Excited-State Symmetry Breaking in Solvent Mixtures

Area of Science:

• Photochemistry
• Chemical Physics
• Spectroscopy

Background:

• Multipolar dyes often exhibit excited-state symmetry breaking (ESSB) in polar environments.
• ESSB involves the localization of electronic excitation onto specific molecular branches.
• Understanding the initial stages of ESSB is crucial for controlling molecular behavior.

Purpose of the Study:

• To investigate the initial stage of excited-state symmetry breaking (ESSB) in a donor-acceptor-donor dye.
• To elucidate the role of solvent mixtures in initiating and influencing ESSB dynamics.
• To explore the impact of local polarity and solvation on ESSB.

Main Methods:

• Utilized time-resolved infrared absorption spectroscopy.
• Employed binary mixtures of nonpolar and polar solvents.
• Investigated a donor-acceptor-donor dye system.

Main Results:

• The presence of a few polar molecules is sufficient to initiate ESSB.
• ESSB dynamics in mixtures are slower than in pure solvents and involve translational diffusion.
• Preferential solvation in mixtures enhances local polarity and leads to inhomogeneous broadening of absorption bands.

Conclusions:

• Solvent mixtures can effectively initiate and modulate ESSB in multipolar dyes.
• Local solvent environment significantly impacts ESSB dynamics and spectral properties.
• Photoselection in mixtures allows probing of different local environments and their associated ESSB behaviors.