Contrasting Response of Two Dipolar Fluorescence Probes in a Leucine‐Based Organogel and Its Implications

Abstract

The microenvironments of a leucine-based organogel are probed by monitoring the fluorescence behavior of coumarin 153 (C153) and 4-aminophthalimide (AP). The steady-state data reveals distinctly different locations of the two molecules in the gel. Whereas AP resides close to the hydroxyl moieties of the gelator and engages in hydrogen-bonding interactions, C153 is found in bulk-toluene-like regions. In contrast to C153, AP exhibits excitation-wavelength-dependent emission, indicating that the environments of the hydrogen-bonded AP molecules are not all identical. A two-component fluorescence decay of AP in gel, unlike C153, supports this model. A time-resolved fluorescence anisotropy study of the rotational motion of the molecules also reveals the strong association of only AP with the gelator. That AP influences the critical gelation concentration implies its direct involvement in the gel-formation process. The results highlight the importance of guest-gelator interactions in gels containing guest molecules.

Steric‐Structure‐Dependent Gel Formation, Hierarchical Structures, Rheological Behavior, and Surface Wettability

“…Supramolecular gels, a type of self‐assembled material, have received a great deal of attention due to their potential applications in biomaterials, catalyzers, electronic devices, templates for nanostructures, sensors, drug carriers, and oil recovery . Supramolecular gels are generated by self‐assembly of the gelator in organic solvent or water through intermolecular noncovalent interactions, such as hydrogen bonding, hydrophobic interactions, coordination bonds, electrostatic interactions, π–π stacking, van der Waals forces, charge‐transfer interactions, and metal–ligand coordination . These noncovalent interactions can provide highly organized molecular architectures that display reversible, instant, and visual changes in response to external stimuli, such as ultrasound, shearing stress, light, heating, magnetism, ions, pH, chiral compounds, enzymes, and gases.…”

“…[14][15][16][17][18][19][20] Supramolecular gels are generated by self-assembly of the gelator in organic solvent or water through intermolecular noncovalent interactions, such as hydrogen bonding, hydrophobic interactions, coordinationb onds, electrostatic interactions, p-p stacking, van der Waals forces, charge-transfer interactions,a nd metal-ligand coordination. [21][22][23][24][25] These noncova-lent interactions can provide highly organized moleculara rchitectures that display reversible, instant,a nd visual changes in responset oe xternals timuli, such as ultrasound, shearing stress, light, heating,m agnetism,i ons, pH, chiral compounds, enzymes,a nd gases. Typically,s upramolecular gels are formed by heatingalow-molecular-weight (LMW) gelator in an appropriate solvent at as pecific concentration, then cooling.…”

Probing Laser‐Induced Heterogeneous Microenvironment Changes in Room‐Temperature Ionic Liquids

“…Both experimental and computational evidence indicate that some organized structures with different microstructural domains could form within ionic liquids because of their polar and nonpolar components . The distinct heterogeneous microenvironment of RTILs can be revealed by examining the dynamics of molecular probes through many spectroscopic methods; this approach has been studied by many research groups . Porphyrins/porphyrinoids, with their excellent triplet excited state properties, are important candidates for photochemical and photoelectric research related to sensing, solar cells, diagnostics, and therapeutics .…”