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The use of perylenediimide (PDI) building blocks in materials for organic electronic is of considerable interest. The introduction of peripheral groups in their ortho and bay positions radically modify their optoelectronic properties. In this article, we describe an efficient method to afford regioisomerically pure 1,6/7-(NO2)2- and (NH2)2-PDIs employing two key steps: the selective crystallization of 1,6-(NO2)2-perylene-3,4,9,10-tetracarboxy tetrabutylester and the nitration of regiopure 1,7-Br2-PDI with silver nitrite. The optoelectronic properties of the resulting regioisomerically pure dinitro, diamino-PDIs and bisazacoronenediimides (BACDs) are reported and demonstrate the need to separate both regioisomers of such n-type organic semiconductors for their inclusion in advanced optoelectronic devices.

Photonastic materials present a directional and repeatable deformation of the material shape due to transduction from light energy to mechanical energy. Among these materials, light-responsive polymers, composed of photochromic molecules embedded in a polymer matrix, are of high interest. The present work aims at laying the foundation stone of the modeling of the photomechanical behavior of such systems by proposing a computational strategy that is able to investigate (i) the impact of the polymer matrix on the photochromic properties of a dithienylethene (DTE) switch and (ii) the impact of the photochromic reaction on the polymer environment. Contrary to previous approaches, the present model is able to propose a realistic arrangement of the photochrome embedded in the polymer film, thanks to the adaptation of the so-called "controlled-like polymerization algorithm" [Lemarchand, C. A.; J. Chem. Phys. 2019, 50, 224902]. Our strategy relies on molecular dynamics (MD) simulations and time-dependent density functional theory (DFT) calculations. Careful analysis of MD trajectories and comparison with simulations in solution have shown the rigidification of the DTE molecule due to the presence of the polymer chains, which hindered the interconversion between the DTE open-form isomers and can probably modify the photocyclization quantum yield. Besides, the UV-vis absorption properties of the DTE open-form isomers are more impacted by the polymer embedding than its closed-form counterpart. Concerning the impact of the photoreaction on the polymer matrix, the time evolution of the pressure tensor and of the atomic displacements in the matrix have shown that (i) the cyclization reaction has a negligible impact; (ii) the cycloreversion reaction induces a locally large and anisotropic pressure increase and leads to a collective displacement of the polymer matrix away from the reactive center; and (iii) the characteristic time scale associated with these coupled processes is below 1 ps. Therefore, the two processes involved in photonastic motions, namely, the photoreaction and the relaxation of the polymer matrix after the photoswitch structural change, cannot be decoupled.

Two families of organic molecules with different backbones have been considered. The first family, composed by a substituted central phenyl is considered as flexible. The second one, based on a macrolactam-like unit, is considered as rigid. They have however a common feature, three amide moieties (as substituents for the phenyl and within the cycle for the macrolactam-like molecule) that allow hydrogen bonding when molecules are stacked. In this study we propose a computational protocol to unravel the ability of the different families to self-assemble into organic nanotubes. Starting from the monomer and going towards larger assemblies like dimers, trimers, and pentamers we applied different theoretical protocols to rationalize the behavior of the different assemblies. Both structures and thermodynamics were investigated to give a complete picture of the process. Thanks to the combination of a quantum mechanics approach and molecular dynamics simulations along with the use of tailored tools (non covalent interaction visualization) and techniques (umbrella sampling), we have been able to differentiate the two families and highlight the best candidate for self-assembling purposes.

A multi-scale and multi-environment computational approach is proposed to study of the modulation of the emission behavior of the triphenylamine (Z)-4-benzylidene-2-methyloxazol-5(4H)-one (TPA-BMO) molecule [Tang et al., J. Phys. Chem. C,119, 21875 (2015)]. Going from (TD-)DFT calculations to classical Molecular Dynamics simulations through the hybrid ONIOM QM/QM’ approach and the in situ chemical polymerization methodology, we have rationalized distinct photophysical phenomena: (1) in low-polar solvents, a polarity-dependent solvatochromic effect as well as a modulation of the emission quantum yield, attributed to possible photophysical energy dissipation caused by low-frequency vibrational modes, (2) in the aggregate, a subtle competition between an excitonic coupling and a restriction of the intramolecular vibrations leading to an Aggregation-Induced Emission behavior, and (3) in the polymer matrix, an antagonist effect between the loss of global flexibility and the presence of vibrational modes similar to those observed in solution, explaining a similar emissive behavior within the polymer.

The dipyrrolyldiphenylethene (DPYDPE) molecule shows a switching between aggregation-induced-emission (AIE) and crystallization-induced emission (CIE) upon modification of the stereochemistry of the molecule. Herein, we propose a theoretical study based on molecular dynamics, time-dependent (TD-) density functional theory (DFT), and QM/QM′ calculations to investigate the structural and optical properties of the E and Z isomers in three different phases (solution, crystal, and aggregate). By computing the Huang–Rhys factors and the reorganization energies, we demonstrate that the fluorescence quenching observed in solution for both isomers is due to a nonradiative decay process involving low-frequency vibrational modes assigned to scissoring motions. In the crystal and in the aggregates, the effects of steric hindrance strongly modify the topology of the potential energy surface of the first excited state, and this results in a restriction of the vibrational modes involved in the energy dissipation. The mo...