Cyanopolyynes as Organic Molecular Wires in the Interstellar Medium

Raul G. E. Morales, Carlos Hernández

Centre for Environmental Sciences and Department of Chemistry Faculty of Sciences, Universidad de Chile, Santiago, Chile.
Department of Chemistry, Faculty of Basic Sciences Universidad Metropolitana de Ciencias de la Educación, Santiago, Chile.

DOI: 10.4236/ijaa.2012.24030                

Abstract

Cyanopolyynes (H[C≡C]_n-CN or HC_2n+1N, where n = 1, 2, 3, …, n) are commonly observed in the interstellar medium (ISM) as well as in the envelopes of carbon-rich stars. These linear molecular structures can be well described with a one-dimensional conduction model, which considers the scattering processes of electrons through the charge transfer conduction bridge of the H[C≡C]_n-molecular wire containing the CN group as an electron-acceptor terminal unit. Therefore, our results using this model enable a better understanding of the longest molecules observed in interstellar space and provide new insight into why these particular cyanopolyynes reach a maximum length, such as is observed from astronomical experimental spectral data and cosmological chemical models. Dipole moments and geometrical parameters of these cyanopolyynes were obtained from ab initio molecular orbital calculations using the restricted Hartree-Fock approach and 6-311G* basis set, in order to obtain the inner resistance as a new parameter of chemical reaction feasibility for this molecular series. Using this last molecular parameter, we have been able to analyze the possibility of identifying long molecular species that can be found under local thermodynamic equilibrium in some ISM such us HC₂₅H, HC₂₇H, and HC₂₉N, which have not been observed at present.

Keywords

Cyanopolyynes Structures; Dipole Moments; Inner Molecular Resistances; Organic Molecular Wires; ISM Radial Column Density

Conflicts of Interest

The authors declare no conflicts of interest.

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