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Ultralarge hyperpolarizability twisted pi-electron system electro-optic chromophores: synthesis, solid-state and
Hu Kang1, Antonio Facchetti, Hua Jiang
1Department of Chemistry and the Materials Research Center, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, USA.
Journal of the American Chemical Society
|February 21, 2007
Summary
Researchers developed novel twisted pi-electron systems for electro-optic applications. These molecules exhibit significant charge separation and maintain their twisted structure in solution, leading to high hyperpolarizabilities and electro-optic coefficients.
Area of Science:
- Organic Chemistry
- Materials Science
- Nonlinear Optics
Background:
- Development of advanced materials for electro-optic (EO) applications is crucial.
- Understanding structure-property relationships in organic chromophores is key to enhancing EO performance.
Purpose of the Study:
- To synthesize and characterize novel twisted pi-electron system electro-optic chromophores.
- To investigate the influence of molecular structure, aggregation, and solvation on optical properties.
- To evaluate the potential of these chromophores in EO devices.
Main Methods:
- Crystallography and Nuclear Magnetic Resonance (NMR) spectroscopy (NOE, PGSE) for structural analysis.
- Optical, IR, and fluorescence spectroscopy for characterization.
- DC electric-field-induced second-harmonic generation (EFISH) measurements.
- Guest-host polymer film fabrication and electro-optic coefficient (r(33)) measurement.
- High-level quantum chemical computations (SA-CASSCF).
Main Results:
- Synthesis of unconventional twisted pi-electron systems with large dihedral angles (80-89 degrees).
- Confirmation of persistent twisted structure and zwitterionic character in solution.
- Observation of centrosymmetric aggregate formation in concentrated solutions and solid states.
- Unprecedented nonlinear optical properties: hyperpolarizabilities (mubeta) up to -488,000 x 10(-48) esu.
- High electro-optic coefficients (r(33) ~ 330 pm/V) in poled polymer films.
- Computational insights into hyperpolarizability origins and solvation effects.
Conclusions:
- The studied twisted chromophores exhibit exceptional nonlinear optical properties due to their unique structure and aggregation behavior.
- These findings suggest new strategies for designing high-performance molecular hyperpolarizabilities and electro-optic materials.
- The research provides a deeper understanding of structure-property correlations in organic EO materials.
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