2] cycloaddition of a 2-naphthol- and benzene-linked hexayne. The collision between two terminal naphthalene rings destabilizes the helical chirality of the S-shaped double Helicene-like molecule, but the introduction of two additional fused benzene rings significantly increases the configurational stability. Thus, no epimerization and racemization were observed even at 100 °C. The enantiopure S-shaped double Helicene-like molecule forms a trimer through the multiple C-H⋅⋅⋅π and C-H⋅⋅⋅O interactions in the solid-state. The trimers stack to form columnar packing structures, in which neighboring stacks have opposite dipole directions. The accumulation of helical structures in the same direction in the S-shaped double Helicene-like molecule enhanced the chiroptical properties.
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synthesis of single and double dibenzoHelicenes by rhodium catalyzed intramolecular 2 2 2 and 2 1 2 1 cycloaddition
Chemistry: A European Journal, 2018Co-Authors: Ryota Yamano, Yu Shibata, Ken TanakaAbstract:Dibenzo[7]Helicenes were synthesized with up to 99 % ee by rhodium(I)/binap-catalyzed enantioselective intramolecular [2+2+2] cycloaddition of 2-phenylnaphthalene-linked triynes. Additionally, [2+1+2+1] cycloaddition products, that is, twisted anthracenes, were also synthesized by using difluorphos as ligand. Although these compounds are not configurationally stable at elevated temperature, their Scholl reactions afforded configurationally stable double dibenzo[6]Helicenes. The thus-obtained dibenzo[7]Helicene exhibited good circularly polarized luminescence property and the double dibenzo[6]Helicene showed high fluorescence quantum yield.
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Enantioselective Helicene Synthesis by Rhodium-Catalyzed [2+2+2] Cycloadditions
Bulletin of the Chemical Society of Japan, 2015Co-Authors: Ken Tanaka, Yuki Kimura, Koichi MurayamaAbstract:The highly enantioselective synthesis of functionalized Helicenes and Helicene-like molecules have been achieved via rhodium-catalyzed [2+2+2] cycloaddition reactions. The rhodium-catalyzed enantio...
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enantioselective synthesis crystal structure and photophysical properties of a 1 1 bitriphenylene based sila 7 Helicene
European Journal of Organic Chemistry, 2015Co-Authors: Koichi Murayama, Ken Tanaka, Yasuaki Oike, Seiichi Furumi, Masayuki Takeuchi, Keiichi NoguchiAbstract:A 1,1′-bitriphenylene-based sila[7]Helicene was synthesized with a high ee value by enantioselective double [2+2+2] cycloaddition of a biaryl-linked tetrayne with a silicon-linked bis(propargylic alcohol) as a key step. This sila[7]Helicene exhibited a high tolerance toward racemization, which could be explained by the X-ray crystal structure analysis. With respect to the photophysical properties, this sila[7]Helicene exhibited a relatively high fluorescence quantum yield and circularly polarized luminescence activity.
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enantioselective synthesis of 9 and 11 Helicene like molecules double intramolecular 2 2 2 cycloaddition
Angewandte Chemie, 2014Co-Authors: Yuki Kimura, Ken Tanaka, Keiichi Noguchi, Naohiro Fukawa, Yuta MiyauchiAbstract:The enantioselective synthesis of completely ortho-fused [9]- and [11]Helicene-like molecules has been achieved through a rhodium-mediated, intramolecular, double [2+2+2] cycloaddition of phenol- or 2-naphthol-linked hexaynes. Crystal structures and photophysical properties of these [9]- and [11]Helicene-like molecules have also been disclosed.
Andrzej Rajca - One of the best experts on this subject based on the ideXlab platform.
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radical cation and neutral radical of aza thia 7 Helicene with somo homo energy level inversion
Journal of the American Chemical Society, 2016Co-Authors: Ying Wang, Maren Pink, Suchada Rajca, Hui Zhang, Arnon Olankitwanit, Andrzej RajcaAbstract:We report a relatively persistent, open-shell aza-thia[7]Helicene with cross-conjugated electron-rich π-system. The singly occupied molecular orbital (SOMO) energy levels of both radical cation and neutral radical of the [7]Helicene are below the highest occupied molecular orbital (HOMO) energy levels, thereby violating the Aufbau principle. The aza-thia[7]Helicene is prepared from β-hexathiophene by a three-step one-pot reaction, in which the pyrrole ring is constructed by two consecutive C–N bond formations. Chemical oxidation converts the Helicene to its radical cation, while in the presence of base (Cs2CO3), the oxidation gives neutral aminyl radical, likely via proton dissociation from the aminium radical cation with a low pKa. Reaction of the aza-thia[7]Helicene with NaH provides the corresponding anion, which shows characteristic cyclic voltammetry wave at anodic peak potential Epa ≈ +0.2 V. Chemical oxidation of the anion with ferrocenium hexafluorophosphate at room temperature gives persistent ne...
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Radical Cation and Neutral Radical of Aza-thia[7]Helicene with SOMO–HOMO Energy Level Inversion
2016Co-Authors: Ying Wang, Maren Pink, Suchada Rajca, Hui Zhang, Arnon Olankitwanit, Andrzej RajcaAbstract:We report a relatively persistent, open-shell aza-thia[7]Helicene with cross-conjugated electron-rich π-system. The singly occupied molecular orbital (SOMO) energy levels of both radical cation and neutral radical of the [7]Helicene are below the highest occupied molecular orbital (HOMO) energy levels, thereby violating the Aufbau principle. The aza-thia[7]Helicene is prepared from β-hexathiophene by a three-step one-pot reaction, in which the pyrrole ring is constructed by two consecutive C–N bond formations. Chemical oxidation converts the Helicene to its radical cation, while in the presence of base (Cs2CO3), the oxidation gives neutral aminyl radical, likely via proton dissociation from the aminium radical cation with a low pKa. Reaction of the aza-thia[7]Helicene with NaH provides the corresponding anion, which shows characteristic cyclic voltammetry wave at anodic peak potential Epa ≈ +0.2 V. Chemical oxidation of the anion with ferrocenium hexafluorophosphate at room temperature gives persistent neutral aminyl radical. Structure of the aza-thia[7]Helicene is supported by NMR, IR, X-ray crystallography, and cyclic voltammetry. The radical cation and neutral radical are characterized by EPR and UV–vis-NIR spectroscopies. DFT computations of the radical cation and neutral radical predict the SOMO–HOMO energy level inversion, which is supported experimentally by electrochemical data for the radical cation
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Functionalized Thiophene-Based [7]Helicene: Chirooptical Properties versus Electron Delocalization
The Journal of Organic Chemistry, 2009Co-Authors: Andrzej Rajca, Maren Pink, Shuzhang Xiao, Makoto Miyasaka, Suchada Rajca, Kausik Das, Kristin N. PlesselAbstract:The functionalized, enantiomerically pure [7]Helicene 1 derived from bis(benzodithiophene) functionalized with four heptyl groups is prepared from 1,8-dibromo-4,5-diheptylbenzo[1,2-b:4,3-b′]dithiophene building block 2. Such [7]Helicene structure, functionalized with bromines at the terminal positions of the Helicene inner rim and multiple solubilizing alkyl groups, is an attractive building block for long [n]Helicenes and oligo[7]Helicenes. Chirooptical properties and the degree of electron delocalization are determined and compared to those of analogous carbon−sulfur [7]Helicene and [7]Helicenes derived from benzodithiophene to provide a correlation between chirooptical properties and the degree of electron delocalization. [7]Helicene 1 possesses a moderately increased electron delocalization, but its chirooptical properties are similar to those for analogous [7]Helicenes with relatively lower electron delocalization, indicating that chirooptical properties are not significantly affected by electron del...
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cross conjugated oligothiophenes derived from the c2s n helix asymmetric synthesis and structure of carbon sulfur 11 Helicene
Journal of the American Chemical Society, 2005Co-Authors: Makoto Miyasaka, Andrzej Rajca, Maren Pink, Suchada RajcaAbstract:(−)-Sparteine-mediated asymmetric synthesis of di-n-octyl-substituted carbon−sulfur [11]Helicene, a helical (C2S)n β-undecathiophene, is described. The atom-efficient routes rely on one-step tri-annelation or two-step di- and mono-annelation to provide enantiomeric excess of (+)- or (−)-[11]Helicene, respectively. X-ray structures for homologous [11] and [7]Helicenes indicate similar helical curvatures. The optical band gap, Eg ≈ 3.5 eV, is estimated for the (C2S)n helix polymer, with onset of electron localization at n ≤ 7.
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cross conjugated oligothiophenes derived from the c2s n helix asymmetric synthesis and structure of carbon sulfur 11 Helicene
Journal of the American Chemical Society, 2005Co-Authors: Makoto Miyasaka, Andrzej Rajca, Maren Pink, Suchada RajcaAbstract:(-)-Sparteine-mediated asymmetric synthesis of di-n-octyl-substituted carbon-sulfur [11]Helicene, a helical (C2S)n beta-undecathiophene, is described. The atom-efficient routes rely on one-step tri-annelation or two-step di- and mono-annelation to provide enantiomeric excess of (+)- or (-)-[11]Helicene, respectively. X-ray structures for homologous [11] and [7]Helicenes indicate similar helical curvatures. The optical band gap, Eg approximately 3.5 eV, is estimated for the (C2S)n helix polymer, with onset of electron localization at n
Suchada Rajca - One of the best experts on this subject based on the ideXlab platform.
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radical cation and neutral radical of aza thia 7 Helicene with somo homo energy level inversion
Journal of the American Chemical Society, 2016Co-Authors: Ying Wang, Maren Pink, Suchada Rajca, Hui Zhang, Arnon Olankitwanit, Andrzej RajcaAbstract:We report a relatively persistent, open-shell aza-thia[7]Helicene with cross-conjugated electron-rich π-system. The singly occupied molecular orbital (SOMO) energy levels of both radical cation and neutral radical of the [7]Helicene are below the highest occupied molecular orbital (HOMO) energy levels, thereby violating the Aufbau principle. The aza-thia[7]Helicene is prepared from β-hexathiophene by a three-step one-pot reaction, in which the pyrrole ring is constructed by two consecutive C–N bond formations. Chemical oxidation converts the Helicene to its radical cation, while in the presence of base (Cs2CO3), the oxidation gives neutral aminyl radical, likely via proton dissociation from the aminium radical cation with a low pKa. Reaction of the aza-thia[7]Helicene with NaH provides the corresponding anion, which shows characteristic cyclic voltammetry wave at anodic peak potential Epa ≈ +0.2 V. Chemical oxidation of the anion with ferrocenium hexafluorophosphate at room temperature gives persistent ne...
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Radical Cation and Neutral Radical of Aza-thia[7]Helicene with SOMO–HOMO Energy Level Inversion
2016Co-Authors: Ying Wang, Maren Pink, Suchada Rajca, Hui Zhang, Arnon Olankitwanit, Andrzej RajcaAbstract:We report a relatively persistent, open-shell aza-thia[7]Helicene with cross-conjugated electron-rich π-system. The singly occupied molecular orbital (SOMO) energy levels of both radical cation and neutral radical of the [7]Helicene are below the highest occupied molecular orbital (HOMO) energy levels, thereby violating the Aufbau principle. The aza-thia[7]Helicene is prepared from β-hexathiophene by a three-step one-pot reaction, in which the pyrrole ring is constructed by two consecutive C–N bond formations. Chemical oxidation converts the Helicene to its radical cation, while in the presence of base (Cs2CO3), the oxidation gives neutral aminyl radical, likely via proton dissociation from the aminium radical cation with a low pKa. Reaction of the aza-thia[7]Helicene with NaH provides the corresponding anion, which shows characteristic cyclic voltammetry wave at anodic peak potential Epa ≈ +0.2 V. Chemical oxidation of the anion with ferrocenium hexafluorophosphate at room temperature gives persistent neutral aminyl radical. Structure of the aza-thia[7]Helicene is supported by NMR, IR, X-ray crystallography, and cyclic voltammetry. The radical cation and neutral radical are characterized by EPR and UV–vis-NIR spectroscopies. DFT computations of the radical cation and neutral radical predict the SOMO–HOMO energy level inversion, which is supported experimentally by electrochemical data for the radical cation
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Functionalized Thiophene-Based [7]Helicene: Chirooptical Properties versus Electron Delocalization
The Journal of Organic Chemistry, 2009Co-Authors: Andrzej Rajca, Maren Pink, Shuzhang Xiao, Makoto Miyasaka, Suchada Rajca, Kausik Das, Kristin N. PlesselAbstract:The functionalized, enantiomerically pure [7]Helicene 1 derived from bis(benzodithiophene) functionalized with four heptyl groups is prepared from 1,8-dibromo-4,5-diheptylbenzo[1,2-b:4,3-b′]dithiophene building block 2. Such [7]Helicene structure, functionalized with bromines at the terminal positions of the Helicene inner rim and multiple solubilizing alkyl groups, is an attractive building block for long [n]Helicenes and oligo[7]Helicenes. Chirooptical properties and the degree of electron delocalization are determined and compared to those of analogous carbon−sulfur [7]Helicene and [7]Helicenes derived from benzodithiophene to provide a correlation between chirooptical properties and the degree of electron delocalization. [7]Helicene 1 possesses a moderately increased electron delocalization, but its chirooptical properties are similar to those for analogous [7]Helicenes with relatively lower electron delocalization, indicating that chirooptical properties are not significantly affected by electron del...
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cross conjugated oligothiophenes derived from the c2s n helix asymmetric synthesis and structure of carbon sulfur 11 Helicene
Journal of the American Chemical Society, 2005Co-Authors: Makoto Miyasaka, Andrzej Rajca, Maren Pink, Suchada RajcaAbstract:(−)-Sparteine-mediated asymmetric synthesis of di-n-octyl-substituted carbon−sulfur [11]Helicene, a helical (C2S)n β-undecathiophene, is described. The atom-efficient routes rely on one-step tri-annelation or two-step di- and mono-annelation to provide enantiomeric excess of (+)- or (−)-[11]Helicene, respectively. X-ray structures for homologous [11] and [7]Helicenes indicate similar helical curvatures. The optical band gap, Eg ≈ 3.5 eV, is estimated for the (C2S)n helix polymer, with onset of electron localization at n ≤ 7.
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cross conjugated oligothiophenes derived from the c2s n helix asymmetric synthesis and structure of carbon sulfur 11 Helicene
Journal of the American Chemical Society, 2005Co-Authors: Makoto Miyasaka, Andrzej Rajca, Maren Pink, Suchada RajcaAbstract:(-)-Sparteine-mediated asymmetric synthesis of di-n-octyl-substituted carbon-sulfur [11]Helicene, a helical (C2S)n beta-undecathiophene, is described. The atom-efficient routes rely on one-step tri-annelation or two-step di- and mono-annelation to provide enantiomeric excess of (+)- or (-)-[11]Helicene, respectively. X-ray structures for homologous [11] and [7]Helicenes indicate similar helical curvatures. The optical band gap, Eg approximately 3.5 eV, is estimated for the (C2S)n helix polymer, with onset of electron localization at n
Nicolas Vanthuyne - One of the best experts on this subject based on the ideXlab platform.
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Stereoselective Syntheses, Structures and Properties of Extremely Distorted Chiral Nanographenes Embedding Hextuple Helicenes
Angewandte Chemie International Edition, 2020Co-Authors: Myriam Roy, Nicolas Vanthuyne, Veronika Berezhnaia, Marco Villa, Michel Giorgi, Jean-valère Naubron, Salomé Poyer, Valérie Monnier, Laurence Charles, Yannick CarissanAbstract:We report a molecular design and concept using π‐system elongation and steric effects from Helicenes surrounding a triphenylene core toward stable chiral polycyclic aromatic hydrocarbons (PAHs) with a maximal π‐distortion to tackle their aromaticity, supramolecular and molecular properties. The selective syntheses, and the structural, conformational and chiroptical properties of two diastereomeric large multi‐Helicenes of formula C90H48 having a triphenylene core and embedding three [5]Helicene units on their inner edges and three [7]Helicene units at their periphery are reported based on diastereoselective and, when applicable, enantiospecific Yamamoto‐type cyclotrimerizations of racemic or enantiopure 9,10‐dibromo[7]Helicene. Both molecules have an extremely distorted triphenylene core, and one of them exhibits the largest torsion angle recorded so far for a benzene ring (twist=36.9°).
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Exciton coupling in diketopyrrolopyrrole-Helicene derivatives leads to red and near-infrared circularly polarized luminescence
Chemical Science, 2018Co-Authors: Kais Dhbaibi, Nicolas Vanthuyne, Jochen Autschbach, Monika Srebro, Ludovic Favereau, Marion Jean, Francesco Zinna, Bassem Jamoussi, Lorenzo Di Bari, Jeanne CrassousAbstract:Molecular and macromolecular chiral -conjugated diketopyrrolopyrrole (DPP)-Helicene derivatives were prepared and their chiroptical properties examined experimentally and theoretically. Exciton coupling leads to red and near-infrared circularly polarized luminescence arising from the achiral DPP units in the helical environment, highlighting an interesting synergy between the chiral Helicene and the organic dye.
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Chiral Nanographene Propeller Embedding Six Enantiomerically Stable [5]Helicene Units
Journal of the American Chemical Society, 2017Co-Authors: Veronika Berezhnaia, Nicolas Vanthuyne, Myriam Roy, Jean-valère Naubron, Marc Villa, Jean Rodriguez, Yoann Coquerel, Marc GingrasAbstract:A one-step synthesis of a nanographene propeller with a D 3-symmetry was obtained starting from 7,8-dibromo[5]Helicene by Yamamoto nickel(0) couplings. It afforded a chiral polyaromatic hydrocarbon (PAH) embedding six enantiomerically stable [5]Helicene units. This dense accumulation of helical strain resulted in a distorted geometry, but stable stereochemistry. The conformational, structural, chiroptical, and photophysical properties of the molecule are reported.
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Chiral Nanographene Propeller Embedding Six Enantiomerically Stable [5]Helicene Units
2017Co-Authors: Veronika Erezhnaia, Nicolas Vanthuyne, Myriam Roy, Marco Villa, Jean-valère Naubro, Jea Rodriguez, Yoa Coquerel, Marc GingrasAbstract:A one-step synthesis of a nanographene propeller with a D3-symmetry was obtained starting from 7,8-dibromo[5]Helicene by Yamamoto nickel(0) couplings. It afforded a chiral polyaromatic hydrocarbon (PAH) embedding six enantiomerically stable [5]Helicene units. This dense accumulation of helical strain resulted in a distorted geometry, but stable stereochemistry. The conformational, structural, chiroptical, and photophysical properties of the molecule are reported
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bimetallic gold i complexes with ethynyl Helicene and bis phosphole ligands understanding the role of aurophilic interactions in their chiroptical properties
Chemistry: A European Journal, 2016Co-Authors: Mehdi Elsayed Moussa, Christian Roussel, Nicolas Vanthuyne, Hui Chen, Zuoyong Wang, Soizic Chevance, Monika Srebrohooper, J Gareth A Williams, Jochen AutschbachAbstract:Monometallic gold(I)-alkynyl-Helicene complexes (1 a,b) and bimetallic gold(I)-alkynyl-Helicene architectures featuring the presence (2 a,b) or absence (3 a,b) of aurophilic intramolecular interactions were prepared by using different types of phosphole ligands (mono-phosphole L1 or bis-phospholes L2,3). The influence of the Au(I) d(10) metal center(s) on the electronic, photophysical, and chiroptical properties of these unprecedented phosphole-gold(I)-alkynyl-Helicene complexes was examined. Experimental and theoretical results highlight the importance of ligand-to-ligand-type charge transfers and the strong effect of the presence or absence of Au(I) -Au(I) interactions in 2 a,b.
Jeanne Crassous - One of the best experts on this subject based on the ideXlab platform.
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Circularly polarized luminescence in Helicene and helicenoid derivatives
Circularly Polarized Luminescence of Isolated Small Organic Molecules, 2020Co-Authors: Jeanne CrassousAbstract:In this chapter, we discuss the circularly polarized luminescence (CPL) of Helicene and helicenoid derivatives. The organic helicenic derivatives are classified according to the type of atom (heteroatom or carbon) incorporated within the helical backbone. Transition-metal complexes and chiroptical devices incorporating Helicene derivatives and exhibiting CPL activity are also presented.
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Helicene derived aggregation induced emission conjugates with highly tunable circularly polarized luminescence
Materials Chemistry Frontiers, 2020Co-Authors: Jeanne Crassous, Chengshuo Shen, Fuwei Gan, Guoli Zhang, Yongle Ding, Jinghao Wang, Ruibin Wang, Huibin QiuAbstract:Chiral organic molecules play an important role in generating circularly polarized luminescence (CPL) with high quantum yield and tunable colours. However, their CPL performance is virtually limited by the small dissymmetric factor |glum| value and the aggregation-caused quenching issue in the solid state. Here, we report a series of luminescent molecules with tailored marriage of Helicenes and aggregation-induced emission (AIE) luminophores. The resulting adducts are highly fluorescent in the aggregated state with colour varying from blue to green and quantum yield up to 37.0%, depending on the linkage position, conjugation and length. The efficient association of the helical conjugated skeleton of Helicene and the AIE moiety also enables a relatively high |glum| value ranging from 0.001 to 0.011. Notably the |glum| value could be further enhanced to ca. 0.015 by the substitution of two AIE luminophores onto a single Helicene. This work provides a practical synthetic strategy for advanced molecular CPL materials, and would also favour the fabrication of high-performance circularly polarized organic light-emitting devices.
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Exciton coupling in diketopyrrolopyrrole-Helicene derivatives leads to red and near-infrared circularly polarized luminescence
Chemical Science, 2018Co-Authors: Kais Dhbaibi, Nicolas Vanthuyne, Jochen Autschbach, Monika Srebro, Ludovic Favereau, Marion Jean, Francesco Zinna, Bassem Jamoussi, Lorenzo Di Bari, Jeanne CrassousAbstract:Molecular and macromolecular chiral -conjugated diketopyrrolopyrrole (DPP)-Helicene derivatives were prepared and their chiroptical properties examined experimentally and theoretically. Exciton coupling leads to red and near-infrared circularly polarized luminescence arising from the achiral DPP units in the helical environment, highlighting an interesting synergy between the chiral Helicene and the organic dye.
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Helicene-based chiroptical switches
Comptes Rendus Chimie, 2016Co-Authors: Helena Isla, Jeanne CrassousAbstract:Abstract Helicenes are molecules with ortho -fused aromatic rings that adopt an inherently chiral helical shape. This helical topology combined with the extended π-conjugated system provides them with excellent chiroptical and photophysical properties. These properties and peculiarities make Helicenes important candidates for the conception of new chiroptical switches. Several examples of light-, redox- and pH-triggered Helicene-based switches have recently appeared in the literature including examples from our group. Some of them are multi-input and/or multi-output systems in which the changes can be triggered by different stimuli and/or read-out by different techniques, an attractive advantage for functional materials.
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aza 6 Helicene platinum complexes chirality control of cis trans isomerism
Angewandte Chemie, 2014Co-Authors: Nidal Saleh, Franca Castiglione, Loic Toupet, Christian Roussel, Nicolas Vanthuyne, Tullio Caronna, Daniele Mendola, Andrea Mele, Jeanne CrassousAbstract:It was serendipitously observed that cis-[PtCl2(NCEt)PPh3] reacted differently with either racemic or enantiopure 4-aza[6]Helicene, giving respectively cis (racemic) and trans (enantiopure) [(PtCl2)-Cl-II(4-aza[6]Helicene)PPh3] complexes. This unexpected reactivity is explained through a dynamic process (crystallization-induced diastereoselective transformation) and enables a new aspect of reactivity in chiral transition-metal complexes to be addressed.
