Issue 17, 2016

From linear to cyclic oligoparaphenylenes: electronic and molecular changes traced in the vibrational Raman spectra and reformulation of the bond length alternation pattern

Abstract

Cyclic paraphenylenes, [n]CPPs, and linear paraphenylenes, [n]LPPs, formed by n benzenes, are investigated by Raman spectroscopy for n = 5 to 12 and density functional theory (DFT) for n = 4 to 20. The information on the experimental Raman frequencies and intensities, combined with DFT computations and reported X-ray diffraction structures, provides a consistent interpretation of the Raman spectra and allows establishing relevant structure–property trends. Structural and electronic effects such as benzene ring bending, inter-ring torsions, π-conjugation (aromaticity) and orbital energy gaps as a function of the linear elongation in [n]LPPs versus the macrocyclic curvature in [n]CPPs and of the molecular size (i.e., polymer limit) are systematically analyzed on the basis of the vibrational Raman properties. Changes in the BLA as an indicator of the degree of quinonoid character are analyzed and linked to the Effective Conjugation Coordinate (ECC) model. The BLA patterns involved in twisted and non-twisted conformations and in different species (bipolarons, quinonoid tautomers, and ECC active modes) are compared and their differences are discussed. This paper offers a unified interpretation of structural and electronic aspects in relation to the evolution from linear 1D π-systems to cyclic 2D structures.

Graphical abstract: From linear to cyclic oligoparaphenylenes: electronic and molecular changes traced in the vibrational Raman spectra and reformulation of the bond length alternation pattern

Supplementary files

Article information

Article type
Paper
Submitted
14 sep 2015
Accepted
18 nov 2015
First published
18 nov 2015

Phys. Chem. Chem. Phys., 2016,18, 11683-11692

Author version available

From linear to cyclic oligoparaphenylenes: electronic and molecular changes traced in the vibrational Raman spectra and reformulation of the bond length alternation pattern

M. Peña-Alvarez, L. Qiu, M. Taravillo, V. G. Baonza, M. C. R. Delgado, S. Yamago, R. Jasti, J. T. L. Navarrete, J. Casado and M. Kertesz, Phys. Chem. Chem. Phys., 2016, 18, 11683 DOI: 10.1039/C5CP05500H

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements