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Sanchez A, Gurajapu A, Guo W, Kong WY, Laconsay CJ, Settineri NS, Tantillo DJ, Maimone TJ. A Shapeshifting Roadmap for Polycyclic Skeletal Evolution. J Am Chem Soc 2023. [PMID: 37279177 DOI: 10.1021/jacs.3c03960] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Polycyclic ring systems are ubiquitous three-dimensional (3D) structural motifs central to the function of many biologically active small molecules and organic materials. Indeed, subtle changes to the overall molecular shape and connectivity of atoms in a polycyclic framework (i.e., isomerism) can drastically alter its function and properties. Unfortunately, direct evaluation of these structure-function relationships typically requires the development of distinct synthetic strategies toward a specific isomer. Dynamic, "shapeshifting" carbon cages present a promising approach for sampling isomeric chemical space but are often difficult to control and are largely limited to thermodynamic mixtures of positional isomers about a single core scaffold. Here, we describe the development of a new shapeshifting C9-chemotype and a chemical blueprint for its evolution into structurally and energetically diverse isomeric ring systems. By leveraging the unique molecular topology of π-orbitals interacting through-space (homoconjugation), a common skeletal ancestor evolved into a complex network of valence isomers. This unusual system represents an exceedingly rare small molecule capable of undergoing controllable and continuous isomerization processes through the iterative use of just two chemical steps (light and organic base). Computational and photophysical studies of the isomer network provide fundamental insight into the reactivity, mechanism, and role of homoconjugative interactions. Importantly, these insights may inform the rational design and synthesis of new dynamic, shapeshifting systems. We anticipate this process could be a powerful tool for the synthesis of structurally diverse, isomeric polycycles central to many bioactive small molecules and functional organic materials.
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Affiliation(s)
- Andre Sanchez
- Department of Chemistry, University of California-Berkeley, 826 Latimer Hall, Berkeley, California 94720, United States
| | - Anjali Gurajapu
- Department of Chemistry, University of California-Berkeley, 826 Latimer Hall, Berkeley, California 94720, United States
| | - Wentao Guo
- Department of Chemistry, University of California-Davis, 1 Shields Ave, Davis, California 95616, United States
| | - Wang-Yeuk Kong
- Department of Chemistry, University of California-Davis, 1 Shields Ave, Davis, California 95616, United States
| | - Croix J Laconsay
- Department of Chemistry, University of California-Davis, 1 Shields Ave, Davis, California 95616, United States
| | - Nicholas S Settineri
- Department of Chemistry, University of California-Berkeley, 826 Latimer Hall, Berkeley, California 94720, United States
| | - Dean J Tantillo
- Department of Chemistry, University of California-Davis, 1 Shields Ave, Davis, California 95616, United States
| | - Thomas J Maimone
- Department of Chemistry, University of California-Berkeley, 826 Latimer Hall, Berkeley, California 94720, United States
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Jorner K, Jahn BO, Bultinck P, Ottosson H. Triplet state homoaromaticity: concept, computational validation and experimental relevance. Chem Sci 2018; 9:3165-3176. [PMID: 29732099 PMCID: PMC5916107 DOI: 10.1039/c7sc05009g] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Accepted: 02/16/2018] [Indexed: 01/15/2023] Open
Abstract
Conjugation through space can give rise to aromaticity in the lowest excited triplet state, with impact for photochemistry.
Cyclic conjugation that occurs through-space and leads to aromatic properties is called homoaromaticity. Here we formulate the homoaromaticity concept for the triplet excited state (T1) based on Baird's 4n rule and validate it through extensive quantum-chemical calculations on a range of different species (neutral, cationic and anionic). By comparison to well-known ground state homoaromatic molecules we reveal that five of the investigated compounds show strong T1 homoaromaticity, four show weak homoaromaticity and two are non-aromatic. Two of the compounds have previously been identified as excited state intermediates in photochemical reactions and our calculations indicate that they are also homoaromatic in the first singlet excited state. Homoaromaticity should therefore have broad implications in photochemistry. We further demonstrate this by computational design of a photomechanical “lever” that is powered by relief of homoantiaromatic destabilization in the first singlet excited state.
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Affiliation(s)
- Kjell Jorner
- Department of Chemistry - Ångström Laboratory , Uppsala University , Box 523 , 751 20 Uppsala , Sweden .
| | - Burkhard O Jahn
- Department of Chemistry - Ångström Laboratory , Uppsala University , Box 523 , 751 20 Uppsala , Sweden . .,SciClus GmbH & Co. KG , Moritz-von-Rohr-Str. 1a , 07745 Jena , Germany
| | - Patrick Bultinck
- Department of Chemistry , Ghent University , Krijgslaan 281 (S3) , 9000 Gent , Belgium .
| | - Henrik Ottosson
- Department of Chemistry - Ångström Laboratory , Uppsala University , Box 523 , 751 20 Uppsala , Sweden .
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Wentrup C. Roger F. C. Brown Memorial Issue. Aust J Chem 2014. [DOI: 10.1071/ch14419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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