Molecular Modelling of Ground- and Excited-States Vibrations in Organic Conducting Devices: Hexakis(n-hexyloxy)triphenylene (HAT6) as Case Study

M. Zbiri; M. R. Johnson; L. Haverkate; F. M. Mulder; G. J. Kearley

doi:10.1071/CH09459

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Molecular Modelling of Ground- and Excited-States Vibrations in Organic Conducting Devices: Hexakis(n-hexyloxy)triphenylene (HAT₆) as Case Study

M. Zbiri ^A , M. R. Johnson ^A , L. Haverkate ^B , F. M. Mulder ^B and G. J. Kearley ^C ^D

+ Author Affiliations

- Author Affiliations

^A Institut Laue Langevin, Boîte Postale 156, 38042 Grenoble, Cedex 9, France.

^B Department of Radiation, Radionuclides and Reactors, Delft University of Technology, 2629 JB Delft, the Netherlands.

^C Bragg Institute, Australian Nuclear Science and Technology Organisation, Menai, NSW 2234, Australia.

^D Corresponding author. Email: gke@ansto.gov.au

Australian Journal of Chemistry 63(3) 388-395 https://doi.org/10.1071/CH09459
Submitted: 31 August 2009 Accepted: 24 January 2010 Published: 26 March 2010

Abstract

In order to gain insight into fundamental aspects of organic photocell materials, we have calculated ground and excited electronic-state structures and molecular vibrations for an isolated HAT₆ molecule (hexakis(n-hexyloxy)triphenylene). Excited-state calculations are carried out using time-dependent density functional theory and frequencies are evaluated analytically using coupled perturbed Kohn–Sham equations. These model calculations have been validated against new infrared and ultraviolet data on HAT₆ in solution. The main allowed valence excitation, having the largest oscillator strength, is chosen for the structural and vibrational investigations. Comparison with the ground-state vibrational dynamics reveals surprisingly large spectral differences. In addition, the alkoxy tails, which are usually considered to play only a structural role, are clearly involved in the molecular vibrations and the structural distortion of the excited electronic state compared with the ground state. The tails may play a more important role in charge separation, transport and excited-state relaxation than was previously thought. In this case, chemical modification of the tails would allow vibrational and related properties of organic photocell materials to be tailored.

Acknowledgement

The authors are grateful to U. D. Woroniecka for help with the IR measurements.

References

Molecular Modelling of Ground- and Excited-States Vibrations in Organic Conducting Devices: Hexakis(n-hexyloxy)triphenylene (HAT6) as Case Study

Abstract

Acknowledgement

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Molecular Modelling of Ground- and Excited-States Vibrations in Organic Conducting Devices: Hexakis(n-hexyloxy)triphenylene (HAT₆) as Case Study