IJAA  Vol.2 No.4 , December 2012
Cyanopolyynes as Organic Molecular Wires in the Interstellar Medium
Abstract: Cyanopolyynes (H[C≡C]n-CN or HC2n+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.
Cite this paper: R. Morales and C. Hernández, "Cyanopolyynes as Organic Molecular Wires in the Interstellar Medium," International Journal of Astronomy and Astrophysics, Vol. 2 No. 4, 2012, pp. 230-235. doi: 10.4236/ijaa.2012.24030.

[1]   E. Herbst and E. F. van Dishoeck, “Complex Organic Interstellar Molecules,” Annual Review of Astronomy and Astrophysics, Vol. 47, No. 1, 2009, pp. 427-480. doi:10.1146/annurev-astro-082708-101654

[2]   J. R. Pardo, J. Cernicharo and J. R. Goicoechea, “Observational Evidence of the Formation of Cyanopolyynes in CRL 618 through the Polymerization of HCN,” Astrophysical Journal, Vol. 628, No. 1, 2005, pp. 275-282. doi:10.1086/430774

[3]   P. M. Woods, T. J. Millar, E. Herbst and A. A. Zijlstra, “The Chemistry of Protoplanetary Nebulae,” Astronomy and Astrophysics, Vol. 402, No. 1, 2003, pp. 189-199. doi:10.1051/0004-6361:20030215

[4]   T. J. Millar, E. Herbst and R. P. A. Bettens, “Large Molecules in the Envelope Surrounding IRC+10216,” Monthly Notices of the Royal Astronomical Society, Vol. 316, No. 1, 2000, pp. 195-203.

[5]   M. A. Cordiner and T. J. Millar, “Density-Enhanced Gas and Dust Shells in a New Chemical Model for IRC+ 10216,” Astrophysical Journal, Vol. 697, No. 1, 2009, pp. 68-78. doi:10.1088/0004-637X/697/1/68

[6]   M. C. McCarthy, W. Chen, M. J. Travers and P. Thaddeus, “Microwave Spectra of 11 Polyyne Carbon Chains,” Astrophysical Journal, Vol. 129, No. 2, 2000, pp. 611-623.

[7]   M. B. Bell, P. A. Feldman, S. Kwok and H. E. Matthews, “Detection of HC11N in IRC+10216,” Nature, Vol. 295, 1982, pp. 389-391. doi:10.1038/295389a0

[8]   M. B. Bell, P. A. Feldman, M. J. Travers, M. C. McCarthy, C. A. Gottlieband and P. Thaddeus, “Detection of HC11N in the Cold Dust Cloud TMC-1,” Astrophysical Journal Letters, Vol. 483, No. 1, 1997, pp. L61-L64. doi:10.1086/310732

[9]   H. W. Kroto, C. Kirby, R. M. Walton, L. W. Avery, N. W. Broten, J. M. MacLeod and T. Oka, “The Detection of Cyanohexatriyne, H(CC3)CN, in Heiles’ Cloud 2,” Astrophysical Journal Letters, Vol. 219, No. 3, 1978, pp. L133-L137.

[10]   D. Smith, “The Ion Chemistry of Interstellar Clouds,” Chemical Reviews, Vol. 92, No. 7, 1992, pp. 1473-1485. doi:10.1021/cr00015a001

[11]   F. L. Carter, “Molecular Electronic Devices,” Marcel Dekker Inc., New York, 1986.

[12]   C. Joachim and S. Roth, “Atomic and Molecular Wires,” Kluwer Academic Publishers, Dordrecht, 1997. doi:10.1007/978-94-011-5882-4

[13]   D. K. James and J. M. Tour, “Molecular Wires,” Topics in Current Chemistry, Vol. 257, 2005, pp. 33-62. doi:10.1007/b136066

[14]   C. Hernández and R. G. E. Morales, “Bridge Effect in Charge-Transfer Photoconduction Channels. 1. Aromatic Carbonyl Compounds,” Journal of Physical Chemistry, Vol. 97, No. 45, 1993, pp. 11649-11651. doi:10.1021/j100147a016

[15]   R. G. E. Morales and C. González-Rojas, “Dipole Moments of Polyenic Oligomeric Systems. Part I. A One-Dimensional Molecular Wire Model,” Journal of Physical Organic Chemistry, Vol.11, No. 12, 1998, pp. 853- 856. doi:10.1002/(SICI)1099-1395(199812)11:12<853::AID-POC74>3.0.CO;2-Y

[16]   C. González and R. G. E. Morales, “Molecular Resistivities in Organic Polyenic Wires. I. A One-Dimensional Photoconduction Charge Transfer Model,” Chemical Physics, Vol. 250, No. 3, 1999, pp. 279-284. doi:10.1016/S0301-0104(99)00335-3

[17]   R. G. E. Morales and C. González-Rojas, “Dipole Moments of Polyenic Oligomeric Systems. Part II. Molecular Organic Wire Resistivities: Polyacetylenes, Allenes and Polylines,” Journal of Physical Organic Chemistry, Vol. 18, No. 9, 2005, pp. 941-944. doi:10.1002/poc.931

[18]   R. Landauer, “Electrical Resistance of Disordered One-Dimensional Lattices,” Philosophical Magazine, Vol. 21, No. 172, 1970, pp. 863-867. doi:10.1080/14786437008238472

[19]   D. R., Lide, “CRC Handbook of Chemistry and Physics,” 85th Edition, CRC Press Inc., Boca Ranton, 2004, pp. 12-234.

[20]   M. G. Kanatzidis, “Polymeric Electrical Conductors,” Chemical Engineering News, Vol. 68, No. 49, 1990, pp. 36-54. doi:10.1021/cen-v068n049.p036