Level of Theory and Solvent Effects on DASA Absorption Properties Prediction: Comparing TD-DFT, CASPT2 and NEVPT2.

Cristina García-Iriepa,Marco Marazzi

doi:10.3390/ma10091025

Abstract

Donor–acceptor Stenhouse adducts (DASAs) are a very recent class of organic photoswitches that combine excellent properties, such as color and polarity change, a large structural modification, and excellent fatigue resistance. Despite their potential applications in different fields, very few studies have focused on rationalizing their electronic structure properties. Here, by means of different state-of-the-art theoretical methods, including solvent and vibrational effects, we show that while time dependent-density functional theory (TD-DFT) can qualitatively describe DASAs’ excited states, multiconfigurational quantum chemistry methods along with dynamic electron correlation (CASPT2, NEVPT2) are required for a quantitative agreement with the experiment. This finding is reasoned based on the different charge transfer characteristics observed. Moreover, the TD-DFT computed two-photon absorption properties are reported and suggested to red-shift the absorption band, as required for biological applications.

Highlights

Molecular switches are among the most studied molecular devices of the last few decades, mainly due to their versatility and remarkable applications [1,2]
The dynamics and vibrational effects will be given, in order to obtain an estimated excitation energy corresponding to the absorption maximum, and a spectral shape that can be better compared in the experiment
A static and dynamic study of a prototypical Donor–acceptor Stenhouse adducts (DASAs) derivative was performed in gas phase, including various solvents and using different methodologies and levels of theory

Summary

Introduction

Molecular switches are among the most studied molecular devices of the last few decades, mainly due to their versatility and remarkable applications [1,2]. Light-activated molecular switches are commonly known as photoswitches, and the research of novel systems and outstanding applications still attracts the interest of scientists. For this reason, this special issue is dedicated to efficient photoactive building blocks and their use in concrete applications. Molecular photoswitches can be reversibly interconverted between two states with different molecular structures and properties. When the spectral properties (e.g., color) of these two states are clearly and distinguishable, these systems are considered photochromes. Azobenzene, diarylethene and spiropyrans have been the more widely exploited photochromes [5,6,7]

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