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Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach

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Fast photo-processes in triazole-based push-pull systems.

Peter D Zoon¹, Ivo H M van Stokkum, Manuel Parent

¹van't Hoff Institute for Molecular Sciences, University of Amsterdam, Nieuwe Achtergracht 129, 1018 WS Amsterdam, The Netherlands.

Physical Chemistry Chemical Physics : PCCP

|March 5, 2010

Summary

New electron donor-acceptor compounds with triazole linkers exhibit charge-separated excited states. Solvent polarity significantly influences charge separation efficiency in these push-pull molecules.

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Area of Science:

Organic Chemistry
Photophysics
Materials Science

Background:

Electron donor-acceptor compounds are crucial for optoelectronic applications.
Triazole linkers, synthesized via click chemistry, offer versatile molecular architectures.
Push-pull systems enable efficient charge transfer upon excitation.

Purpose of the Study:

To synthesize and characterize novel asymmetrical (1) and symmetrical (2) push-pull electron donor-acceptor compounds.
To investigate the influence of molecular symmetry and solvent polarity on photophysical properties.
To determine the charge separation dynamics and efficiency in these systems.

Main Methods:

Synthesis of compounds 1 and 2 using "click" chemistry.
Steady-state and time-resolved spectroscopic techniques (e.g., absorption, emission, transient absorption).
Solvent polarity variation studies.

Main Results:

Compounds 1 and 2 form highly dipolar charge-separated excited states in moderately polar solvents.
Symmetry breaking is observed in the excited state of the symmetrical compound 2.
Charge separation efficiency is highly dependent on solvent polarity, increasing from toluene to acetonitrile.
Rates of charge separation range from 10^11 to 10^12 s^-1 and increase with solvent polarity.
The bis-triazole biphenyl unit in 2 acts as a superior electron acceptor compared to the mono-triazole unit in 1.

Conclusions:

The synthesized push-pull compounds exhibit efficient charge separation, tunable by solvent polarity.
Molecular symmetry plays a role in excited-state dynamics, leading to symmetry breaking in the symmetrical derivative.
These findings contribute to the design of advanced materials for molecular electronics and photonics.