Search Results (37)

In this study, a novel polyacrylate-co-vinyl imidazole hydrogel-supported palladium (Pd) catalyst (P(AA-co-VI)@Pd) was prepared through heat-initiated polymerization, starting with the formation of a complex between vinyl imidazole and palladium chloride, followed by the addition of 75% neutralized acrylic acid (AA), crosslinking agent, and initiator. The structure and morphology of the catalyst were characterized using ICP-OES, SEM, EDX, Mapping, FT-IR, TGA, XRD, XPS and TEM techniques. It was confirmed that the catalyst exhibited excellent compatibility with water solvent and uniform distribution of Pd. The P(AA-co-VI)@Pd hydrogel catalyst demonstrated remarkable catalytic activity and ease of separation. Notably, in a Tsuji–Trost reaction, employing water as the solvent, it achieved a conversion rate as high as 94% at very low catalyst dosages, indicating its superior catalytic performance. Moreover, after six consecutive cycles, the catalyst maintained good activity and structural stability, highlighting its exceptional reusability and environmental friendliness. Furthermore, the outstanding efficiency of the catalyst was also observed in a Suzuki coupling reaction where both conversion rate and yield reached 100% and 99%, respectively, within just one hour reaction time, thus further validating its universality and efficacy across various chemical reactions. Full article

The branched structures of dendronized polymers can provide good steric stabilization for metal nanoparticle catalysts. In this work, an amphiphilic dendronized copolymer containing hydrophilic branched triethylene glycol moieties and hydrophobic branched ferrocenyl moieties is designed and prepared by one-pot ring-opening metathesis polymerization, and is used as the stabilizer for metal (Au, Ag and Pd) nanoparticles. These metal nanoparticles (Au nanoparticles: 3.5 ± 3.0 nm; Ag nanoparticles: 7.2 ± 4.0 nm; Pd nanoparticles: 2.5 ± 1.0 nm) are found to be highly active in both the 4-nitrophenol reduction and Suzuki–Miyaura reactions. In the 4-nitrophenol reduction, Pd nanoparticles have the highest catalytic ability (TOF: 2060 h⁻¹). In addition, Pd nanoparticles are also an efficient catalyst for Suzuki–Miyaura reactions (TOF: 1980 h⁻¹) and possess good applicability for diverse substrates. The amphiphilic dendronized copolymer will open a new door for the development of efficient metal nanoparticle catalysts. Full article

The modified suspension polymerization technique has been used for the preparation of composite microparticles from the mixture of glycidyl methacrylate (GMA), styrene (S), and divinylbenzene (DVB) in the presence of hydrophobized Fe₃O₄ nanoparticles. The obtained polymer microspheres were characterized using different instrumental and physicochemical techniques, modified with a zero-order PAMAM dendrimer, and impregnated with palladium(II) acetate solutions to immobilize palladium(II) ions. The resulting materials were preliminarily examined as catalysts in the Suzuki reaction between 4-bromotoluene and phenylboronic acid. It was found that the addition of magnetite particles to the composition of monomers provided polymer microparticles with embedded magnetic nanoparticles. The composite microparticles obtained showed a complex, multi-hollow, or raspberry-like morphology. After their modification, they could serve as recyclable catalysts for reactions that include both 4-bromotoluene and several other aryl bromides. Full article

The design of novel acceptor molecular structures based on classical building blocks is regarded as one of the efficient ways to explore the application of organic conjugated materials in conductivity and electronics. Here, a novel acceptor moiety, thiophene-vinyl-diketopyrrolopyrrole (TVDPP), was envisioned and prepared with a longer conjugation length and a more rigid structure than thiophene-diketopyrrolopyrrole (TDPP). The brominated TVDPP can be sequentially bonded to trimethyltin-containing benzo[c][1,2,5]thiadiazole units via Suzuki polycondensation to efficiently prepare the polymer PTVDPP-BSz, which features high molecular weight and excellent thermal stability. The polymerization process takes only 24 h and eliminates the need for chlorinated organic solvents or toxic tin-based reagents. Density functional theory (DFT) simulations and film morphology analyses verify the planarity and high crystallinity of the material, respectively, which facilitates the achievement of high carrier mobility. Conductivity measurements of the polymeric material in the organic transistor device show a hole mobility of 0.34 cm² V⁻¹ s⁻¹, which illustrates its potential for functionalized semiconductor applications. Full article

The cross-linked conjugated polymer poly(tetraphenylethene-co-biphenyl) (PTPEBP) nanoparticles were prepared by Suzuki-miniemulsion polymerization. The structure, morphology, and pore characteristics of PTPEBP nanoparticles were characterized by FTIR, NMR, SEM, and nitrogen adsorption and desorption measurements. PTPEBP presents a spherical nanoparticle morphology with a particle size of 56 nm; the specific surface area is 69.1 m²/g, and the distribution of the pore size is centered at about 2.5 nm. Due to the introduction of the tetraphenylethene unit, the fluorescence quantum yield of the PTPEBP nanoparticles reaches 8.14% in aqueous dispersion. Combining the porosity and nanoparticle morphology, the fluorescence sensing detection toward nitroaromatic explosives in the pure aqueous phase has been realized. The Stern–Volmer quenching constant for 2,4,6-trinitrophenol (TNP) detection is 2.50 × 10⁴ M⁻¹, the limit of detection is 1.07 μM, and the limit of quantification is 3.57 μM. Importantly, the detection effect of PTPEBP nanoparticles toward TNP did not change significantly after adding other nitroaromatic compounds, indicating that the anti-interference and selectivity for TNP detection in aqueous media is remarkable. In addition, the spike recovery test demonstrates the potential of PTPEBP nanoparticles for detecting TNP in natural environmental water samples. Full article

The synthesis of ladder-type 9,9′-bifluorenylidene-based conjugated polymer is reported. Unlike the typical synthetic strategy, the new designed ladder-type conjugated polymer is achieved via tandem Suzuki polymerization/Heck cyclization reaction in one-pot. In the preparation process, Suzuki polymerization reaction occurred first and then the intramolecular Heck cyclization followed smoothly under the same catalyst Pd(PPh₃)₄. The model reaction proved that the introduction of iodine (I) for this tandem reaction can effectively control the sequential bond-forming process and inhibit the additional competitive side reactions. Thus, small-molecule model compounds could be obtained in high yields. The successes of the synthesized small molecule and polymer compounds indicate that the Pd-catalyzed tandem reaction may be an effective strategy for improving extended π-conjugated materials. Full article

A synthetic strategy to access asymmetric dinuclear bis(ansa-metallocene) pre-catalysts is described. As a key step, the Pd-catalyzed Suzuki cross-coupling of 9,9-bis(trimethylsilyl)-fluoren-2-yl-boronic acid with a substituted 2-bromo-9H-fluorene generates an asymmetric 2,2′-bifluorene platform, which can be individually functionalized at the two differentiated 9-positions. Herein, as a first demonstration of this strategy, we report the asymmetric dinuclear bis(ansa-zirconocene) complex 2,2′-[{Me₂C(Flu)(Cp)}ZrCl₂][{Me₂C(^7-tBuFlu)(Cp)}ZrCl₂], which has been characterized with NMR spectroscopy and high-resolution mass spectrometry. The performance of this bimetallic pre-catalyst when combined with MAO has been evaluated in ethylene, propylene, and ethylene/1-hexene (co-)polymerization. This pre-catalyst is revealed to be less productive than the mononuclear reference pre-catalyst {Me₂C(^2,7-tBuFlu)(Cp)}ZrCl₂, likely because of higher steric hindrance induced by the linkage at the difluorenyl platform. The resulting (co-)polymers featured only slight differences in terms of molecular weights, tacticity, and comonomer incorporation. No bimodal molecular weight distribution was achieved at any produced polymer; this might have originated from the close similarity of the connected Cp/Flu moieties or a rapid chain-transfer phenomenon between the different active sites which were quite close to each other. Full article

Polymeric nanoparticles with reactive functional groups are an attractive platform for drug carriers that can be conjugated with drugs through a cleavable covalent linkage. Since the required functional groups vary depending on the drug molecule, there is a need for development of a novel post-modification method to introduce different functional groups to polymeric nanoparticles. We recently reported phenylboronic acid (PBA)-containing nanoparticles (BNP) with a unique framboidal morphology created via one-step aqueous dispersion polymerization. Since BNPs have high surface area due to their framboidal morphology and contain a high density of PBA groups, these particles can be used as nanocarriers for drugs that can bind to PBA groups such as curcumin and a catechol-bearing carbon monoxide donor. To further explore the potential of BNPs, in this article we report a novel strategy to introduce different functional groups to BNPs via the palladium-catalyzed Suzuki–Miyaura cross-coupling reaction between the PBA groups and iodo- and bromo-coupling partners. We developed a new catalytic system that efficiently catalyzes Suzuki–Miyaura reactions in water without the need for an organic solvent, as confirmed by NMR. Using this catalyst system, we show that BNPs can be functionalized with carboxylic acids, aldehyde, and hydrazide groups while keeping their original framboidal morphology as confirmed via IR, alizarin red assay, and TEM. Furthermore, the potential of the functionalized BNP in drug delivery applications was demonstrated by conjugating the hydrogen sulfide (H₂S)-releasing compound anethole dithiolone to carboxylic acid-functionalized BNPs and show their H₂S-releasing capability in cell lysate. Full article

During the last decades, palladium nanoparticles (Pd(0) NPs) and Pd(II) compounds were shown to be attractive catalysts for fine organic synthesis. Nanostructured Pd(0) or Pd(II) catalysts have a relatively low environmental impact, but, at the same time, they are indispensable for such processes as Suzuki cross-coupling. This paper describes the preparation of Pd(0) or Pd(II) supported/embedded in hyper-cross-linked polystyrene (HPS) and compares their activity in Suzuki cross-coupling between phenylboronic acid and 4-bromoanisole. Obviously, the palladium charge (Pd(0) ↔ Pd(II)) changes continuously during the reaction catalytic cycle. It would seem that the use of the starting palladium in the form of Pd(0) or Pd(II) should not affect the reaction’s kinetic laws for both catalysts, but their special individuality is manifested between them. Nanoparticulate Pd(0) catalysts are stable during the reaction. In contrast, catalysts based on Pd(II) are extremely active in the initial period of the reaction, but then the “hot form” of the catalyst is rapidly converted into the form of Pd(0), whose activity is identical to that of the preliminarily reduced catalyst. This work discusses the possible nature of this phenomenon. A mathematical model for Suzuki cross-coupling reaction was suggested that was able to adequately describe experimental data. The level of reliability (R²) of the correlation between the experimental and calculated data was R² = 0.97–0.99. Full article

The strong radioactivity of iodine compounds derived from nuclear power plant wastes has motivated the development of highly efficient adsorbents. Porous aromatic frameworks (PAFs) have attracted much attention due to their low density and diverse structure. In this work, an azo group containing PAF solid, denoted as LNU-58, was prepared through Suzuki polymerization of tris-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-phenyl)-amine and 3,5-dibromoazobenzene building monomers. Based on the specific polarity properities of the azo groups, the electron-rich aromatic fragments in the hierarchical architecture efficiently capture iodine molecules with an adsorption capacity of 3533.11 mg g⁻¹ (353 wt%) for gaseous iodine and 903.6 mg g⁻¹ (90 wt%) for dissolved iodine. The iodine uptake per specific surface area up to 8.55 wt% m⁻² g⁻¹ achieves the highest level among all porous adsorbents. This work illustrates the successful preparation of a new type of porous adsorbent that is expected to be applied in the field of practical iodine adsorption. Full article

This work deals with the synthesis of metal-free and porphyrin-based covalent organic polymers (COPs) by the Suzuki–Miyaura coupling carbon-carbon bond forming reaction to study the photocatalytic overall water splitting performance. Apart from using 5,10,15,20-Tetrakis-(4-bromophenyl)porphyrin, we have chosen different cross-linker monomers to induce 2-dimensional (2D) or 3-dimensional (3D) and different rigidity in their resulting polymeric molecular structure. The synthesised COPs were extensively characterised to reveal that the dimensionality and flexibility of the molecular structure play an intense role in the physical, photochemical, and electronic properties of the polymers. Photoinduced excited state of the COPs was evaluated by nanosecond time-resolved laser transient absorption spectroscopy (TAS) by analysing excited state kinetics and quenching experiments, photocurrent density measurements and photocatalytic deposition of Ru³⁺ to RuO_2, and photocatalysis. In summary, TAS experiments demonstrated that the transient excited state of these polymers has two decay kinetics and exhibit strong interaction with water molecules. Moreover, photocurrent and photocatalytic deposition experiments proved that charges are photoinduced and are found across the COP molecular network, but more important charges can migrate from the surface of the COP to the medium. Among the various COPs tested, COP–3 that has a flexible and 3D molecular structure reached the best photocatalytic performances, achieving a photocatalytic yield of 0.4 mmol H₂ × g_COP–3⁻¹ after 3 h irradiation. Full article

The sensitive and selective detection of nitroaromatic explosives is of great significance to national security and human health. Herein, the novel linear polymer l-PAnTPE and cross-linked polymer PAnTPE nanoparticles based on anthracene and tetraphenylethene groups were designed and successfully synthesized via Suzuki-miniemulsion polymerization. The particle sizes of the polymers are around 73 nm, making them well dispersible in water. The cross-linked polymer PAnTPE exhibits porous structure, which is beneficial for the diffusion/adsorption of analytes. The fluorescence sensing towards nitroaromatics was performed in the aqueous phase, and l-PAnTPE and PAnTPE nanoparticles showed different quenching degree towards different nitroaromatics. Among them, the quenching constant K_SV values of l-PAnTPE and PAnTPE towards 2,4,6-trinitrophenol (TNP) reach 1.8 × 10⁴ M⁻¹ and 4.0 × 10⁴ M⁻¹, respectively, which are 1–2 orders of magnitude higher than other nitroaromatic explosives, thus demonstrating the high sensitivity and selectivity of TNP detection in the aqueous phase. The sensing mechanism was further discussed to clarify this phenomenon by analyzing UV–Vis absorption, excitation, fluorescence spectra, cyclic voltammograms and fluorescence decay measurements. In addition, the paper strips tests exhibit that l-PAnTPE and PAnTPE have great potential in the application of fast, low-cost and on-site nitroaromatics detection. Full article

Because the combination of π-conjugated polymers with biocompatible synthetic counterparts leads to the development of bio-relevant functional materials, this paper reports a new oligo(2-methyl-2-oxazoline) (OMeOx)-containing thiophene macromonomer, denoted Th-OMeOx. It can be used as a reactive precursor for synthesis of a polymerizable 2,2’-3-OMeOx-substituted bithiophene by Suzuki coupling. Also a grafted polythiophene amphiphile with OMeOx side chains was synthesized by its self-acid-assisted polymerization (SAAP) in bulk. The results showed that Th-OMeOx is not only a reactive intermediate but also a versatile functional material in itself. This is due to the presence of 2-bromo-substituted thiophene and ω-hydroxyl functional end-groups, and due to the multiple functionalities encoded in its structure (photosensitivity, water self-dispersibility, self-assembling capacity). Thus, analysis of its behavior in solvents of different selectivities revealed that Th-OMeOx forms self-assembled structures (micelles or vesicles) by “direct dissolution”.Unexpectedly, by exciting the Th-OMeOx micelles formed in water with λ_abs of the OMeOx repeating units, the intensity of fluorescence emission varied in a concentration-dependent manner.These self-assembled structures showed excitation-dependent luminescence as well. Attributed to the clusteroluminescence phenomenon due to the aggregation and through space interactions of electron-rich groups in non-conjugated, non-aromatic OMeOx, this behavior certifies that polypeptides mimic the character of Th-OMeOx as a non-conventional intrinsic luminescent material. Full article

Stimuli-responsive polymeric nanoparticles (NPs) exhibit reversible changes in the dispersion or aggregation state in response to external stimuli. In this context, we designed and synthesized core-shell NPs with threonine-containing weak polyelectrolyte shells and fluorescent cross-linked cores, which are applicable for the detection of pH changes and amine compounds in aqueous solution. Stable and uniform NP(dTh) and NP(Fl), consisting of fluorescent symmetric diphenyl dithiophene (dTh) and diphenyl fluorene (Fl) cross-linked cores, were prepared by site-selective Suzuki coupling reactions in self-assembled block copolymer. NP(Fl) with the Fl unit in the core showed a high fluorescence intensity in different solvents, which is regarded as an aggregation-induced emission-type NP showing strong emission in aggregated states in the cross-linked core. Unimodal NPs were observed in water at different pH values, and the diameter of NP(Fl) changed from 122 (pH = 2) to 220 nm (pH = 11). Furthermore, pH-dependent changes of the fluorescence peak positions and intensities were detected, which may be due to the core aggregation derived from the deprotonation of the threonine-based shell fragment. Specific interactions between the threonine-based shell of NP(Fl) and amine compounds (triethylamine and p-phenylenediamine) resulted in fluorescence quenching, suggesting the feasibility of fluorescent amine detection. Full article

This work addresses the Suzuki cross-coupling between 4-bromoanisole (BrAn) and phenylboronic acid (PBA) in an environmentally benign ethanol–water solvent catalysed by mono- (Pd) and bimetallic (PdAu, PdCu, PdZn) nanoparticles (NPs) stabilised within hyper-cross-linked polystyrene (HPS) bearing tertiary amino groups. Small Pd NPs of about 2 nm in diameters were formed and stabilized by HPS independently in the presence of other metals. High catalytic activity and complete conversion of BrAn was attained at low Pd loading. Introduction of Zn to the catalyst composition resulted in the formation of Pd/Zn/ZnO NPs, which demonstrated nearly double activity as compared to Pd/HPS. Bimetallic core-shell PdAu/HPS samples were 3-fold more active as compared to Pd/HPS. Both Pd/HPS and PdAu/HPS samples revealed promising stability confirmed by catalyst recycling in repeated reaction runs. Full article