Chemistry

16 pages, 3436 KiB

Open AccessArticle

Synthesis and Characterization of Polymethylhydrosiloxane-Modified Phenol–Formaldehyde Resin

by Luong Nhu Hai, Nguyen Van Thao, Pham The Long, Nguyen Xuan Anh, Le Tran Tiep, Hoang Quoc Nam, Nguyen Minh Viet, Tran The Dinh, Le Duy Binh, Ta Kim Thanh Hien and Cong Tien Dung

Chemistry 2025, 7(4), 112; https://doi.org/10.3390/chemistry7040112 - 7 Jul 2025

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Abstract

Resol phenol–formaldehyde (PF) resin was modified with 2.5 and 5.0 wt% polymethylhydrosiloxane (PMHS). This study characterizes the modified resin and its subsequently fabricated glass fiber (GF)-reinforced composites (30–60 wt% GF). Formation of an organic–inorganic hybrid network, via reaction between Si-H groups of PMHS [...] Read more.

Resol phenol–formaldehyde (PF) resin was modified with 2.5 and 5.0 wt% polymethylhydrosiloxane (PMHS). This study characterizes the modified resin and its subsequently fabricated glass fiber (GF)-reinforced composites (30–60 wt% GF). Formation of an organic–inorganic hybrid network, via reaction between Si-H groups of PMHS and hydroxyl (-OH) groups of the resol resin, was confirmed by FTIR and ¹H NMR. DSC and TGA/DTG revealed enhanced thermal stability for PMHS-modified resin: the decomposition temperature of Resol–PMHS 5.0% increased to 483 °C (neat resin: 438 °C), and char yield at 800 °C rose to 57% (neat resin: 38%). The 60 wt% GF-reinforced Resol–PMHS 5.0% composite exhibited tensile, flexural, and impact strengths of 145 ± 7 MPa, 160 ± 7 MPa, and 71 ± 5 kJ/m², respectively, superior to the unmodified resin composite (136 ± 6 MPa, 112 ± 6 MPa, and 51 ± 5 kJ/m²). SEM observations indicated improved fiber–matrix interfacial adhesion and reduced delamination. These results demonstrate that PMHS modification effectively enhances the thermo-mechanical properties of the PF resin and its composites, highlighting potential for industrial applications. Full article

(This article belongs to the Section Supramolecular Chemistry)

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9 pages, 798 KiB

Open AccessCommunication

Synthesis and Cancer Cell Targeting of a Boron-Modified Heat-Stable Enterotoxin Analog for Boron Neutron Capture Therapy (BNCT)

by Sota Okazaki, Yoshihide Hattori, Nana Sakata, Masaya Goto, Sarino Kitayama, Hiroko Ikeda, Toshiki Takei, Shigeru Shimamoto and Yuji Hidaka

Chemistry 2025, 7(4), 111; https://doi.org/10.3390/chemistry7040111 - 30 Jun 2025

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Abstract

Heat-stable enterotoxin (STa) is a peptide toxin that induces acute diarrhea by binding to guanylyl cyclase C (GC-C) in intestinal epithelial cells. Interestingly, GC-C is highly expressed not only in intestinal cells but also in certain colorectal cancer cells, such as T84 and [...] Read more.

Heat-stable enterotoxin (STa) is a peptide toxin that induces acute diarrhea by binding to guanylyl cyclase C (GC-C) in intestinal epithelial cells. Interestingly, GC-C is highly expressed not only in intestinal cells but also in certain colorectal cancer cells, such as T84 and Caco-2 cells. This unique expression pattern provides STa as an effective candidate for therapeutic applications in cancer suppression or as a probe for detecting cancer cells. Recently, we developed attenuated forms of several STa analogs, including STa topological isomers, and evaluated their efficacy in detecting GC-C on Caco-2 cells, which enables the use of STa in human applications. Therefore, in this study, we investigated the potential application of a ¹⁰B-labeled STa derivative, [Mpr⁵,D-Lys¹⁶(BSH)]-STp(5–17) topological isomer, in boron neutron capture therapy (BNCT), for establishing a novel therapeutic strategy for colorectal cancer. The ¹⁰B-labeled STa peptide clearly exhibited Caco-2 cell killing activity upon neutron irradiation in a concentration-dependent manner, indicating that STa is an effective candidate drug for BNCT. To our knowledge, this is the first report of using STa in boron neutron capture therapy (BNCT). Full article

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21 pages, 10536 KiB

Open AccessArticle

Synthesis, Phase Formation, and Raman Spectroscopy of Ni and Zn(Mg) Codoped Bismuth Stibate Pyrochlore

by Nadezhda A. Zhuk, Sergey V. Nekipelov, Olga V. Petrova, Boris A. Makeev, Sergey I. Isaenko, Maria G. Krzhizhanovskaya, Kristina N. Parshukova, Roman I. Korolev and Ruslana A. Simpeleva

Chemistry 2025, 7(4), 110; https://doi.org/10.3390/chemistry7040110 - 30 Jun 2025

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Abstract

Complex antimony pyrochlores Bi_2.7M_0.46Ni_0.70Sb₂O_10+Δ (M = Zn, Mg) were synthesized from oxide precursors, using the solid-state reaction method. For each composition variant, the pyrochlore phase formation process was studied during solid-state synthesis in the [...] Read more.

Complex antimony pyrochlores Bi_2.7M_0.46Ni_0.70Sb₂O_10+Δ (M = Zn, Mg) were synthesized from oxide precursors, using the solid-state reaction method. For each composition variant, the pyrochlore phase formation process was studied during solid-state synthesis in the range of 500–1050 °C. The influence of zinc and magnesium on the phase formation process was established. The interaction of oxide precursors occurs at a temperature of 600 °C and higher, resulting in the formation of bismuth stibate (Bi₃SbO₇) as a binary impurity phase. Oxide precursors, including bismuth(III) and antimony(III,V) oxides, are fixed in the samples up to 750 °C, at which point the intermediate cubic phase Bi₃M_2/3Sb_7/3O₁₁ (sp. gr. Pn-3, M = Zn, Ni) is formed in the zinc system. Interacting with transition element oxides, it is transformed into pyrochlore. An intermediate phase with the Bi_4.66Ca_1.09VO_10.5 structure (sp. gr. Pnnm) was found in the magnesium system. The unit cell parameter of pyrochlore for two samples has a minimum value at 800 °C, which is associated with the onset of high-temperature synthesis of pyrochlore. The synthesis of phase-pure pyrochlores is confirmed by high-resolution Raman spectroscopy. The data interpretation showed that the cations in Ni/Zn pyrochlore are more likely to be incorporated into bismuth positions than in Ni/Mg pyrochlore. The nickel–magnesium pyrochlore is characterized by a low-porosity microstructure, with grain sizes of up to 3 μm, according to SEM data. Zinc oxide has a sintering effect on ceramics. Therefore, the grain size in ceramics is large and varies from 2 to 7 μm. Full article

(This article belongs to the Section Inorganic and Solid State Chemistry)

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20 pages, 5044 KiB

Open AccessReview

Cocktail of Catalysts: A Dynamic Advance in Modern Catalysis

by Mikhail P. Egorov, Vladimir Ya. Lee and Igor V. Alabugin

Chemistry 2025, 7(4), 109; https://doi.org/10.3390/chemistry7040109 - 26 Jun 2025

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Abstract

Cocktail-type catalysis represents a significant shift in the understanding of catalytic processes, recognizing that multiple interconverting species—such as metal complexes, clusters, and nanoparticles—can coexist and cooperate within a single reaction environment. Originating from mechanistic studies on palladium-catalyzed systems, this concept challenges the classical [...] Read more.

Cocktail-type catalysis represents a significant shift in the understanding of catalytic processes, recognizing that multiple interconverting species—such as metal complexes, clusters, and nanoparticles—can coexist and cooperate within a single reaction environment. Originating from mechanistic studies on palladium-catalyzed systems, this concept challenges the classical division between homogeneous and heterogeneous catalysis. Instead, it introduces a dynamic framework where catalysts adapt and evolve under reaction conditions, often enhancing efficiency, selectivity, and durability. Using advanced spectroscopic, microscopic, and computational techniques, researchers have visualized the formation and transformation of catalytic species in real time. The cocktail-type approach has since been extended to platinum, nickel, copper, and other transition metals, revealing a general principle in catalysis. This approach not only resolves long-standing mechanistic inconsistencies, but also opens new directions for catalyst design, green chemistry, and sustainable industrial applications. Embracing the complexity of catalytic systems may redefine future strategies in both fundamental research and applied catalysis. Full article

(This article belongs to the Special Issue Celebrating the 50th Anniversary of Professor Valentine Ananikov)

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11 pages, 3231 KiB

Open AccessArticle

A Nitrogen-Rich Luminescent Zn(II) Coordination Polymer Based on a 2,4,6-Tris(di-2-pyridylamino)-1,3,5-triazine for Differential Fluorescent Sensing of Antibiotics in Aqueous Medium

by Sajeetha Parveen Banu, Mannanthara Kunhumon Noushija, Binduja Mohan and Sankarasekaran Shanmugaraju

Chemistry 2025, 7(4), 108; https://doi.org/10.3390/chemistry7040108 - 25 Jun 2025

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Abstract

The design of suitable chemosensors for environmental pollutants and toxins detection at trace levels remains a critical area of research. Among various chemosensors, Zn(II) coordination polymers have garnered special interest as fluorescent probes for environmental applications. In this article, we report the synthesis [...] Read more.

The design of suitable chemosensors for environmental pollutants and toxins detection at trace levels remains a critical area of research. Among various chemosensors, Zn(II) coordination polymers have garnered special interest as fluorescent probes for environmental applications. In this article, we report the synthesis of a nitrogen-rich luminescent Zn(II) coordination polymer, TDPAT-Zn-CP, designed for differential fluorescent sensing of antibiotics in an aqueous medium. TDPAT-Zn-CP was synthesized using a star-shaped 2,4,6-tris(di-2-pyridylamino)-1,3,5-triazine (TDPAT) fluorophore, a promising blue-emitting compound. The morphological and structural properties of TDPAT-Zn-CP were thoroughly analyzed using conventional spectroscopic and analytical techniques. The fluorescence titration studies in aqueous medium demonstrated that TDPAT-Zn-CP exhibits remarkable selectivity, sensitivity, and differential fluorescence sensing responses towards various antibiotics. Among the antibiotics tested, TDPAT-Zn-CP displayed a significant fluorescence quenching and high selectivity for sulfamethazine (SMZ), with a Stern–Volmer quenching constant of K_SV = 1.68 × 10⁴ M⁻¹ and an impressive sensitivity of 4.95 ppb. These results highlight the potential of TDPAT-Zn-CP as a practically useful, highly effective polymeric sensor for the differential fluorescence-based detection of antibiotics in water, offering a promising approach for environmental monitoring and contamination control. Full article

(This article belongs to the Section Supramolecular Chemistry)

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Graphical abstract

12 pages, 2780 KiB

Open AccessArticle

Catalytic Ozonation of Diclofenac Using CuO/Al₂O₃- and MnO₂/Al₂O₃-Supported Catalysts

by Wenli Zhou, Xiaoxia Wang, Yanghong Xu, Qingsong Xu, Zheng Shen and Junlian Qiao

Chemistry 2025, 7(4), 107; https://doi.org/10.3390/chemistry7040107 - 25 Jun 2025

Viewed by 364

Abstract

Pharmaceuticals such as diclofenac (DCF), a widely used anti-inflammatory drug, are frequently detected in water bodies and pose serious environmental and health risks due to their persistence and low biodegradability. Although ozonation is an effective method for pollutant removal, its efficiency is often [...] Read more.

Pharmaceuticals such as diclofenac (DCF), a widely used anti-inflammatory drug, are frequently detected in water bodies and pose serious environmental and health risks due to their persistence and low biodegradability. Although ozonation is an effective method for pollutant removal, its efficiency is often limited by low ozone utilization and incomplete mineralization. In this work, CuO/Al₂O₃- and MnO₂/Al₂O₃-supported catalysts were prepared via an impregnation method and evaluated for their performance in catalytic ozonation of diclofenac (DCF) in an aqueous solution. The catalysts were characterized by TEM, N₂ adsorption–desorption, FTIR, and XPS analyses. The effects of catalyst type, dosage, initial pH, and ozone flow rate on degradation efficiency were systematically investigated. Under optimal conditions, the DCF removal efficiencies reached 73.99% and 76.33% using CuO/Al₂O₃ and MnO₂/Al₂O₃, respectively, while COD removal efficiencies were 77.6% and 89.3%. Quenching experiments indicated that hydroxyl radicals (•OH) were the predominant reactive species involved in the catalytic ozonation process. The results demonstrate that supported CuO and MnO₂ catalysts can effectively enhance diclofenac degradation by ozone, offering potential for advanced water treatment applications. Full article

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36 pages, 5930 KiB

Open AccessReview

Pyrazolopyridines and Pyrazolopyrimidines as Functional Dipolar Scaffolds: An Approach Regarding Synthesis and Photophysics

by Silvia Cruz and Jaime Portilla

Chemistry 2025, 7(4), 106; https://doi.org/10.3390/chemistry7040106 - 24 Jun 2025

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Abstract

Pyrazolopyridines and pyrazolopyrimidines are 5:6 aza-fused N-heteroaromatic compounds (NHACs) comprising a pyrazole ring fused to a pyridine or pyrimidine ring. They exhibit dipolar behavior due to their π-excessive and π-deficient characteristics conferred by their five- and six-membered rings. These features favor their stability, [...] Read more.

Pyrazolopyridines and pyrazolopyrimidines are 5:6 aza-fused N-heteroaromatic compounds (NHACs) comprising a pyrazole ring fused to a pyridine or pyrimidine ring. They exhibit dipolar behavior due to their π-excessive and π-deficient characteristics conferred by their five- and six-membered rings. These features favor their stability, reactivity, and structural diversity, offering numerous modular and functional derivatives (e.g., pyrazolo[1,2-a]pyridines, pyrazolo[1,5-a]pyrimidines, etc.). They have been utilized to obtain relevant chemicals in pharmaceuticals, photophysics, industry, and materials science; thus, their synthesis is highly desirable for discovering novel or improved applications. Therefore, this review focuses on recent advances in the synthesis and applications of these compounds, considering reports from the last decade (2015–2024), with particular emphasis on photophysics, as they contain dipolar 5:6 aza-fused rings as essential scaffolds for this purpose. Full article

(This article belongs to the Section Molecular Organics)

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Graphical abstract

11 pages, 1107 KiB

Open AccessArticle

Piplartine, a Bioactive Amide from Piper truncatum, Displays Potent Anthelmintic Activity Against the Zoonotic Nematode Angiostrongylus cantonensis

by Lucas Fukui-Silva, Sophia C. Spoladore, Bruna L. Lemes, Camila S. Amorim, Marina M. Gonçalves, João Henrique G. Lago and Josué de Moraes

Chemistry 2025, 7(4), 105; https://doi.org/10.3390/chemistry7040105 - 23 Jun 2025

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Abstract

Parasitic nematodes, such as the zoonotic rat lungworm Angiostrongylus cantonensis, pose a significant global health burden, with current anthelmintics like albendazole showing limited efficacy. Here, we report the isolation of piplartine from Piper truncatum Vell. (Piperaceae) and its potent in vitro activity [...] Read more.

Parasitic nematodes, such as the zoonotic rat lungworm Angiostrongylus cantonensis, pose a significant global health burden, with current anthelmintics like albendazole showing limited efficacy. Here, we report the isolation of piplartine from Piper truncatum Vell. (Piperaceae) and its potent in vitro activity against A. cantonensis larvae. Piplartine demonstrated superior efficacy to albendazole, with EC₅₀ values of 8.3 µM for first-stage larvae (L1) and 10.4 µM for infective third-stage larvae (L3), compared to 14.2 µM (L1) and 15.6 µM (L3) for albendazole. Notably, piplartine exhibited no toxicity in the Caenorhabditis elegans model at therapeutic concentrations, underscoring its selective antiparasitic action. In silico profiling further revealed favorable drug-likeness and pharmacokinetic properties, including high gastrointestinal absorption and blood–brain barrier permeability, which are critical for targeting neurotropic infections. As the first study to characterize the activity of piplartine against A. cantonensis, our work highlights its potential as a structurally novel anthelmintic lead. Based on the obtained results, piplartine may be considered a promising and accessible candidate for combating angiostrongyliasis and related helminthic infections. Full article

(This article belongs to the Section Biological and Natural Products)

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14 pages, 5368 KiB

Open AccessArticle

HClO as a Disinfectant: Assessment of Chemical Sustainability Aspects by a Morphological Study

by Alessandro Gessi, Giuseppe Marghella, Stefania Bruni, Alberto Ubaldini and Elena Tamburini

Chemistry 2025, 7(4), 104; https://doi.org/10.3390/chemistry7040104 - 23 Jun 2025

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Abstract

Hypochlorous acid solutions are used as effective disinfectants in many settings, including operating rooms and other hospital environments. During and after the COVID-19 pandemic, their use increased significantly, and this work stems from that development. In fact, despite their undoubtedly excellent properties, these [...] Read more.

Hypochlorous acid solutions are used as effective disinfectants in many settings, including operating rooms and other hospital environments. During and after the COVID-19 pandemic, their use increased significantly, and this work stems from that development. In fact, despite their undoubtedly excellent properties, these solutions can constitute a very aggressive system for a variety of different materials that are very common in those environments. Materials that can be subject to corrosion include steels, copper-based alloys, and components in electronic devices. This work aims to investigate the responses of these materials to long but intermittent exposures to HClO disinfectant solutions. It consists of a compatibility test, performed on several reference materials with HClO used as a surface disinfectant, connected with NaCl’s eventual presence/deposition over them. To perform the investigations in a manner consistent with the duration of compatible laboratory analyses, the samples were immersed in electrolytically prepared HClO solutions for 750 h, which is a duration considered equivalent to normal exposure to disinfectant aerosols over 3 years. Analyzing the large amount of experimental data gathered yielded interesting results. Where the exposure of non-metallic materials or steel did not lead to compatibility issues, bare metals showed degradation due to salt deposition. This article summarizes the morphological studies, i.e., a huge experimental work conducted at the ENEA IMPACT lab in Bologna and part of the PhD work of the corresponding author. Full article

(This article belongs to the Section Green and Environmental Chemistry)

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12 pages, 2672 KiB

Open AccessArticle

Visible-Light-Mediated Dehydrogenative Cross-Coupling of Azaarenes and Ethers

by Junsong Song, Wanyu Chen, Xin Chen, Yi Zhou, Bin Han, Yao Wang, Honghua Jia, Kai Guo, Jiangkai Qiu, Jian Wang and Canliang Ma

Chemistry 2025, 7(4), 103; https://doi.org/10.3390/chemistry7040103 - 23 Jun 2025

Viewed by 394

Abstract

Heteroaromatic motifs are prevalent in natural products and numerous high-value drug molecules. Consequently, the construction of alkylated heterocyclic frameworks holds significant importance. The Minisci reaction of heteroarenes has evolved into a flexible technique for the synthesis of substituted heterocyclic derivatives. However, the use [...] Read more.

Heteroaromatic motifs are prevalent in natural products and numerous high-value drug molecules. Consequently, the construction of alkylated heterocyclic frameworks holds significant importance. The Minisci reaction of heteroarenes has evolved into a flexible technique for the synthesis of substituted heterocyclic derivatives. However, the use of strong oxidants and external acid is inevitable during the reaction process. Herein, we present a versatile and accessible method for achieving cross dehydrogenation coupling between quinoline derivatives and inactive ether. This strategy utilizes inexpensive NaI and PPh₃ to support the reaction, obviating the need for metal complexes or sacrificial oxidants, and enables the straightforward synthesis of a diverse library of alkyl-substituted N-heteroarenes. Additionally, radical trapping experiments and fluorescence quenching experiments have been conducted to gain a more comprehensive understanding of the reaction mechanism. Full article

(This article belongs to the Special Issue Organic Chalcogen Chemistry: Recent Advances)

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17 pages, 1028 KiB

Open AccessArticle

Angular 6/6/5/6-Annelated Pyrrolidine-2,3-Diones: Growth-Regulating Activity in Chlorella vulgaris

by Anastasia D. Novokshonova, Pavel V. Khramtsov and Ekaterina E. Khramtsova

Chemistry 2025, 7(4), 102; https://doi.org/10.3390/chemistry7040102 - 21 Jun 2025

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Abstract

Chlorella vulgaris, a unicellular microalga with broad industrial applications, is a valuable source of bioactive compounds, including proteins, pigments, and lipids. However, optimizing its growth and metabolite production remains a challenge. This study investigates the potential of angular 6/6/5/6-annelated pyrrolidine-2,3-diones—structurally complex small [...] Read more.

Chlorella vulgaris, a unicellular microalga with broad industrial applications, is a valuable source of bioactive compounds, including proteins, pigments, and lipids. However, optimizing its growth and metabolite production remains a challenge. This study investigates the potential of angular 6/6/5/6-annelated pyrrolidine-2,3-diones—structurally complex small molecules resembling alkaloids and 13(14 → 8)abeo-steroids—as novel growth stimulants for C. vulgaris. A series of these compounds (20 structurally diverse derivatives, including 7 previously unreported ones) were synthesized and screened for their ability to enhance microalgal growth. Primary screening identified one compound as a promising candidate, significantly increasing algae cell concentration in microplate cultures. Subsequent validation in flask-scale experiments revealed that this candidate induced a 19% increase in protein content at 1 μmol/L, suggesting potential for protein enrichment in algal biomass. Stability studies of the candidate compound revealed its significant hydrolytic degradation in aqueous media. These findings highlight the potential of angular 6/6/5/6-annelated pyrrolidine-2,3-diones as modulators of microalgal metabolism, offering a new avenue for enhancing C. vulgaris biomass quality, particularly for protein-rich applications in the food and feed industries. Full article

(This article belongs to the Section Molecular Organics)

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Chemistry, Volume 7, Issue 4 (August 2025) – 11 articles

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