First-principles simulations of the initial phase of self-aggregation of a cyanine dye: structure and optical spectra

Haverkort, F., Stradomska, A. and Knoester, J. (2014) First-principles simulations of the initial phase of self-aggregation of a cyanine dye: structure and optical spectra. Journal of Physical Chemistry B, 118(29), pp. 8877-8890. (doi: 10.1021/jp5049277)

Abstract

Using first-principles simulations, we investigated the initial steps of the self-aggregation of the dye pseudoisocyanine (PIC) in water. First, we performed molecular dynamics (MD) simulations of the self-aggregation process, in which pile-of-coins oligomers ranging from dimers to stacks of about 20 molecules formed. The oligomer structures were found to be very flexible, with the dimers entering a weakly coupled state and then returning to a stable π-π stacked conformation on a nanosecond time scale. The structural information from the MD simulations was combined with quantum chemical calculations to generate a time-dependent Frenkel exciton Hamiltonian for monomers, dimers, and trimers, which included vibronic coupling. This Hamiltonian, in turn, was used to calculate the absorption spectra for these systems. The simulated dimer spectrum compared well to experiment, validating the face-to-face stacked dimer arrangement found in our MD simulations. Comparison of the simulated trimer spectrum to experiment suggested that oligomers larger than the dimer cannot be abundant at the onset of J-aggregation. Finally, the conformation of the PIC J-aggregate was investigated by testing the stability of several possible conformations in our MD simulations; none of the tested structures was found to be stable.

• Item Type: Articles
• Keywords: PIC, excitons, molecular aggregates, molecular dynamics, self-assembly, spectroscopy
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Stradomska-Szymczak, Dr Anna
• Authors: Haverkort, F., 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 Physical Chemistry B
• Publisher: American Chemical Society
• ISSN: 1520-6106
• ISSN (Online): 1520-5207
• Copyright Holders: Copyright © 2014 American Chemical Society
• First Published: First published in Journal of Physical Chemistry B 118(209):8877-8890
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher.