Fluorescence-enhanced organogels and mesomorphic superstructure based on hydrazine derivatives

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Organic Chemistry

Background:

• Low-molecular-mass organic gelators (LMOGs) are crucial for developing novel functional materials.
• Designing LMOGs with specific properties like gelation ability and optical responses is an active research area.
• Hydrazine linkages offer unique structural and electronic properties for molecular design.

Purpose of the Study:

• To design and synthesize novel LMOGs based on hydrazine linkage and phenyl end-capping.
• To investigate the gelation capabilities of these new compounds in various organic solvents.
• To explore the photophysical properties, specifically aggregation-induced emission (AIE), and liquid crystalline behavior of the synthesized LMOGs.

Main Methods:

• Synthesis of 1,4-bis[(3,4-bisalkoxyphenyl)hydrozide]phenylene (BPH-n) derivatives.
• Gelation studies to determine critical gelation concentrations (CGC) in organic solvents.
• Characterization of gel-sol transition temperatures (Tgel).
• Spectroscopic analysis (fluorescence) to study AIE phenomena and quantum yields.
• Differential scanning calorimetry (DSC), polarized optical microscopy (POM), and X-ray diffraction (XRD) for mesophase analysis.

Main Results:

• Successful synthesis of BPH-n (n = 4, 6, 8, 10) organogelators.
• Demonstrated ability to form stable organogels in diverse organic solvents with very low CGC (down to 8.7 x 10⁻⁴ mol L⁻¹).
• Observed high gel-sol transition temperatures (Tgel) at low gelator concentrations.
• Exhibited aggregation-induced emission (AIE) with significantly enhanced fluorescence quantum yields in xerogels compared to dilute solutions.
• BPH-n (n = 6, 8, 10) displayed thermotropic hexagonal columnar (Col(h)) mesophases stable at room temperature.

Conclusions:

• The synthesized BPH-n compounds are effective LMOGs with excellent gelling ability and thermal stability.
• The materials exhibit promising AIE properties, indicating potential for optoelectronic applications.
• The observed liquid crystalline behavior adds another dimension to their functional material potential.
• These findings contribute to the development of advanced supramolecular materials with tunable properties.