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Carbon nanotubes, from the electronic structure of the smallest building unit [n]cyclacene to their application as energy storage devices: a summary of my research at the LCPQ

Stefano Battaglia, LCPQ (Toulouse)

Salle de séminaire IRSAMC, Jeudi 2 Février, 14h - 15h

Since their experimental discovery in 1991,[1] carbon nanotubes (CNT) have been actively studied by both physicists and chemists. This material features a set of interesting properties that can be exploited for applications spanning across several fields. Nonetheless, although much advancement has been done since 1991, still many challenges remain for both theory and experiment and new original applications can always be found.

In this seminar I will summarize the research that I have been carrying out at the LCPQ in the last year and a half and I will present the results achieved so far. In particular, the seminar will be divided into two parts concerning I) a theoretical study on [n]cyclacenes and II) the application of CNT as storage devices for highly energetic nitrogen compounds.
I) [n]cyclacenes, the smallest building unit of zigzag CNT, have challenged many researchers during the last 20 years. Their experimental synthesis has not been achieved yet,[2] and their open-shell nature still poses difficulties in a theoretical description at a quantum chemical level.[3,4⁠] In this part of the seminar I will present a study on the singlet-triplet energy gap and the polyradical character of this molecule as a function of the system size.[5]
II) Polynitrogen compounds have been proposed as high energy-density material because of the incredible energetic difference between single, double and triple bonds. However, their instability at ambient conditions is a limiting factor for their application. In the second part of the seminar I will discuss a possible solution to stabilize them through molecular confinement inside carbon nanotubes and present the results of quantum chemical calculations for the N3- anion and the N5+ cation.

[1] Iijima, S. Helical Microtubules of Graphitic Carbon. Nature 1991, 354 (6348), 56–58.
[2] Omachi, H.; Segawa, Y.; Itami, K. Synthesis of Cycloparaphenylenes and Related Carbon Nanorings: A Step toward the Controlled Synthesis of Carbon Nanotubes. Acc. Chem. Res. 2012, 45 (8), 1378–1389.
[3] Chen, Z.; Jiang, D. E.; Lu, X.; Bettinger, H. F.; Dai, S.; Schleyer, P. von R.; Houk, K. N. Open-Shell Singlet Character of Cyclacenes and Short Zigzag Nanotubes. Org. Lett. 2007, 9 (26), 5449–5452.
[4] Sadowsky, D.; McNeill, K.; Cramer, C. J. Electronic Structures of [N]-Cyclacenes (n=6-12) and Short, Hydrogen-Capped, Carbon Nanotubules. Faraday Discuss. 2010, 145, 507–521.
[5] Battaglia, S.; Andrae, D.; Faginas-Lago, N.; Evangelisti, S.; Leininger, T. Increasing Radical Character of Large [n]cyclacenes Unveiled by Wavefunction Theory. Submitted.