Interplay of Inter- and Intramolecular Interactions in Crystal Structures of 1,3,4-Thiadiazole Resorcinol Derivatives

Hoser, Anna A.; Kamiński, Daniel; Skrzypek, Alicja; Matwijczuk, Arkadiusz; Niewiadomy, Andrzej; Gagoś, Mariusz; Woźniak, Krzysztof

doi:10.1021/acs.cgd.8b00077

Cited by 9 publications

(7 citation statements)

References 36 publications

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“…According to the aforementioned theory, the observed shifts are related to two forms of aggregation: the hypochromic shift corresponds to the formation of “card pack” aggregates while the bathochromic shift stems from “head to tail” aggregation [ 41 ]. Based on the above, it can be concluded that the observed fluorescence effects are clearly related to the effect of aggregation of FABT molecules in selected micellar systems [ 4 , 20 , 42 ] and indeed may be associated with Aggregation-induced emission (AIE) [ 43 ]. In contrary, our findings suggest that the aggregation can only favour the intermolecular CT processes, which in turn give rise to the dual emission in FABT.…”

Section: Resultsmentioning

confidence: 99%

“…Apart from the aforementioned pharmacological properties, FABT is also characterised by very interesting spectroscopic effects, e.g., the effect of keto-enol tautomerism induced by changes in medium polarizability [ 19 ] as well as the effects of crystal polymorphism and solvatomorphism [ 20 ] and effects on lipid membranes entailing significant influence on their dynamics [ 21 ]. Moreover, other analysed analogues have been demonstrated to show a very interesting dual fluorescence effect induced, among other factors, by changes in the pH, concentration and temperature of the medium [ 4 ].…”

Section: Introductionmentioning

confidence: 99%

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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

et al. 2018

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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.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2018

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“…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.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2020

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In our previous work, we discussed the emergence of the dual fluorescence phenomenon in selected compounds from the group of 1,3,4-thiadiazoles. The results obtained in a number of experimental studies, supported by [TD]DFT calculations, clearly indicated that the phenomenon of dual fluorescence stemmed from an overlap of several factors, including the correct conformation of the analyzed molecule and, very significantly in this context, aggregation effects. Where those two conditions were met, we could observe the phenomenon of intermolecular charge transfer (CT) and the emergence of electronic states responsible for long wave emissions. However, in light of the new studies presented in this paper, we were able, for the first time, to provide a specific theory for the effect of dual fluorescence observed in the analyzed group of 1,3,4-thiadiazoles. We present the results of spectroscopic measurements conducted for two selected analogues from the 1,3,4-thiadiazole group, both in polar and non-polar solvents, which clearly evidence (as we have already suspected in the past, albeit have not shown in publications to date) the possibility of processes related to emission from the tautomer formed in the process of excited state intramolecular proton transfer, which is responsible for the long-wavelength emissions observed in the selected analogues. The presented results obtained with the use of UV-Vis, fluorescence (stationary and time-resolved), FTIR, and Raman spectroscopy, as well as from calculations of dipole moment changes between the ground and excited state with the use of two derivatives with different structures of the resorcylic system, corroborated our standing hypothesis. At the same time, they excluded the presence of ground state keto forms of the analyzed analogues unless necessitated by the structure of the molecule itself. In this case, aggregation factors enhance the observed effects related to the dual fluorescence of the analyzed compounds (by way of AIE—aggregated induced emissions).

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“…It is also noteworthy that the aforementioned 1,3,4-thiadiazole analogues show, apart from promising biological properties, also rather interesting spectroscopic properties. The same include the atypical effect of the tautomeric shift induced by changes in medium polarizability (changes of the keto/enol equilibrium [5]), effects related to crystal polymorphism [6] and solvatomorphism [7], changes in the fluidity dynamics of lipid membranes [8], or the effects of the emergence of various spectral forms (such as monomers/aggregates) in micellar systems [9]. Associating the aforementioned spectroscopic effects with changes of the photophysical/structural properties of said molecules can significantly contribute to our understanding of the phenomena underlying the pharmacological properties of the analyzed analogues.…”

Section: Introductionmentioning

confidence: 99%

Non-Typical Fluorescence Effects and Biological Activity in Selected 1,3,4-thiadiazole Derivatives: Spectroscopic and Theoretical Studies on Substituent, Molecular Aggregation, and pH Effects

Budziak

Karcz

Makowski

et al. 2019

IJMS

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The below article presents the results of spectroscopic research, theoretical (time-dependent density functional theory (TD-DFT)), microbiological, and antioxidative calculations for three compounds from the group of 1,3,4-thiadiazoles: 2-amino-5-phenyl-1,3,4-thiadiazole (TB), 2-amino-5-(2-hydroxyphenyl)-1,3,4-thiadiazole (TS), 2-amino-5-(2-hydroxy-5-sulfobenzoyl)-1,3,4-thiadiazole (TSF). In the fluorescence emission spectra (TS) of solutions with varying concentrations of hydrogen ions, a particularly interesting effect of dual fluorescence was observed. The aforementioned effect was observed even more clearly in the environment of butan-1-ol, relative to the compound’s concentration. Depending on the modification of the resorcylic substituent (TS and TSF), we observed the emergence of two separate, partially overlapping, fluorescence emission spectra or a single emission spectrum. Interpretation of the obtained spectra using stationary and time-resolved spectroscopy allowed the correlation of the effect’s emergence with the phenomenon of molecular aggregation (of a particular type) as well as, above all, the structure of the substituent system. The overlap of said effects most likely induces the processes related to the phenomenon of charge transfer (in TS) and is responsible for the observed fluorescence effects. Also, the position of the –OH group (in the resorcylic ring) is significant and can facilitate the charge transfer (CT). The determinations of the changes in the dipole moment and TD-DFT calculations further corroborate the above assumption. The following paper presents the analysis (the first for this particular group of analogues) of the fluorescence effects relative to the changes in the structure of the resorcylic group combined with pH effects. The results of biological studies also indicate the highest pharmacological potential of the analogue in the case where the effects of dual fluorescence emission are observed, which predisposes this particular group of fluorophores as effective fluorescence probes or potential pharmaceuticals with antimycotic properties.

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Interplay of Inter- and Intramolecular Interactions in Crystal Structures of 1,3,4-Thiadiazole Resorcinol Derivatives

Cited by 9 publications

References 36 publications

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

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

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

Non-Typical Fluorescence Effects and Biological Activity in Selected 1,3,4-thiadiazole Derivatives: Spectroscopic and Theoretical Studies on Substituent, Molecular Aggregation, and pH Effects

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