Conformational dynamics of the pyrene excimer

Area of Science:

• Photochemistry
• Computational Chemistry
• Materials Science

Background:

• The fluorescence properties of pyrene excimers are linked to their conformational dynamics.
• The impact of multiple local minima on excited-state behavior is not well understood.

Purpose of the Study:

• To identify and characterize stable excimer geometries in the excited state.
• To elucidate the influence of conformational dynamics on pyrene excimer photophysics.

Main Methods:

• Time-dependent density functional theory (TD-DFT) calculations.
• Unsupervised machine learning for analyzing molecular geometries.
• Computational modeling of excited-state dynamics.

Main Results:

• Identification of a diverse set of stable excimer geometries in the first excited state.
• Demonstration that rapid structural reorganization to a stacked-twisted conformer dominates photophysics.
• Explanation of characteristic red-shifted, structureless fluorescence and long lifetimes.

Conclusions:

• The stacked-twisted conformer is crucial for pyrene excimer fluorescence.
• Understanding these dynamics can guide the development of new materials for organic electronics and sensing.