No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Pd/Cu-Catalyzed Sonogashira Cross-Coupling Polycondensation: A Promising Approach for Synthesizing Conjugated Polymers with Useful Applications
... Although the addition of copper enhances reactivity, it also necessitates oxygen exclusion to prevent unwanted alkyne homocoupling [12,13]. The product of Sonogashira coupling has found applications in diverse area such as dyes, sensors, electronics, polymers, natural products and pharmaceutical drugs [14][15][16][17][18][19][20][21][22]. The diphenyl acetylenes known as versatile biologically active motif having significant pharmacological potential across various disciplines and selective heterogeneous catalysts that can be customized for specific reactions [61,62]. ...
... The broad peak at 2θ = 15.84°, 22.54° and 34.61° presents due to semi-crystalline nature of cellulosesilica composite [18,19]. The peak at 2θ = 40.08°, ...
... Interestingly, 1,4-diiodobenzene exhibit good yields of di-coupled products ( Table 2, entries 17-18). Moreover, aryl halides such as 5-iodovanillin undergo coupling and subsequent cyclization with phenylacetylene, 4-methyl phenylacetylene and propargyl alcohol resulting in good yields of corresponding benzofuran derivatives ( Table 2, entries [19][20][21]. Bulky aryl halides for instance, 1-iodonaphthalene exhibited good yields of the desired products when coupled with phenylacetylene, 4-methyl phenylacetylene and propargyl alcohol ( Table 2, entries [22][23][24][25]. On the other hand, less reactive 4-bromobenzoic acid resulted moderate yields of substituted acetylenes when coupled with phenylacetylene, 4-methyl phenylacetylene and propargyl alcohol ( Table 2, entries [26][27][28][29]. ...
In present investigation, a cellulose/silica supported Schiff base Pd(II) catalyst, acronym as Cell/SiO2-Sal-Pd(II), has been designed and synthesized using cellulose as support. The catalyst was comprehensively characterized by advanced techniques such as FTIR, XRD, TGA, SEM, EDS, and BET/BJH. From the EDX analysis, the loading of palladium found to be 0.017 mol%. TEM analysis revealed ~ 70 nm particle size of the catalyst. The catalytic efficiency of Cell/SiO2-Sal-Pd(II) was thoroughly scrutinized in the context of the Sonogashira cross-coupling. Varity of functionalized diary acetylene derivatives have been achieved with admirable yields from coupling of aryl halides and phenyl acetylenes. The XRD, SEM and TGA analysis of recycled catalyst revealed remarkable catalytic activity. The proposed approach exhibits remarkable merits such as impressively low catalyst loading (0.009 mol%), elevated turnover numbers (up to 10,556), commendable turnover frequencies (up to 3519), exceptional thermal stability (up to 356.75 °C), high surface area (94.825 m²/g), superior catalyst reusability (up to 5 times) and the employment of an environmentally friendly aqueous acetonitrile solvent system.
Graphical abstract
Donor-acceptor (D-A) conjugated polymers are promising materials in optoelectronic applications, especially those forming ordered thin films. The processability of such conjugated macromolecules is typically enhanced by introducing bulky side chains, but it may affect their ordering and/or photophysical properties of the films. We show here the synthesis of surfacegrafted D-A polymer brushes using alternating attachment of tailored monomers serving as electron donors (D) and acceptors (A) via coupling reactions. In such a stepwise procedure, alternating copolymer brushes consisting of thiophene and benzothiadiazole-based moieties with precisely tailored thickness and no bulky substituents were formed. The utilization of Sonogashira coupling was shown to produce densely packed molecular wires of tailored thickness, while Stille coupling and Huisgen cycloaddition were less efficient, likely because of the higher flexibility of D-A bridging groups. The D-A brushes exhibit reduced bandgaps, semiconducting properties and can form aggregates, which can be adjusted by changing the grafting density of the chains.
A series of new linear conjugated co-polymers, incorporating different substituted thieno[3,2- b]thiophenes (TTs) as donor, acetylene as -bridge and benzothiadiazole (BT) as acceptor units, were synthesized via palladium-catalyzed Sonogashira cross-coupling polymerization. Optical, electrochemical, and thermal properties of these conjugated polymers were evaluated by means of UV-Vis, fluorescence, cyclic voltammetry, and thermogravimetric analysis. These readily soluble TT-BT co-polymers were employed as the semiconducting channel materials in bottom- gate, top-contact (BGTC) organic field-effect transistors (OFETs). The OFET devices showed p-channel field-effect behavior and successfully operated below -3 V with high yield. The polymeric materials comprising of TTs with aliphatic side chains exhibited better OFET performance compared to those with aromatic side chains. The OFETs using TT-BT with thienothiophene bearing nonyl (C9H19) side chain showed the highest hole average carrier mobility in the saturation regime, sat = 0.1 cm2/VS, on/off current ratio, ION/IOFF = 3.5 × 103 and smallest subthreshold swing, SS <200 mV/dec. The observed differentiation in device characteristics can be benefited in applications where selectivity is as essential as the filed- effect behavior.
Conjugated organic polymers have shown potential as photocatalysts for hydrogen production by water splitting. Taking advantage of a high throughput screening workflow, two series of acetylene-linked co-polymers were prepared and studied for their potential as photocatalysts for sacrificial hydrogen production from water. It was found that a triethynylbenzene-based polymer with a dibenzo[b,d]thiophene sulfone linker (TE11) had the highest performance in terms of hydrogen evolution rate under visible illumination in the presence of a sacrificial hole-scavenger. Synthetically elaborating the triethynylbenzene linker in TE11 by changing the core and by introducing nitrogen, the resulting hydrogen evolution rate was further increased by a factor of nearly two.
The effect of ethynylene spacers on the bandgap of alternating polymers, comprising 4,7-linked benzothiadiazole units and 2,7-linked fluorene, 2,7-linked carbazole or 2,6-linked anthracene repeat units has been investigated. The three novel polymers PFDEBT, PCDEBT and PPADEBT were prepared via the Sonogashira coupling reaction. The optical, electrochemical and thermal properties of the resulting polymers were compared and analysed. All polymers displayed low solubility in common organic solvents and have moderate molecular weights. Optical studies revealed that all the new ethynylene based-polymers displayed large bandgaps in excess of 2.1 eV. Results highlighted that incorporation of acetylene units between the benzothiadiazole electron accepting units and the other electron donor units over polymer chains leads to wide bandgaps as a result of the electron accepting properties of the acetylene units. The HOMO levels of the resulting polymers are unaffected by the different donor moieties used. However, varying the electron donor units can perturb the electron accepting ability of the main chain of polymers in this series and their LUMO levels. Anthracene-based polymer (PPADEBT) displayed the lowest LUMO level, while the fluorene-based polymer (PFDEBT) displayed the highest LUMO level. All polymers showed good stability to thermal degradation. The amorphous nature of these polymers was confirmed with powder X-ray diffraction studies.
Porous organic polymers (POPs), allowing fine synthetic control over their chemical structures, have shown great promise for addressing environmental issues. The high specific surface area and abundant porous structures of POPs can provide large storage space to adsorb dye molecules. Meanwhile, the introduction of polar groups, such as oxygen-containing functional groups in POPs, can not only improve the hydrophilicity, but also provide a strong interaction with dye molecules, thereby improving their adsorption performance. In this paper, an oxygen-rich porous polymer, POP-O, containing polar carbonyl and hydroxyl groups, was prepared by Sonogashira-Hagihara cross-coupling polycondensation. The characteristic results show that POP-O exhibits a hierarchical pore structure with a high specific surface area of 619 m2 g-1. The combination of abundant polar functional groups and high porosity endows POP-O with decent dye adsorption performance, and its theoretical maximum adsorption capacity for Rhodamine B (Rh B) is calculated to be 1012 mg g-1.
Anthracene is a highly valuable building block for luminescent conjugated polymers, particularly when a large singlet-triplet energy gap (ΔE ST ) is desired. Unfortunately, the extended π system of anthracene imparts a...
New conjugated polymers that incorporate dihexylanthradithiophene (DHADT) in the main chain were prepared by Stille, Sonogashira, and Yamamoto cross-coupling polymerization reactions. The polymerization chemistry is enabled by a soluble 5,11-dibromodihexylanthradithiophene monomer that is capable of cross-coupling reactions. Five readily soluble DHADT containing polymers were prepared and characterized experimentally and computationally. These polymers possess HOMO energies of −5.18 eV to −5.43 eV and LUMO energies of −3.0 eV to −2.82 eV. The notable optical features include broad absorption and band gaps ranging from 1.62 eV to 2.15 eV. Polymers were tested in organic field effect transistors and were found to operate in the p-type regime.
Calix[4]pyrrole‐based porous organic polymers (P1–P3) for removing organic micropollutants from water were prepared. A bowl‐shaped α,α,α,α‐tetraalkynyl calix[4]pyrrole and diketopyrrolopyrrole monomer were crosslinked via Sonogashira coupling to produce a 3D network polymer, P1. P1 proved too hydrophobic for use as an adsorbent and was converted to the corresponding neutral polymer P2 (containing carboxylic acid groups) and its anionic derivative P3 (containing carboxylate anion groups). Anionic P3 outperformed P2 in screening studies involving a variety of model organic micropollutants of different charge, hydrophilicity and functionality. P3 proved particularly effective for cationic micropollutants. The theoretical maximum adsorption capacity (qmax,e) of P3 reached 454 mg g⁻¹ for the dye methylene blue, 344 mg g⁻¹ for the pesticide paraquat, and 495 mg g⁻¹ for diquat. These uptake values are significantly higher than those of most synthetic adsorbent materials reported to date.
A process for the de novo synthesis of imino‐C‐glycosides is described. The methodology is based on the reaction of 1‐C‐stannylated iminosugars with various electrophiles under the conditions of Migita‐Kosugi‐Stille cross‐couplings, which gives 1‐C‐substituted iminosugar derivatives in a stereoretentive process. The required iminoglycosyl stannanes are obtained by way of the highly stereoselective addition of tributylstannyllithium to (SR)‐ or (SS)‐N‐tert‐butanesulfinyl glycosylamines, followed by an activation cyclization sequence. Most interestingly, the methodology is tunable: the configuration of the tin adduct is controlled exclusively by the tert‐butanesulfinyl auxiliary, thus giving access after ring formation to ‘α’‐configured or ‘β’‐configured iminoglycosyl stannanes. With the subsequent stereoretentive C−C bond‐forming process, the methodology allows the synthesis of pseudo anomers of imino‐C‐glycosyl compounds in a controlled fashion.
image
The heteroleptic dirhodium paddlewheel catalyst 7 with a chiral carboxylate/acetamidate ligand sphere is uniquely effective in asymmetric [2+1] cycloadditions with α‐diazo‐α‐trimethylstannyl (silyl, germyl) acetate. Originally discovered as a trace impurity in a sample of the homoleptic parent complex [Rh2((R)‐TPCP)4] (5), it is shown that the protic acetamidate ligand is quintessential for rendering 7 highly enantioselective. The ‐NH group is thought to lock the ensuing metal carbene in place via interligand hydrogen bonding. The resulting stannylated cyclopropanes undergo “stereoretentive” cross coupling, which shows for the first time that even chiral quarternary carbon centers can be made by the Stille–Migita reaction.
Less is more : Take one chiral ligand from a standard paddlewheel dirhodium tetracarboxylate complex out and replace it by acetamidate and you switch on reactivity and harness outstanding enantioselectivity in cyclopropanations with α‐stannylated‐α‐diazoesters. Even though the products contain a tert ‐alkylstannane moiety, „stereoretentive“ Stille cross coupling is shown to be possible.
Abstract
The heteroleptic dirhodium paddlewheel catalyst 7 with a chiral carboxylate/acetamidate ligand sphere is uniquely effective in asymmetric [2+1] cycloadditions with α‐diazo‐α‐trimethylstannyl (silyl, germyl) acetate. Originally discovered as a trace impurity in a sample of the homoleptic parent complex [Rh2((R )‐TPCP)4] (5 ), it is shown that the protic acetamidate ligand is quintessential for rendering 7 highly enantioselective. The ‐NH group is thought to lock the ensuing metal carbene in place via interligand hydrogen bonding. The resulting stannylated cyclopropanes undergo “stereoretentive” cross coupling, which shows for the first time that even chiral quarternary carbon centers can be made by the Stille–Migita reaction.
Palladium supported magnetic nanoparticle (Pd@Fe3O4/AMOCAA) was easily prepared in the presence of Scrophularia striata extract and fully characterized by FT‐IR, SEM, VSM, TEM, TGA, XRD and EDAX. It was successfully employed as an easily separable and reusable effective heterogeneous catalyst classical Suzuki and Sonogashira cross‐coupling reaction. Sustainability of the methodology was reserved by easy recovery of the catalyst using an external magnet and reusing it for 7 times without appreciable loss of its catalytic activity. A new simpler methodology has been developed for the C‐C bond formation reaction following classical Suzuki andSonogashira coupling by using Pd complexed with coumarin‐3‐acetic acidderivative tailored magnetic nanoparticles as a novel nanocatalyst.
Thiophene-based conjugated polymers hold an irreplaceable position among the continuously growing plethora of conjugated polymers due to their exceptional optical and conductive properties, which has made them a centre of attention for the past few decades and many researchers have contributed tremendously by designing novel strategies to reach more efficient materials for electronic applications. This review aims to highlight the recent (2012–2019) findings in design and synthesis of novel thiophene-based conjugated polymers for optical and electronic devices using organometallic polycondensation strategies. Nickel- and palladium-based protocols are the main focus of this account. Among them nickel-catalyzed Kumada catalyst-transfer polycondensation, nickel-catalyzed deprotonative cross-coupling polycondensation, palladium-catalyzed Suzuki–Miyaura and Migita–Kosugi–Stille couplings are the most popular strategies known so far for the synthesis of functionalized regioregular polythiophenes exhibiting fascinating properties such as electronic, optoelectronic, chemosensitivity, liquid crystallinity and high conductivity. This account also presents a brief overview of direct arylation polymerization (DArP) protocol that has shown a great potential to lessen the drawbacks of conventional polymerization techniques. DArP is a cost-effective and green method as it circumvents the need for the synthesis of arylene diboronic acid/diboronic ester and distannyl arylenes using toxic precursors. DArP also puts off the need to preactivate the C–H bonds, hence, presenting a facile route to synthesize polymers with controlled molecular weight, low polydispersity index, high regioregularity and tunable optoelectronic properties using palladium-based catalytic systems.
In the present work, a new type of semiconducting acetophenone and thiophene side‐arm based polyaryleneethynylene (PAE) conjugated polymers (CPs) were synthesized using the Heck–Sonogashira cross‐coupling reaction. The new type of monomers and APAEC8, APAEC12, APAEF8, TPAEC8, TPAEC12, and TPAEF8 (PAE CPs) were synthesized and characterized using Fourier transform IR, NMR and high resolution mass spectrometry studies. The average molecular weight of the CPs was determined using gel permeation chromatography. The data obtained from optical properties in the UV–visible and photoluminescence spectral studies were used to calculate the values of the Stokes shift. Among the six CPs studied, TPAEC8 was found to possess a lower optical band gap (Eg = 2.112 eV) than those of the other CPs. The data obtained from different studies, it was found that TPAEC8 exhibits better properties than the other CPs and can be used in the field of organic based photonic, electronic and other sensor applications. © 2020 Society of Chemical Industry
The commercially available and cheap Pd/C was found to promote Sonogashira couplings in the environmentally friendly choline chloride/glycerol eutectic mixture in the absence of external ligands. Under heterogeneous conditions, (hetero)aryl iodides were successfully coupled with both aromatic and aliphatic alkynes in yields ranging from 50 to 99 % within 3 h at 60 °C. The aforementioned catalytic system proved to be effective also towards electron‐rich iodides, which are notoriously known to be poorly reactive in Pd‐catalyzed Sonogashira coupling reactions. The eutectic mixture and the catalyst could easily and successfully be recycled up to four times with an E‐factor as low as 24.4.
The acyl Sonogashira reaction represents an extension of Sonogashira cross-coupling to acid chlorides which replace aryl or vinyl halides, while terminal acetylenes are used as coupling partners in both reactions. The introduction of a carbonyl functional group on the alkyne backbone determines a radical change in the reactivity of the products. Indeed, α,β-alkynyl ketones can be easily converted into different heterocyclic compounds depending on the experimental conditions employed. Due to its potential, the acyl Sonogashira reaction has been deeply studied with particular attention to the nature of the catalysts and to the structures of both coupling compounds. Considering these two aspects, in this review, a detailed analysis of the literature data regarding the acyl Sonogashira reaction and its role in the synthesis of several heterocyclic derivatives is reported.
A highly enantioselective dicarbofunctionalization of unactivated alkenes was implemented by a Pd‐catalyzed asymmetric tandem Heck/Suzuki coupling reaction. This reaction represents the first example of a highly enantioselective intramolecular cyclization/cross‐coupling of olefin‐tethered aryl halides with alkyl‐, alkenyl‐ or arylboronic acids, and provides rapid access to a number of chiral compounds, such as dihydrobenzofurans, indolines, chromanes, and indanes bearing a quaternary stereocenter, in good yields with excellent enantioselectivities. The practicality of this reaction was validated in the modification of biologically complex molecules such as peptides, piperitol, CB2 receptor agonists, etc. Moreover, the synthesis of two enantiomers can be easily realized by simple change in the order of the steps in the coupling sequence.
The Suzuki–Miyaura cross-coupling reaction is one of the most reliable methods for the construction of carbon–carbon bonds in solution. However, examples for the corresponding solid-state cross-coupling reactions remain scarce. Herein, we report the first broadly applicable mechanochemical protocol for a solid-state palladium-catalyzed organoboron cross-coupling reaction using an olefin additive. Compared to previous studies, the newly developed protocol shows a substantially broadened substrate scope. Our mechanistic data suggest that olefin additives might act as dispersants for the palladium-based catalyst to suppress higher aggregation of the nanoparticles, and also as stabilizer for the active monomeric Pd(0) species, thus facilitating these challenging solid-state C–C bond forming cross-coupling reactions.
A novel π-stacked polymer based on a pseudo–meta–linked [2.2]paracyclophane moieties was synthesized by Sonogashira-Hagihara coupling. The UV-vis absorption spectra of the synthesized polymer and model compounds revealed an extension of the conjugation length owing to the through-space conjugation. The optical properties of the π-stacked dimer with the pseudo–meta–linked [2.2]paracyclophane unit were compared with those of the corresponding dimers with the pseudo–ortho– and pseudo–para–linked [2.2]paracyclophane units.
Two indolo[3,2‐b]carbazole (ICZ)‐based polymers have been designed and synthesized using Sonogashira cross‐coupling based on dibromoindolo[3,2‐b]carbazoles and 2,7‐diethynylfluorene or 9,10‐diethynylanthracene. The 2, 8 positions of the ICZ moiety has been used for the bridging of arylene ethynylene structure to form the polymer backbone. The characterization has been done by Fourier transform infrared, proton nuclear magnetic resonance, ultraviolet–visible and (UV–vis) fluorescence spectroscopic methods. The polymers, moderately soluble in aprotic and chlorinated solvents, have been found to possess thermal stability above 300°C. The band gap examinations, executed through cyclic voltammetry and complemented by UV–vis studies, indicated their semiconducting nature and the possibility for their utilization for the fabrication of polymer solar cells and for optical switching applications. Interestingly, the new diethynylindolocarbazole systems have been found to act as Bronsted acid sensors as well as a Hg²⁺ receptors. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 46940
An organometallic monomer containing fused metallacyclic building block, a diiododithienotitanacyclopentadiene derivative, was prepared by the reaction of 3,3′-dilithiobithiophene and titanocene dichloride followed by the iodination with N-iodosuccinimide. The polymerization of the diiodinated monomer with 1,4-dioctyloxy-2,5-diethynylbenzene was carried out in the presence of palladium dichloride/4,5-bis(diphenylphosphino)-9,9-dimethylxanthene as a catalyst and diisopropylamine as a base to produce a black-colored organometallic polymer in 53% yield, which is soluble in organic solvents and stable towards both air and moisture. The absorption maximum (λmax) of the polymer is observed at 435 nm, which appeared in the longer wavelength compared to those of a model compound, a 2,7-bis(phenylethynyl)dithienotitanacyclopentadiene derivative (λmax = 309 nm and 393 nm). The optical band gap (Eg) of the polymer was estimated to be 2.24 eV, which is narrower than that of the model compound (2.47 eV) and the corresponding polymer possessing titanafluorene units (2.80 eV), which we described previously.
The Migita-Kosugi-Stille coupling reaction is a powerful method for the formation of carboncarbon bonds but often requires high temperatures that are not tolerated by all substrates. Herein, we report that irradiation with UV light accelerates this coupling reaction at room temperature in air in the presence of the commercially available PdCl2(PPh3)2 catalyst. This UVlight- assisted coupling reaction requires the presence of molecular oxygen, with mechanistic studies revealing that singlet oxygen is most likely involved in the reaction.
Heck cross-coupling reaction (HCR) is one of the few transition metal catalyzed CC bond-forming reactions, which has been considered as the most effective, direct, and atom economical synthetic method using various catalytic systems. Heck reaction is widely employed in numerous syntheses including preparation of pharmaceutical and biologically active compounds, agrochemicals, natural products, fine chemicals, etc. Commonly, Pd-based catalysts have been used in HCR. In recent decades, the application of biopolymers as natural and effective supports has received attention due to their being cost effective, abundance, and non-toxicity. In fact, recent studies demonstrated that biopolymer-based catalysts had high sorption capacities, chelating activities, versatility, and stability, which make them potentially applicable as green materials (supports) in HCR. These catalytic systems present high stability and recyclability after several cycles of reaction. This review aims at providing an overview of the current progresses made towards the application of various polysaccharide and gelatin-supported metal catalysts in HCR in recent years. Natural polymers such as starch, gum, pectin, chitin, chitosan, cellulose, alginate and gelatin have been used as natural supports for metal-based catalysts in HCR. Diverse aspects of the reactions, different methods of preparation and application of polysaccharide and gelatin-based catalysts and their reusability have been reviewed.
We have reported a waste-minimized protocol for the Sonogashira cross-coupling exploiting the safe use of a CPME/water azeotropic mixture and the utilization of a heterogeneous hybrid palladium catalyst supported onto a silica/β-cyclodextrin matrix in continuous flow. The use of the aq CPME azeotrope has proven to be crucial to enhance the catalyst performance including very low metal leaching. In addition, we have also completed the flow protocol by setting a downstream in-line liquid/liquid separation that allows the continuous recovery and reuse of the CPME fraction leading to consistent waste reduction. Finally,E-factor distribution and safety/hazard analysis have been performed highlighting the chemical and environmental efficiency of our protocol.
Developing ambipolar organic semiconducting materials is essential for complementary-like inverters and light-emitting transistors. In this study, three new dithienocoronenediimide (DTCDI)-derived triads, DTCDI-BT , DTCDI-BBT and DTCDI-BNT , were designed and synthesized, in...
Covalent triazine frameworks (CTFs), as a burgeoning type of porous organic material, have attracted increasing attention in a lot of research fields, including gas separation, heterogeneous catalysis, etc. In particular, stemming from their heteroatom effect (HAE), incorporated with the merits of π-conjugated frameworks, electron-rich triazine units and extraordinary chemical stability, they exhibit prospective potential applications in chemical sensing. In this paper, a triazine-based conjugated porous organic polymer (DPA-CTF) containing anthracene units was used to study the sensing effects on nitroaromatic compounds and metal ions. Intriguingly, DPA-CTF showed sensitive detection performance towards nitroaromatic explosives, especially p-nitroaniline (p-NA). Besides, it also exhibited high sensitivity toward Fe3+ ions compared to other metal ions. A series of characterization studies and computational simulations were used to explain the mechanism of the luminescence quenching effect. These results manifest that the new synthesized CTF is a promising candidate as a chemical sensor for p-NA and Fe3+ ions.
In this paper, we describe the preparation and characterization of a new magnetic nanocatalyst supported palladium(II) acetate, which has a core-shell structure that developed based on the Fe3O4 functionalization using triethanolamine. Finally, palladium(II) was immobilized onto the Fe3O4@TEA core-shell structure, and the nanocatalyst (Fe3O4@TEA-Pd) was synthesized. This catalyst was characterized by Map analysis, Fourier-transform infrared spectroscopy, X-ray diffraction analysis, Thermogravimetric analysis, Transmission electron microscopy, Scanning electron microscopy, Vibrating-sample magnetometer, Inductively coupled plasma emission spectroscopy, Energy-dispersive X-ray spectroscopy techniques, and Hot-filtration test. This novel catalyst can be a cost-effective and practical catalyst for carbon-carbon bond construction reactions, and it has shown significant reactivity, stability, and high efficiency in the Heck coupling reactions with olefins and various aryl halides. Fe3O4@TEA-Pd, as a heterogeneous palladium catalyst, can be quickly recovered and can be reused in several runs without significantly reducing its catalytic activity. Other advantages of this catalyst include easy workup methods, affordable, and minimal palladium leaching.
A novel catalyst with a yolk-shell structure was designed to overcome the leaching of noble metals in heterogeneous catalysis. Through a template method, palladium (Pd) nanoparticles were encapsulated by hollow spherical covalent organic frameworks (COFs) consisting of 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde (Tp) and p-phenylenediamine (Pa). The final catalyst with a yolk-shell structure was denoted as (Pd/C)@TpPa COFs. The unique morphology and chemical structure of this novel composite (Pd/C)@TpPa COFs were confirmed by a transmission electron microscope (TEM), a laser particle analyzer, X-ray diffraction (XRD), and N2 adsorption and desorption. Subsequently, to demonstrate its catalytic performance brought by structural design, this novel catalyst was applied to catalyze the Suzuki reaction. Interestingly, this catalyst exhibited a brilliant size cutoff efficiency for aryl benzene amounting to 100 % and achieved a high conversion with only 0.05 mol% Pd loading. Besides, this catalyst could be readily recovered via filtration and reused for at least five consecutive cycles without any significant loss in its activity.
The synthesis of a polymer containing alternating titanafluorene and arylene ethynylene moieties is described. The polymerization of a 2,7-dibromo-9-titanafluorene derivative with 1,4-dioctyloxy-2,5-diethynylbenzene is carried out at 70 °C for 48 h in tetrahydrofuran (THF) in the presence of palladium dichloride/4,5-bis(diphenylphosphino)-9,9-dimethylxanthene as a catalyst and diisopropylamine as a base to produce a dark red polymer. The polymer thus obtained is soluble in organic solvents, and stable towards both air and moisture. In the UV-vis absorption spectrum of the polymer, the absorption maxima (λmax) are observed at 321 nm and 395 nm, which are bathochromically shifted compared to those of a model compound of the repeating unit, a 2,7-bis(phenylethynyl)titanafluorene derivative (λmax = 309 nm and 364 nm). The optical band gap (Eg) of the polymer is estimated to be 2.8 eV on the basis of the absorption onset, which is narrower than that of the model compound (3.1 eV).
Air and water pollution poses a serious threat to public health and the sustainable development of the ecological environment. Here, we report the fabrication of new low-resistance nanofilters based on thiophene-based conjugated microporous polymer (T-CMP) nanotubes to remove harmful particulate matter (PM) from air effectively. T-CMP nanotube filters feature inherent superhydrophobicity and hierarchical pores and are prepared by a facile one-pot synthesis. The PM removal efficiency of T-CMP nanotube filters at 90 ± 5% relative humidity exceeds 99.798 ± 0.055% for PM0.3 and 99.998 ± 0.002% for PM2.5, while the lowest pressure drop in the filtration system is only 5 Pa, which is 1-2 orders of magnitude lower than that of traditional fiber-based filters. Benefitting from their excellent porous feature and intrinsic superhydrophobicity, T-CMP nanotube filters also display higher flux during continuous oil-water separation. Based on this superior separation performance, better physicochemical stability, facile manufacturing, and easy scaling-up, such T-CMP nanotube filters might hold great potential for a wide range of applications even under harsh conditions, including PM removal, water treatment, and so on.
Calix[4]pyrrole‐based porous organic polymers have been prepared for water purification. The structure of the polymer P1 could be easily modified to yield the anionic polymer P3, which showed particularly effective adsorption for cationic micropollutants. Theoretical maximum adsorption capacities of 454 mg g⁻¹ for the dye methylene blue, 344 mg g⁻¹ for the pesticide paraquat, and 495 mg g⁻¹ for diquat were determined for P3.
Abstract
Calix[4]pyrrole‐based porous organic polymers (P1–P3) for removing organic micropollutants from water were prepared. A bowl‐shaped α,α,α,α‐tetraalkynyl calix[4]pyrrole and diketopyrrolopyrrole monomer were crosslinked via Sonogashira coupling to produce a 3D network polymer, P1. P1 proved too hydrophobic for use as an adsorbent and was converted to the corresponding neutral polymer P2 (containing carboxylic acid groups) and its anionic derivative P3 (containing carboxylate anion groups). Anionic P3 outperformed P2 in screening studies involving a variety of model organic micropollutants of different charge, hydrophilicity and functionality. P3 proved particularly effective for cationic micropollutants. The theoretical maximum adsorption capacity (qmax,e) of P3 reached 454 mg g⁻¹ for the dye methylene blue, 344 mg g⁻¹ for the pesticide paraquat, and 495 mg g⁻¹ for diquat. These uptake values are significantly higher than those of most synthetic adsorbent materials reported to date.
Three thiophene-based conjugated microporous polymers (CMPs: TTPTh, DBTh, and TBTh) were prepared by Sonogashira–Hagihara cross-coupling polymerization, and their structures were characterized by FTIR, ss ¹³C NMR, and elemental analyses. The obtained TTPTh, DBTh, and TBTh have excellent thermal stability with decomposition temperatures of 615, 298, and 290 °C and high porosity with BET surface areas of 564.97, 416.99, and 521.30 m² g⁻¹, respectively. The results reveal that the conjugation of the CMPs plays an essential role in determining the fluorescence sensing performance. Because of the perfect conjugation arising from a low volume of the building block or low degree of cross-linking, DBTh has high fluorescence sensing sensitivity to 2,4-dinitrophenol (DNP) and iodine with Ksv values of 5.76 × 10⁴ and 4.52 × 10⁴ L mol⁻¹ and LODs of 1.56 × 10⁻¹⁰ and 3.32 × 10⁻¹² mol L⁻¹, respectively. To the best of our knowledge, the sensitivity to DNP and iodine of DBTh is the highest among all thiophene-based CMPs reported to date. Our study provides an essential understanding for the structure design of fluorescent sensors of CMPs.
Designing new materials for effective detoxification of chemical warfare agents (CWAs) is of current interest given the recent use of CWAs. Although halogenated boron-dipyrromethene derivatives (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene or BDP or BODIPY) at the 2 and 6 positions have been extensively explored as efficient photosensitizers for generating singlet oxygen (1O2) in homogenous media, their utilization in the design of porous organic polymers (POPs) has remained elusive due to the difficulty of controlling polymerization processes through cross-coupling synthetic pathways. Our approach to overcome these difficulties and prepare halogenated BODIPY-based porous organic polymers (X-BDP-POP where X = Br or I) represents an attractive alternative through post-synthetic modification (PSM) of the parent hydrogenated-polymer. Upon synthesis of both the parent polymer, H-BDP-POP, and its post-synthetically modified derivatives, Br-BDP-POP and I-BDP-POP, the BET surface areas of all POPs have been measured and found to be 640, 430, and 400 m2·g-1, respectively. In addition, the insertion of heavy halogen atoms at the 2 and 6 positions of the BODIPY unit leads to quenching of fluorescence (both polymer and solution-phase monomer forms) and enhancement of phosphorescence (detectable for polymer form only), as a result of efficient intersystem crossing. The heterogeneous photocatalytic activities of both the parent POP and its derivative for the detoxification of the sulfur mustard simulant, 2-chloroethyl ethyl sulfide (CEES), have been examined; the results show significant enhancement in the generation of the singlet oxygen (1O2). Both bromination and iodination of H-BDP-POP served to shorten by five-fold the time needed for selective and catalytic photo-oxidation of CEES to 2-chloroethyl ethyl sulfoxide (CEESO).
Energy transfer was explored in a series of poly(phenylene ethynylene) (PPE) polymers with increasing lengths that were end-capped with thiophene-benzothiadiazole (TBT) groups to form fully conjugated donor-acceptor polymers. For the polymers in solution, ultrafast transient absorption and time-resolved fluorescence spectroscopy reveal the majority of energy transfer from the PPE backbone to the TBT endcaps occurs rapidly, with sub-picosecond and picosecond kinetics, and the rates independent of the size of the polymer. The quantum efficiency for energy transfer was inversely proportional to the length of the polymers. Despite the highly conjugated structure, intrachain exciton hopping along the PPE backbone is significantly slower than the rate of radiative decay. The presence of an additional deleterious decay pathway for PPE excited state was also uncovered for the TBT-capped polymers. The photophysical phenomena are viewed in the context of the positioning of molecular orbitals, conjugation, and torsional effects, as determined by density functional theory calculations. The results of the photophysical characterization of this structurally well-defined system provide critical insight into the design of highly conjugated light-harvesting systems and their behavior as “molecular wires."
Amorphous network materials are increasingly important with applications including as supercapacitors, battery anodes, and proton conduction membranes. Design of these materials is hampered by the amorphous nature of the structure and sensitivity to synthetic conditions. Here, we show that through artificial synthesis, fully mimicking the catalytic formation cycle and full synthetic conditions, we can generate structural models that can fully describe the physical properties of these amorphous network materials. This opens up pathways for rational design where complex structural influences, such as solvent and catalyst choice, can be taken into account.
The synthesis and transformations of a π-conjugated tellurophene-containing polymer are described. A π-conjugated tellurophene-containing polymer was obtained in 56% yield by the Sonogashira-Hagihara cross-coupling polycondensation of 2,5-di(4-bromophenyl)tellurophene and 1,4-bis(2-ethylhexyloxy)-2,5-diethynylbenzene at 80 °C for 24 h using tris(dibenzylideneacetone)dipalladium(0) (Pd2(dba)3)/2-dicyclohexylphosphino-2,4,6-triisopropylbiphenyl (XPhos) as a catalyst and triethylamine as a base. The resulting polymer was transformed to a reactive lithiated polymer by the reaction with n-butyllithium (2.4 equiv) at −78 °C to −60 °C for 3 h, which was further converted into a butadiene-containing and a germole-containing π-conjugated polymers by the reactions with hydrochloric acid and dimethylgermanium dichloride at −60 °C to ambient temperature for 12 h in 83% and 85% yields, respectively, by precipitation into MeOH. The obtained germole-containing polymer reveals the absorption onset (λonset) at 492 nm which is longer than those of the tellurophene-containing polymer and butadiene-containing polymer (λonset = 488 nm and 472 nm, respectively), presumably due to the lowering of the LUMO energy level by the σ*-π* orbital interaction. The germole-containing polymer exhibit a blue photoluminescence with an emission maxima (Emax) at 471 nm.
Here we report a polymeric semiconductor (ODATT) comprising alkoxy anthracene (ODA) and thienothiophene (TT) polymerized by stille coupling reaction with the Pd catalyst. The optical properties of the polymer: PC71BM blend films are used by the UV-Visible absorption spectroscopy. The ODATT blends with PC71BM exhibit a maximal power conversion efficiency of 2.2% via thermal annealing treatment. Morphological analysis of the polymer: PC71BM blend films demonstrate the influence of ODATT polymer segregation on device performance by atomic force microscopy and transmission electron microscopy. We confirmed that ODATT has enhanced fill factor after thermal annealing treatment from the reduced series and shunt resistance from morphological enhancement.
The effective synthesis of functional nanoplatforms for simple, selective, and sensitive hydrogen sulfide detection has received significant attention due to the toxicity of hydrogen sulfide. Here, a new porphyrin-based porous organic polymer, FePPOPEPA, was fabricated through a Pd/CuI-catalyzed Sonogashira cross-coupling reaction between tris(4-ethynylphenyl)amine and iron(III) 5,10,15,20-tetrakis-(4’-bromophenyl)porphytinato (FeTBrPP). Results showed that FePPOPEPA has a porous framework, high BET surface areas, wide pore size distribution, abundant surface catalytic active sites, and excellent stability as well as reusability. In the presence of H2O2, FePPOPEPA had high peroxidase-like activity toward 3,3′,5,5′-tetramethylbenzidine (TMB). Based on these findings, FePPOPEPA was used for the first time as an efficient colorimetric probe for sensitive and selective detection of sulfide ions with a low detection limit (0.013 μM) within 3 min. The feasibility of this method for real water samples was validated via a standard addition experiment. Moreover, the catalytic inhibition mechanism of S2- to FePPOPEPA was disclosed by XPS spectra.
A series of novel polysiloxane compounds possessing third-order non-linear optical properties were synthesized using PMMS (poly[3-mercaptopropylmethylsiloxane]) as the main chain structure. The electron-rich alkyne side chain containing a dialkylamine substituent was grafted to the backbone via a thiol-ene click polymerization followed by a Sonogashira cross-coupling reaction. The donor-acceptor chromophores were inserted into the side chain of the polymer by a [2 + 2] click reaction allowing the molecule to have a broader absorption in the visible and near-infrared regions and a narrower optical band gap. After the click reaction, the polymer undergoes a transition from reverse saturation absorption to saturable absorption (RSA-SA). All polymers displayed good solubility and photophysical properties, and were thermally stable. Z-scan experiments showed that all compounds possess unique non-linear optical properties.
Poly(aryleneethynylene)s-based conjugated polymers have attracted significant interests for the fundamental understanding of the aggregation behavior, fluorescence emission and the electronic coupling through noncovalent stacking interactions. Herein, we investigated the aggregation-induced red-shift emission of a recently synthesized conjugated polymer P1 with AIEgen substituents on the side chain, and a similar counterpart P2 with the same backbone was also prepared to imply their electronic coupling processes and aggregation behaviors from the photophysical properties. The result from 2D-WAXD indicated that P1 had a sheet-like structure and the smectic phase was observed to present the interdigitated molecular packing along the smectic layer. The photoluminescence emission was distinctly red-shifted about 110 nm from 454 nm in THF solution to 564 nm in the solid state, which is due to the rotation of the main chain and the stacking behavior of the side-chain substituents. The poly(aryleneethynylene)s derivatives were easy to crystallize because of their high degree of rigid conjugation, herein, the introction of multi-alkyl tails into the terminal of the side chains improved the rheological properties and made them suitable for fabricating high-resolution high-ordered fluorescent patterns by nanoimprinting lithography, which would open an avenue to extend the future optoelectronic applications.
We report herein an investigation on the use of eucalyptol as new solvent for organic transformations applied to the Migita-Kosugi-Stille palladium-catalyzed cross-coupling reaction. Heterocycles containing oxygen, sulfur and nitrogen were chosen as starting materials. Eucalyptol turned out to be a viable sustainable alternative to common solvents for this reaction.
There has been a growing interest in discovering new approaches for the preparation of step-growth polymers as they hold a large margin of polymer manufacture since the beginning of the synthetic polymer era. After their distinctive advantages have been realized, light induced processes have been adapted to almost all kinds of polymerization processes including step-growth polymerizations. This mini review focuses mainly on the new developments in the field of step-growth polymerizations activated by light induced processes. The new discoveries are generally based on light induced pericyclic reactions, ketene chemistry and radical coupling processes. In comparison to the conventional strategies, the advantages of these particular approaches are also discussed.
In this study, diketopyrrolopyrrole-alt-thiophene (P1 and P2) and perylene-diimide-alt-thiophene (P3 and P4) based donor-π-acceptor (D-π-A) copolymers have been synthesized from the corresponding monomers through Pd-catalyzed Sonogashira polymerization protocol. The well defined and soluble π-conjugated copolymers having alkyl and fluoroalkyl substituents (P1-P4) have been characterized by multinuclear NMR spectra as well as by tetradetector GPC studies showing molecular weight (Mn) in the range of 18–20 kDa with good polydispersity indices of 1.31–1.48. The donor-acceptor based copolymers absorb broadly throughout the visible region. Notably, perylene diimide-thiophene based copolymers (P3 and P4) exhibits an absorption onset at ca. 800 nm corresponding to a bandgap of 1.63 and 1.61 eV (Egopt). DFT computational studies of the model π-conjugated units have also been investigated to understand the molecular geometries and electronic properties of the polymeric unit. The synthesized D-π-A polymers have been utilized as active materials for polymer-sensitized solar cells (PSSCs). The copolymers are effectively adsorbed onto the surface of nanostructured TiO2 photoanode as a result of facile interaction of the anchored –CO units with the metal oxide surface. The spectral profile of the polymer films on mesoporous oxide surface approximately similar to the solution absorption spectra of the polymer. Interestingly, the polymers featuring perylene diimide unit (P3 and P4) exhibit promising power conversion efficiency (PCE) of 2.71 and 2.96% with a short circuit current (JSC) of 7.54 and 7.85 mA cm⁻² respectively, and IPCE of 42–45% under 1.5 AM illumination.
The first synthesis of the fully conjugated ethynylene‐linked polymer incorporating boron dipyrrine complex (BODIPY) and zinc porphyrin in the main chain was performed based on the exclusive Sonogashira polycondensation. Comprehensive experimental and theoretical investigations lead to an elaborate synthetic route to circumvent the possible side reactions of BODIPY in the presence of the palladium catalyst. Additionally, optimization of the synthetic conditions found that dichloromethane as the solvent suppresses the formation of the pseudo‐trans dimer of the copper acetylide and mitigates the undesired oxidative homocoupling reaction. Eventually, the exclusive Sonogashira polycondensation in dichloromethane provided the alternating BODIPY–porphyrin ethynylene‐conjugated polymer, which displayed absorption up to the near‐infrared wavelengths. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 The first synthesis of the fully conjugated ethynylene‐linked polymer incorporating boron dipyrrin complex (BODIPY) and zinc porphyrin in the main chain was performed based on the exclusive Sonogashira polycondensation. Optimization of the synthetic conditions found that dichloromethane as the solvent suppresses the formation of the pseudo‐trans dimer of the copper acetylide and mitigates the undesired oxidative homocoupling reaction. The alternating BODIPY–porphyrin ethynylene‐conjugated polymer, which displayed absorption up to the near‐infrared wavelengths.
The oxidation pathways and products of a discrete, sulfide endcapped donor-acceptor-donor (D/A/D) molecule, namely propylenedioxythiophene-benzothiadiazole-propylenedioxythiophene, are investigated. The electrochemical and chemical oxidations proceed by two distinct pathways. Specifically, electrochemical oxidation undergoes a sequential two-step, one-electron (1e–) oxidation with a 117 mV difference between consecutive half wave potentials. In contrast, chemical oxidation by antimony(V) chloride (SbCl5) led to the identification of four different oxidized species; (a) the 1e– oxidized state and (b) its decomposition route to a two-electron (2e–) oxidized molecule with a ketone terminal group, (c) the 2e– oxidized state and (d) its generation by atom transfer oxidation via formation of a chloride-adduct. The latter is deter-mined to be a product of electrophilic chloronium ion (2e–) oxidation at a critical SbCl5 concentration (0.1 M or higher) in dichloromethane, via formation of a chloride adduct intermediate which we confirm by high-resolution mass spectrometry. This gives new insight into the concentration dependent reactivity of SbCl5 as a chemical oxidant. More notably, the decomposition of the sulfide endcapped radical cation to a ketone endcapped, 2e– oxidized product under ambient air proved the instability of the 1e– oxidized state. The electronic, optical, and magnetic properties and geometric structures of the 1e– and 2e– oxidized hexachloroantimonate salts are fully characterized by a combination of electrochemistry, x-ray crystallography, UV-vis-NIR, EPR, NMR spectroscopies, and density functional theory (DFT) calculations. The aim of this study is to provide a thorough understanding of the electron transfer pathways of a D/A/D -conjugated molecule for potential application in organic electrochromic devices.
Sonogashira coupling of two different diketopyrrolopyrrole (DPP)-containing dihaloarenes with the same aromatic bisalkyne resulted in two new conjugated polymers with the same backbone but different pendant groups on the DPP moiety. The polymers were found to have designed chemical structures via structural characterizations in comparison with three monomers. The molecular weight measurement further demonstrated the formation of polymers with polydispersity index around 2, consistent with the polycondensation nature of the polymerization based on Sonogashira coupling. Both polymers could dissolve in many organic solvents, and the one with long alkyl side group on DPP moiety had better solubility. Photophysical investigation showed that both polymers had typical absorption/emission of conjugated polymers, and varying the solvent did not have large influence. Compared with other polar solvents, toluene reduced the quantum yield of fluorescence of the polymers, especially for the one with long alkyl pedant group, accompanying with slight red-shift in absorption/emission. The difference in the absorption/emission wavelengths between the polymers was similar to that between the corresponding monomers. Adding water into the THF solution of polymers reduced the emission intensity but no redshift was observed. Discussion about the structure-property relationships was carried out in detail.
The formation of the C–C bond is a major and important reaction in synthetic organic chemistry and frequently catalyzed by transition-metal catalysts. Among them, Kumada–Tamao–Corriu coupling reaction is providing a simple methodology and extensively employed in the art of organic synthesis. In this review, we try to highlight the recent advances in the applications of Kumada–Tamao–Corriu coupling reaction by updating of our previous review from 2012 up to date.
Graphical abstract
Open image in new window
A porphyrin-containing polymers exhibiting various degrees of Glaser-Hay coupling is reported. Sonogashira polycondensation of ethynyl-porphyrin (EP) with tetrafluoroquinone diimine (fQI) is found to be prone to homo-coupling; a problem underestimated in the literature. 1H-NMR and photophysical analysis are used to assess the ratio of Glaser vs. Sonogashira couplings. Optimized conditions to perform Glaser-free Sonogashira polycondensations are provided and the optimization increases Mn from 9700 to 18900. Applied to a conjugated polymer it shows both decreasing homo-coupling and 180% enhancement in Mn.
A novel method for photochemical step-growth synthesis of poy(N-ethyl carbazole) (PEC) via consecutive diphenyl iodonium hexafluorophospate (Ph2I+PF6-) mediated electron transfer and coupling reactions is reported. The photoinduced electron transfer reaction of the excited N-ethyl carbazole (EC) in the presence of Ph2I+PF6- as the oxidizing salt proceeded to efficiently give EC radical cations (EC+.). Subsequently, the protons released concomitantly with coupling of two EC radical cations. The successive reactions involving excitation, electron transfer, proton release, and coupling lead to the formation of PEC. The electrochemical properties and surface morphology of the thin films of the formed polymers before and after dedoping were investigated by cyclic voltammetry, differential pulse voltammetry and atomic force microscopy techniques, respectively.