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Room-temperature chemical synthesis of C₂.

ABSTRACT: Diatomic carbon (C₂) is historically an elusive chemical species. It has long been believed that the generation of C₂ requires extremely high physical energy, such as an electric carbon arc or multiple photon excitation, and so it has been the general consensus that the inherent nature of C₂ in the ground state is experimentally inaccessible. Here, we present the chemical synthesis of C₂ from a hypervalent alkynyl-?³-iodane in a flask at room temperature or below, providing experimental evidence to support theoretical predictions that C₂ has a singlet biradical character with a quadruple bond, thus settling a long-standing controversy between experimental and theoretical chemists, and that C₂ serves as a molecular element in the bottom-up chemical synthesis of nanocarbons such as graphite, carbon nanotubes, and C₆₀.

SUBMITTER: Miyamoto K

PROVIDER: S-EPMC7195449 | biostudies-literature | 2020 May

REPOSITORIES: biostudies-literature

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Room-temperature chemical synthesis of C2.

Miyamoto Kazunori K Narita Shodai S Masumoto Yui Y Hashishin Takahiro T Osawa Taisei T Kimura Mutsumi M Ochiai Masahito M Uchiyama Masanobu M

Nature communications 20200501 1

Diatomic carbon (C2) is historically an elusive chemical species. It has long been believed that the generation of C2 requires extremely high physical energy, such as an electric carbon arc or multiple photon excitation, and so it has been the general consensus that the inherent nature of C2 in the ground state is experimentally inaccessible. Here, we present the chemical synthesis of C2 from a hypervalent alkynyl-λ3-iodane in a flask at roo ...[more]

PMID: 32358541

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Project description:Fluorescent proteins (FPs) have revolutionized cell biology by allowing genetic tagging of specific proteins inside living cells. In conjunction with Förster's resonance energy transfer (FRET) measurements, FP-tagged proteins can be used to study protein-protein interactions and estimate distances between tagged proteins. FRET is mediated by weak Coulombic dipole-dipole coupling of donor and acceptor fluorophores that behave independently, with energy hopping discretely and incoherently between fluorophores. Stronger dipole-dipole coupling can mediate excitonic coupling in which excitation energy is distributed near instantaneously between coherently interacting excited states that behave as a single quantum entity. The interpretation of FP energy transfer measurements to estimate separation often assumes that donors and acceptors are very weakly coupled and therefore use a FRET mechanism. This assumption is considered reasonable as close fluorophore proximity, typically associated with strong excitonic coupling, is limited by the FP β-barrel structure. Furthermore, physiological temperatures promote rapid vibrational dephasing associated with a rapid decoherence of fluorophore-excited states. Recently, FP dephasing times that are 50 times slower than traditional organic fluorophores have been measured, raising the possibility that evolution has shaped FPs to allow stronger than expected coupling under physiological conditions. In this study, we test if excitonic coupling between FPs is possible at physiological temperatures. FRET and excitonic coupling can be distinguished by monitoring spectral changes associated with fluorophore dimerization. The weak coupling mediating FRET should not cause a change in fluorophore absorption, whereas strong excitonic coupling causes Davydov splitting. Circular dichroism spectroscopy revealed Davydov splitting when the yellow FP VenusA206 dimerizes, and a novel approach combining photon antibunching and fluorescence correlation spectroscopy was used to confirm that the two fluorophores in a VenusA206 homodimer behave as a single-photon emitter. We conclude that excitonic coupling between VenusA206 fluorophores is possible at physiological temperatures.

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Room-temperature chemical synthesis of C₂.

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Room-temperature chemical synthesis of C<sub>2</sub>.

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