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Meador WE, Saucier MA, Tucker MR, Kruse NA, Mobley AJ, Brower CR, Parkin SR, Clark KM, Hammer NI, Tschumper GS, Delcamp JH. Extended shortwave infrared absorbing antiaromatic fluorenium-indolizine chromophores. Chem Sci 2024; 15:12349-12360. [PMID: 39118622 PMCID: PMC11304523 DOI: 10.1039/d4sc00733f] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2024] [Accepted: 05/21/2024] [Indexed: 08/10/2024] Open
Abstract
Shortwave infrared (SWIR, 1000-1700 nm) and extended SWIR (ESWIR, 1700-2700 nm) absorbing materials are valuable for applications including fluorescence based biological imaging, photodetectors, and light emitting diodes. Currently, ESWIR absorbing materials are largely dominated by inorganic semiconductors which are often costly both in raw materials and manufacturing processes used to produce them. The development of ESWIR absorbing organic molecules is thus of interest due to the tunability, solution processability, and low cost of organic materials compared to their inorganic counterparts. Herein, through the combination of heterocyclic indolizine donors and an antiaromatic fluorene core, a series of organic chromophores with absorption maxima ranging from 1470-2088 nm (0.84-0.59 eV) and absorption onsets ranging from 1693-2596 nm (0.73-0.48 eV) are designed and synthesized. The photophysical and electrochemical properties of these chromophores, referred to as FluIndz herein, are described via absorption spectroscopy in 17 solvents, cyclic voltammetry, solution photostability, and transient absorption spectroscopy. Molecular orbital energies, predicted electronic transitions, and antiaromaticity are compared to higher energy absorbing chromophores using density functional theory. The presence of thermally accessible diradical states is demonstrated using density functional theory and EPR spectroscopy, while XRD crystallography confirms structural connectivity and existence as a single molecule. Overall, the FluIndz chromophore scaffold exhibits a rational means to access organic chromophores with extremely narrow optical gaps.
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Affiliation(s)
- William E Meador
- University of Mississippi, Department of Chemistry and Biochemistry Coulter Hall, University MS 38677 USA
| | - Matthew A Saucier
- University of Mississippi, Department of Chemistry and Biochemistry Coulter Hall, University MS 38677 USA
| | - Max R Tucker
- University of Mississippi, Department of Chemistry and Biochemistry Coulter Hall, University MS 38677 USA
| | - Nicholas A Kruse
- University of Mississippi, Department of Chemistry and Biochemistry Coulter Hall, University MS 38677 USA
| | - Alexander J Mobley
- University of Mississippi, Department of Chemistry and Biochemistry Coulter Hall, University MS 38677 USA
| | - Connor R Brower
- University of Mississippi, Department of Chemistry and Biochemistry Coulter Hall, University MS 38677 USA
| | - Sean R Parkin
- Department of Chemistry, University of Kentucky Lexington Kentucky 40506 USA
| | - Kensha M Clark
- University of Mississippi, Department of Chemistry and Biochemistry Coulter Hall, University MS 38677 USA
| | - Nathan I Hammer
- University of Mississippi, Department of Chemistry and Biochemistry Coulter Hall, University MS 38677 USA
| | - Gregory S Tschumper
- University of Mississippi, Department of Chemistry and Biochemistry Coulter Hall, University MS 38677 USA
| | - Jared H Delcamp
- University of Mississippi, Department of Chemistry and Biochemistry Coulter Hall, University MS 38677 USA
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2
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Salikov RF, Belyy AY, Ilyushchenko MK, Platonov DN, Sokolova AD, Tomilov YV. Antiaromaticity of Cycloheptatrienyl Anions: Structure, Acidity, and Magnetic Properties. Chemistry 2024; 30:e202401041. [PMID: 38785416 DOI: 10.1002/chem.202401041] [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: 03/14/2024] [Revised: 05/23/2024] [Accepted: 05/24/2024] [Indexed: 05/25/2024]
Abstract
Investigations of the nature and degree of antiaromaticity of cycloheptatrienyl anion derivatives using both experimental and computational tools are presented. The ground state of cycloheptatrienyl anion in the gas phase is triplet, planar and Baird-aromatic. In DMSO, it assumes a singlet distorted allylic form with a paratropic ring current. The other derivatives in both phases assume either allylic or diallylic conformations depending on the substituent pattern. A combination of experimental and computational methods was used to determine the pKa values of 16 derivatives in DMSO, which ranged from 36 to -10.7. We revealed that the stronger stabilization of the anionic system, which correlates with acidity, does not necessarily imply a lower degree of antiaromaticity in terms of magnetic properties. Conversely, the substitution pattern first affects the geometry of the ring through the bulkiness of the substituents and their better conjugation with a more distorted system. Consequently, the distortion reduces the cyclic conjugation in the π-system and thereby decreases the paratropic current in a magnetic field, which manifests itself as a decrease in the NICS. The triplet-state geometries and magnetic properties are nearly independent on the substitution pattern, which is typical for simple aromatic systems.
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Affiliation(s)
- Rinat F Salikov
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., Moscow, 119991, Russian Federation
- Department of Chemistry, Higher School of Economics National Research University, Moscow, 101000, Russian Federation
| | - Alexander Y Belyy
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., Moscow, 119991, Russian Federation
| | - Matvey K Ilyushchenko
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., Moscow, 119991, Russian Federation
| | - Dmitry N Platonov
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., Moscow, 119991, Russian Federation
| | - Alena D Sokolova
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., Moscow, 119991, Russian Federation
| | - Yury V Tomilov
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., Moscow, 119991, Russian Federation
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Greis K, Kirschbaum C, Ober K, Taccone MI, Torres-Boy A, Meijer G, Pagel K, von Helden G. Infrared Spectroscopy of Fluorenyl Cations at Cryogenic Temperatures. J Phys Chem Lett 2023; 14:11313-11317. [PMID: 38064287 PMCID: PMC10749476 DOI: 10.1021/acs.jpclett.3c02928] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Revised: 12/01/2023] [Accepted: 12/05/2023] [Indexed: 12/22/2023]
Abstract
The notion of (anti)aromaticity is a successful concept in chemistry to explain the structure and stability of polycyclic hydrocarbons. Cyclopentadienyl and fluorenyl cations are among the most studied classical antiaromatic systems. In this work, fluorenyl cations are investigated by high-resolution gas-phase infrared spectroscopy in helium droplets. Bare fluorenyl cations are generated in the gas phase by electrospray ionization. After mass-to-charge selection, ions are captured in ultracold helium nanodroplets and probed by infrared spectroscopy using a widely tunable free-electron laser in the 600-1700 cm-1 range. The highly resolved cryogenic infrared spectra confirm, in combination with DFT computations, that all cations are present in their singlet states.
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Affiliation(s)
- Kim Greis
- Fritz
Haber Institute of the Max Planck Society, Berlin, Faradayweg 4-6, 14195 Berlin, Germany
- Institute
of Chemistry and Biochemistry, Freie Universität
Berlin, Altensteinstraße 23A, 14195 Berlin, Germany
| | - Carla Kirschbaum
- Fritz
Haber Institute of the Max Planck Society, Berlin, Faradayweg 4-6, 14195 Berlin, Germany
- Institute
of Chemistry and Biochemistry, Freie Universität
Berlin, Altensteinstraße 23A, 14195 Berlin, Germany
| | - Katja Ober
- Fritz
Haber Institute of the Max Planck Society, Berlin, Faradayweg 4-6, 14195 Berlin, Germany
| | - Martín I. Taccone
- Fritz
Haber Institute of the Max Planck Society, Berlin, Faradayweg 4-6, 14195 Berlin, Germany
| | - América
Y. Torres-Boy
- Fritz
Haber Institute of the Max Planck Society, Berlin, Faradayweg 4-6, 14195 Berlin, Germany
| | - Gerard Meijer
- Fritz
Haber Institute of the Max Planck Society, Berlin, Faradayweg 4-6, 14195 Berlin, Germany
| | - Kevin Pagel
- Fritz
Haber Institute of the Max Planck Society, Berlin, Faradayweg 4-6, 14195 Berlin, Germany
- Institute
of Chemistry and Biochemistry, Freie Universität
Berlin, Altensteinstraße 23A, 14195 Berlin, Germany
| | - Gert von Helden
- Fritz
Haber Institute of the Max Planck Society, Berlin, Faradayweg 4-6, 14195 Berlin, Germany
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Rygus JPG, Hall DG. Direct nucleophilic and electrophilic activation of alcohols using a unified boron-based organocatalyst scaffold. Nat Commun 2023; 14:2563. [PMID: 37142592 PMCID: PMC10160031 DOI: 10.1038/s41467-023-38228-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Accepted: 04/18/2023] [Indexed: 05/06/2023] Open
Abstract
Organocatalytic strategies for the direct activation of hydroxy-containing compounds have paled in comparison to those applicable to carbonyl compounds. To this end, boronic acids have emerged as valuable catalysts for the functionalization of hydroxy groups in a mild and selective fashion. Distinct modes of activation in boronic acid-catalyzed transformations are often accomplished by vastly different catalytic species, complicating the design of broadly applicable catalyst classes. Herein, we report the use of benzoxazaborine as a general scaffold for the development of structurally related yet mechanistically divergent catalysts for the direct nucleophilic and electrophilic activation of alcohols under ambient conditions. The utility of these catalysts is demonstrated in the monophosphorylation of vicinal diols and the reductive deoxygenation of benzylic alcohols and ketones respectively. Mechanistic studies of both processes reveal the contrasting nature of key tetravalent boron intermediates in the two catalytic manifolds.
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Affiliation(s)
- Jason P G Rygus
- Department of Chemistry, Centennial Center for Interdisciplinary Science, University of Alberta, Edmonton, AB, T6G 2G2, Canada
| | - Dennis G Hall
- Department of Chemistry, Centennial Center for Interdisciplinary Science, University of Alberta, Edmonton, AB, T6G 2G2, Canada.
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Duvinage D, Mebs S, Beckmann J. Isolation of an Antiaromatic 9-Hydroxy Fluorenyl Cation. Chemistry 2021; 27:8105-8109. [PMID: 33835609 PMCID: PMC8252458 DOI: 10.1002/chem.202100786] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Indexed: 11/12/2022]
Abstract
Fluorenyl cations are textbook examples of 4π electron antiaromatic five-membered ring systems. So far, they were reported only as short-lived intermediates generated under superacidic conditions or by flash photolysis. Attempts to prepare a m-terphenyl acylium cation by fluoride abstraction from a benzoyl fluoride gave rise to an isolable 9-hydroxy fluorenyl cation that formed by an intramolecular electrophilic attack at a flanking mesityl group prior to a 1,2-methyl shift and proton transfer to oxygen.
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Affiliation(s)
- Daniel Duvinage
- Institut für Anorganische Chemie und KristallographieUniversität BremenLeobener Straße 728359BremenGermany
| | - Stefan Mebs
- Institut für ExperimentalphysikFreie Universität BerlinArnimallee 1414195BerlinGermany
| | - Jens Beckmann
- Institut für Anorganische Chemie und KristallographieUniversität BremenLeobener Straße 728359BremenGermany
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