1
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Lee CK, Gangadharappa C, Fahrenbach AC, Kim DJ. Harnessing Radicals: Advances in Self-Assembly and Molecular Machinery. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024:e2408271. [PMID: 39177115 DOI: 10.1002/adma.202408271] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2024] [Revised: 07/25/2024] [Indexed: 08/24/2024]
Abstract
Radicals, with their unpaired electrons, exhibit unique chemical and physical properties that have long intrigued chemists. Despite early skepticism about their stability, the discovery of persistent radicals has opened new possibilities for molecular interactions. This review examines the mechanisms and applications of radically driven self-assembly, focusing on key motifs such as naphthalene diimides, tetrathiafulvalenes, and viologens, which serve as models for radical assembly. The potential of radical interactions in the development of artificial molecular machines (AMMs) are also discussed. These AMMs, powered by radical-radical interactions, represent significant advancements in non-equilibrium chemistry, mimicking the functionalities of biological systems. From molecular switches to ratchets and pumps, the versatility and unique properties of radically powered AMMs are highlighted. Additionally, the applications of radical assembly in materials science are explored, particularly in creating smart materials with redox-responsive properties. The review concludes by comparing AMMs to biological molecular machines, offering insights into future directions. This overview underscores the impact of radical chemistry on molecular assembly and its promising applications in both synthetic and biological systems.
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Affiliation(s)
| | | | - Albert C Fahrenbach
- School of Chemistry, University of New South Wales, Sydney, NSW, 2052, Australia
- Australian Centre for Astrobiology, University of New South Wales, Sydney, NSW, 2052, Australia
- UNSW RNA Institute, University of New South Wales, Sydney, NSW, 2052, Australia
| | - Dong Jun Kim
- School of Chemistry, University of New South Wales, Sydney, NSW, 2052, Australia
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2
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Kessler BJO, Mansoor IF, Wozniak DI, Emge TJ, Lipke MC. Controlling Intramolecular and Intermolecular Electronic Coupling of Radical Ligands in a Series of Cobaltoviologen Complexes. J Am Chem Soc 2023; 145:15924-15935. [PMID: 37460450 DOI: 10.1021/jacs.3c03725] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/27/2023]
Abstract
Controlling electronic coupling between multiple redox sites is of interest for tuning the electronic properties of molecules and materials. While classic mixed-valence (MV) systems are highly tunable, e.g., via the organic bridges connecting the redox sites, metal-bridged MV systems are difficult to control because the electronics of the metal cannot usually be altered independently of redox-active moieties embedded in its ligands. Herein, this limitation was overcome by varying the donor strengths of ancillary ligands in a series of cobalt complexes without directly perturbing the electronics of viologen-like redox sites bridged by the cobalt ions. The cobaltoviologens [1X-Co]n+ feature four 4-X-pyridyl donor groups (X = CO2Me, Cl, H, Me, OMe, NMe2) that provide gradual electronic tuning of the bridging CoII centers, while a related complex [2-Co]n+ with NHC donors supports exclusively CoIII states even upon reduction of the viologen units. Electrochemistry and IVCT band analysis indicate that the MV states of these complexes have electronic structures ranging from fully localized ([2-Co]4+; Robin-Day Class I) to fully delocalized ([1CO2Me-Co]3+; Class III) descriptions, demonstrating unprecedented control over electronic coupling without changing the identity of the redox sites or bridging metal. Additionally, single-crystal XRD characterization of the homovalent complexes [1H-Co]2+ and [1H-Zn]2+ revealed radical-pairing interactions between the viologen ligands of adjacent complexes, representing a type of through-space electronic coupling commonly observed for organic viologen radicals but never before seen in metalloviologens. The extended solid-state packing of these complexes produces 3D networks of radical π-stacking interactions that impart unexpected mechanical flexibility to these crystals.
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Affiliation(s)
- Brice J O Kessler
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, 123 Bevier Road, Piscataway, New Jersey 08854, United States
| | - Iram F Mansoor
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, 123 Bevier Road, Piscataway, New Jersey 08854, United States
| | - Derek I Wozniak
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, 123 Bevier Road, Piscataway, New Jersey 08854, United States
| | - Thomas J Emge
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, 123 Bevier Road, Piscataway, New Jersey 08854, United States
| | - Mark C Lipke
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, 123 Bevier Road, Piscataway, New Jersey 08854, United States
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3
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Wang Z, Mei L, Guo C, Huang S, Shi WQ, Li X, Feng W, Li X, Yang C, Yuan L. Supramolecular Shish Kebabs: Higher Order Dimeric Structures from Ring-in-Rings Complexes with Conformational Adaptivity. Angew Chem Int Ed Engl 2023; 62:e202216690. [PMID: 36652350 DOI: 10.1002/anie.202216690] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Revised: 01/13/2023] [Accepted: 01/16/2023] [Indexed: 01/19/2023]
Abstract
Use of abiotic chemical systems for understanding higher order superstructures is challenging. Here we report a ring-in-ring(s) system comprising a hydrogen-bonded macrocycle and cyclobis(paraquat-o-phenylene) tetracation (o-Box) or cyclobis(paraquat-p-phenylene) tetracation (CBPQT4+ , p-Box) that assembles to construct discrete higher order structures with adaptive conformation. As indicated by mass spectrometry, computational modeling, NMR spectroscopy, and single-crystal X-ray diffraction analysis, this ring-in-ring(s) system features the box-directed aggregation of multiple macrocycles, leading to generation of several stable species such as H4G (1 a/o-Box) and H5G (1 a/o-Box). Remarkably, a dimeric shish-kebab-like ring-in-rings superstructure H7G2 (1 a/o-Box) or H8G2 (1 a/p-Box) is formed from the coaxial stacking of two ring-in-rings units. The formation of such unique dimeric superstructures is attributed to the large π-surface of this 2D planar macrocycle and the conformational variation of both host and guest.
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Affiliation(s)
- Zhenwen Wang
- College of Chemistry, Key Laboratory of Radiation Physics and Technology of Ministry of Education, Sichuan University, Chengdu, Sichuan, 610064, China) (The first email address should be
| | - Lei Mei
- Laboratory of Nuclear Energy Chemistry, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China
| | - Chenxing Guo
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, Guangdong, 518071, China
| | - Song Huang
- College of Chemistry, Key Laboratory of Radiation Physics and Technology of Ministry of Education, Sichuan University, Chengdu, Sichuan, 610064, China) (The first email address should be
| | - Wei-Qun Shi
- Laboratory of Nuclear Energy Chemistry, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China
| | - Xiaowei Li
- College of Chemistry, Key Laboratory of Radiation Physics and Technology of Ministry of Education, Sichuan University, Chengdu, Sichuan, 610064, China) (The first email address should be
| | - Wen Feng
- College of Chemistry, Key Laboratory of Radiation Physics and Technology of Ministry of Education, Sichuan University, Chengdu, Sichuan, 610064, China) (The first email address should be
| | - Xiaopeng Li
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, Guangdong, 518071, China.,University General Hospital, Shenzhen University Clinical Medical Academy, Shenzhen University, Shenzhen, Guangdong, 518055, China
| | - Cheng Yang
- College of Chemistry, Key Laboratory of Radiation Physics and Technology of Ministry of Education, Sichuan University, Chengdu, Sichuan, 610064, China) (The first email address should be
| | - Lihua Yuan
- College of Chemistry, Key Laboratory of Radiation Physics and Technology of Ministry of Education, Sichuan University, Chengdu, Sichuan, 610064, China) (The first email address should be
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4
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Khang TM, Nhien PQ, Cuc TTK, Weng CC, Wu CH, Wu JI, Hue BTB, Li YK, Lin HC. Dual and Sequential Locked/Unlocked Photochromic Effects on FRET Controlled Singlet Oxygen Processes by Contracted/Extended Forms of Diarylethene-Based [1]Rotaxane Nanoparticles. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023; 19:e2205597. [PMID: 36504441 DOI: 10.1002/smll.202205597] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2022] [Revised: 11/22/2022] [Indexed: 06/17/2023]
Abstract
Manipulations of singlet oxygen (1 O2 ) generations by the integration of both aggregation-induced emission luminogen (AIEgen) photosensitizer and photochromic moieties have diversified features in photodynamic therapy applications. Through Förster resonance energy transfer (FRET) pathway to induce red PL emissions (at 595 nm) for 1 O2 productions, [1]rotaxane containing photosensitive tetraphenylethylene (TPE) donor and photochromic diarylethene (DAE) acceptor is introduced to achieve dual and sequential locked/unlocked photoswitching effects by pH-controlled shuttling of its contracted/extended forms. Interestingly, the UV-enabled DAE ring closure speeds follow the reversed trend of DAE self-constraint degree as: contracted < extended < noninterlocked forms in [1]rotaxane analogues, thus FRET processes can be adjusted in contracted/extended forms of [1]rotaxane upon UV irradiations. Accordingly, the contracted form of [1]rotaxane is FRET-OFF locked and inert to UV exposure due to the larger bending conformation of DAE parallel (p-)conformer, compared with its extended and noninterlocked analogues possessing switchable FRET-OFF/ON behaviors activated by dual and sequential pH- and photoswitching. Owing to the advantages of 1 O2 productions tuned by multistimuli inputs (pH, UV, and blue light), an useful logic circuit for toxicity outputs of the surface modified [1]rotaxane nanoparticles (NPs) has been demonstrated to offer promising 1 O2 productions and managements based on mechanically interlocked molecules for future bioapplications.
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Affiliation(s)
- Trang Manh Khang
- Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, Hsinchu, 300093, Taiwan
| | - Pham Quoc Nhien
- Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, Hsinchu, 300093, Taiwan
- Department of Chemistry, College of Natural Sciences, Can Tho University, Can Tho City, 94000, Viet Nam
| | - Tu Thi Kim Cuc
- Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, Hsinchu, 300093, Taiwan
| | - Chang-Ching Weng
- Department of Applied Chemistry, National Yang Ming Chiao Tung University, Hsinchu, 300093, Taiwan
| | - Chia-Hua Wu
- Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, Hsinchu, 300093, Taiwan
| | - Judy I Wu
- Department of Chemistry, University of Houston, Houston, TX, 77204, USA
| | - Bui Thi Buu Hue
- Department of Chemistry, College of Natural Sciences, Can Tho University, Can Tho City, 94000, Viet Nam
| | - Yaw-Kuen Li
- Department of Applied Chemistry, National Yang Ming Chiao Tung University, Hsinchu, 300093, Taiwan
- Center for Emergent Functional Matter Science, National Yang Ming Chiao Tung University, Hsinchu, 300093, Taiwan
| | - Hong-Cheu Lin
- Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, Hsinchu, 300093, Taiwan
- Center for Emergent Functional Matter Science, National Yang Ming Chiao Tung University, Hsinchu, 300093, Taiwan
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5
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Chen X, Chen H, Fraser Stoddart J. The Story of the Little Blue Box: A Tribute to Siegfried Hünig. Angew Chem Int Ed Engl 2023; 62:e202211387. [PMID: 36131604 PMCID: PMC10099103 DOI: 10.1002/anie.202211387] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Indexed: 02/02/2023]
Abstract
The tetracationic cyclophane, cyclobis(paraquat-p-phenylene), also known as the little blue box, constitutes a modular receptor that has facilitated the discovery of many host-guest complexes and mechanically interlocked molecules during the past 35 years. Its versatility in binding small π-donors in its tetracationic state, as well as forming trisradical tricationic complexes with viologen radical cations in its doubly reduced bisradical dicationic state, renders it valuable for the construction of various stimuli-responsive materials. Since the first reports in 1988, the little blue box has been featured in over 500 publications in the literature. All this research activity would not have been possible without the seminal contributions carried out by Siegfried Hünig, who not only pioneered the syntheses of viologen-containing cyclophanes, but also revealed their rich redox chemistry in addition to their ability to undergo intramolecular π-dimerization. This Review describes how his pioneering research led to the design and synthesis of the little blue box, and how this redox-active host evolved into the key component of molecular shuttles, switches, and machines.
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Affiliation(s)
- Xiao‐Yang Chen
- Department of ChemistryNorthwestern University2145 Sheridan RoadEvanstonIllinois 60208USA
| | - Hongliang Chen
- Stoddart Institute of Molecular ScienceDepartment of ChemistryZhejiang UniversityHangzhou310027China
- ZJU-Hangzhou Global Scientific and Technological Innovation CenterHangzhou311215China
| | - J. Fraser Stoddart
- Department of ChemistryNorthwestern University2145 Sheridan RoadEvanstonIllinois 60208USA
- Stoddart Institute of Molecular ScienceDepartment of ChemistryZhejiang UniversityHangzhou310027China
- ZJU-Hangzhou Global Scientific and Technological Innovation CenterHangzhou311215China
- School of ChemistryUniversity of New South WalesSydneyNSW 2052Australia
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6
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Jiao Y, Mao H, Qiu Y, Wu G, Chen H, Zhang L, Han H, Li X, Zhao X, Tang C, Chen XY, Feng Y, Stern CL, Wasielewski MR, Stoddart JF. Mechanical Bond-Assisted Full-Spectrum Investigation of Radical Interactions. J Am Chem Soc 2022; 144:23168-23178. [DOI: 10.1021/jacs.2c10882] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Yang Jiao
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Haochuan Mao
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
- Institute for Sustainability and Energy at Northwestern, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Yunyan Qiu
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Guangcheng Wu
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Hongliang Chen
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
- Stoddart Institute of Molecular Science, Department of Chemistry, Zhejiang University, Hangzhou 310027, China
- ZJU-Hangzhou Global Scientific and Technological Innovation Center, Hangzhou 311215, China
| | - Long Zhang
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Han Han
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Xuesong Li
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Xingang Zhao
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Chun Tang
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Xiao-Yang Chen
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Yuanning Feng
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Charlotte L. Stern
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Michael R. Wasielewski
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
- Institute for Sustainability and Energy at Northwestern, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - J. Fraser Stoddart
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
- Stoddart Institute of Molecular Science, Department of Chemistry, Zhejiang University, Hangzhou 310027, China
- ZJU-Hangzhou Global Scientific and Technological Innovation Center, Hangzhou 311215, China
- School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia
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7
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Chen Q, Lei Y, Wu G, Li Q, Pan Y, Li H. Ultramacrocyclization in water via external templation. Chem Sci 2022; 13:798-803. [PMID: 35173945 PMCID: PMC8768864 DOI: 10.1039/d1sc06236k] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Accepted: 12/19/2021] [Indexed: 12/04/2022] Open
Abstract
Condensing a dihydrazide and each of a series of cationic bisaldehyde compounds bearing polymethylene chains in weakly acidic water produces either a macrocycle in a [1 + 1] manner or its dimer namely a [2]catenane, or their mixture. The product distribution is determined by the length of the bisaldehydes. Addition of cucurbit[8]uril (CB[8]) drives the catenane/macrocycle equilibria to the side of macrocycles, by forming ring-in-ring complexes with the latter. When the polymethylene unit of the bisaldehyde is replaced with a more rigid p-xylene linker, its self-assembly with the dihydrazide leads to quantitative formation of a [2]catenane. Upon addition of CB[8], the [2]catenane is transformed into an ultra-large macrocycle condensed in a [2 + 2] manner, which is encircled by two CB[8] rings. The framework of this macrocycle contains one hundred and two atoms, whose synthesis would be a formidable task without the external template CB[8]. Removal of CB[8] with a competitive guest leads to recovery of the [2]catenane.
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Affiliation(s)
- Qiong Chen
- Department of Chemistry Institution, Zhejiang University Hangzhou 310027 China
| | - Ye Lei
- Department of Chemistry Institution, Zhejiang University Hangzhou 310027 China
| | - Guangcheng Wu
- Department of Chemistry Institution, Zhejiang University Hangzhou 310027 China
| | - Qing Li
- Key Laboratory of Macrocyclic and Supramolecular Chemistry, Guizhou University Guiyang 550025 China
| | - Yuanjiang Pan
- Department of Chemistry Institution, Zhejiang University Hangzhou 310027 China
| | - Hao Li
- Department of Chemistry Institution, Zhejiang University Hangzhou 310027 China
- ZJU-Hangzhou Global Scientific and Technological Innovation Center Hangzhou 310027 China
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8
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Sartin MM, Osawa M, Takeuchi S, Tahara T. Ultrafast dynamics of an azobenzene-containing molecular shuttle based on a rotaxane. Chem Commun (Camb) 2021; 58:961-964. [PMID: 34935779 DOI: 10.1039/d1cc06093g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
An ultrafast spectroscopic study was carried out for a photoisomerizable, rotaxane-based molecular shuttle, in which photoisomerization of the azobenzene moiety of the thread-like guest drives a shuttling motion of a cyclodextrin host. Femtosecond upconversion and time-resolved absorption measurements revealed distinct S1 dynamics with time constants of 1.2 and 17 ps. Both time constants are smaller when the cyclodextrin host is absent, implying that, within the S1 state, there are mutiple barriers to the isomerization and subsequent shuttling, due to steric interference from the cyclodextrin.
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Affiliation(s)
- Matthew M Sartin
- Molecular Spectroscopy Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
| | - Masahisa Osawa
- Molecular Spectroscopy Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
| | - Satoshi Takeuchi
- Molecular Spectroscopy Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan. .,Ultrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics (RAP), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Tahei Tahara
- Molecular Spectroscopy Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan. .,Ultrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics (RAP), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
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9
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Chen X, Mao H, Feng Y, Cai K, Shen D, Wu H, Zhang L, Zhao X, Chen H, Song B, Jiao Y, Wu Y, Stern CL, Wasielewski MR, Stoddart JF. Radically Enhanced Dual Recognition. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202109647] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Xiao‐Yang Chen
- Department of Chemistry Northwestern University 2145 Sheridan Road Evanston IL 60208 USA
| | - Haochuan Mao
- Department of Chemistry Northwestern University 2145 Sheridan Road Evanston IL 60208 USA
- Institute for Sustainability and Energy at Northwestern Northwestern University 2145 Sheridan Road Evanston IL 60208 USA
| | - Yuanning Feng
- Department of Chemistry Northwestern University 2145 Sheridan Road Evanston IL 60208 USA
| | - Kang Cai
- Department of Chemistry Nankai University 94 Weijin Road, Nankai District Tianjin 300071 China
| | - Dengke Shen
- Institutes of Physical Science and Information Technology Anhui University Hefei 230601 China
| | - Huang Wu
- Department of Chemistry Northwestern University 2145 Sheridan Road Evanston IL 60208 USA
| | - Long Zhang
- Department of Chemistry Northwestern University 2145 Sheridan Road Evanston IL 60208 USA
| | - Xingang Zhao
- Department of Chemistry Northwestern University 2145 Sheridan Road Evanston IL 60208 USA
| | - Hongliang Chen
- Department of Chemistry Northwestern University 2145 Sheridan Road Evanston IL 60208 USA
| | - Bo Song
- Department of Chemistry Northwestern University 2145 Sheridan Road Evanston IL 60208 USA
| | - Yang Jiao
- Department of Chemistry Northwestern University 2145 Sheridan Road Evanston IL 60208 USA
| | - Yong Wu
- Department of Chemistry Northwestern University 2145 Sheridan Road Evanston IL 60208 USA
| | - Charlotte L. Stern
- Department of Chemistry Northwestern University 2145 Sheridan Road Evanston IL 60208 USA
| | - Michael R. Wasielewski
- Department of Chemistry Northwestern University 2145 Sheridan Road Evanston IL 60208 USA
- Institute for Sustainability and Energy at Northwestern Northwestern University 2145 Sheridan Road Evanston IL 60208 USA
| | - J. Fraser Stoddart
- Department of Chemistry Northwestern University 2145 Sheridan Road Evanston IL 60208 USA
- School of Chemistry University of New South Wales Sydney NSW 2052 Australia
- Stoddart Institute of Molecular Science Department of Chemistry Zhejiang University Hangzhou 310027 China
- ZJU-Hangzhou Global Scientific and Technological Innovation Center Hangzhou 311215 China
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10
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Cherraben S, Scelle J, Hasenknopf B, Vives G, Sollogoub M. Precise Rate Control of Pseudorotaxane Dethreading by pH-Responsive Selectively Functionalized Cyclodextrins. Org Lett 2021; 23:7938-7942. [PMID: 34582212 DOI: 10.1021/acs.orglett.1c02940] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A family of cyclodextrins functionalized with zero, one, two, or six amines was shown to control the rate of their threading and dethreading on a molecular axle depending on the pH and their substitution pattern. The originality of this system lies in the rate control of the switch by operating the stimulus directly on the macrocycle.
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Affiliation(s)
- Sawsen Cherraben
- Sorbonne Université, CNRS UMR8232, Institut Parisien de Chimie Moléculaire, 4 place Jussieu, 75005 Paris, France
| | - Jérémy Scelle
- Sorbonne Université, CNRS UMR8232, Institut Parisien de Chimie Moléculaire, 4 place Jussieu, 75005 Paris, France
| | - Bernold Hasenknopf
- Sorbonne Université, CNRS UMR8232, Institut Parisien de Chimie Moléculaire, 4 place Jussieu, 75005 Paris, France
| | - Guillaume Vives
- Sorbonne Université, CNRS UMR8232, Institut Parisien de Chimie Moléculaire, 4 place Jussieu, 75005 Paris, France
| | - Matthieu Sollogoub
- Sorbonne Université, CNRS UMR8232, Institut Parisien de Chimie Moléculaire, 4 place Jussieu, 75005 Paris, France
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11
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Chen XY, Mao H, Feng Y, Cai K, Shen D, Wu H, Zhang L, Zhao X, Chen H, Song B, Jiao Y, Wu Y, Stern CL, Wasielewski MR, Stoddart JF. Radically Enhanced Dual Recognition. Angew Chem Int Ed Engl 2021; 60:25454-25462. [PMID: 34342116 DOI: 10.1002/anie.202109647] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Indexed: 11/08/2022]
Abstract
Complexation between a viologen radical cation (V.+ ) and cyclobis(paraquat-p-phenylene) diradical dication (CBPQT2(.+) ) has been investigated and utilized extensively in the construction of mechanically interlocked molecules (MIMs) and artificial molecular machines (AMMs). The selective recognition of a pair of V.+ using radical-pairing interactions, however, remains a formidable challenge. Herein, we report the efficient encapsulation of two methyl viologen radical cations (MV.+ ) in a size-matched bisradical dicationic host - namely, cyclobis(paraquat-2,6-naphthalene)2(.+) , i.e., CBPQN2(.+) . Central to this dual recognition process was the choice of 2,6-bismethylenenaphthalene linkers for incorporation into the bisradical dicationic host. They provide the space between the two bipyridinium radical cations in CBPQN2(.+) suitable for binding two MV.+ with relatively short (3.05-3.25 Å) radical-pairing distances. The size-matched bisradical dicationic host was found to exhibit highly selective and cooperative association with the two MV.+ in MeCN at room temperature. The formation of the tetrakisradical tetracationic inclusion complex - namely, [(MV)2 ⊂CBPQN]4( .+) - in MeCN was confirmed by VT 1 H NMR, as well as by EPR spectroscopy. The solid-state superstructure of [(MV)2 ⊂CBPQN]4( .+) reveals an uneven distribution of the binding distances (3.05, 3.24, 3.05 Å) between the three different V.+ , suggesting that localization of the radical-pairing interactions has a strong influence on the packing of the two MV.+ inside the bisradical dicationic host. Our findings constitute a rare example of binding two radical guests with high affinity and cooperativity using host-guest radical-pairing interactions. Moreover, they open up possibilities of harnessing the tetrakisradical tetracationic inclusion complex as a new, orthogonal and redox-switchable recognition motif for the construction of MIMs and AMMs.
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Affiliation(s)
- Xiao-Yang Chen
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA
| | - Haochuan Mao
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA.,Institute for Sustainability and Energy at Northwestern, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA
| | - Yuanning Feng
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA
| | - Kang Cai
- Department of Chemistry, Nankai University, 94 Weijin Road, Nankai District, Tianjin, 300071, China
| | - Dengke Shen
- Institutes of Physical Science and Information Technology, Anhui University, Hefei, 230601, China
| | - Huang Wu
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA
| | - Long Zhang
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA
| | - Xingang Zhao
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA
| | - Hongliang Chen
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA
| | - Bo Song
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA
| | - Yang Jiao
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA
| | - Yong Wu
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA
| | - Charlotte L Stern
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA
| | - Michael R Wasielewski
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA.,Institute for Sustainability and Energy at Northwestern, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA
| | - J Fraser Stoddart
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA.,School of Chemistry, University of New South Wales, Sydney, NSW, 2052, Australia.,Stoddart Institute of Molecular Science, Department of Chemistry, Zhejiang University, Hangzhou, 310027, China.,ZJU-Hangzhou Global Scientific and Technological Innovation Center, Hangzhou, 311215, China
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12
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Cai K, Zhang L, Astumian RD, Stoddart JF. Radical-pairing-induced molecular assembly and motion. Nat Rev Chem 2021; 5:447-465. [PMID: 37118435 DOI: 10.1038/s41570-021-00283-4] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/16/2021] [Indexed: 12/25/2022]
Abstract
Radical-pairing interactions between conjugated organic π-radicals are relative newcomers to the inventory of molecular recognition motifs explored in supramolecular chemistry. The unique electronic, magnetic, optical and redox-responsive properties of the conjugated π-radicals render molecules designed with radical-pairing interactions useful for applications in various areas of chemistry and materials science. In particular, the ability to control formation of radical cationic or anionic species, by redox stimulation, provides a flexible trigger for directed assembly and controlled molecular motions, as well as a convenient means of inputting energy to fuel non-equilibrium processes. In this Review, we provide an overview of different examples of radical-pairing-based recognition processes and of their emerging use in (1) supramolecular assembly, (2) templation of mechanically interlocked molecules, (3) stimuli-controlled molecular switches and, by incorporation of kinetic asymmetry in the design, (4) the creation of unidirectional molecular transporters based on pumping cassettes powered by fuelled switching of radical-pairing interactions. We conclude the discussion with an outlook on future directions for the field.
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13
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Wu H, Wang Y, Jones LO, Liu W, Song B, Cui Y, Cai K, Zhang L, Shen D, Chen XY, Jiao Y, Stern CL, Li X, Schatz GC, Stoddart JF. Ring-in-Ring(s) Complexes Exhibiting Tunable Multicolor Photoluminescence. J Am Chem Soc 2020; 142:16849-16860. [PMID: 32886881 DOI: 10.1021/jacs.0c07745] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
One ring threaded by two other rings to form a non-intertwined ternary ring-in-rings motif is a challenging task in noncovalent synthesis. Constructing multicolor photoluminescence systems with tunable properties is also a fundamental research goal, which can lead to applications in multidimensional biological imaging, visual displays, and encryption materials. Herein, we describe the design and synthesis of binary and ternary ring-in-ring(s) complexes, based on an extended tetracationic cyclophane and cucurbit[8]uril. The formation of these complexes is accompanied by tunable multicolor fluorescence outputs. On mixing equimolar amounts of the cyclophane and cucurbit[8]uril, a 1:1 ring-in-ring complex is formed as a result of hydrophobic interactions associated with a favorable change in entropy. With the addition of another equivalent of cucurbit[8]uril, a 1:2 ring-in-rings complex is formed, facilitated by additional ion-dipole interactions involving the pyridinium units in the cyclophane and the carbonyl groups in cucurbit[8]uril. Because of the narrowing in the energy gaps of the cyclophane within the rigid hydrophobic cavities of cucurbit[8]urils, the binary and ternary ring-in-ring(s) complexes emit green and bright yellow fluorescence, respectively. A series of color-tunable emissions, such as sky blue, cyan, green, and yellow with increased fluorescence lifetimes, can be achieved by simply adding cucurbit[8]uril to an aqueous solution of the cyclophane. Notably, the smaller cyclobis(paraquat-p-phenylene), which contains the same p-xylylene linkers as the extended tetracationic cyclophane, does not form ring-in-ring(s) complexes with cucurbit[8]uril. The encapsulation of this extended tetracationic cyclophane by both one and two cucurbit[8]urils provides an incentive to design and synthesize more advanced supramolecular systems, as well as opening up a feasible approach toward achieving tunable multicolor photoluminescence with single chromophores.
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Affiliation(s)
- Huang Wu
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Yu Wang
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Leighton O Jones
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Wenqi Liu
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Bo Song
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Yunpeng Cui
- Department of Chemistry, University of South Florida, Tampa, Florida 33620, United States
| | - Kang Cai
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Long Zhang
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Dengke Shen
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Xiao-Yang Chen
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Yang Jiao
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Charlotte L Stern
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Xiaopeng Li
- College of Chemistry and Environmental Engineering, Shenzhen University, 3688 Nanhai Avenue, Shenzhen, Guangdong 518055, P.R. China
| | - George C Schatz
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - J Fraser Stoddart
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States.,School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia.,Institute for Molecular Design and Synthesis, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072, P.R. China
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14
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Schröder HV, Schalley CA. Electrochemically switchable rotaxanes: recent strides in new directions. Chem Sci 2019; 10:9626-9639. [PMID: 32110308 PMCID: PMC7020790 DOI: 10.1039/c9sc04118d] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2019] [Accepted: 10/03/2019] [Indexed: 12/13/2022] Open
Abstract
Are they still electrifying? Electrochemically switchable rotaxanes are well known for their ability to efficiently undergo changes of (co-)conformation and properties under redox-control. Thus, these mechanically interlocked assemblies represent an auspicious liaison between the fields of molecular switches and molecular electronics. Since the first reported example of a redox-switchable molecular shuttle in 1994, improved tools of organic and supramolecular synthesis have enabled sophisticated new architectures, which provide precise control over properties and function. This perspective covers recent advances in the area of electrochemically active rotaxanes including novel molecular switches and machines, metal-containing rotaxanes, non-equilibrium systems and potential applications.
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Affiliation(s)
- Hendrik V Schröder
- Institut für Chemie und Biochemie , Freie Universität Berlin , Takustr. 3 , 14195 Berlin , Germany .
| | - Christoph A Schalley
- Institut für Chemie und Biochemie , Freie Universität Berlin , Takustr. 3 , 14195 Berlin , Germany .
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15
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Abstract
The design and synthesis of artificial molecular switches (AMSs) displaying architectures of increased complexity would constitute significant progress in meeting the challenging task of realizing artificial molecular machines (AMMs). Here, we report the synthesis and characterization of a molecular shuttle composed of a cyclobis(paraquat-4,4'-biphenylene) cyclophane ring and a dumbbell incorporating a cyclobis(paraquat-m-phenylene) cyclophane "head" and a bifurcated, tawse-like "tail" composed of two oligoether chains, each containing a 1,5-dioxynaphthalene ring. In its reduced state the ring-in-ring recognition motif, between the meta and para bisradical dicationic cyclophanes (rings), defines the [2]rotaxane, whereas in the oxidized state, the cyclobis(paraquat-4,4'-biphenylene) cyclophane encircles the two 1,5-dioxynaphthalene rings in the bifurcated "tail". The redox-controlled molecular shuttling, which can be likened to the action of a zipper in the macroscopic world, exhibits slow kinetics dampened by the opening and closing of the bifurcated "tail" of the molecular shuttle. Cyclic voltammetry reveals that this slow shuttling is associated with electrochemical hysteresis.
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Affiliation(s)
- Melissa Dumartin
- Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208 , United States
| | - Mark C Lipke
- Department of Chemistry and Chemical Biology , Rutgers, The State University of New Jersey , 610 Taylor Road , Piscataway , New Jersey 08854 , United States
| | - J Fraser Stoddart
- Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208 , United States.,Institute of Molecular Design and Synthesis , Tianjin University , 92 Weijin Road, Nankai District , Tianjin 300072 , P. R. China.,School of Chemistry , University of New South Wales , Sydney , NSW 2052 , Australia
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16
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Xu G, Wu L, Chang X, Ang TWH, Wong W, Huang J, Che C. Solvent‐Induced Cluster‐to‐Cluster Transformation of Homoleptic Gold(I) Thiolates between Catenane and Ring‐in‐Ring Structures. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201909980] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Guang‐Tao Xu
- State Key Laboratory of Synthetic ChemistryInstitute of Molecular Functional MaterialsHKU-CAS Joint Laboratory on New Materials, and Department of ChemistryThe University of Hong Kong Pokfulam Road Hong Kong SAR China
| | - Liang‐Liang Wu
- State Key Laboratory of Synthetic ChemistryInstitute of Molecular Functional MaterialsHKU-CAS Joint Laboratory on New Materials, and Department of ChemistryThe University of Hong Kong Pokfulam Road Hong Kong SAR China
| | - Xiao‐Yong Chang
- State Key Laboratory of Synthetic ChemistryInstitute of Molecular Functional MaterialsHKU-CAS Joint Laboratory on New Materials, and Department of ChemistryThe University of Hong Kong Pokfulam Road Hong Kong SAR China
| | - Tim Wai Hung Ang
- State Key Laboratory of Synthetic ChemistryInstitute of Molecular Functional MaterialsHKU-CAS Joint Laboratory on New Materials, and Department of ChemistryThe University of Hong Kong Pokfulam Road Hong Kong SAR China
| | - Wai‐Yeung Wong
- Department of Applied Biology and Chemical TechnologyThe Hong Kong Polytechnic University, Hung Hom Hong Kong SAR China
| | - Jie‐Sheng Huang
- State Key Laboratory of Synthetic ChemistryInstitute of Molecular Functional MaterialsHKU-CAS Joint Laboratory on New Materials, and Department of ChemistryThe University of Hong Kong Pokfulam Road Hong Kong SAR China
| | - Chi‐Ming Che
- State Key Laboratory of Synthetic ChemistryInstitute of Molecular Functional MaterialsHKU-CAS Joint Laboratory on New Materials, and Department of ChemistryThe University of Hong Kong Pokfulam Road Hong Kong SAR China
- HKU Shenzhen Institute of Research and Innovation Shenzhen 518053 China
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17
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Xu G, Wu L, Chang X, Ang TWH, Wong W, Huang J, Che C. Solvent‐Induced Cluster‐to‐Cluster Transformation of Homoleptic Gold(I) Thiolates between Catenane and Ring‐in‐Ring Structures. Angew Chem Int Ed Engl 2019; 58:16297-16306. [DOI: 10.1002/anie.201909980] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Revised: 08/30/2019] [Indexed: 12/22/2022]
Affiliation(s)
- Guang‐Tao Xu
- State Key Laboratory of Synthetic Chemistry Institute of Molecular Functional Materials HKU-CAS Joint Laboratory on New Materials, and Department of Chemistry The University of Hong Kong Pokfulam Road Hong Kong SAR China
| | - Liang‐Liang Wu
- State Key Laboratory of Synthetic Chemistry Institute of Molecular Functional Materials HKU-CAS Joint Laboratory on New Materials, and Department of Chemistry The University of Hong Kong Pokfulam Road Hong Kong SAR China
| | - Xiao‐Yong Chang
- State Key Laboratory of Synthetic Chemistry Institute of Molecular Functional Materials HKU-CAS Joint Laboratory on New Materials, and Department of Chemistry The University of Hong Kong Pokfulam Road Hong Kong SAR China
| | - Tim Wai Hung Ang
- State Key Laboratory of Synthetic Chemistry Institute of Molecular Functional Materials HKU-CAS Joint Laboratory on New Materials, and Department of Chemistry The University of Hong Kong Pokfulam Road Hong Kong SAR China
| | - Wai‐Yeung Wong
- Department of Applied Biology and Chemical Technology The Hong Kong Polytechnic University, Hung Hom Hong Kong SAR China
| | - Jie‐Sheng Huang
- State Key Laboratory of Synthetic Chemistry Institute of Molecular Functional Materials HKU-CAS Joint Laboratory on New Materials, and Department of Chemistry The University of Hong Kong Pokfulam Road Hong Kong SAR China
| | - Chi‐Ming Che
- State Key Laboratory of Synthetic Chemistry Institute of Molecular Functional Materials HKU-CAS Joint Laboratory on New Materials, and Department of Chemistry The University of Hong Kong Pokfulam Road Hong Kong SAR China
- HKU Shenzhen Institute of Research and Innovation Shenzhen 518053 China
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18
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Feng H, Gao W, Lin Y, Jin G. Selective Synthesis of Discrete Mono‐, Interlocked‐, and Borromean Ring Ensembles Based on a
π
‐Electron‐Deficient Ligand. Chem Asian J 2019; 14:2712-2718. [DOI: 10.1002/asia.201900741] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Indexed: 12/14/2022]
Affiliation(s)
- Hui‐Jun Feng
- Shanghai Key Laboratory of Molecular Catalysis and Innovative MaterialsState Key Laboratory of Molecular Engineering of PolymersDepartment of ChemistryFudan University Shanghai 200433 P. R. China
| | - Wen‐Xi Gao
- Shanghai Key Laboratory of Molecular Catalysis and Innovative MaterialsState Key Laboratory of Molecular Engineering of PolymersDepartment of ChemistryFudan University Shanghai 200433 P. R. China
| | - Yue‐Jian Lin
- Shanghai Key Laboratory of Molecular Catalysis and Innovative MaterialsState Key Laboratory of Molecular Engineering of PolymersDepartment of ChemistryFudan University Shanghai 200433 P. R. China
| | - Guo‐Xin Jin
- Shanghai Key Laboratory of Molecular Catalysis and Innovative MaterialsState Key Laboratory of Molecular Engineering of PolymersDepartment of ChemistryFudan University Shanghai 200433 P. R. China
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19
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Abstract
The host-guest recognition between two macrocycles to form hierarchical non-intertwined ring-in-ring assemblies remains an interesting and challenging target in noncovalent synthesis. Herein, we report the design and characterization of a box-in-box assembly on the basis of host-guest radical-pairing interactions between two rigid diradical dicationic cyclophanes. One striking feature of the box-in-box complex is its ability to host various 1,4-disubstituted benzene derivatives inside as a third component in the cavity of the smaller of the two diradical dicationic cyclophanes to produce hierarchical Russian doll like assemblies. These results highlight the utility of matching the dimensions of two different cyclophanes as an efficient approach for developing new hybrid supramolecular assemblies with radical-paired ring-in-ring complexes and smaller neutral guest molecules.
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20
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Roy I, Bobbala S, Zhou J, Nguyen MT, Nalluri SKM, Wu Y, Ferris DP, Scott EA, Wasielewski MR, Stoddart JF. ExTzBox: A Glowing Cyclophane for Live-Cell Imaging. J Am Chem Soc 2018; 140:7206-7212. [PMID: 29771509 DOI: 10.1021/jacs.8b03066] [Citation(s) in RCA: 67] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The ideal fluorescent probe for live-cell imaging is bright and non-cytotoxic and can be delivered easily into the living cells in an efficient manner. The design of synthetic fluorophores having all three of these properties, however, has proved to be challenging. Here, we introduce a simple, yet effective, strategy based on well-established chemistry for designing a new class of fluorescent probes for live-cell imaging. A box-like hybrid cyclophane, namely ExTzBox·4X (6·4X, X = PF6-, Cl-), has been synthesized by connecting an extended viologen (ExBIPY) and a dipyridyl thiazolothiazole (TzBIPY) unit in an end-to-end fashion with two p-xylylene linkers. Photophysical studies show that 6·4Cl has a quantum yield ΦF = 1.00. Furthermore, unlike its ExBIPY2+ and TzBIPY2+ building units, 6·4Cl is non-cytotoxic to RAW 264.7 macrophages, even with a loading concentration as high as 100 μM, presumably on account of its rigid box-like structure which prevents its intercalation into DNA and may inhibit other interactions with it. After gaining an understanding of the toxicity profile of 6·4Cl, we employed it in live-cell imaging. Confocal microscopy has demonstrated that 64+ is taken up by the RAW 264.7 macrophages, allowing the cells to glow brightly with blue laser excitation, without any hint of photobleaching or disruption of normal cell behavior under the imaging conditions. By contrast, the acyclic reference compound Me2TzBIPY·2Cl (4·2Cl) shows very little fluorescence inside the cells, which is quenched completely under the same imaging conditions. In vitro cell investigations underscore the significance of using highly fluorescent box-like rigid cyclophanes for live-cell imaging.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - J Fraser Stoddart
- Institute of Molecular Design and Synthesis , Tianjin University , 92 Weijin Road , Nankai District , Tianjin 300072 , P. R. China
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