Enhanced Two-Photon Absorption in Two Triphenylamine-Based All-Organic Compounds.

Area of Science:

• Organic chemistry
• Photophysics
• Materials science

Background:

• Two-photon absorption (TPA) utilizes lower energy photons for molecular excitation, offering deeper penetration and precise spatial control.
• Organic molecules with TPA properties are valuable in diverse applications.

Purpose of the Study:

• To synthesize and characterize novel organic molecules with strong TPA and fluorescent emission.
• To investigate the structure-property relationships governing TPA and fluorescence.
• To evaluate the photostability and potential applications of these molecules.

Main Methods:

• Synthesis of all-organic molecules C42H33N (compound 3) and C138H168N4 (compound 14).
• Density functional theory (DFT) calculations to analyze electronic structure and oscillator strengths.
• Solid-state measurements to confirm band gap and electron transition properties.
• Photostability assessment under focused laser illumination.

Main Results:

• Compounds 3 and 14 demonstrated strong TPA and fluorescent emission.
• Compound 14 exhibited enhanced TPA and emission activity compared to compound 3, attributed to increased oscillator strengths.
• Compound 14 showed negligible degradation over 5 hours under laser illumination, indicating high photostability.
• Solid-state measurements confirmed a direct band gap, influencing energy relaxation pathways.

Conclusions:

• Molecular design principles for high TPA cross-section and controlled energy relaxation are crucial.
• Compound 14 is a promising candidate for laser dye applications due to its TPA, fluorescence, and stability.
• Understanding energy relaxation channels (fluorescence vs. heat dissipation) is key for advanced TPA material development.