Searches for bridged bicyclic molecules in space-norbornadiene and its cyano derivatives
Journal article, 2023

The norbornadiene (NBD) molecule, C7H8, owes its fame to its remarkable photoswitching properties that are promising for molecular solar-thermal energy storage systems. Besides this photochemical interest, NBD is a rather unreactive species within astrophysical conditions and it should exhibit high photostability, properties that might also position this molecule as an important constituent of the interstellar medium (ISM)-especially in environments that are well shielded from short-wavelength radiation, such as dense molecular clouds. It is thus conceivable that, once formed, NBD can survive in dense molecular clouds and act as a carbon sink. Following the recent interstellar detections of large hydrocarbons, including several cyano-containing ones, in the dense molecular cloud TMC-1, it is thus logical to consider searching for NBD-which presents a shallow but non-zero permanent electric dipole moment (0.06 D)-as well as for its mono- and dicyano-substituted compounds, referred to as CN-NBD and DCN-NBD, respectively. The pure rotational spectra of NBD, CN-NBD, and DCN-NBD have been measured at 300 K in the 75-110 GHz range using a chirped-pulse Fourier-transform millimetre-wave spectrometer. Of the three species, only NBD was previously studied at high resolution in the microwave domain. From the present measurements, the derived spectroscopic constants enable prediction of the spectra of all three species at various rotational temperatures (up to 300 K) in the spectral range mapped at high resolution by current radio observatories. Unsuccessful searches for these molecules were conducted toward TMC-1 using the QUIJOTE survey, carried out at the Yebes telescope, allowing derivation of the upper limits to the column densities of 1.6 x 10(14) cm(-2), 4.9 x 10(10) cm(-2), and 2.9 x 10(10) cm(-2) for NBD, CN-NBD, and DCN-NBD, respectively. Using CN-NBD and cyano-indene as proxies for the corresponding bare hydrocarbons, this indicates that-if present in TMC-1-NBD would be at least four times less abundant than indene.

Author

Marie-Aline Martin-Drumel

University Paris-Saclay

Jean-Thibaut Spaniol

University Paris-Saclay

Helen Hölzel

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry

Marcelino Agundez

Spanish National Research Council (CSIC)

Jose Cernicharo

Spanish National Research Council (CSIC)

Kasper Moth-Poulsen

Institute of Material Science of Barcelona (ICMAB)

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry

Catalan Institution for Research and Advanced Studies

Polytechnic University of Catalonia

Ugo Jacovella

University Paris-Saclay

Faraday Discussions

1359-6640 (ISSN) 1364-5498 (eISSN)

Vol. 245 284-297

Photo Thermal Management Materials.Acronym: PHOTERM

European Commission (EC) (EC/H202/101002131), 2021-10-01 -- 2026-09-30.

Molecular Solar Thermal energy storage systems (MOST)

Swedish Energy Agency (2019-010724), 2019-05-07 -- 2019-09-03.

European Commission (EC) (EC/H2020/951801), 2020-09-01 -- 2024-02-29.

Subject Categories

Astronomy, Astrophysics and Cosmology

Atom and Molecular Physics and Optics

Theoretical Chemistry

DOI

10.1039/d3fd00016h

PubMed

37305958

More information

Latest update

3/7/2024 9