Coumarins into Polyurethanes for Smart and Functional Materials

Synthesis and Application Dichalcogenides as Radical Reagents with Photochemical Technology

Dichalcogenides (disulfides and diselenides), as reactants for organic transformations, are important and widely used because of their potential to react with nucleophiles, electrophilic reagents, and radical precursors. In recent years, in combination with photochemical technology, the application of dichalcogenides as stable radical reagents has opened up a new route to the synthesis of various sulfur- and selenium-containing compounds. In this paper, synthetic strategies for disulfides and diselenides and their applications with photochemical technology are reviewed: (i) Cyclization of dichalcogenides with alkenes and alkynes; (ii) direct selenylation/sulfuration of C-H/C-C/C-N bonds; (iii) visible-light-enabled seleno- and sulfur-bifunctionalization of alkenes/alkynes; and (iv) Direct construction of the C(sp)-S bond. In addition, the scopes, limitations, and mechanisms of some reactions are also described.

Synthesis, computational study, solvatochromism and biological studies of thiazole-owing hydrazone derivatives

In the present work, we have synthesized thiazole-hydrazone conjugates 5(a–h) and characterized them using various analytical techniques such as UV, IR, NMR, and mass spectrometry. Solvatochromic properties were evaluated in ten solvents with different polarity and quantum chemical parameters using a DFT study. The antibacterial activity results revealed that compounds 5c, 5d and 5g exhibited good efficacy and that the remaining compounds displayed significant activity. The synthesized compounds were screened for their cytotoxic activity against HepG2 and MCF-7 cell lines, and all the synthesized compounds exhibited significant potency towards the screened cancer cell lines. The anti-inflammatory efficacy of the synthesized thiazole derivatives was determined against MMP-2 and MMP-9, and some of the compounds showed significant activity. Furthermore, the in silico molecular docking was performed with the COX-2 receptor.

En Route to Stabilized Compact Conformations of Single-Chain Polymeric Nanoparticles in Complex Media

Precise control over the folding pathways of polypeptides using a combination of noncovalent and covalent interactions has evolved into a wide range of functional proteins with a perfectly defined 3D conformation. Inspired hereby, we develop a series of amphiphilic copolymers designed to form compact, stable, and structured single-chain polymeric nanoparticles (SCPNs) of defined size, even in competitive conditions. The SCPNs are formed through a combination of noncovalent interactions (hydrophobic and hydrogen-bonding interactions) and covalent intramolecular cross-linking using a light-induced [2 + 2] cycloaddition. By comparing different self-assembly pathways of the nanoparticles, we show that, like for proteins in nature, the order of events matters. When covalent cross-links are formed prior to the folding via hydrophobic and supramolecular interactions, larger particles with less structured interiors are formed. In contrast, when the copolymers first fold via hydrophobic and hydrogen-bonding interactions into compact conformations, followed by covalent cross-links, good control over the size of the SCPNs and microstructure of the hydrophobic interior is achieved. Such a structured SCPN can stabilize the solvatochromic dye benzene-1,3,5-tricarboxamide-Nile Red via molecular recognition for short periods of time in complex media, while showing slow exchange dynamics with the surrounding complex media at longer time scales. The SCPNs show good biocompatibility with cells and can carry cargo into the lysosomal compartments of the cells. Our study highlights the importance of control over the folding pathway in the design of stable SCPNs, which is an important step forward in their application as noncovalent drug or catalyst carriers in biological settings.

Synthesis and Characterization of Crosslinked Castor Oil-Based Polyurethane Nanocomposites Based on Novel Silane-Modified Isocyanate and Their Potential Application in Heat Insulating Coating

An isocyanate with trimethoxysilane groups at the side chains (IPDI-M) was synthesized via an addition between the mercaptopropyl trimethoxysilane groups (MPTMS) and IPDI tripolymer (IPDI-T). Then, silane grafted isocyanate as the functional hard segment, castor oil as the soft segment, poly (ethylene adipate) diol (PEA) as the chain extender, and MPTMS as an end-capping reagent were applied to form a series of organosilicon hybrid bio-based polyurethane (CPUSi). The effect of the IPDI-M contents on the thermal stability, mechanical properties, and surface properties of the resulting product was systematically investigated. Profit from the Si–O–Si crosslinked structures formed from MPTMS curing, the tensile strength, and Young’s modulus of the resulting products increased from 9.5 MPa to 22.3 Mpa and 4.05 Mpa to 81.59 Mpa, respectively, whereas the elongation at break decreased from 342% to 101%. The glass transition temperature, thermal stability, transparency, hydrophobicity, and chemical resistance were remarkably strengthened for the obtained organosilicon-modified polyurethane with the increasing MPTMS content. At the end of the work, the thermal insulation coating that was based on CPUSi and ATO can effectively block near-infrared rays, and the temperature difference between the inside and outside of the film reached 15.1 °C.

Enhancing the photochemical reversibility of coumarin-containing polymers by molecular orientation control

With the use of an intramolecular approach and restrictions in the mobility, the reversibility of photoresponsive coumarin dimer-containing polymers was enhanced.

Light-mediated Seleno-Functionalization of Organic Molecules: Recent Advances

Organoselenium compounds constitute an important class of substances with applications in the biological, medicinal and material sciences as well as in modern organic synthesis, attracting considerable attention from the scientific community. Therefore, the construction of the C-Se bond via facile, efficient and sustainable strategies to access complex scaffolds from simple substrates are an appealing and hot topic. Visible light can be regarded as an alternative source of energy and is associated with environmentally-friendly processes. Recently, the use of visible-light mediated seleno-functionalization has emerged as an ideal and powerful route to obtain high-value selenylated products, with diminished cost and waste. This approach, involving photo-excited substrates/catalyst and single-electron transfer (SET) between substrates in the presence of visible light has been successfully used in the versatile and direct insertion of organoselenium moieties in activated and unactivated C(sp³ )-H, C(sp² )-H, C(sp)-H bonds as well as C-heteroatom bonds. In most cases, ease of operation and accessibility of the light source (LEDs or commercial CFL bulbs) makes this approach more attractive and sustainable than the traditional strategies.

Trending Topics on Coumarin and Its Derivatives in 2020

Coumarins are naturally occurring molecules with a versatile range of activities. Their structural and physicochemical characteristics make them a privileged scaffold in medicinal chemistry and chemical biology. Many research articles and reviews compile information on this important family of compounds. In this overview, the most recent research papers and reviews from 2020 are organized and analyzed, and a discussion on these data is included. Multiple electronic databases were scanned, including SciFinder, Mendeley, and PubMed, the latter being the main source of information. Particular attention was paid to the potential of coumarins as an important scaffold in drug design, as well as fluorescent probes for decaging of prodrugs, metal detection, and diagnostic purposes. Herein we do an analysis of the trending topics related to coumarin and its derivatives in the broad field of drug discovery.

Recent Advances in Functional Polymers Containing Coumarin Chromophores

Natural and synthetic coumarin derivatives have gained increased attention in the design of functional polymers and polymer networks due to their unique optical, biological, and photochemical properties. This review provides a comprehensive overview over recent developments in macromolecular architecture and mainly covers examples from the literature published from 2004 to 2020. Along with a discussion on coumarin and its photochemical properties, we focus on polymers containing coumarin as a nonreactive moiety as well as polymer systems exploiting the dimerization and/or reversible nature of the [2πs + 2πs] cycloaddition reaction. Coumarin moieties undergo a reversible [2πs + 2πs] cycloaddition reaction upon irradiation with specific wavelengths in the UV region, which is applied to impart intrinsic healability, shape-memory, and reversible properties into polymers. In addition, coumarin chromophores are able to dimerize under the exposure to direct sunlight, which is a promising route for the synthesis and cross-linking of polymer systems under "green" and environment-friendly conditions. Along with the chemistry and design of coumarin functional polymers, we highlight various future application fields of coumarin containing polymers involving tissue engineering, drug delivery systems, soft robotics, or 4D printing applications.

Coumarin-Modified CQDs for Biomedical Applications-Two-Step Synthesis and Characterization

Waste biomass such as lignin constitutes a great raw material for eco-friendly carbon quantum dots (CQDs) synthesis, which find numerous applications in various fields of industry and medicine. Carbon nanodots, due to their unique luminescent properties as well as water-solubility and biocompatibility, are superior to traditional organic dyes. Thus, obtainment of CQDs with advanced properties can contribute to modern diagnosis and cell visualization method development. In this article, a new type of coumarin-modified CQD was obtained via a hybrid, two-step pathway consisting of hydrothermal carbonization and microwave-assisted surface modification with coumarin-3-carboxylic acid and 7-(Diethylamino) coumarin-3-carboxylate. The ready products were characterized over their chemical structure and morphology. The nanomaterials were confirmed to have superior fluorescence characteristics and quantum yield up to 18.40%. They also possessed the ability of biomolecules and ion detection due to the fluorescence quenching phenomena. Their lack of cytotoxicity to L929 mouse fibroblasts was confirmed by XTT assay. Moreover, the CQDs were proven over their applicability in real-time bioimaging. Obtained results clearly demonstrated that proposed surface-modified carbon quantum dots may become a powerful tool applicable in nanomedicine and pharmacy.

A novel strategy to polyurethanes with improved mechanical properties by photoactivation of amidocoumarin moieties

An attractive strategy involving photodimerization of a novel amidocoumarin moiety is presented to prepare polyurethane coatings with excellent mechanical properties. Two families of polyurethanes containing these chromophore units into soft or hard segments were easily synthesized by inserting a small fraction of amidocoumarin-diol (5 wt% or 10 wt%). A systematic study has been carried out comparing hard segment, chromophore content and the influence of this amidocoumarin unit within the hard or soft segment. For all synthetized polymers, mechanical properties of the coatings have been evaluated before and after an excitation of the coumarin units with UV light. The results show that the insertion of coumarin into the hard segment leads to a considerable improvement of the mechanical properties after irradiation. Additionally, the photochemical activity of amidocoumarin was studied by UV-Vis and Raman spectroscopies.

An attractive strategy involving photodimerization of a novel amidocoumarin moiety is presented to prepare polyurethane coatings with excellent mechanical properties.

Structural Characterization of Mono and Dihydroxylated Umbelliferone Derivatives

Coumarin derivatives are a class of compounds with a pronounced wide range of applications, especially in biological activities, in the medicine, pharmacology, cosmetics, coatings and food industry. Their potential applications are highly dependent on the nature of the substituents attached to their nucleus. These substituents modulate their photochemical and photophysical properties, as well as their interactions in their crystalline form, which largely determines the final field of application. Therefore, in this work a series of mono and dihydroxylated coumarin derivatives with different chemical substituents were synthesized and characterized by UV-Visible spectroscopy, thermal analysis (differential scanning calorimetry (DSC) and TGA), ¹H NMR and X-Ray Diffraction to identify limitations and possibilities as a function of the molecular structure for expanding their applications in polymer science.

Estimation of Photophysical and Electrochemical Parameters of Bioactive Thiadiazole Derivative

The absorption and fluorescence spectra of synthesized 4-[5-(2,5-Dimethyl-pyrrol-1-yl)-[1, 3, 4] thiadiazol-2-ylsulfanylmethyl]-6-methoxy-chromen-2-one (DTYMC) compound were recorded in various solvents like acetone, acetonitrile, chloroform, dimethyl formamide (DMF),1,4-dioxane, ethanol, ethyl acetate, methanol, tetrahydrofuran (THF) and dimethylsulphoxide (DMSO) at room temperature in order to estimate the ground and excited state dipole moment. The ground state dipole moment (μ_g) and excited state dipole moment (μ_e) were calculated using solvatochromic shift method which involve equations proposed by Lippert, Bakshiev and Kawski-Chamma-Viallete. The results were signified that the excited state dipole moment is greater than the ground state dipole moment, which indicates the excited state is more polar than the ground state of the molecule. The bond angle between the ground state and excited state dipole moments were found to be 0⁰, The change in dipole moment (∆μ) was calculated using microscopic solvent polarity parameter ([Formula: see text]). Further multiple linear regression analysis of Kamlet-Taft parameter, HOMO-LUMO energy were determined by cyclic voltammetry using phosphate buffer solution.