The metal sensing applications of chalcones: The synthesis, characterization and theoretical calculations

Synthesis and photophysical properties of novel bis-quinolin-3-yl-chalcones

A novel series of unsymmetrical bis-quinolin-3-yl chalcones has been synthesized under visible light using a Claisen-Schmidt condensation reaction between the 2-(morpholine-piperidine-pyrrolidine-thiomorpholine) substituted quinoline-3-carbaldehyde and 1-(2-methyl-4-phenylquinolin-3-yl) ethan-1-one derivatives, conducted at room temperature in the presence of NaOH/EtOH. The structures of the synthesized compounds have been confirmed by NMR spectroscopy and high-resolution mass spectroscopy. The synthesized compounds exhibit λ max values ranging from 215 nm to 290 nm in non-polar to polar solvents, demonstrating positive solvatochromism. Compounds containing nitro group substituent exhibit a significant blue shift owing to their strong electron-withdrawing ability, which also contributes to fluorescence quenching. Geometrical optimization and the calculation of HOMO, LUMO, and energy gap are calculated by using the DFT/B3LYP/6-31G(d) method.

A selective bis-thiophene chalcone-based spectrofluorimetric sensor for Fe3

A highly selective bis thiophene-based chalcone as a chemosensor for detecting Fe3+ metal ions in DMF: H2O (9:1). This sensor was selective toward ferric ions over other metal ions with a detection limit in micromolar range.

Stability Constant and Potentiometric Sensitivity of Heavy Metal-Organic Fluorescent Compound Complexes: QSPR Models for Prediction and Design of Novel Coumarin-like Ligands

Industrial wastewater often consists of toxic chemicals and pollutants, which are extremely harmful to the environment. Heavy metals are toxic chemicals and considered one of the major hazards to the aquatic ecosystem. Analytical techniques, such as potentiometric methods, are some of the methods to detect heavy metals in wastewaters. In this work, the quantitative structure-property relationship (QSPR) was applied using a range of machine learning techniques to predict the stability constant (logβ_ML) and potentiometric sensitivity (PS_ML) of 200 ligands in complexes with the heavy metal ions Cu²⁺, Cd²⁺, and Pb²⁺. In result, the logβML models developed for four ions showed good performance with square correlation coefficients (R²) ranging from 0.80 to 1.00 for the training and 0.72 to 0.85 for the test sets. Likewise, the PSML displayed acceptable performance with an R² of 0.87 to 1.00 for the training and 0.73 to 0.95 for the test sets. By screening a virtual database of coumarin-like structures, several new ligands bearing the coumarin moiety were identified. Three of them, namely NEW02, NEW03, and NEW07, showed very good sensitivity and stability in the metal complexes. Subsequent quantum-chemical calculations, as well as physicochemical/toxicological profiling were performed to investigate their metal-binding ability and developability of the designed sensors. Finally, synthesis schemes are proposed to obtain these three ligands with major efficiency from simple resources. The three coumarins designed clearly demonstrated capability to be suitable as good florescent chemosensors towards heavy metals. Overall, the computational methods applied in this study showed a very good performance as useful tools for designing novel fluorescent probes and assessing their sensing abilities.

Enzymatic PCL-grafting to NH2-end grouped silica and development of microspheres for pH-stimulated release of a hydrophobic model drug

This study set out to evaluate novel PCL-based silica containing nanohybrids as the polymer matrix in a hydrophobic drug-loaded microsphere system. Nanohybrids were synthesized by PCL-grafting to NH₂-end grouped silica by in situ enzymatic ring opening polymerization of ε-caprolactone. Molecular weight and monomer conversion, PCL grafting percentage, thermal properties and crystallinity of the nanohybrids were determined by ¹H NMR, TGA, DSC and XRD. Synthesized nanohybrids had low crystallinity percentage (32 and 39 %) and molecular weight (4800 and 8700 g/mol), promising for controlled drug release applications. The nanohybrids were used for fabrication of trans-chalcone-loaded microspheres by O/W single emulsion solvent evaporation. Mean particle diameter of the microspheres were between 15 and 30 µm. The result of release studies showed that optimum microsphere formulations (AP4 and A2, respectively) had 61 and 64 % encapsulation efficiency. One of the more significant findings to emerge from this investigation is that TC release was extended to 16 and 37 days, in a controlled manner. TC release was significantly enhanced in acidic pH media (pH 3.6 and 5.6) indicating pH-dependent release from nanohybrid microspheres; releasing 80-100 % of the loaded drug in 4-14 days. Drug/polymer interactions and molecular structures were investigated by FT-IR spectroscopy and DSC analysis. According to the results obtained, enzymatically synthesized nanohybrids have potential for pH-dependent release of the model drug, trans-chalcone.

Structural Modifications on Chalcone Framework for Developing New Class of Cholinesterase Inhibitors

Due to the multifaceted pharmacological activities of chalcones, these scaffolds have been considered one of the most privileged frameworks in the drug discovery process. Structurally, chalcones are α, β-unsaturated carbonyl functionalities with two aryl or heteroaryl units. Amongst the numerous pharmacological activities explored for chalcone derivatives, the development of novel chalcone analogs for the treatment of Alzheimer's disease (AD) is among the research topics of most interest. Chalcones possess numerous advantages, such as smaller molecular size, opportunities for further structural modification thereby altering the physicochemical properties, cost-effectiveness, and convenient synthetic methodology. The present review highlights the recent evidence of chalcones as a privileged structure in AD drug development processes. Different classes of chalcone-derived analogs are summarized for the easy understanding of the previously reported analogs as well as the importance of certain functionalities in exhibiting cholinesterase inhibition. In this way, this review will shed light on the medicinal chemistry fraternity for the design and development of novel promising chalcone candidates for the treatment of AD.

Guide to tuning the chalcone molecular properties based on the push-pull effect energy scale created via the molecular tailoring approach

Using the molecular tailoring approach, a total energy scale for the push-pull effect in the range from -40 to 100 kcal/mol is created for the wide series of neutral, charged and doubly charged compounds on the chalcone platform. Taking into account similar energy scale for hydrogen bonds, the strength of the push-pull effect is ranked in the seven categories, ranging from negative (anti-push-pull) to very weak and very strong push-pull effect. It is demonstrated that the molecular properties of chalcone can be tuned prior synthesis due to the created energy scale for the push-pull effect. The single bonds of the π-spacer in the chalcones are shortened, the double ones are lengthened, and the C=O bond vibrations are red shifted when the push-pull effect is enhanced along the energy scale. The HOMO and LUMO energies change systematically while the HOMO-LUMO energy gap narrows as the strength of the push-pull effect increases.