Ultrafast photoinduced dynamics of a donor-([Formula: see text])bridge-acceptor based merocyanine dye.

Sci Rep

State Key Laboratory of Precision Spectroscopy, School of Physics and Electronic Science, East China Normal University, Shanghai, 200241 People's Republic of China.

Published: October 2022

AI Article Synopsis

  • Merocyanine dyes, valued for their nonlinear optical properties and solvatochromism, have a molecular structure that facilitates charge transfer between donor and acceptor groups.
  • A study of the merocyanine dye HB194 reveals its excited state dynamics, particularly how different solvents affect its charge transfer behavior and emission properties.
  • Findings indicate that polar solvents enhance intramolecular charge transfer states while non-polar solvents like cyclohexane stabilize different states, and red-shifted emission in ethylene glycol suggests dimer formation, emphasizing the need for understanding solvent interactions in future dye design.

Article Abstract

Merocyanine dyes are of great interest amongst researchers due to their nonlinear optical (NLO) properties and solvatochromism. Molecular structure of these dyes constitutes conjugated pathway between the donor and acceptor substituents, with lowest energy transition of [Formula: see text]-[Formula: see text]* character. To rationalize the design of these dyes and deduce structure-property relationship, it is eminent to unravel the excited state dynamics in these complex molecular structures in different solvents. Here we have studied excited state dynamics of a merocyanine dye known as HB194, which has shown commendable efficiency in small molecule based bulk heterojuction solar cells. We have employed femtosecond transient absorption in combination with the quantum chemistry calculations to unravel the solvent dependent charge transfer dynamics of HB194. The excited state decays of the HB194 in different solvents show multi-exponential components. The analysis of the time-resolved data reveals that the polar solvents induce conformationally relaxed intramolecular charge transfer state. In non-polar solvent cyclohexane, only solvent-stabilized ICT state is observed. Additionally, we observe an anomalously red-shifted emission in ethylene glycol centred at [Formula: see text] 750 nm. Our computational calculations suggest the presence of molecular dimers resulting into observed red-shifted emission band. Our work therefore underscores the importance of gathering molecular-level insight into the system-bath interactions for designing next generation merocynanine-based solvatochromic dyes.

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Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9617881PMC
http://dx.doi.org/10.1038/s41598-022-23080-5DOI Listing

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