Photoisomerization among ring-open merocyanines. II. A computational study.

Area of Science:

• Computational Chemistry
• Photochemistry
• Spectroscopy

Background:

• The photochemical isomerization of merocyanine dyes is crucial for understanding their functional properties.
• Previous studies utilized femtosecond transient absorption spectroscopy to probe this process in 6-nitro BIPS.

Purpose of the Study:

• To computationally investigate the photochemical isomerization pathway of 6-nitro BIPS merocyanine.
• To elucidate the role of solvation models in accurately describing the potential energy surface.

Main Methods:

• Time-dependent density functional theory (TD-DFT) with polarizable continuum models.
• Relaxed scans on ground and excited state potential energy surfaces.
• Benchmark calculations using SCS-ADC(2) to validate CAM-B3LYP functional.

Main Results:

• The potential energy surface (PES) shape is highly sensitive to solvation, with state-specific solvation being critical.
• Calculated harmonic frequencies in S1 minima agree with experimental observations.
• The study provides a clear interpretation of experimental results through computational modeling.

Conclusions:

• Computational modeling, particularly with appropriate solvation models, can accurately reproduce experimental photochemical isomerization dynamics.
• Understanding solvation effects is key to predicting the behavior of merocyanine dyes.