Category Archives: ChemistryOpen

Decoration of 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid (DOTA) with N‐oxides increases the T1 relaxivity of Gd‐complexes

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Decoration of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) with N-oxides increases the T1 relaxivity of Gd-complexes

Decoration with N -oxide groups is a valuable method to increase the T 1-relaxivity of the well-known cyclic Gd-chelator DOTA. The synthesis of Gd-DOTA-NOx has been achieved via copper catalyzed alkyne azide cycloaddition. The complex is water soluble, stable against transchelation, has a twisted square antiprismatic (TSAP) complex geometry and a high T 1-relaxivity of 7.7 mm −1 s−1 (1.41 T, 37 °C).


Abstract

High complex stability and longitudinal relaxivity of Gd-based contrast agents are important requirements for magnetic resonance imaging (MRI) because they ensure patient safety and contribute to measurement sensitivity. Charged and zwitterionic Gd3+-complexes of the well-known chelator 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) provide an excellent basis for the development of safe and sensitive contrast agents. In this report, we describe the synthesis of DOTA-NOx, a DOTA derivative with four N-oxide functionalities via “click” functionalization of the tetraazide DOTAZA. The resulting complexes Gd-DOTA-NOx and Eu-DOTA-NOx are stable compounds in aqueous solution. NMR-spectroscopic characterization revealed a high excess of the twisted square antiprismatic (TSAP) coordination geometry over square antiprismatic (SAP). The longitudinal relaxivity of Gd-DOTA-NOx was found to be r 1=7.7 mm −1 s−1 (1.41 T, 37 °C), an unusually high value for DOTA complexes of comparable weight. We attribute this high relaxivity to the steric influence and an ordering effect on outer sphere water molecules surrounding the complex generated by the strongly hydrated N-oxide groups. Moreover, Gd-DOTA-NOx was found to be stable against transchelation with high excess of EDTA (200 eq) over a period of 36 h, and it has a similar in vitro cell toxicity as clinically used DOTA-based GBCAs.

Photoluminescence lifetime stability studies of β‐diketonate europium complexes based phenanthroline derivatives in poly(methyl methacrylate) films

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Photoluminescence lifetime stability studies of β-diketonate europium complexes based phenanthroline derivatives in poly(methyl methacrylate) films

This study contributes to a deeper understanding of the design and development of stable β-diketonate europium complexes based on phenanthroline ligands in PMMA films. The synthesis, characterization, thermal, and photoluminescence properties are provided accompanied by long lifetime stability tests in different conditions which indicate the potential for these complexes as candidates for future optoelectronic devices, including luminescent solar concentrators.


Abstract

In this work, five phenanthroline derivatives substituted with different methyl groups have been selected to synthesize β-diketonate-based europium complexes to check the influence of the substitutions on the degradation effect of those complexes in poly(methyl methacrylate) (PMMA) films. The photophysical properties of Eu(III) complexes, including absorbance, excitation, and emission have been carefully investigated in solution, solid-state, and doped in PMMA film. In all these states, the complexes exhibit an impressive red emission at 614 nm with a high photoluminescence quantum yield of up to 85 %. The films have been exposed under outdoor, indoor, and dark storage stability lifetime conditions for 1200 hours. The photoluminescence measurements recorded every 400, 800, and 1200 hours demonstrated that the film containing europium complex with phenanthroline ligand substituted by a high number of methyl groups (Eu(TTA)3L5) showed good photoluminescent stability in indoor and dark conditions, and exhibited better resistance to degradation in outdoor conditions compared to other complexes. This study has proved that phenanthroline ligands could be tuned chemically leading to better stability of those types of complexes in films which can be end-used for future stable optoelectronic devices such as luminescent solar concentrators.

Ethylenediamine Salt Enhances the Solubility and Dissolution of Flurbiprofen

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Ethylenediamine Salt Enhances the Solubility and Dissolution of Flurbiprofen

A novel flurbiprofen-ethylenediamine salt (FLU-EDA) was successfully prepared via solvent crystallization. Its crystal structure was determined via single-crystal X-ray diffraction (SXRD). Further, the physicochemical properties of FLU-EDA salt were characterized by powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FT-IR). The solubility and intrinsic dissolution rate (IDR) of FLU-EDA salt in water were investigated.


Abstract

Drugs that are poorly soluble in water are difficult to absorb orally, resulting in low bioavailability. Flurbiprofen (FLU) is an arylpropionic acid nonsteroidal anti-inflammatory drug belonging to BCS class II, with low water solubility. In this study, a novel flurbiprofen-ethylenediamine salt (FLU-EDA) was successfully prepared via solvent crystallization. Its crystal structure was determined via single-crystal X-ray diffraction (SXRD). Further, the physicochemical properties of FLU-EDA salt were characterized by powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FT-IR). The solubility and intrinsic dissolution rate (IDR) of FLU-EDA salt in water were investigated. The results showed that compared with FLU, the solubility and IDR of FLU-EDA salt increased by 57-fold and 32-fold, respectively. This indicates that FLU-EDA salt can significantly enhance the solubility and dissolution rate of flurbiprofen in water. This study provides basic data and theory for the development of new formulations of flurbiprofen.

Preparation of green high‐performance biomass‐derived hard carbon materials from bamboo powder waste

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Preparation of green high-performance biomass-derived hard carbon materials from bamboo powder waste

This study used pre-treatment and template carbonization methods to extract a hard carbon material from a large amount of discarded biomass in bamboo powder waste. Template activation method produces rich and uniform pore structures that are beneficial for sodium storage.


Abstract

Efficient energy storage systems are crucial for the optimal utilization of renewable energy. Sodium-ion batteries (SIBs) are considered potential substitutes for next-generation low-cost energy storage systems due to the low cost and abundance of sodium resources. However, the industrialization of SIBs faces a great challenge in terms of the anode. Hard carbon could be a promising anode material due to its high capacity and low cost which originates from biomass. This study used pre-treatment and template carbonization methods to extract a hard carbon material from a large amount of discarded biomass in bamboo powder waste. This material has a good initial Coulombic efficiency of 78.6 % and good cycling stability when applied to sodium ion batteries.Typically, the optimal hard carbon material is used as the anode to prepare sodium ion battery prototypes to demonstrate their potential applications. The anode exhibited excellent sodium storage performance with a reversible capacity of 303 mAh ⋅ g−1 at 1 C rate and good cycling performance, retaining 92.0 % of its capacity after 100 cycles. These results demonstrate that BPPHC is a promising candidate for anode material in sodium-ion batteries. This work suggests that bamboo powder could be a low-cost anode material for SIBs.

Synthesis and properties of RNA constrained by a 2’‐O‐disulfide bridge

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Synthesis and properties of RNA constrained by a 2’-O-disulfide bridge

This work describes the synthesis and properties of oligoribonucleotides containing diethylene (DEE) and dipropylene (DPE) disulfide bridge between two adjacent uridines.


Abstract

We recently reported the properties of RNA hairpins constrained by a dimethylene (DME) disulfide (S−S) linker incorporated between two adjacent nucleosides in the loop and showed that this linker locked the hairpin conformation thus disturbing the duplex/hairpin equilibrium. We have now investigated the influence of the length of the linker and synthesized oligoribonucleotides containing diethylene (DEE) and dipropylene (DPE) S−S bridges. This was achieved via the preparation of building blocks, namely 2′-O-acetylthioethyl (2′-O-AcSE) and 2′-O-acetylthiopropyl (2′-O-AcSP) uridine phosphoramidites, which were successfully incorporated into RNA sequences. Thermal denaturation analysis revealed that the DEE and DPE disulfide bridges destabilize RNA duplexes but do not disrupt the hairpin conformation. Furthermore, our investigation of the duplex/hairpin equilibrium indicated that sequences modified with DME and DEE S−S linkers predominantly lock the hairpin form, whereas the DPE S−S linker provides flexibility. These findings highlight the potential of S−S linkers to study RNA interactions.

Carbon Nanofibers‐Based Anodes for Potassium‐Ion Battery

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Carbon Nanofibers-Based Anodes for Potassium-Ion Battery

This article explores the key issues faced by carbon nanofibers (CNFs)-based materials and future development directions, and proposes improvement suggestions for providing new ideas for the development of CNFs-based materials.


Abstract

In recent years, with the global warming getting worse and increasing demand for energy, countries around the world are trying to develop new energy storage technologies to solve this problem. Currently, potassium-ion batteries (PIBs) have attracted tremendous attention from researchers as low-cost and high-performance energy storage devices. However, due to the huge ionic radius of K+, PIBs face significant volume expansion during cycling, which can easily lead to the collapse of electrode structures. In addition, the poor diffusion kinetics of K+ seriously affect the electrochemical performance of the battery. Carbon nanofibers (CNFs)-based materials (including CNFs, metal/CNFs composites, chalcogenide/CNFs composites, and other CNFs-based materials) are widely used as PIBs electrode anode materials due to their three-dimensional conductive network, heteroatom doping and excellent mechanical properties. This review discusses in detail the research progress of CNFs-based materials in PIBs, including material preparation, structural design, and performance optimization. On this basis, this article explores the key issues faced by CNFs-based materials and future development directions, and proposes improvement suggestions for providing new ideas for the development of CNFs-based materials.

Analysis of Photocatalytic Degradation of Phenol by Zinc Oxide Using Response Surface Methodology

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Analysis of Photocatalytic Degradation of Phenol by Zinc Oxide Using Response Surface Methodology

Phenol and phenolic compounds pose a serious threat to the ecosystem, human health, and water resources. Photocatalytic degradation is the most suitable technique for removing organic pollutants from wastewater, and ZnO is an effective photocatalyst. This study evaluated both the photocatalytic degradation of phenol and the measurement of TOC using a ZnO photocatalyst, demonstrating the feasibility of employing RSM.


Abstract

In this study, the photocatalytic degradation of phenol, which is commonly found in industrial wastewater at high rates, was investigated using a zinc oxide (ZnO) catalyst. It is thought that our findings will contribute to the removal of phenol in industrial wastewater. The experimental study was conducted in a batch-type air-fed cylindrical photocatalytic reactor, and a central composite design (CCD) was chosen and analyzed using response surface methodology (RSM). The study aimed to explore the effects of initial phenol concentration, catalyst concentration, airflow rate, and degradation time on the photocatalytic degradation of phenol and the removal efficiency of total organic carbon (TOC). A quadratic regression model was developed to establish the relationship between phenol degradation, TOC removal effectiveness, and the four factors mentioned. The validity of the model was assessed through an analysis of variance (ANOVA). A good agreement was observed between the model results and the experimental data. As a result of the experiments carried out under optimized conditions, the degradation percentage of phenol was found to be 77.15 %, and the degradation percentage of TOC was 59.87 %. Additionally, pseudo-first-order kinetics were used in the photocatalytic degradation of phenol.

Interaction of N2, O2 and H2 Molecules with Superalkalis

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Interaction of N2, O2 and H2 Molecules with Superalkalis

N2 (blue), O2 (red) and H2 (grey) interact differently with superalkali clusters. Their interaction varies from strong covalent to weak van der Waals interaction leading to the possibility of reduction or adsorption of these small molecules.


Abstract

Superalkalis (SAs) are exotic clusters having lower ionization energy than alkali atoms, which makes them strong reducing agents. In the quest for the reduction of diatomic molecules (X2) such as N2, O2, and H2 using Møller-Plesset perturbation theory (MP2), we have studied their interaction with typical superalkalis such as FLi2, OLi3, and NLi4 and calculated various parameters of the resulting SA−X2 complexes. We noticed that the SA−O2 complex and its isomers possess strong ionic interaction, which leads to the reduction of O2 to O2 − anion. On the contrary, there are both ionic and covalent interactions in SA−N2 complexes such that the lowest energy isomers are covalently bonded with no charge transfer from SA. Further, the interaction between SA and H2 leads to weakly bound complexes, which results in the adsorption of H2 molecules. The nature of interaction is found to be closely related to the electron affinity of diatomic molecules. These findings might be useful in the study of the activation, reduction, and adsorption of small molecules, which can be further explored for their possible applications.

Green Synthesis of Copper Nanoparticles Using Sargassum spp. for Electrochemical Reduction of CO2

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Green Synthesis of Copper Nanoparticles Using Sargassum spp. for Electrochemical Reduction of CO2

CuNPs were synthesized using a cost-effective and environmentally friendly extract applying Sargassum spp. as versatile reducing agent. In this study, CuNPs with nanoflower morphology were synthesized. The experimental characterizations (XRD, SEM, and TEM,) recommend that the green synthesis method has promising effect for the synthesis of CuNPs, stable and homogeneously dispersed onto biochar. The CuNPs-CSKPH is promising electrocatalyst for the electrochemical reduction of CO2.


Abstract

This study presents a green method of producing copper nanoparticles (CuNPs) using aqueous extracts from Sargassum spp. as reducing, stabilizing, and capping agents. The CuNPs created using this algae-based method are not hazardous, they are eco-friendly, and less toxic than their chemically synthesized counterparts. The XRD characterization of the CuNPs revealed the presence of Cu and CuO, with a crystallite size ranging from 13 to 17 nm. Following this, the CuNPs were supported onto a carbon substrate, also derived from Sargassum spp. (biochar CSKPH). The CuNPs in biochar (CuNPs-CSKPH) did not appear in the XRD diffractograms, but the SEM-EDS results showed that they accounted for 36 % of the copper weight. The voltamperometric study of CuNps-CSKPH in acid media validated the presence of Cu and the amount was determined to be 2.58 μg. The catalytic activity of CuNPs-CSKPH was analyzed for the electrochemical reduction of CO2. The use of Sargassum spp. has great potential to tackle two environmental problems simultaneously, by using it as raw material for the synthesis of activated biochar as support, as well as the synthesis of CuNPs, and secondly, by using it as a sustainable material for the electrochemical conversion of CO2.

Cinchona‐Based Hydrogen‐Bond Donor Organocatalyst Metal Complexes: Asymmetric Catalysis and Structure Determination

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Cinchona-Based Hydrogen-Bond Donor Organocatalyst Metal Complexes: Asymmetric Catalysis and Structure Determination

Three different cinchona-based organocatalysts containing different hydrogen-bond donor moieties worked together with inorganic transition metal salts to catalyze pharmaceutically relevant asymmetric reactions. They were also studied experimentally and quantum chemically, providing insight into the complex structures of these catalytically active species. In many cases, the application of these catalysts led to significant increases in both yield and enantioselectivity.


Abstract

In this study, we describe the synthesis of cinchona (thio)squaramide and a novel cinchona thiourea organocatalyst. These catalysts were employed in pharmaceutically relevant catalytic asymmetric reactions, such as Michael, Friedel–Crafts, and A3 coupling reactions, in combination with Ag(I), Cu(II), and Ni(II) salts. We identified several organocatalyst-metal salt combinations that led to a significant increase in both yield and enantioselectivity. To gain insight into the active catalyst species, we prepared organocatalyst-metal complexes and characterized them using HRMS, NMR spectroscopy, and quantum chemical calculations (B3LYP-D4/def2-TZVP), which allowed us to establish a structure-activity relationship.