Elucidating Structural Evolution of Perylene Diimide Aggregates Using Vibrational Spectroscopy and Molecular Dynamics Simulations

Abstract

Perylene diimides (PDIs) are a family of molecules that have potential applications to organic photovoltaics. These systems typically aggregate cofacially due to π-stacking interactions between the aromatic perylene cores. In this study, the structure and characteristics of aggregated N, N'-bis(2,6-diisopropylphenyl)-3,4,9,10-perylenetetracarboxylic diimide (common name lumogen orange), a perylene diimide (PDI) with sterically bulky imide functional groups, were investigated using both experimental vibrational spectroscopy and molecular dynamics (MD) simulations. Samples of lumogen orange dispersed in chloroform exhibited complex aggregation behavior, as evidenced by the evolution of the FTIR spectrum over a period of several hours. While for many PDI systems with less bulky imide functional groups aggregation is dominated by π-stacking interactions between perylene cores, MD simulations of lumogen orange dimers indicated a second, more energetically favorable aggregate structure mediated by "edge-to-edge" interactions between PDI units. Two-dimensional infrared spectroscopy together with orientational statistics obtained from MD simulations were employed to identify and rationalize aggregation-induced coupling between vibrational modes.

Structural dynamics of an excited donor–acceptor complex from ultrafast polarized infrared spectroscopy, molecular dynamics simulations, and quantum chemical calculations

“…A similar approach was recently used to predict the relative orientation of the individual constituents in perylene diimide aggregates. 69 The out-of-plane vectors of neutral Bz/TCNE show a strong preference for mutual orientations of 0 and p, as would be expected for a face-to-face sandwich structure. There are much weaker preferences for orientations of 0 and p for the in-plane angle.…”

In-depth characterization of self-healing polymers based on π–π nteractions

“…The C=O vibrations at 1656 and 1698 cm −1 on the other hand both shift to higher wavenumbers, indicating a strengthening of the carbon-oxygen bond. This is caused by a weakening of inter-perylene C–H–O interactions that also contribute to the stacking behavior [ 28 – 29 ], which in turn increases the electron density in the C=O bond.…”

“…These regions are specific to the perylene moieties in the polymers and, therefore, allow a direct observation of the π-π interactions in the polymer. Both the C=C and C=O vibrations are sensitive to the electron density in the perylene systems, which changes depending on the strength of π-π interactions [28][29][30].…”

Copper oxide integrated perylene diimide self-assembled graphitic pencil for robust non-enzymatic dopamine detection

“…The absorption bands witnessed at 3242 and 3323 cm À1 corresponded to the stretching frequency of the -NH group of PDI, while a sharp band at 1696 cm À1 was due to the C]O functionality. Moreover, strong absorption bands at 1656 and 1546 cm À1 were due to C]C and C-C of PDI, 42 as shown in Fig. 4(A)(a).…”