Probing the structural features and the micro-heterogeneity of various deep eutectic solvents and their water dilutions by the photophysical behaviour of two fluorophores

Study of fluconazole drug behavior in deep eutectic solvents: thermodynamic properties, solubility measurement, and fluorescence spectroscopy

Fluconazole is a crucial antifungal medication with a broad spectrum of activity against various fungal infections. This study thermodynamic properties, solubility measurements and spectrofluorometric method were used for investigating the interactions between fluconazole (FCZ) and deep eutectic solvents (DESs). Five choline chloride-based deep eutectic solvents (DESs) were synthesized. Each DES was prepared by combining choline chloride (a hydrogen bond acceptor, HBA) with a different hydrogen bond donor (HBD): oxalic acid (OX), malonic acid (MA), ethylene glycol (EG), glycerol (G), or urea (U). Subsequently, the interactions between fluconazole (FCZ) and these synthesized DESs were investigated using fluorescence spectroscopy at a temperature of 298.15 K. Fluorescence spectroscopy revealed a strong interaction between fluconazole (FCZ) and deep eutectic solvents (DESs). This was evident from the significant quenching of FCZ's intrinsic fluorescence upon DES addition. The association constant and binding sites were determined. Among the tested DESs, the choline chloride-oxalic acid mixture exhibited the strongest interaction with FCZ. Furthermore, the solubility of FCZ in DES-water mixtures studied at a temperature range of (298.15 to 313.15) K was found to increase with increasing DES concentration. The solubility data were accurately fitted using the e-NRTL and Wilson thermodynamic models. To gain deeper insights, conductor-like screening model (COSMO) calculations were performed on the studied systems. The obtained surface cavity volume and dielectric solvation energy provide valuable information about the intermolecular interactions. Finally, thermodynamic analysis using Gibbs and van't Hoff equations indicated that the dissolution of FCZ in these systems is an endothermic process.

Quantitative estimation of chemical microheterogeneity through the determination of fuzzy entropy

Chemical micro-heterogeneity is an attribute of all living systems and most of the soft and crystalline materials. Its characterization requires a plethora of techniques. This work proposes a strategy for quantifying the degree of chemical micro-heterogeneity. First of all, our approach needs the collection of time-evolving signals that can be fitted through poly-exponential functions. The best fit is determined through the Maximum Entropy Method. The pre-exponential terms of the poly-exponential fitting function are used to estimate Fuzzy Entropy. Related to the possibility of implementing Fuzzy sets through the micro-heterogeneity of chemical systems. Fuzzy Entropy becomes a quantitative estimation of the Fuzzy Information that can be processed through micro-heterogeneous chemical systems. We conclude that our definition of Fuzzy Entropy can be extended to other kinds of data, such as morphological and structural distributions, spectroscopic bands and chromatographic peaks. The chemical implementation of Fuzzy sets and Fuzzy logic will promote the development of Chemical Artificial Intelligence.

The role of twisting in driving excited-state symmetry breaking and enhanced two-photon absorption in quadrupolar cationic pyridinium derivatives

Two symmetric quadrupolar cationic push-pull compounds with a central electron-acceptor (N+-methylpyrydinium, A+) and different lateral electron-donors, (N,N-dimethylamino and N,N-diphenylamino, D) in a D-π-A+-π-D arrangement, were investigated together with their dipolar counterparts (D-π-A+) for their excited-state dynamics and NLO properties. As for the quadrupolar compounds, attention was focused on excited-state symmetry breaking (ESSB), which leads to a relaxed dipolar excited state. Both electron charge displacements and structural rearrangements were recognized in the excited-state dynamics of these molecules by resorting to femtosecond-resolved broadband fluorescence up-conversion experiments and advanced data analysis, used as a valuable alternative approach for fluorescent molecules compared to time-resolved IR spectroscopy, only suitable for compounds bearing IR markers. Specifically, intramolecular charge transfer (ICT) was found to be guided by ultrafast inertial solvation, while diffusive solvation can drive the twisting of lateral groups to originate twisted-ICT (TICT) states on a picosecond time scale. Yet still, only the bis-N,N-diphenylamino-substituted compound undergoes ESSB, in both highly and sparingly polar solvents, provided that it can experience large amplitude motions to a fully symmetry-broken TICT state. Besides well-known solvation effects, this structural requirement proved to be a necessary condition for these quadrupolar cations to undergo ESSB. In fact, a more efficient uncoupling between the out-of-plane D and A+ groups in the TICT state allows a greater stabilization gained through solvation, relative to the bis-N,N-dimethylamino-substituted derivative, which instead maintains its symmetry. This different behavior parallels the two-photon absorption (TPA) ability, which is greatly enhanced in the case of the bis-N,N-diphenylamino-substituted compound, paving the way for cutting-edge bio-imaging applications.