Evaluation of tight-binding DFT performance for the description of organic photochromes properties

Abstract

Photochrome molecules are widely studied for their many potential applications. It exists a considerable chemical space to explore for the optimization of the required properties and a necessity to understand their incorporation in devices. Thus, cheap and reliable computational methods can be powerful tools to steer synthetic developments. As DFT methods remain costly for any extensive studies, semi-empirical methods like Density Functional Tight-Binding (TB) could offer a good compromise between accuracy computational cost. However, these approaches necessitate benchmarking on the families of compounds of interest. Thus, the aim of the present study is to evaluate the accuracy of key features calculated with TB methods (DFTB2, DFTB3, GFN2-xTB, and LC-DFTB2) for three sets of photochromic molecules: azobenzene (AZO), norbornadiene/quadricyclane (NBD/QC) and dithienylethene (DTE) derivatives. The features considered are the optimized geometries, the difference in energy between the two isomers (ΔE), and the energies of the first relevant excited states. All the TB results are compared to those obtained with DFT methods and state-of-the-art electronic structure calculation methods: DLPNO-CCSD(T) for ground states and DLPNO-STEOM-CCSD for excited states. Our results show that, overall, DFTB3 is the TB method leading to the best results for the geometries and the ΔE values and can be use alone for these purposes for NBD/QC and DTE derivatives. Single point calculations using r2SCAN-3c with TB geometries allow circumvent the deficiencies of the TB methods in the AZO series. For the electronic transitions, the range-separated LC-DFTB2 method is the most accurate TB method tested for AZO and NBD/QC derivatives.

Kinetic Delay in Cooperative Supramolecular Polymerization by Redefining the Trade‐Off Relationship between H‐Bonds and Van der Waals/π–π Stacking Interactions

“…This study thus reveals that an increase of the head‐to‐tail dimer population D1 within the solution should lead to the emergence of a growing band located in the blue part of the absorption spectrum (≈245 nm), while a decrease of the absorption in the red part of the spectrum (≈270 nm) should be observed for an increase of the face‐to‐face D2 population. Despite the fact that the calculated spectrum of the monomer is slightly blue shifted compared to experiment probably owing to the computational method with and the absence of solvent effects [16] . only the latter situation corresponds to the experimental observations (Figure 2 top), thereby further supporting the fact that the face‐to‐face D2 packing is accessed prior to the head‐to‐tail D1.…”

“…Despite the fact that the calculated spectrum of the monomer is slightly blue shifted compared to experiment probably owing to the computational method with and the absence of solvent effects. [16] only the latter situation corresponds to the experimental observations (Figure 2 Angewandte Chemie supporting the fact that the face-to-face D2 packing is accessed prior to the head-to-tail D1.…”

“…As these compounds can be easily functionalized, with acetylenic or with extended aromatic moieties (Scheme 1), some of us recently used such ligands to selfassemble bulky Ru II bis-acetylide complexes. [8] Herein, we further demonstrate for the first time that (i) the increase of π-π stacking interactions in TBAÀ PhA 12 compared to TBAÀ A 12 and (ii) the regulation of interchain VdW interactions in TBA derivatives functionalized with alkyl side chains of various length from new TBAÀ PhA 12 to new TBAÀ PhA 16 enables not only the control of the kinetic metastable states existence but also operates on the polymerization kinetic barrier to form 1D fibers. The characteristics of this state and of the polymerization process were determined experimentally, in particular with the observations of hysteresis loops, and modeled with the help of theoretical calculations.…”

Kinetic Delay in Cooperative Supramolecular Polymerization by Redefining the Trade‐Off Relationship between H‐Bonds and Van der Waals/π–π Stacking Interactions

“…Despite the fact that the calculated spectrum of the monomer is slightly blue shifted compared to experiment probably owing to the computational method with and the absence of solvent effects. [16] only the latter situation corresponds to the experimental observations (Figure 2…”

Multipole Expansion of Atomic Electron Density Fluctuation Interactions in the Density-Functional Tight-Binding Method

“…, and f AB (22) are nonzero. In the on-site limit, f AB (02) , f AB (11) , and f AB (22) are diagonal matrices.…”