1
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Liu J, Yang J, Xue B, Cao Y, Cheng W, Li Y. Understanding the Mechanochemistry of Mechano-Radicals in Self-Growth Materials by Single-Molecule Force Spectroscopy. Chemphyschem 2024:e202300880. [PMID: 38705870 DOI: 10.1002/cphc.202300880] [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: 11/18/2023] [Revised: 04/02/2024] [Accepted: 05/03/2024] [Indexed: 05/07/2024]
Abstract
Recent research on mechano-radicals has provided valuable insights into self-growth and adaptive responsive materials. Typically, mechanophores must remain inert in the absence of force but respond quickly to external tension before other linkages within the polymer network. Azo compounds exhibit promising combinations of mechanical stability and force-triggered reactivity, making them widely used as mechano-radicals in force-responsive materials. However, the activation conditions and behavior of azo compounds have yet to be quantitatively explored. In this study, we investigated the mechanical strength of three azo compounds using single-molecule force spectroscopy. Our results revealed that these compounds exhibit rupture forces ranging from ~500 to 1000 pN, at a loading rate of 3×104 pN s-1. Importantly, these mechanophores demonstrate distinct kinetic properties. Their unique mechanical attributes enable azo bond scission and free radical generation before causing major polymer backbone damage of entire material during polymer network deformation. This fundamental understanding of mechanophores holds significant promise for the development of self-growth materials and their related applications.
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Affiliation(s)
- Jing Liu
- Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid-State Microstructure, Key Laboratory of Intelligent Optical Sensing and Manipulation, Ministry of Education, Department of Physics, Nanjing University, Nanjing, Jiangsu, 210093, China
| | - Jiahui Yang
- Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid-State Microstructure, Key Laboratory of Intelligent Optical Sensing and Manipulation, Ministry of Education, Department of Physics, Nanjing University, Nanjing, Jiangsu, 210093, China
| | - Bin Xue
- Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid-State Microstructure, Key Laboratory of Intelligent Optical Sensing and Manipulation, Ministry of Education, Department of Physics, Nanjing University, Nanjing, Jiangsu, 210093, China
| | - Yi Cao
- Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid-State Microstructure, Key Laboratory of Intelligent Optical Sensing and Manipulation, Ministry of Education, Department of Physics, Nanjing University, Nanjing, Jiangsu, 210093, China
| | - Wei Cheng
- Department of Oral Implantology, Nanjing Stomatological Hospital, Medical School of Nanjing University, Nanjing, Jiangsu, 210008, China
| | - Yiran Li
- Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid-State Microstructure, Key Laboratory of Intelligent Optical Sensing and Manipulation, Ministry of Education, Department of Physics, Nanjing University, Nanjing, Jiangsu, 210093, China
- School of Chemistry and Chemical Engineering, Ningxia University, Yinchuan, Ningxia, 750021, China
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2
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Ding S, Wang W, Germann A, Wei Y, Du T, Meisner J, Zhu R, Liu Y. Bicyclo[2.2.0]hexene: A Multicyclic Mechanophore with Reactivity Diversified by External Forces. J Am Chem Soc 2024; 146:6104-6113. [PMID: 38377579 DOI: 10.1021/jacs.3c13589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2024]
Abstract
Polymer mechanochemistry has been established as an enabling tool in accessing chemical reactivity and reaction pathways that are distinctive from their thermal counterparts. However, eliciting diversified reaction pathways by activating different constituent chemical bonds from the same mechanophore structure remains challenging. Here, we report the design of a bicyclo[2.2.0]hexene (BCH) mechanophore to leverage its structural simplicity and relatively low molecular symmetry to demonstrate this idea of multimodal activation. Upon changing the attachment points of pendant polymer chains, three different C-C bonds in bicyclo[2.2.0]hexene are specifically activated via externally applied force by sonication. Experimental characterization confirms that in different scenarios of polymer attachment, the regioisomers of BCH undergo different activation reactions, entailing retro-[2+2] cycloreversion, 1,3-allylic migration, and retro-4π ring-opening reactions, respectively. Control experiments with small-molecule analogues reveal that the observed diversified reactivity of BCH regioisomers is possible only with mechanical force. Theoretical studies further elucidate that the differences in the positions of substitution between regioisomers have a minimal impact on the potential energy surface of the parent BCH scaffold. The mechanochemical selectivity between different C-C bonds in each constitutional isomer is a result of selective and effective coupling of force to the aligned C-C bond in each case.
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Affiliation(s)
- Shihao Ding
- Beijing National Laboratory for Molecular Sciences, Center for Soft Matter Science and Engineering, Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, and College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Wenkai Wang
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, and College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Anne Germann
- Institute for Physical Chemistry, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Düsseldorf, Düsseldorf, 40225, Germany
| | - Yiting Wei
- Beijing National Laboratory for Molecular Sciences, Center for Soft Matter Science and Engineering, Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, and College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Tianyi Du
- Beijing National Laboratory for Molecular Sciences, Center for Soft Matter Science and Engineering, Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, and College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Jan Meisner
- Institute for Physical Chemistry, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Düsseldorf, Düsseldorf, 40225, Germany
| | - Rong Zhu
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, and College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Yun Liu
- Beijing National Laboratory for Molecular Sciences, Center for Soft Matter Science and Engineering, Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, and College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
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3
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Bhuiyan FH, Li YS, Kim SH, Martini A. Shear-activation of mechanochemical reactions through molecular deformation. Sci Rep 2024; 14:2992. [PMID: 38316829 PMCID: PMC10844542 DOI: 10.1038/s41598-024-53254-2] [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: 10/25/2023] [Accepted: 01/30/2024] [Indexed: 02/07/2024] Open
Abstract
Mechanical stress can directly activate chemical reactions by reducing the reaction energy barrier. A possible mechanism of such mechanochemical activation is structural deformation of the reactant species. However, the effect of deformation on the reaction energetics is unclear, especially, for shear stress-driven reactions. Here, we investigated shear stress-driven oligomerization reactions of cyclohexene on silica using a combination of reactive molecular dynamics simulations and ball-on-flat tribometer experiments. Both simulations and experiments captured an exponential increase in reaction yield with shear stress. Elemental analysis of ball-on-flat reaction products revealed the presence of oxygen in the polymers, a trend corroborated by the simulations, highlighting the critical role of surface oxygen atoms in oligomerization reactions. Structural analysis of the reacting molecules in simulations indicated the reactants were deformed just before a reaction occurred. Quantitative evidence of shear-induced deformation was established by comparing bond lengths in cyclohexene molecules in equilibrium and prior to reactions. Nudged elastic band calculations showed that the deformation had a small effect on the transition state energy but notably increased the reactant state energy, ultimately leading to a reduction in the energy barrier. Finally, a quantitative relationship was developed between molecular deformation and energy barrier reduction by mechanical stress.
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Affiliation(s)
- Fakhrul H Bhuiyan
- Department of Mechanical Engineering, University of California Merced, 5200 N. Lake Road, Merced, CA, 95343, USA
| | - Yu-Sheng Li
- Department of Chemical Engineering and Materials Research Institute, Pennsylvania State University, University Park, PA, 16802, USA
| | - Seong H Kim
- Department of Chemical Engineering and Materials Research Institute, Pennsylvania State University, University Park, PA, 16802, USA
| | - Ashlie Martini
- Department of Mechanical Engineering, University of California Merced, 5200 N. Lake Road, Merced, CA, 95343, USA.
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4
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Zhou Q, Kukier G, Gordiy I, Hoffmann R, Seeman JI, Houk KN. A 21st Century View of Allowed and Forbidden Electrocyclic Reactions. J Org Chem 2024; 89:1018-1034. [PMID: 38153322 PMCID: PMC10804416 DOI: 10.1021/acs.joc.3c02103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Revised: 11/09/2023] [Accepted: 11/15/2023] [Indexed: 12/29/2023]
Abstract
In 1965, Woodward and Hoffmann proposed a theory to predict the stereochemistry of electrocyclic reactions, which, after expansion and generalization, became known as the Woodward-Hoffmann Rules. Subsequently, Longuet-Higgins and Abrahamson used correlation diagrams to propose that the stereoselectivity of electrocyclizations could be explained by the correlation of reactant and product orbitals with the same symmetry. Immediately thereafter, Hoffmann and Woodward applied correlation diagrams to explain the mechanism of cycloadditions. We describe these discoveries and their evolution. We now report an investigation of various electrocyclic reactions using DFT and CASSCF. We track the frontier molecular orbitals along the intrinsic reaction coordinate and modeled trajectories and examine the correlation between HOMO and LUMO for thermally forbidden systems. We also investigate the electrocyclizations of several highly polarized systems for which the Houk group had predicted that donor-acceptor substitution can induce zwitterionic character, thereby providing low-energy pathways for formally forbidden reactions. We conclude with perspectives on the field of pericyclic reactions, including a refinement as the meaning of Woodward and Hoffmann's "Violations. There are none!" Lastly, we comment on the burgeoning influence of computations on all fields of chemistry.
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Affiliation(s)
- Qingyang Zhou
- Department
of Chemistry and Biochemistry, University
of California, Los Angeles, California90095, United States
| | - Garrett Kukier
- Department
of Chemistry and Biochemistry, University
of California, Los Angeles, California90095, United States
| | - Igor Gordiy
- Department
of Chemistry and Biochemistry, University
of California, Los Angeles, California90095, United States
| | - Roald Hoffmann
- Department
of Chemistry and Chemical Biology, Cornell
University, Ithaca, New York14850, United States
| | - Jeffrey I. Seeman
- Department
of Chemistry, University of Richmond, Richmond, Virginia 23173United States
| | - K. N. Houk
- Department
of Chemistry and Biochemistry, University
of California, Los Angeles, California90095-1569. United States
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5
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Alonso M, Bettens T, Eeckhoudt J, Geerlings P, De Proft F. Wandering through quantum-mechanochemistry: from concepts to reactivity and switches. Phys Chem Chem Phys 2023; 26:21-35. [PMID: 38086672 DOI: 10.1039/d3cp04907h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2023]
Abstract
Mechanochemistry has experienced a renaissance in recent years witnessing, at the molecular level, a remarkable interplay between theory and experiment. Molecular mechanochemistry has welcomed a broad spectrum of quantum-chemical methods to evaluate the influence of an external mechanical force on molecular properties. In this contribution, an overview is given on recent work on quantum mechanochemistry in the Brussels Quantum Chemistry group (ALGC). The effect of an external force was scrutinized both in fundamental topics, like reactivity descriptors in Conceptual DFT, and in applied topics, such as designing molecular force probes and tuning the stereoselectivity of certain types of reactions. In the conceptual part, a brief overview of the techniques introducing mechanical forces into a quantum-mechanical description of a molecule is followed by an introduction to conceptual DFT. The evolution of the electronic chemical potential (or electronegativity), chemical hardness and electrophilicity are investigated when a chemical bond in a series of diatomics is put under mechanical stress. Its counterpart, the influence of mechanical stress on bond angles, is analyzed by varying the strain present in alkyne triple bonds by applying a bending force, taking the strain promoted alkyne-azide coupling cycloaddition as an example. The increase of reactivity of the alkyne upon bending is probed by Fukui functions and the local softness. In the applied part, a new molecular force probe is presented based on an intramolecular 6π-electrocyclization in constrained polyenes operating under thermal conditions. A cyclic process is conceived where ring opening and closure are triggered by applying or removing an external pulling force. The efficiency of mechanical activation strongly depends on the magnitude of the applied force and the distance between the pulling points. The idea of pulling point distances as a tool to identify new mechanochemical processes is then tested in [28]hexaphyrins with an intricate equilibrium between Möbius aromatic and Hückel antiaromatic topologies. A mechanical force is shown to trigger the interconversion between the two topologies, using the distance matrix as a guide to select appropriate pulling points. In a final application, the Felkin-Anh model for the addition of nucleophiles to chiral carbonyls under the presence of an external mechanical force is scrutinized. By applying a force for restricting the conformational freedom of the chiral ketone, otherwise inaccessible reaction pathways are promoted on the force-modified potential energy surfaces resulting in a diastereoselectivity different from the force-free reaction.
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Affiliation(s)
- Mercedes Alonso
- Eenheid Algemene Chemie (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050 Brussels, Belgium.
| | - Tom Bettens
- Eenheid Algemene Chemie (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050 Brussels, Belgium.
| | - Jochen Eeckhoudt
- Eenheid Algemene Chemie (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050 Brussels, Belgium.
| | - Paul Geerlings
- Eenheid Algemene Chemie (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050 Brussels, Belgium.
| | - Frank De Proft
- Eenheid Algemene Chemie (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050 Brussels, Belgium.
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6
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Jiang L, Peng Z, Liang Y, Tang ZB, Liang K, Liu J, Liu Z. Strain-Driven Formal [1,3]-Aryl Shift within Molecular Bows. Angew Chem Int Ed Engl 2023; 62:e202312238. [PMID: 37656430 DOI: 10.1002/anie.202312238] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Revised: 09/01/2023] [Accepted: 09/01/2023] [Indexed: 09/02/2023]
Abstract
Delving into the influence of strain on organic reactions in small molecules at the molecular level can unveil valuable insight into developing innovative synthetic strategies and structuring molecules with superior properties. Herein, we present a molecular-strain engineering approach to facilitate the consecutive [1,2]-aryl shift (formal [1,3]-aryl shift) in molecular bows (MBs) that integrate 1,4-dimethoxy-2,5-cyclohexadiene moieties. By introducing ring strain into MBs through tethering the bow limb, we can harness the intrinsic mechanical forces to drive multistep aryl shifts from the para- to the meta- to the ortho-position. Through the use of precise intramolecular strain, the seemingly impractical [1,3]-aryl shift was realized, resulting in the formation of ortho-disubstituted products. The solvent and temperature play a crucial role in the occurrence of the [1,3]-aryl shift. The free energy calculations with inclusion of solvation support a feasible mechanism, which entails multistep carbocation rearrangements, for the formal [1,3]-aryl shift. By exploring the application of molecular strain in synthetic chemistry, this research offers a promising direction for developing new tools and strategies towards precision organic synthesis.
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Affiliation(s)
- Liang Jiang
- Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang 310027, China
- Key Laboratory of Precise Synthesis of Functional Molecules of Zhejiang Province, Department of Chemistry, School of Science and Research Center for Industries of the Future, Westlake University, Westlake Institute for Advanced Study, 600 Dunyu Road, Hangzhou, Zhejiang 310030, China
| | - Zhen Peng
- Key Laboratory of Precise Synthesis of Functional Molecules of Zhejiang Province, Department of Chemistry, School of Science and Research Center for Industries of the Future, Westlake University, Westlake Institute for Advanced Study, 600 Dunyu Road, Hangzhou, Zhejiang 310030, China
| | - Yimin Liang
- Key Laboratory of Precise Synthesis of Functional Molecules of Zhejiang Province, Department of Chemistry, School of Science and Research Center for Industries of the Future, Westlake University, Westlake Institute for Advanced Study, 600 Dunyu Road, Hangzhou, Zhejiang 310030, China
| | - Zheng-Bin Tang
- Key Laboratory of Precise Synthesis of Functional Molecules of Zhejiang Province, Department of Chemistry, School of Science and Research Center for Industries of the Future, Westlake University, Westlake Institute for Advanced Study, 600 Dunyu Road, Hangzhou, Zhejiang 310030, China
| | - Kejiang Liang
- Key Laboratory of Precise Synthesis of Functional Molecules of Zhejiang Province, Department of Chemistry, School of Science and Research Center for Industries of the Future, Westlake University, Westlake Institute for Advanced Study, 600 Dunyu Road, Hangzhou, Zhejiang 310030, China
| | - Jiali Liu
- Key Laboratory of Precise Synthesis of Functional Molecules of Zhejiang Province, Department of Chemistry, School of Science and Research Center for Industries of the Future, Westlake University, Westlake Institute for Advanced Study, 600 Dunyu Road, Hangzhou, Zhejiang 310030, China
| | - Zhichang Liu
- Key Laboratory of Precise Synthesis of Functional Molecules of Zhejiang Province, Department of Chemistry, School of Science and Research Center for Industries of the Future, Westlake University, Westlake Institute for Advanced Study, 600 Dunyu Road, Hangzhou, Zhejiang 310030, China
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7
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Seeman JI. Revolutions in Chemistry: Assessment of Six 20th Century Candidates (The Instrumental Revolution; Hückel Molecular Orbital Theory; Hückel's 4 n + 2 Rule; the Woodward-Hoffmann Rules; Quantum Chemistry; and Retrosynthetic Analysis). JACS AU 2023; 3:2378-2401. [PMID: 37772184 PMCID: PMC10523497 DOI: 10.1021/jacsau.3c00278] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 08/04/2023] [Accepted: 08/07/2023] [Indexed: 09/30/2023]
Abstract
Six 20th century candidates for revolutions in chemistry are examined, using a definitional scheme published recently by the author. Six groupings of 13 characteristics of revolutions in science are considered: causes and birthings of revolutions, relationships between the old and the new, conceptual qualities of the candidate revolutions, instrumental and methodological functions, social construction of knowledge and practical considerations, and testimonials. The Instrumental Revolution was judged to be a revolution in chemistry because of the enormous increase in community-wide knowledge provided by the new instruments and the intentionality in the identification of specific target instruments, in the mindfulness in their design, manufacture, testing, use, and ultimately commercialization. The Woodward-Hoffmann rules were judged to precipitate the Quantum Chemistry Revolution because of theoretical, practical, and social construction of knowledge characteristics. Neither Hückel molecular orbital theory nor Hückel's 4n + 2 rule was considered an initiator of a revolution in chemistry but rather participants in the Quantum Chemistry Revolution. Retrosynthetic analysis was not judged to initiate a revolution in chemistry.
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Affiliation(s)
- Jeffrey I. Seeman
- Department of Chemistry University of Richmond, Richmond, Virginia 23173, United States
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8
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Tang R, Gao W, Jia Y, Wang K, Datta BK, Zheng W, Zhang H, Xu Y, Lin Y, Weng W. Mechanochemically assisted morphing of shape shifting polymers. Chem Sci 2023; 14:9207-9212. [PMID: 37655017 PMCID: PMC10466301 DOI: 10.1039/d3sc02404k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Accepted: 08/03/2023] [Indexed: 09/02/2023] Open
Abstract
Morphing in creatures has inspired various synthetic polymer materials that are capable of shape shifting. The morphing of polymers generally relies on stimuli-active (typically heat and light active) units that fix the shape after a mechanical load-based shape programming. Herein, we report a strategy that uses a mechanochemically active 2,2'-bis(2-phenylindan-1,3-dione) (BPID) mechanophore as a switching unit for mechanochemical morphing. The mechanical load on the polymer triggers the dissociation of the BPID moiety into stable 2-phenylindan-1,3-dione (PID) radicals, whose subsequent spontaneous dimerization regenerates BPID and fixes the temporary shapes that can be effectively recovered to the permanent shapes by heating. A greater extent of BPID activation, through a higher BPID content or mechanical load, leads to higher mechanochemical shape fixity. By contrast, a relatively mechanochemically less active hexaarylbiimidazole (HABI) mechanophore shows a lower fixing efficiency when subjected to the same programing conditions. Another control system without a mechanophore shows a low fixing efficiency comparable to the HABI system. Additionally, the introduction of the BPID moiety also manifests remarkable mechanochromic behavior during the shape programing process, offering a visualizable indicator for the pre-evaluation of morphing efficiency. Unlike conventional mechanical mechanisms that simultaneously induce morphing, such as strain-induced plastic deformation or crystallization, our mechanochemical method allows for shape programming after the mechanical treatment. Our concept has potential for the design of mechanochemically programmable and mechanoresponsive shape shifting polymers.
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Affiliation(s)
- Rui Tang
- Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University 422 South Siming Road Xiamen Fujian 361005 P. R. China
| | - Wenli Gao
- Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University 422 South Siming Road Xiamen Fujian 361005 P. R. China
| | - Yulin Jia
- Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University 422 South Siming Road Xiamen Fujian 361005 P. R. China
| | - Kai Wang
- Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University 422 South Siming Road Xiamen Fujian 361005 P. R. China
| | - Barun Kumar Datta
- Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University 422 South Siming Road Xiamen Fujian 361005 P. R. China
| | - Wei Zheng
- College of Materials Science, Xiamen University 422 South Siming Road Xiamen Fujian 361005 P. R. China
| | - Huan Zhang
- Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University 422 South Siming Road Xiamen Fujian 361005 P. R. China
| | - Yuanze Xu
- Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University 422 South Siming Road Xiamen Fujian 361005 P. R. China
| | - Yangju Lin
- Department of Chemical Engineering, Stanford University 443 Via Ortega, Stanford California 94305 USA
| | - Wengui Weng
- Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University 422 South Siming Road Xiamen Fujian 361005 P. R. China
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9
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Das A, Datta A. Designing Site Specificity in the Mechanochemical Cargo Release of Small Molecules. J Am Chem Soc 2023. [PMID: 37291056 DOI: 10.1021/jacs.3c05116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Mechanical force can trigger the predictable and precise release of small molecules from macromolecular carriers. In this article, based on mechanochemical simulations, we show that norborn-2-en-7-one (NEO), I, and its derivatives can selectively release CO, N2, and SO2 and produce two distinctly different products, A ((3E,5Z,7E)-dimethyl-5,6-diphenyldeca-3,5,7-triene-1,10-diyl bis(2-bromo-2-methylpropanoate)) and B (4',5'-dimethyl-4',5'-dihydro-[1,1':2',1''-terphenyl]-3',6'-diyl)bis(ethane-2,1-diyl) bis(2-bromo-2-methylpropanoate). Site-specific design in the pulling points (PP) ensures that by changing the regioselectivity, either A or B can be exclusively generated. Controlling the rigidity of the NEO scaffold by replacing a 6-membered ring with an 8-membered ring and concomitantly tuning the pulling groups makes it mechanolabile toward the selective formation of B. The diradical intermediate formed during I → A is predicted to be persistent for ∼150 fs. The structural design holds the key to the trade-off between mechanochemical rigidity and lability.
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Affiliation(s)
- Ankita Das
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A and 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, West Bengal, India
| | - Ayan Datta
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A and 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, West Bengal, India
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10
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Cardosa-Gutierrez M, De Bo G, Duwez AS, Remacle F. Bond breaking of furan-maleimide adducts via a diradical sequential mechanism under an external mechanical force. Chem Sci 2023; 14:1263-1271. [PMID: 36756317 PMCID: PMC9891376 DOI: 10.1039/d2sc05051j] [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] [Received: 09/09/2022] [Accepted: 12/27/2022] [Indexed: 01/06/2023] Open
Abstract
Substituted furan-maleimide Diels-Alder adducts are bound by dynamic covalent bonds that make them particularly attractive mechanophores. Thermally activated [4 + 2] retro-Diels-Alder (DA) reactions predominantly proceed via a concerted mechanism in the ground electronic state. We show that an asymmetric mechanical force along the anchoring bonds in both the endo and exo isomers of proximal dimethyl furan-maleimide adducts favors a sequential pathway. The switching from a concerted to a sequential mechanism occurs at external forces of ≈1 nN. The first bond rupture occurs for a projection of the pulling force on the scissile bond at ≈4.3 nN for the exo adduct and ≈3.8 nN for the endo one. The reaction is inhibited for external forces up to ≈3.4 nN for the endo adduct and 3.6 nN for the exo one after which it is activated. In the activated region, at 4 nN, the rupture rate of the first bond for the endo adduct is computed to be ≈3 orders of magnitude larger than for the exo one in qualitative agreement with recent sonication experiments [Z. Wang and S. L. Craig, Chem. Commun., 2019, 55, 12263-12266]. In the intermediate region of the path between the rupture of the first and the second bond, the lowest singlet state exhibits a diradical character for both adducts and is close in energy to a diradical triplet state. The computed values of spin-orbit coupling along the path are too small for inducing intersystem crossings. These findings open the way for the rational design of DA mechanophores for polymer science and photochemistry.
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Affiliation(s)
| | - Guillaume De Bo
- Department of Chemistry, University of ManchesterManchesterM13 9PLUK
| | - Anne-Sophie Duwez
- UR Molecular Systems, Department of Chemistry, University of Liège 4000 Liège Belgium
| | - Francoise Remacle
- UR Molecular Systems, Department of Chemistry, University of Liège 4000 Liège Belgium
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11
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Craig SL. Concluding remarks: Fundamentals, applications and future of mechanochemistry. Faraday Discuss 2023; 241:485-491. [PMID: 36472143 DOI: 10.1039/d2fd00141a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This paper provides a summary of the Faraday Discussions meeting on "Mechanochemistry: fundamentals, applications, and future" in the context of broad themes whose exploration might contribute to a unified framework of mechanochemical phenomena.
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Affiliation(s)
- Stephen L Craig
- Department of Chemistry, Duke University, Durham, NC 27708-0346, USA.
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12
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Bhuiyan FH, Li YS, Kim SH, Martini A. Shear-activated chemisorption and association of cyclic organic molecules. Faraday Discuss 2023; 241:194-205. [PMID: 36134558 DOI: 10.1039/d2fd00086e] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Mechanochemical activation has created new opportunities for applications such as solvent-free chemical synthesis, polymer processing, and lubrication. However, mechanistic understanding of these processes is still limited because the mechanochemical response of a system is a complex function of many variables, including the direction of applied stress and the chemical features of the reactants in non-equilibrium conditions. Here, we studied shear-activated reactions of simple cyclic organic molecules to isolate the effect of chemical structure on reaction yield and pathway. Reactive molecular dynamics simulations were used to model methylcyclopentane, cyclohexane, and cyclohexene subject to pressure and shear stress between silica surfaces. Cyclohexene was found to be more susceptible to mechanochemical activation of oxidative chemisorption and subsequent oligomerization reactions than either methylcyclopentane or cyclohexane. The oligomerization trend was consistent with shear-driven polymerization yield measured in ball-on-flat sliding experiments. Analysis of the simulations showed the distribution of carbon atom sites at which oxidative chemisorption occurred and identified the double bond in cyclohexene as being the origin of its shear susceptibility. Lastly, the most common reaction pathways for association were identified, providing insight into how the chemical structures of the precursor molecules determined their response to mechanochemical activation.
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Affiliation(s)
- Fakhrul H Bhuiyan
- Department of Mechanical Engineering, University of California Merced, 5200 N. Lake Road, Merced, California 95343, USA.
| | - Yu-Sheng Li
- Department of Chemical Engineering and Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Seong H Kim
- Department of Chemical Engineering and Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Ashlie Martini
- Department of Mechanical Engineering, University of California Merced, 5200 N. Lake Road, Merced, California 95343, USA.
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13
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Küng R, Göstl R, Schmidt BM. Release of Molecular Cargo from Polymer Systems by Mechanochemistry. Chemistry 2021; 28:e202103860. [PMID: 34878679 PMCID: PMC9306765 DOI: 10.1002/chem.202103860] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Indexed: 11/15/2022]
Abstract
The design and manipulation of (multi)functional materials at the nanoscale holds the promise of fuelling tomorrow's major technological advances. In the realm of macromolecular nanosystems, the incorporation of force‐responsive groups, so called mechanophores, has resulted in unprecedented access to responsive behaviours and enabled sophisticated functions of the resulting structures and advanced materials. Among the diverse force‐activated motifs, the on‐demand release or activation of compounds, such as catalysts, drugs, or monomers for self‐healing, are sought‐after since they enable triggering pristine small molecule function from macromolecular frameworks. Here, we highlight examples of molecular cargo release systems from polymer‐based architectures in solution by means of sonochemical activation by ultrasound (ultrasound‐induced mechanochemistry). Important design concepts of these advanced materials are discussed, as well as their syntheses and applications.
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Affiliation(s)
- Robin Küng
- Heinrich-Heine-Univerität Düsseldorf, Department of Chemistry, GERMANY
| | - Robert Göstl
- DWI-Leibniz-Institut für Interaktive Materialien: DWI-Leibniz-Institut fur Interaktive Materialien, Department of Chemistry, GERMANY
| | - Bernd M Schmidt
- Heinrich-Heine-Universitat Dusseldorf, Institute of Organic Chemistry and Macromolecular Chemistry, Universitätsstraße 1, 26.33.U1.R38, 40225, Düsseldorf, GERMANY
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14
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O’Neill RT, Boulatov R. The Contributions of Model Studies for Fundamental Understanding of Polymer Mechanochemistry. Synlett 2021. [DOI: 10.1055/a-1710-5656] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
AbstractThe exciting field of polymer mechanochemistry has made great empirical progress in discovering reactions in which a stretching force accelerates scission of strained bonds using single molecule force spectroscopy and ultrasonication experiments. Understanding why these reactions happen, i.e., the fundamental physical processes that govern coupling of macroscopic motion to chemical reactions, as well as discovering other patterns of mechanochemical reactivity require complementary techniques, which permit a much more detailed characterization of reaction mechanisms and the distribution of force in reacting molecules than are achievable in SMFS or ultrasonication. A molecular force probe allows the specific pattern of molecular strain that is responsible for localized reactions in stretched polymers to be reproduced accurately in non-polymeric substrates using molecular design rather than atomistically intractable collective motions of millions of atoms comprising macroscopic motion. In this review, we highlight the necessary features of a useful molecular force probe and describe their realization in stiff stilbene macrocycles. We describe how studying these macrocycles using classical tools of physical organic chemistry has allowed detailed characterizations of mechanochemical reactivity, explain some of the most unexpected insights enabled by these probes, and speculate how they may guide the next stage of mechanochemistry.
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Affiliation(s)
| | - Roman Boulatov
- Department of Chemistry, University of Liverpool
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University
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15
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Abstract
AbstractThis Account covers the recent progress made on heterocyclic mechanophores in the field of polymer mechanochemistry. In particular, the types of such mechanophores as well as the mechanisms and applications of their force-induced structural transformations are discussed and related perspectives and future challenges proposed.1 Introduction2 Types of Mechanophores3 Methods to Incorporate Heterocycle Mechanophores into Polymer Systems4 Mechanochemical Reactions of Heterocyclic Mechanophores4.1 Three-Membered-Ring Mechanophores4.2 Four-Membered-Ring Mechanophores4.3 Six-Membered-Ring Mechanophores4.4 Bicyclic Mechanophores5 Applications5.1 Cross-Linking of Polymer5.2 Degradable Polymer5.3 Mechanochromic Polymer6 Concluding Remarks and Outlook
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16
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Qi Q, Sekhon G, Chandradat R, Ofodum NM, Shen T, Scrimgeour J, Joy M, Wriedt M, Jayathirtha M, Darie CC, Shipp DA, Liu X, Lu X. Force-Induced Near-Infrared Chromism of Mechanophore-Linked Polymers. J Am Chem Soc 2021; 143:17337-17343. [PMID: 34586805 DOI: 10.1021/jacs.1c05923] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A near-infrared (NIR) mechanophore was developed and incorporated into a poly(methyl acrylate) chain to showcase the first force-induced NIR chromism in polymeric materials. This mechanophore, based on benzo[1,3]oxazine (OX) fused with a heptamethine cyanine moiety, exhibited NIR mechanochromism in solution, thin-film, and bulk states. The mechanochemical activity was validated using UV-vis-NIR absorption/fluorescence spectroscopies, gel permeation chromatography (GPC), NMR, and DFT simulations. Our work demonstrates that NIR mechanochromic polymers have considerable potential in mechanical force sensing, damage detection, bioimaging, and biomechanics.
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Affiliation(s)
| | | | | | | | - Tianruo Shen
- Fluorescence Research Group, Singapore University of Technology and Design, 8 Somapah Road, 487372 Singapore
| | | | | | | | | | | | | | - Xiaogang Liu
- Fluorescence Research Group, Singapore University of Technology and Design, 8 Somapah Road, 487372 Singapore
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