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Open AccessArticle

Stacks of Azobenzene Stars: Self-Assembly Scenario and Stabilising Forces Quantified in Computer Modelling

1
Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, 01062 Dresden, Germany
2
Institute Theory of Polymers, Leibniz Institute of Polymer Research Dresden, Hohe Str. 6, 01069 Dresden, Germany
3
Department of Physical Chemistry, Faculty of Chemistry and Technology, Tver State University, Sadovyj per. 35, Tver 170002, Russia
*
Author to whom correspondence should be addressed.
These authors contributed equally to this work.
Academic Editors: Alessandro D’Urso and Maria Elena Fragala
Molecules 2019, 24(23), 4387; https://doi.org/10.3390/molecules24234387
Received: 12 November 2019 / Revised: 25 November 2019 / Accepted: 28 November 2019 / Published: 30 November 2019
(This article belongs to the Special Issue Self-Aggregation in Supramolecular Systems)
In this paper, the columnar supramolecular aggregates of photosensitive star-shaped azobenzenes with benzene-1,3,5-tricarboxamide core and azobenzene arms are analyzed theoretically by applying a combination of computer simulation techniques. Without a light stimulus, the azobenzene arms adopt the trans-state and build one-dimensional columns of stacked molecules during the first stage of the noncovalent association. These columnar aggregates represent the structural elements of more complex experimentally observed morphologies—fibers, spheres, gels, and others. Here, we determine the most favorable mutual orientations of the trans-stars in the stack in terms of (i) the π π distance between the cores lengthwise the aggregate, (ii) the lateral displacements due to slippage and (iii) the rotation promoting the helical twist and chirality of the aggregate. To this end, we calculate the binding energy diagrams using density functional theory. The model predictions are further compared with available experimental data. The intermolecular forces responsible for the stability of the stacks in crystals are quantified using Hirshfeld surface analysis. Finally, to characterize the self-assembly mechanism of the stars in solution, we calculate the hydrogen bond lengths, the normalized dipole moments and the binding energies as functions of the columnar length. For this, molecular dynamics trajectories are analyzed. Finally, we conclude about the cooperative nature of the self-assembly of star-shaped azobenzenes with benzene-1,3,5-tricarboxamide core in aqueous solution. View Full-Text
Keywords: azobenzenes; self-assembly; cooperativity; hydrogen bonding; computer simulations azobenzenes; self-assembly; cooperativity; hydrogen bonding; computer simulations
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Savchenko, V.; Koch, M.; Pavlov, A.S.; Saphiannikova, M.; Guskova, O. Stacks of Azobenzene Stars: Self-Assembly Scenario and Stabilising Forces Quantified in Computer Modelling. Molecules 2019, 24, 4387.

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