A model for calculating the photophysical characteristics of molecules

Knowledge of molecules’ photophysical and photochemical properties is essential for some physics, chemistry, and biology zones. Specifically, it is utilized to create OLED structures for steady and bright displays of gadgets and photosensitizers in photodynamic treatment tasks. It is essential to make a scheme for the efficient generation of oxidizing agents that kill cancer cells. 

The calculation of the lifetime of molecules in an excited electronic state is essential for astrophysics and astrochemistry while anticipating dye lasers’ proficiency and the productivity of charge transfer and charge separation to expand solar effectiveness cells.

Scientists have created a model for calculating the photophysical characteristics of molecules—one that is applicable for molecules of any nature, including rare-earth lanthanides. Due to the introduction of the anharmonicity effect, the model can predict molecules’ properties even before their synthesis, without carrying out experiments.

Scientists introduced the anharmonicity effect to the model. The results show that anharmonic products are essential when calculating conversion rate constants between electronic states that are energetically separated. 

Rashid Valiev, associate professor at TSU’s Faculty of Physics, said, “We can study molecules that emit in the infrared, visible, and even ultraviolet ranges, based only on theoretical calculations, without involving experimental fitting information. And this makes it possible to predict the properties of molecules even before their synthesis, which is much more economical than synthesizing blindly.”

The effect of anharmonicity occurs when the vibrations of atoms in a molecule are strong, and the energies are large. In this case, atoms’ vibrations will no longer be correctly described in the harmonic approximation, and it is necessary to introduce a deviation from it.

The inclusion of the anharmonicity effect is especially required when calculating the characteristics of molecules that emit light in the blue and ultraviolet ranges because their vibrations occur with high energy.

Other co-authors of the study include Viktor Cherepanov (TSU), Gleb Baryshnikov (TSU and Royal Technological University, Sweden), and Dage Sundholm (University of Helsinki, Finland).

Journal Reference:

1. Rashid R. Valiev et al. First-principles calculations of anharmonic and deuteration effects on photophysical properties of polyacenes and porphyrinoids, Physical Chemistry Chemical Physics (2020). DOI: 10.1039/D0CP03231J