A program for automatically predicting supramolecular aggregates and its application to urea and porphin

Abstract

Not only the molecular structure but also the presence or absence of aggregates determines many properties of organic materials. Theoretical investigation of such aggregates requires the prediction of a suitable set of diverse structures. Here, we present the open-source program EnergyScan for the unbiased prediction of geometrically diverse sets of small aggregates. Its bottom-up approach is complementary to existing ones by performing a detailed scan of an aggregate's potential energy surface, from which diverse local energy minima are selected. We crossvalidate this approach by predicting both literature-known and heretofore unreported geometries of the urea dimer. We also predict a diverse set of dimers of the less intensely studied case of porphin, which we investigate further using quantum chemistry. For several dimers, we find strong deviations from a reference absorption spectrum, which we explain using computed transition densities. This proof of principle clearly shows that EnergyScan successfully predicts aggregates exhibiting large structural and spectral diversity. © 2018 Wiley Periodicals, Inc.

Supramolecular Reorientation During Deposition Onto Metal Surfaces of Quasi-Two-Dimensional Langmuir Monolayers Composed of Bifunctional Amphiphilic, Twisted Perylenes

“…To better understand why introducing flexibility via alkyl chains yields more rigid films, we analyzed the structures and binding motifs of different possible dimer structures as models for Langmuir layer building blocks. The dimer structures are generated using the program EnergyScan, 48 where a grid-based assembly yields millions of dimer structures. 48 From this, a set of local energy minima according to force field energy calculations is determined, as detailed in the Supporting Information (SI).…”

“…The dimer structures are generated using the program EnergyScan, 48 where a grid-based assembly yields millions of dimer structures. 48 From this, a set of local energy minima according to force field energy calculations is determined, as detailed in the Supporting Information (SI). This set of local minima of dimers is further refined by selecting only energetically favorable dimers not exceeding the energy of the global minimum by 250 meV, i.e., 10 times the thermal energy at room temperature.…”

“…The dimer search was conducted by the program Energyscan (see the Supporting Information for more details). Electrostatic potential figures were made at the B3LYP/LANL2DZ level.…”

Controlling Intermolecular Interactions at Interfaces: Case of Supramolecular Tuning of Fullerene's Electronic Structure

“…Further details on the supramolecular geometry can be gained from UV–vis absorption spectra, which are influenced by supramolecular geometries, symmetry, and aggregate size according to the particle in the box picture . The reduction of the supramolecular symmetry is known to cause increased vis‐absoption and decreased UV‐absorption according to the Herzberg–Teller intensity borrowing (HTIB) mechanism;[12a,27b,29] the aggregate growth causes absorption redshifts, and reduction of intermolecular distances causes an apparent redshift because of the rise of low‐energy electronic transitions.…”

Macroscopic Quantum Electrodynamics and Density Functional Theory Approaches to Dispersion Interactions between Fullerenes

“…via fitting Lennard-Jones potentials to quantum chemically derived energies, accounting for rotations to explore the full energy hypersurfaces might be computationally demanding using grid-based methods. [81,82] Here we combine (time dependent) density functional theory and macroscopic quantum electrodynamics via the orbital coupling described by van der Waals interactions to provide energies for distinct grid-points of the energy hypersurface and analytic functions to describe the latter, respectively. 1: Results of the fitting routine for the three tracked transitions estimated via TDDFT simulations (|Φ n → |Φ n−1 ), the corresponding eccentricities of the excited state, and the fitting agreement (fit.…”