1
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Pazos A, Cruz CM, Cuerva JM, Rivilla I, Cossío FP, Freixa Z. Enantiopure [6]-Azairidahelicene by Dynamic Kinetic Resolution of a Configurationally Labile [4]-Helicene. Angew Chem Int Ed Engl 2024; 63:e202406663. [PMID: 38655628 DOI: 10.1002/anie.202406663] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2024] [Revised: 04/23/2024] [Accepted: 04/23/2024] [Indexed: 04/26/2024]
Abstract
A pair of enantiopure [6]-azairidahelicenes incorporating chirality at the metal center and on the helicenic ligand were synthesized by dynamic kinetic resolution (dkr) of a configurationally labile [4]-helicenic ligand (4-(2-pyridyl)-benzo[g]phenanthrene, L1H) using bis-cyclometalated chiral-at-metal only iridium(III) precursors as chiral inductors. The origin of the observed dkr is attributed to the different conformation and stability of diastereomeric reaction intermediates formed during the cyclometalation process. The isolated enantiomers exhibited circularly polarized phosphorescence (CPP), with |gphos| values of 1.8×10-3.
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Affiliation(s)
- Ariadna Pazos
- Department of Applied Chemistry, Faculty of Chemistry, University of the Basque Country (UPV/EHU), 20018, Donostia, Spain
| | - Carlos M Cruz
- Department of Organic Chemistry, Unidad de Excelencia de Química (UEQ), Faculty of Sciences, University of Granada, Avda. Fuente Nueva s/n, 18071, Granada, Spain
| | - Juan M Cuerva
- Department of Organic Chemistry, Unidad de Excelencia de Química (UEQ), Faculty of Sciences, University of Granada, Avda. Fuente Nueva s/n, 18071, Granada, Spain
| | - Ivan Rivilla
- IKERBASQUE, Basque Foundation for Science, 48011, Bilbao, Spain
- Department of Organic Chemistry II, Faculty of Chemistry, University of the Basque Country (UPV/EHU), 20018, Donostia, Spain
- Donostia International Physics Center (DIPC), 20018, Donostia, Spain
| | - Fernando P Cossío
- Department of Organic Chemistry II, Faculty of Chemistry, University of the Basque Country (UPV/EHU), 20018, Donostia, Spain
- Donostia International Physics Center (DIPC), 20018, Donostia, Spain
| | - Zoraida Freixa
- Department of Applied Chemistry, Faculty of Chemistry, University of the Basque Country (UPV/EHU), 20018, Donostia, Spain
- IKERBASQUE, Basque Foundation for Science, 48011, Bilbao, Spain
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2
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Xu WL, Zhang RX, Wang H, Chen J, Zhou L. Helicoselective Synthesis of Indolohelicenoids through Organocatalytic Central-to-Helical Chirality Conversion. Angew Chem Int Ed Engl 2024; 63:e202318021. [PMID: 38196108 DOI: 10.1002/anie.202318021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2023] [Revised: 01/03/2024] [Accepted: 01/09/2024] [Indexed: 01/11/2024]
Abstract
We report the helicoselective and convergent construction of indolohelicenoids with excellent efficiency and stereocontrol. This reaction proceeds through a chiral-phosphoric-acid-catalyzed enantioselective cycloaddition and eliminative aromatization sequence, which can be finely controlled by adjusting the reaction temperature. Mechanistic studies reveal that the chiral phosphoric acid cooperatively serves as both a bifunctional and Brønsted acid catalyst, enabling one-pot central-to-helical chirality conversion. Additionally, the optical properties of the synthesized indolohelicenoids were characterized to explore their potential applications in organic photoelectric materials.
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Affiliation(s)
- Wen-Lei Xu
- Key Laboratory of Synthetic and Natural Functional Molecule of the Ministry of Education, College of Chemistry & Materials Science, Northwest University, Xi'an, 710127, P. R. China
- Henan Key Laboratory of Function-Oriented Porous Materials, College of Chemistry and Chemical Engineering, Luoyang Normal University, Luoyang, 471934, P. R. China
| | - Ru-Xia Zhang
- Key Laboratory of Synthetic and Natural Functional Molecule of the Ministry of Education, College of Chemistry & Materials Science, Northwest University, Xi'an, 710127, P. R. China
| | - Hui Wang
- Key Laboratory of Synthetic and Natural Functional Molecule of the Ministry of Education, College of Chemistry & Materials Science, Northwest University, Xi'an, 710127, P. R. China
| | - Jie Chen
- Key Laboratory of Synthetic and Natural Functional Molecule of the Ministry of Education, College of Chemistry & Materials Science, Northwest University, Xi'an, 710127, P. R. China
| | - Ling Zhou
- Key Laboratory of Synthetic and Natural Functional Molecule of the Ministry of Education, College of Chemistry & Materials Science, Northwest University, Xi'an, 710127, P. R. China
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3
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Bao ST, Louie S, Jiang H, Jiang Q, Sun S, Steigerwald ML, Nuckolls C, Jin Z. Near-Infrared, Organic Chiroptic Switch with High Dissymmetry Factors. J Am Chem Soc 2024; 146:51-56. [PMID: 38110244 DOI: 10.1021/jacs.3c10578] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2023]
Abstract
Here we unveil a chiral molecular redox switch derived from PDI-based twistacenes─chPDI[2] that has the remarkable attributes of high-intensity and a broadband chiral response. This material exhibits facile, stable, and reversible multistate chiroptical switching behavior over a broad active wavelength range close to 700 nm, encompassing ultraviolet, visible, and near-infrared regions. Upon reduction, chPDI[2] exhibits a substantial increase in the amplitude of its circular dichroic response, with an outstanding |ΔΔε| > 300 M-1 cm-1 and a high dissymmetry factor of 3 × 10-2 at 960 nm. DFT calculations suggest that the long wavelength CD signal for doubly reduced chPDI[2] originates from excitation of the PDI backbone to the π* orbital of the bridging alkene. Importantly, the dimer's molecular contortion facilitates ionic diffusion, enabling chiral switching in solid state films. The high dissymmetry factors and near-infrared response establish chPDI[2] as a unique chiroptic switch.
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Affiliation(s)
- Si Tong Bao
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Shayan Louie
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Haoyu Jiang
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Qifeng Jiang
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Shantao Sun
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Michael L Steigerwald
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Colin Nuckolls
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Zexin Jin
- Research Center for Industries of the Future, Westlake University, Hangzhou, Zhejiang 310030, China
- School of Engineering, Westlake University, Hangzhou, Zhejiang 310030, China
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4
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Li C, Shao YB, Gao X, Ren Z, Guo C, Li M, Li X. Enantioselective synthesis of chiral quinohelicenes through sequential organocatalyzed Povarov reaction and oxidative aromatization. Nat Commun 2023; 14:3380. [PMID: 37291164 DOI: 10.1038/s41467-023-39134-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Accepted: 05/31/2023] [Indexed: 06/10/2023] Open
Abstract
Heterohelicenes are of increasing importance in the fields of materials science, molecular recognition, and asymmetric catalysis. However, enantioselective construction of these molecules, especially by organocatalytic methods, is challenging, and few methods are available. In this study, we synthesize enantioenriched 1-(3-indol)-quino[n]helicenes through chiral phosphoric acid-catalyzed Povarov reaction followed by oxidative aromatization. The method has a broad substrate scope and offers rapid access to an array of chiral quinohelicenes with enantioselectivities up to 99%. Additionally, the photochemical and electrochemical properties of selected quinohelicenes are explored.
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Affiliation(s)
- Chengwen Li
- State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin, 300071, China
| | - Ying-Bo Shao
- State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin, 300071, China
| | - Xi Gao
- State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin, 300071, China
| | - Zhiyuan Ren
- State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin, 300071, China
| | - Chenhao Guo
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Molecular Recognition and Function, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
| | - Meng Li
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Molecular Recognition and Function, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
| | - Xin Li
- State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin, 300071, China.
- Haihe Laboratory of Sustainable Chemical Transformations, Tianjin, 300192, China.
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5
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Yu T, Li ZQ, Li J, Cheng S, Xu J, Huang J, Zhong YW, Luo S, Zhu Q. Palladium-Catalyzed Modular Synthesis of Enantioenriched Pyridohelicenes through Double Imidoylative Cyclization. ACS Catal 2022. [DOI: 10.1021/acscatal.2c04461] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- Ting Yu
- State Key Laboratory of Respiratory Disease, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, 190 Kaiyuan Avenue, Guangzhou 510530, People’s Republic of China
- University of Chinese Academy of Sciences, No. 19(A) Yuquan Road, Shijingshan District, Beijing, 100049, People’s Republic of China
| | - Zhong-Qiu Li
- Key Laboratory of Photochemistry, Beijing National Laboratory for Molecular Sciences CAS, Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China
| | - Jing Li
- State Key Laboratory of Respiratory Disease, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, 190 Kaiyuan Avenue, Guangzhou 510530, People’s Republic of China
- University of Chinese Academy of Sciences, No. 19(A) Yuquan Road, Shijingshan District, Beijing, 100049, People’s Republic of China
| | - Sidi Cheng
- State Key Laboratory of Respiratory Disease, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, 190 Kaiyuan Avenue, Guangzhou 510530, People’s Republic of China
- University of Chinese Academy of Sciences, No. 19(A) Yuquan Road, Shijingshan District, Beijing, 100049, People’s Republic of China
| | - Jiali Xu
- Guangxi Key Laboratory of Natural Polymer Chemistry and Physics, College of Chemistry and Materials, Nanning Normal University, Nanning 530001, People’s Republic of China
| | - Jun Huang
- Guangxi Key Laboratory of Natural Polymer Chemistry and Physics, College of Chemistry and Materials, Nanning Normal University, Nanning 530001, People’s Republic of China
| | - Yu-Wu Zhong
- Key Laboratory of Photochemistry, Beijing National Laboratory for Molecular Sciences CAS, Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China
| | - Shuang Luo
- State Key Laboratory of Respiratory Disease, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, 190 Kaiyuan Avenue, Guangzhou 510530, People’s Republic of China
- University of Chinese Academy of Sciences, No. 19(A) Yuquan Road, Shijingshan District, Beijing, 100049, People’s Republic of China
| | - Qiang Zhu
- State Key Laboratory of Respiratory Disease, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, 190 Kaiyuan Avenue, Guangzhou 510530, People’s Republic of China
- University of Chinese Academy of Sciences, No. 19(A) Yuquan Road, Shijingshan District, Beijing, 100049, People’s Republic of China
- Guangxi Key Laboratory of Natural Polymer Chemistry and Physics, College of Chemistry and Materials, Nanning Normal University, Nanning 530001, People’s Republic of China
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6
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Yasukawa T, Nakajima H, Masuda R, Yamashita Y, Kobayashi S. Effect of Activation Methods of Molecular Sieves on Ketimine Synthesis. J Org Chem 2022; 87:13750-13756. [PMID: 36173811 DOI: 10.1021/acs.joc.2c01411] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Although the use of molecular sieves for imine synthesis is a common protocol, there have been no comprehensive studies on heat-drying methods. This can be crucial for reproducibility. It was found that molecular sieve 5A dried at 160 °C for 5 h under vacuum efficiently promoted the condensation of various ketones and amines to afford even relatively bulky ketimines. Several control experiments and analyses revealed that only a small amount of Brønsted acid sites was important for the activity, rather than dehydration ability. Other types of molecular sieves could be utilized for the reaction after treatment with water followed by heat drying. A continuous-flow acetalization reaction of alcohols using the activated molecular sieve 5A was also demonstrated.
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Affiliation(s)
- Tomohiro Yasukawa
- Department of Chemistry, School of Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Hanako Nakajima
- Department of Chemistry, School of Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Ryusuke Masuda
- Department of Chemistry, School of Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Yasuhiro Yamashita
- Department of Chemistry, School of Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Shu Kobayashi
- Department of Chemistry, School of Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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7
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van de Griend C, van de Vijver JJ, Siegler MA, Dame RT, Bonnet S. Ruthenium-Locked Helical Chirality: A Barrier of Inversion and Formation of an Asymmetric Macrocycle. Inorg Chem 2022; 61:16045-16054. [PMID: 36171738 PMCID: PMC9554910 DOI: 10.1021/acs.inorgchem.2c02447] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
Upon coordination to metal centers, tetradentate ligands
based
on the 6,6′-bis(2″-aminopyridyl)-2,2′-bipyridine
(bapbpy) structure form helical chiral complexes due to the steric
clash between the terminal pyridines of the ligand. For octahedral
ruthenium(II) complexes, the two additional axial ligands bound to
the metal center, when different, generate diastereotopic aromatic
protons that can be distinguished by NMR. Based on these geometrical
features, the inversion barrier of helical [RuII(L)(RR′SO)Cl]+ complexes, where L is a sterically hindered bapbpy derivative
and RR′SO is a chiral or achiral sulfoxide ligand, was studied
by variable-temperature 1H NMR. The coalescence energies
for the inversion of the helical chirality of [Ru(bapbpy)(DMSO)(Cl)]Cl
and [Ru(bapbpy)(MTSO)(Cl)]Cl (where MTSO is (R)-methyl p-tolylsulfoxide) were found to be 43 and 44 kJ/mol, respectively.
By contrast, in [Ru(biqbpy)(DMSO)(Cl)]Cl (biqbpy = 6,6′-bis(aminoquinolyl)-2,2′-bipyridine),
increased strain caused by the larger terminal quinoline groups resulted
in a coalescence temperature higher than 376 K, which pointed to an
absence of helical chirality inversion at room temperature. Further
increasing the steric strain by introducing methoxy groups ortho to
the nitrogen atoms of the terminal pyridyl groups in bapbpy resulted
in the serendipitous discovery of a ring-closing reaction that took
place upon trying to make [Ru(OMe-bapbpy)(DMSO)Cl]+ (OMe-bapbpy
= 6,6′-bis(6-methoxy-aminopyridyl)-2,2′-bipyridine).
This reaction generated, in excellent yields, a chiral complex [Ru(L″)(DMSO)Cl]Cl,
where L″ is an asymmetric tetrapyridyl macrocycle. This unexpected
transformation appears to be specific to ruthenium(II) as macrocyclization
did not occur upon coordination of the same ligand to palladium(II)
or rhodium(III). Ruthenium
complexes based on the bapbpy ligand form helical
chiral complexes due to the steric clash between their terminal pyridyl
groups. The coalescence energy for the inversion of this helical chirality
was 43 kJ/mol according to variable temperature NMR. Increasing the
steric strain by replacing terminal pyridyl groups with quinolyl groups
blocked helical interconversion, while introducing ortho-methoxy groups resulted in an unexpected ring-closing reaction,
forming a dissymmetric macrocycle bound to ruthenium in excellent
yields.
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Affiliation(s)
- Corjan van de Griend
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, Leiden 2333CC, The Netherlands
| | - Johannes J van de Vijver
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, Leiden 2333CC, The Netherlands
| | - Maxime A Siegler
- Small molecule X-ray facility, Department of Chemistry, John Hopkins University, Baltimore, Maryland 21218, United States
| | - Remus T Dame
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, Leiden 2333CC, The Netherlands
| | - Sylvestre Bonnet
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, Leiden 2333CC, The Netherlands
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8
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Nemez DB, Lozada IB, Braun JD, Williams JAG, Herbert DE. Synthesis and Coordination Chemistry of a Benzannulated Bipyridine: 6,6'-Biphenanthridine. Inorg Chem 2022; 61:13386-13398. [PMID: 35972335 DOI: 10.1021/acs.inorgchem.2c01514] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The synthesis, characterization, and coordination chemistry of a doubly π-extended bipyridine analogue, 6,6'-biphenanthridine (biphe), is presented. The structure of the molecule has been determined in the solid state by X-ray diffraction, showing an angle of 72.6° between the phenanthridine planes. The free, uncoordinated organic molecule displays blue fluorescence in solution. It can be singly protonated with strong acids, and the protonated form displays more intense yellow emission. The effect of acid on the excited states is interpreted with the aid of TDDFT calculations. Two Ru(II) coordination complexes, tris(6,6'-biphenanthridine)ruthenium(II) dichloride, [Ru(biphe)3]Cl2, and bis(2,2'-bipyridine)(6,6'-biphenanthridine)ruthenium(II) tetraphenylborate, [Ru(bpy)2(biphe)](BPh4)2, are also reported and their structures determined in the solid state by X-ray diffraction. Both complexes display emission at 77 K that is strongly bathochromically shifted by almost 200 nm compared to that of the archetypal 3MLCT emitter [Ru(bpy)3]2+. Such a red shift is consistent with the more extended conjugation and lower-energy π* orbitals associated with the biphe ligand, lowering the energy of the 3MLCT excited state, as revealed by TDDFT calculations. The efficient non-radiative decay that is typical of such low-energy emitters renders the phosphorescence extremely weak and short-lived at ambient temperature, and rapid ligand photodissociation also competes with radiative decay, especially in the heteroleptic complex. Electrochemical analysis illustrates the effect of biphe's stabilized vacant π* manifold, with multiple reversible reductions evident at much less negative potentials than those observed for [Ru(bpy)3]2+.
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Affiliation(s)
- Dion B Nemez
- Department of Chemistry and the Manitoba Institute for Materials, University of Manitoba, 144 Dysart Road, Winnipeg, Manitoba R3T 2N2, Canada
| | - Issiah B Lozada
- Department of Chemistry and the Manitoba Institute for Materials, University of Manitoba, 144 Dysart Road, Winnipeg, Manitoba R3T 2N2, Canada
| | - Jason D Braun
- Department of Chemistry and the Manitoba Institute for Materials, University of Manitoba, 144 Dysart Road, Winnipeg, Manitoba R3T 2N2, Canada
| | | | - David E Herbert
- Department of Chemistry and the Manitoba Institute for Materials, University of Manitoba, 144 Dysart Road, Winnipeg, Manitoba R3T 2N2, Canada
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9
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Váňa L, Jakubec M, Sýkora J, Císařová I, Žádný J, Storch J, Církva V. Synthesis of Aza[ n]helicenes ( n = 4-7) via Photocyclodehydrochlorination of 1-Chloro- N-aryl-2-naphthamides. J Org Chem 2022; 87:7150-7166. [PMID: 35549349 DOI: 10.1021/acs.joc.2c00375] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
A series of aza[n]helicenes (n = 4-7) was synthesized using a photocyclodehydrochlorination of 1-chloro-N-aryl-2-naphthamides as a general synthetic procedure introducing the nitrogen atom to the third ring of the helicene framework. The effect of the nitrogen presence in the helicene skeleton on the physicochemical properties of the prepared aza[n]helicenes was studied and compared to those of the parent carbo-analogues. The insertion of a nitrogen atom into the outer edge of the helicene molecule has a severe impact on certain physicochemical properties such as optical rotation, electrostatic potentials, and intermolecular interactions. On the other hand, some other properties such as UV/vis, fluorescence, and phosphorescence spectra remained almost unaffected when compared to the parent carbohelicenes. A nitrogen atom can be also used for further derivatization, which can lead to further modification of helicene properties, as manifested here in the fluorescence changes induced by protonation.
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Affiliation(s)
| | | | | | - Ivana Císařová
- Department of Inorganic Chemistry, Faculty of Science, Charles University in Prague, Hlavova 2030, 128 40 Prague 2, Czech Republic
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10
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Takaishi K, Nakatsuka Y, Asano H, Yamada Y, Ema T. Ruthenium Complexes Bearing Axially Chiral Bipyridyls: The Mismatched Diastereomer Showed Red Circularly Polarized Phosphorescence. Chemistry 2021; 28:e202104212. [PMID: 34837262 DOI: 10.1002/chem.202104212] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Indexed: 12/21/2022]
Abstract
RutheniumII complexes bearing three axially chiral bipyridyl ligands were synthesized as a new family of chiral complex dyes, and Δ-(S)- and Λ-(S)-diastereomers were obtained. The X-ray crystal structure analyses, spectroscopy, and DFT calculations suggested that all the bipyridyls maintained chirality in both the ground and excited states, and the Δ-(S)- and Λ-(S)-isomers are the matched (more relaxed) and mismatched (more constrained) pairs, respectively. The mismatched Λ-(S)-isomer exhibited red circularly polarized phosphorescence (CPP) both in solution and in the solid state. The solution state CPP is the most intense of ruthenium complexes, while the solid state CPP is the first example of them. It is supposed that, for the Λ-(S)-isomer, the six cumulative CH/π interactions suppress further distortion in the T1 state.
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Affiliation(s)
- Kazuto Takaishi
- Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University Tsushima, Okayama, 700-8530, Japan
| | - Yusuke Nakatsuka
- Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University Tsushima, Okayama, 700-8530, Japan
| | - Hitomi Asano
- Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University Tsushima, Okayama, 700-8530, Japan
| | - Yuya Yamada
- Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University Tsushima, Okayama, 700-8530, Japan
| | - Tadashi Ema
- Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University Tsushima, Okayama, 700-8530, Japan
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11
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Yoshida J, Yamazaki K, Tateyama K, Yuge H, Sato H. Chiroptical switching behavior of heteroleptic ruthenium complexes bearing acetylacetonato and tropolonato ligands. Dalton Trans 2021; 50:14611-14617. [PMID: 34605516 DOI: 10.1039/d1dt02592a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Four types of tris-chelate ruthenium complexes bearing acetylacetonato (acac) and tropolonato (trop) ligands were synthesized and optically resolved into Δ and Λ isomers: [Ru(acac)3] (Ru-0), [Ru(acac)2(trop)] (Ru-1), [Ru(acac)(trop)2] (Ru-2), and [Ru(trop)3] (Ru-3). Chiral HPLC chromatograms, electronic circular dichroism (ECD), and vibrational circular dichroism (VCD) of the four ruthenium complexes were systematically investigated. As a result, the absolute configurations of the newly prepared enantiomeric complexes Ru-2 and Ru-3 were determined. For the case of Ru-2, its absolute configuration was also confirmed by single crystal X-ray diffraction analysis. The ECD changes upon chemical oxidation were further investigated for the four complexes. An ECD change in enantiomeric Ru-1 was observed upon oxidation, but the oxidized species soon returned to the neutral state within a few minutes. Enantiomers of Ru-3 also showed explicit ECD changes upon oxidation. Further, the lifetime of the oxidized state was the longest among the four investigated complexes, whereas they racemized in solution at room temperature. In contrast, the enantiomers of heteroleptic complexes (Ru-1 and Ru-2) concurrently exhibited ECD changes, relatively long lifetime of the oxidized state, and nil or quite slow racemization behavior. The coexistence of acac and trop ligands was key to making the competing factors compatible in the resultant ruthenium complexes.
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Affiliation(s)
- Jun Yoshida
- Department of Chemistry, College of Humanities & Sciences, Nihon University, 3-25-40 Sakurajosui, Setagaya-ku, Tokyo 156-8550, Japan.
| | - Kana Yamazaki
- Department of Chemistry, School of Science, Kitasato University, 1-15-1 Kitasato Minami-ku, Sagamihara, 252-0373, Japan
| | - Kazunori Tateyama
- Department of Chemistry, School of Science, Kitasato University, 1-15-1 Kitasato Minami-ku, Sagamihara, 252-0373, Japan
| | - Hidetaka Yuge
- Department of Chemistry, School of Science, Kitasato University, 1-15-1 Kitasato Minami-ku, Sagamihara, 252-0373, Japan
| | - Hisako Sato
- Graduate School of Science and Engineering, Ehime University, 2-5 Bunkyo-chou, Matsuyama, Ehime 790-8577, Japan
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