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Dual Fluorescence of 2-(4'-N,N-dimethylaminophenyl)pyrido
1Department of Chemistry, Indian Institute of Technology, Kanpur, Kanpur, 208016, India
Journal of Colloid and Interface Science
|August 5, 2000
Summary
The spectral properties of 2-(4'-N,N-dimethylaminophenyl)-pyrido[3,4-d]imidazole (DMAPPI) were studied in reverse micelles. DMAPPI exhibits dual fluorescence, stabilized by hydrogen bonding, and its location within the micelle depends on water content.
Area of Science:
- Supramolecular Chemistry
- Photophysics
- Physical Organic Chemistry
Background:
- Reverse micelles offer unique microenvironments for studying molecular behavior.
- The compound 2-(4 '-N,N-dimethylaminophenyl)-pyrido[3,4-d]imidazole (DMAPPI) is a fluorescent molecule with potential applications in sensing.
- Understanding solute-solubilization interactions within reverse micelles is crucial for designing advanced materials.
Purpose of the Study:
- To investigate the spectral characteristics of DMAPPI within a TritonX-100/n-hexanol/water reverse micelle system.
- To elucidate the influence of water content, surfactant, cosurfactant, pH, and trifluoroacetic acid on DMAPPI's photophysical behavior.
- To determine the location and aggregation state of DMAPPI within the reverse micellar structure.
Main Methods:
- Spectroscopic analysis (UV-Vis absorption and fluorescence spectroscopy) of DMAPPI.
- Systematic variation of water content (w(0)), surfactant (TritonX-100), cosurfactant (n-hexanol), pH, and trifluoroacetic acid concentration.
- Investigation of DMAPPI in cyclohexane as the continuous phase.
Main Results:
- Dual fluorescence, including normal and twisted intramolecular charge transfer (TICT) states, was observed for DMAPPI, even at low water content.
- The TICT state is stabilized by hydrogen bonding from n-hexanol, indicating DMAPPI's proximity to the micellar interface.
- Changes in spectral characteristics with varying water content are attributed to reverse micelle formation and cosurfactant alignment around DMAPPI.
- DMAPPI remains unaffected by pH variations (3-10) but is protonated by trifluoroacetic acid to form monocations (MCs).
- Biprotonic phototautomerism was observed in MC1, leading to the formation of MC2 in the S(1) state.
Conclusions:
- DMAPPI resides near the interface of the water pool and the micellar phase in the studied reverse micelle system.
- The photophysical behavior of DMAPPI is sensitive to the microenvironment within the reverse micelle, particularly water content and hydrogen bonding.
- Protonation by trifluoroacetic acid leads to distinct cationic species with unique phototautomeric behavior within the reverse micelle.