π-Conjugation and End Group Effects in Long Cumulenes: Raman Spectroscopy and DFT Calculations

Tommasini M, Milani A, Fazzi D, Lucotti A, Castiglioni C, Januszewski J, Wendinger D, Tykwinski R (2014)

Publication Type: Journal article

Publication year: 2014

Journal

Journal of Physical Chemistry C American Chemical Society

Book Volume: 118

Pages Range: 26415-26425

Journal Issue: 45

DOI: 10.1021/jp509724d

Abstract

We have investigated the structure and spectroscopic properties of cumulenic carbon chains, focusing on the peculiar \textgreekp-conjugation properties and end-group effects that influence their behavior. With support from Density Functional Theory (DFT) calculations, we have analyzed the IR and Raman spectra of cumulenes characterized by different end-capping groups and we have related them to the bond length alternation (BLA) pattern and local spectroscopic parameters associated with the CC bonds along the sp-carbon chain. For cumulenes we observe a breakdown of the correlation existing in polyynes among frequencies, Raman intensities of the R line (longitudinal CC stretching modes), and BLA. While the low line frequency and equalized CC bonds would indicate the ``metallic'' character of cumulenic species, we obtain an unusually strong Raman intensity, which is typical of bond-alternated (semiconductive) structures. DFT calculations reveal that this is a consequence of \textgreekp-electron conjugation, which markedly extends from the sp-carbon chain to the aryl rings belonging to the end groups. These findings suggest the existence of a strong electronic, vibrational and structural coupling between sp-carbon chains and sp2-carbon species, which could play a key role in nanostructured sp/sp2-hybrid carbon materials (e.g., linear carbon chains coupled to graphene domains). Within this context, Raman spectroscopy is a valuable tool for the detailed characterization of the molecular properties of this kind of materials.

Authors with CRIS profile

Johanna Januszewski Lehrstuhl für Organische Chemie I Dominik Wendinger Sonderforschungsbereich 953/3 Synthetische Kohlenstoffallotrope Rik Tykwinski Lehrstuhl für Organische Chemie I

Additional Organisation(s)

Exzellenz-Cluster Engineering of Advanced Materials

Involved external institutions

Politecnico di Milano IT Italy (IT) Max-Planck-Institut für Kohlenforschung (MPI KoFo) / Max Planck Institute for Coal Research DE Germany (DE)

How to cite

APA:

Tommasini, M., Milani, A., Fazzi, D., Lucotti, A., Castiglioni, C., Januszewski, J.,... Tykwinski, R. (2014). π-Conjugation and End Group Effects in Long Cumulenes: Raman Spectroscopy and DFT Calculations. Journal of Physical Chemistry C, 118(45), 26415-26425. https://dx.doi.org/10.1021/jp509724d

MLA:

Tommasini, Matteo, et al. "π-Conjugation and End Group Effects in Long Cumulenes: Raman Spectroscopy and DFT Calculations." Journal of Physical Chemistry C 118.45 (2014): 26415-26425.

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