Spectroscopic Studies of Dual Fluorescence in 2-(4-Fluorophenylamino)-5-(2,4-dihydroxybenzeno)-1,3,4-thiadiazole: Effect of Molecular Aggregation in a Micellar System

Abstract

The article presents the results of spectroscopic studies focused on a selected compound from the 1,3,4-thiadiazole group—2-(4-fluorophenylamino)-5-(2,4-dihydroxybenzeno)-1,3,4-thia-diazole (FABT)—in a micellar system formed by Triton X-100, a non-ionic detergent. Fluorescence measurements revealed the phenomenon of dual fluorescence whose emergence is related to the particular molecular organisation of the compound, which depends both on the concentration of the detergent and, most of all, the concentration of the compound itself. Dual fluorescence of FABT in a micellar system was observed for the compound dissolved in a methanol aqueous system, i.e., an environment wherein the dual fluorescence of the compound had never been reported before. Based on the interpretation of UV-Vis electronic absorption, resonance light scattering (RLS), emission and excitation fluorescence spectra, as well as measurements of dynamic light scattering (DLS) and Principal Component Analysis (PCA), we were able to relate the occurrence of this effect to the process of molecular aggregation taking place between FABT molecules in the micellar system in question. Results of fluorescence spectra measurements and time-correlated single photon counting (TCSPC) indicate that dual fluorescence occurs at detergent concentrations necessary to form micellar systems, which in turn facilitate the process of aggregation of FABT molecules. The correlation between the observed fluorescence effects and the previous measurements performed for analogues from this group suggests the possibility of charge transfer (CT) within the range of detergent concentrations wherein the aforementioned fluorescence effects are observed. It ought to be emphasised that this type of fluorescence effects are relatively easy to induce, which predisposes this groups of fluorophores as ideal fluorescence probes in the context of biological samples.

ESIPT-Related Origin of Dual Fluorescence in the Selected Model 1,3,4-Thiadiazole Derivatives

“…The significance of compounds from the 2-amino-1,3,4-thiadiazole group [ 1 , 2 , 3 , 4 , 5 ] stems from their potential value in the fight against some of the most challenging diseases of the 21st century, including, e.g., cancer, neurodegenerative diseases, or various continuously mutating mycoses. These compounds show a wide spectrum of pharmacological properties, including neuroprotective [ 6 , 7 ], anti-cancer [ 8 ], antibacterial [ 9 ], antioxidative [ 10 , 11 ], and antimycotic [ 12 , 13 ] effects.…”

“…These compounds show a wide spectrum of pharmacological properties, including neuroprotective [ 6 , 7 ], anti-cancer [ 8 ], antibacterial [ 9 ], antioxidative [ 10 , 11 ], and antimycotic [ 12 , 13 ] effects. Contemporary researchers working in the fields of biophysics and photophysics or photochemistry and utilizing the methods of molecular spectroscopy are faced with the extremely difficult task, posed by medical and pharmaceutical sciences, of determining the molecular properties of continuously developed new compounds [ 1 , 2 , 14 , 15 , 16 , 17 , 18 ].…”

“…It should be noted that the selected analogues are characterized by not only very promising biological effects but also very interesting spectroscopic and crystallographic properties. The same include effects related to crystal polymorphism and solvatomorphism [ 19 ], impact on the dynamics of model biological membranes [ 20 ], changing fluorescence properties in micellar systems [ 1 ], as well as metal-chelating ability [ 21 ]. It is evident that the ability to correlate said spectroscopic and structural properties of the analyzed molecules may play a very important part in explaining the phenomena responsible for their pharmacological effects.…”

Spectroscopic and theoretical studies of fluorescence effects induced by the ESIPT process in a new derivative 2-Hydroxy-N-(2-phenylethyl)benzamide – Study on the effects of pH and medium polarity changes

“…The effects related to the dual nature of fluorescence [17,18] may be induced by changes in the solvent's polarity, pH [17], temperature, or concentration of the analyzed compound [19,20]. The most prevalent explanations offered for this type of effects include the emergence of intramolecular CT (charge transfer) states [19], particularly the twisted intramolecular charge transfer (TICT) [21,22].…”

Micelles Mediated Zone Fluidics Method for Hydrazine Determination in Environmental Samples

“…In brief, above a concentration level that is characteristic for each surfactant (critical micelle concentration), the molecules tend to self-aggregate pointing out the polar groups, while the hydrophobic ones are orientated towards the center [26]. From an analytical point of view, poorly soluble reagents can be easily solubilized in micellar media, fluorescent signals can be enhanced [27], they can serve as additives in chromatographic mobile phases, or even be applied to sample treatment schemes (e.g., cloud point extraction [28]). Analytical applications of micelles can be found in both batch and flow configurations [29,30].…”