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Synthesis and Properties of Open Fullerenes Encapsulating Ammonia and Methane.

ABSTRACT: We describe the synthesis and characterisation of open fullerene (1) and its reduced form (2) in which CH₄ and NH₃ are encapsulated, respectively. The ¹ H?NMR resonance of endohedral NH₃ is broadened by scalar coupling to the quadrupolar ¹⁴ N nucleus, which relaxes rapidly. This broadening is absent for small satellite peaks, which are attributed to natural abundance ¹⁵ N. The influence of the scalar relaxation mechanism on the linewidth of the ¹ H ammonia resonance is probed by variable temperature NMR. A rotational correlation time of ?_c =1.5?ps. is determined for endohedral NH₃ , and of ?_c =57±5?ps. for the open fullerene, indicating free rotation of the encapsulated molecule. IR spectroscopy of NH₃ @2 at 5?K identifies three vibrations of NH₃ (?₁ , ?₃ and ?₄ ) redshifted in comparison with free NH₃ , and temperature dependence of the IR peak intensity indicates the presence of a large number of excited translational/ rotational states. Variable temperature ¹ H?NMR spectra indicate that endohedral CH₄ is also able to rotate freely at 223?K, on the NMR timescale. Inelastic neutron scattering (INS) spectra of CH₄ @1 show both rotational and translational modes of CH₄ . Energy of the first excited rotational state (J=1) of CH₄ @1 is significantly lower than that of free CH₄ .

SUBMITTER: Bloodworth S

PROVIDER: S-EPMC5838534 | biostudies-literature | 2018 Feb

REPOSITORIES: biostudies-literature

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Synthesis and Properties of Open Fullerenes Encapsulating Ammonia and Methane.

Bloodworth Sally S Gräsvik John J Alom Shamim S Kouřil Karel K Elliott Stuart J SJ Wells Neil J NJ Horsewill Anthony J AJ Mamone Salvatore S Jiménez-Ruiz Mónica M Rols Stéphane S Nagel Urmas U Rõõm Toomas T Levitt Malcolm H MH Whitby Richard J RJ

Chemphyschem : a European journal of chemical physics and physical chemistry 20180104 3

We describe the synthesis and characterisation of open fullerene (1) and its reduced form (2) in which CH4 and NH3 are encapsulated, respectively. The 1 H NMR resonance of endohedral NH3 is broadened by scalar coupling to the quadrupolar 14 N nucleus, which relaxes rapidly. This broadening is absent for small satellite peaks, which are attributed to natural abundance 15 N. The influence of the scalar relaxation mechanism on the li ...[more]

PMID: 29131544

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Project description:Supramolecular chemistry allows the construction of complex molecular architectures and the design of collective photophysical properties. DNA is an attractive template to build such supramolecular architectures due to its helical structure, the defined distances between the bases and the canonical base pairing that results in precise control of the chromophore position. The tailored properties of DNA-templated supramolecules eventually allow their implementation into optoelectronic applications. For the generation of free charge carriers from photo-generated excitons, fullerenes can be utilized. We synthesized two fullerene derivates, one of which binds by electrostatic interactions to single-stranded DNA, while the other contains two 2'-deoxyuridine moieties and assembles specifically along oligo-2'-deoxyadenosines (dA20) as DNA template. The DNA-directed assembly of both fullerenes in aqueous solution was investigated by UV/Vis absorbance and circular dichroism (CD) spectroscopy. The specific interactions with DNA make fullerenes with the 2'-deoxyuridine moieties a significantly better component for supramolecular DNA architectures. We studied the fluorescence quenching of both fullerenes with a DNA chromophore assembly. To investigate one of the key properties for optoelectronic applications, that is the supramolecular structure of the DNA-based assemblies in the solid phase, we characterized the CD of supramolecular chromophore-DNA architectures in thin films. Remarkably, the helical chirality of the chromophore assemblies that is induced by the DNA template is conserved even in the solid state. Upon implementation into organic solar cells, the external quantum efficiency measurements showed charge carrier generation on all three chromophore components of the DNA assemblies. The fullerenes with the 2'-deoxyuridine moieties enhance the quantum efficiency of the conversion process significantly, demonstrating the potential of DNA as structural element for ordering chromophores into functional π-systems, which may be employed in future organic solar cells.

Dataset Information

Synthesis and Properties of Open Fullerenes Encapsulating Ammonia and Methane.

Publications

Synthesis and Properties of Open Fullerenes Encapsulating Ammonia and Methane.

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