Shape of the Q band in the absorption spectra of porphyrin nanotubes: vibronic coupling or exciton effects?

Stradomska, A. and Knoester, J. (2010) Shape of the Q band in the absorption spectra of porphyrin nanotubes: vibronic coupling or exciton effects? Journal of Chemical Physics, 133(9), 094701. (doi: 10.1063/1.3481654)

Abstract

Absorption and linear dichroism spectra of self-assembled tubular aggregates of TPPS(4) porphyrin are studied theoretically with special emphasis on the low energy part of the spectra (the Q band region) where the coupling with intramolecular vibrations is pronounced. The model Hamiltonian includes both the excitonic coupling between four molecular electronic excited states contributing to the porphyrin Q and B bands as well as the intermediate-strength linear exciton-phonon coupling to one effective high-frequency molecular vibrational mode. Good agreement between the calculated and experimental spectra is obtained. The results allow us to identify the nature of the peaks observed in the Q band region of the aggregate's absorption spectrum; we show that the two most prominent peaks within the Q band originate from two different excitonic subbands. It is shown that the coupling between the Q and B bands plays an important role and the vibronic coupling affects the details of the absorption lineshape.

• Item Type: Articles
• Keywords: 2-particle approximation, TPPS4,excitons, molecular aggregates, phonons, porphyrins, tubular aggregates, vibronic coupling
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Stradomska-Szymczak, Dr Anna
• Authors: Stradomska, A., and Knoester, J.
• Subjects: Q Science > QC Physics; Q Science > QD Chemistry
• College/School: College of Science and Engineering > School of Chemistry
• Journal Name: Journal of Chemical Physics
• Publisher: American Institute of Physics
• ISSN: 0021-9606
• ISSN (Online): 1089-7690