Sonogashira Coupling Reaction Research Articles

Synthesis, optical properties, and dual‐color halochromic fluorescence of novel π‐conjugated polymers bearing coumarin unit in the main chain

AbstractA series of novel π‐conjugated polymers bearing alternating coumarin and phenylene units in the main chain backbone was synthesized via Sonogashira coupling reaction. The red‐shifts in the absorption maxima of the polymers indicate the expansion of π‐conjugated system in the polymer main chains. These polymers exhibited strong green fluorescence in organic solvents. Clearly perceptible dual‐color halochromic fluorescence was confirmed for the polymers by the significantly reversible changes of emission color from green to blue during alkalization and acidification processes. The lactone ring opening and closing property in the coumarin molecule functioned as a controllable switch, broadening the applications of the coumarin‐based π‐conjugated polymers as acid–base responsive fluorescence materials.

Synthesis of inverse push-pull coumarin dyes and their application as solvatochromic probes and labelling agents for bacterial cell membranes

Coumarin derivatives have been widely employed across a great number of applications, such as laser dyes, bioimaging or chemossensors, owing to their strong fluorescence and high-quantum yields. These properties are highly tunable through structural modification, namely by the inclusion of electron-withdrawing groups (EWG) and electron-donating groups (EDG) at positions 3 and 7 of the coumarin scaffold, respectively. Comparatively, there aren't many reports of EDGs being employed at position 3, prompting us to investigate this new class of potential fluorophores.We undertook the synthesis of three novel ethynyl-linked aminophenyl-coumarin dyes, employing a key Sonogashira-coupling reaction to introduce the electron-rich tertiary aniline moiety. Two different amine donors were used, diphenylamino (coumarins A and B) and dimethylamino (coumarin C), as well as two alkoxy substituents, dibenzyloxy (A and C) and methylenedioxy (B), in the phenyl ring of the coumarin. All dyes show strong emission and significant positive solvatochromism. Additionally, they were employed as staining agents for the cellular membrane of S. pneumoniae, a Gram-positive bacterial pathogen. None of the three derivatives presented cytotoxic effects. Only A and B successfully labelled the bacterial membrane. In the case of B a very similar staining pattern and performance to that of standard dye Nile Red was observed, while A seemed to possess a more selective distribution.

4,4’-(Thiophene-2,5-diylbis(ethyne-2,1-diyl))bis(1-methyl-1-pyridinium) Iodide

In the vast field of organic functional materials, viologens are widely recognized as an extremely versatile family of substances, due in part to the possibility of extending conjugation between the terminal pyridinium rings, for instance through the insertion of additional aromatic moieties. In this work, a new, extended viologen with a thiophene core and two acetylene bonds is presented. It was synthesized through a straightforward route, using well-established Sonogashira coupling reactions, and its optical properties were investigated by UV–visible absorption and fluorescence spectroscopy, revealing a very interesting material for diverse fluorescence-related applications.

Designing strategically functionalized conjugated microporous polymers with pyrene and perylenetetracarboxylic dianhydride moieties with single-walled carbon nanotubes to enhance supercapacitive energy storage efficiency

We utilize straightforward and traditional Sonogashira coupling reactions to synthesize two conjugated microporous polymers linked with pyrene (referred to as PyT-PTCDA and PyT-PHTD CMPs) by combining the common precursor of 1,3,6,8-tetraethynylpyrene (PyT) with 1,7-dibromo-3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA-Br2) and 3,6-dibromophenanthrene-9,10-dione (PHTD-Br2). Various analytical techniques, including spectroscopy and microscopy, are employed to characterize these two PyT-CMP materials. The PyT-PTCDA CMP exhibits notable thermal stability (with a decomposition temperature of 351 °C and a char yield of 61 wt %). We combine the PyT-PTCDA and PyT-PHTD CMPs with exceptionally conducting single-walled carbon nanotubes (SWCNTs) through π-π stacking interactions between SWCNTs and PyT unit to improve their electrical conductivity and electrochemical performance. Electrochemical evaluations reveal that the PyT-PTCDA CMP/SWCNTs nanocomposite shows an impressive capacitance of 376 F g−1 (at 0.5 A g−1) in a three-electrode system. After undergoing 5000 cycles of charging and discharging, it maintained 98 % of its original capacitance while demonstrating an energy density of 52 Wh/kg. Additionally, in a symmetric coin cell system, the energy density is 17 Wh/kg and the capacitance is 119 F g−1 for PyT-PTCDA CMP/SWCNTs. This approach presents a promising avenue for developing high-performance supercapacitors by strategically blending PyT-CMPs with highly conductive SWCNTs.

Solvatochromic fluorescent ethynyl naphthalimide derivatives for detection of water in organic solvents

Three new derivatives of (4-methoxyphenyl) ethynyl-naphthalimide were synthesized by Sonogashira coupling reaction. These compounds showed robust and strong fluorescent signals, which shift from blue to orange as the solvent polarity increases. Computational calculations revealed that in low-polarity solvents, the molecules preferred a 90° rotation between the naphthalimide and ethynyl benzene fragments. In high-polarity solvents, where the energy barrier for rotation of the alkyne bond was higher, the molecules favored the 0° conformer, leading to longer emission wavelengths. The compound with a 2-methoxyethyl group tethered to the naphthalimide nitrogen demonstrated sensitivity to water presence in the ranges of 0–30 % (v/v) in THF, 0–15 % (v/v) in DMSO, 0–30 % (v/v) in MeCN, 0–15 % (v/v) in acetone, and 0–40 % (v/v) in EtOH. The detection limits for water were determined to be 0.0523 %, 0.1365 %, 0.0337 %, 0.0570 %, and 0.1170 % (v/v) in THF, DMSO, MeCN, acetone, and EtOH, respectively. The effectiveness of this compound in quantifying ethanol content in spirit samples was successfully demonstrated.

Hydrazine electrooxidation performance of cyano-substituted indole derivatives as organic anode catalyst

Here we present the new EWG-substituted indole derivatives, namely 2-((5-(1-methyl-2-phenyl-1 H-indol-3-yl)thiophen-2-yl)methylene) malonitrile (IPTM), 2-((5-(1-methyl-2-phenyl-1 H-indol-3-yl)furan-2yl)methyl)malonitrile(IPFM) and 2-((4-(1-methyl-2-phenyl-1 H-indol-3-yl)benzylidene) malonitrile (IPPM) was synthesized by using Sonogashira coupling, electrophilic cyclization, Suzuki-Miyaura coupling and condensation reactions. The isolated yields were obtained as 86 %, 71 %, and 69 % yields, respectively. Cyclic voltammetry(CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) were used for the electrochemical measurements to observe the electrocatalytic behavior of IPTM, IPFM and IPPM. The results exhibited that the highest-performance organic-based catalyst was 2.601 mA/cm2 (0.073 mA/mg) for IPPM which could be a good candidate as a metal-free electrocatalyst for hydrazine electrooxidation.

Cross-coupling and dehalogenation reactions of novel π-conjugated polymers bearing high-soluble coumarin unit in the main chain and their acid-base responsive fluorescence

A highly soluble coumarin monomer, 3,7-dibromo-4-octyloxycoumarin, was developed as the novel building block for π−conjugated polymers. Sonogashira coupling reaction, dehalogenation reaction, and Suzuki-Miyaura coupling reaction were carried out by using this new monomer as the main chain unit of π−conjugated polymer for polymerization. Introduction of a long alkoxy chain into coumarin monomer unit significantly improved the solubility of thus obtained polymers. The absorption and emission spectra of polymers showed red-shift compared to those of monomer, indicating the expansion of the π−conjugated system in the polymer main chain. Especially the polymers synthesized via Sonogashira coupling formed excimer in film state. The polymers showed acid-base responsibility with the addition of KOHaq and HClaq.

Construction of cationic conjugated microporous polymers containing pyrene units through post-cationic modification for enhanced antibacterial performance

BackgroundThe development of effective antibacterial agents with minimal cytotoxicity to human cells is a subject of great interest. Conjugated microporous polymers (CMPs) are a rapidly expanding and significant class of porous organic polymers. They are distinguished by their robust microporous architecture and π-conjugated framework. The molecular-level control over the pore structure and chemical composition of CMPs allows for precise customization to fulfill particular requirements. MethodsWe synthesized a cationic conjugated microporous polymer named Pyr-T-DPM Me CMP. This was achieved through post-synthetic modification of a pyrene-T-linked conjugated microporous polymer, Pyr-T-DPM CMP, formed via the Sonogashira coupling reaction of ethynyl pyrene (Pyr-T) and 2,5-dibromopyrimidine (Pyrimidine-Br2). The comprehensive analysis involved various techniques, including Fourier transform infrared (FTIR) spectroscopy, N2 adsorption/desorption isotherm, 13C solid-state NMR, X-ray photoelectron spectroscopy (XPS), thermogravimetry, transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Significant findingsThe antimicrobial efficacy of the newly synthesized CMPs was tested against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria. Due to the formation of N-methylpyrimidinium salts after quaternization, the cationic Pyr-T-DPM Me CMP exhibited enhanced bactericidal effectiveness against S. aureus compared to Pyr-T-DPM CMP, which lacked a positive charge. The viability of bacteria decreased with increasing concentrations of Pyr-T-DPM Me CMP, reaching maximum antimicrobial effectiveness at a concentration of 5 mg mL−1. To assess their impact on cell compatibility, we evaluated the cytotoxic effects on L929 cell fibroblasts, revealing minimal cytotoxicity towards L929 cells. Inspired by the superior antibacterial characteristics and exceptionally low toxicity of Pyr-T-DPM Me CMP, the novel cationic CMP developed in this study holds potential for application as beneficial antibacterial agent in the fields of environmental engineering and healthcare.

Low symmetry and functionalised organic cages prepared using Eglinton and Sonogashira coupling reactions

ABSTRACT Cages prepared using irreversible reactions in the cage-forming step typically give relatively low yields, but are more robust than cages formed through reversible bond formation reactions. The irreversible reactions are also well-suited to preparing functionalised and/or low symmetry species that are difficult to prepare using self – assembly. In this work, we prepare two hexanitrile-functionalised cages and a hexabromo-functionalised cage using Eglinton coupling reactions, with both hexanitrile-functionalised cages structurally characterised by X-ray crystallography. Yields for the functionalised cages (3–28%) were significantly lower than those previously reported for analogous unfunctionalised cages. We also prepared three cages using Sonogashira coupling reactions, including a tri-nitrile functionalised lower symmetry cage. Unfortunately, these reactions also suffered from low yields (3–11%), with the reaction to give the functionalised cage particularly low-yielding (3%). While the low yields meant we were unable to obtain sufficient amounts of compounds to measure their gas sorption properties, we were able to demonstrate that a hexanitrile cage could be post-synthetically modified to give a hexa-amidinium species.

Unique biomedical application of fluorescence derivatization based on palladium-catalyzed coupling reactions for HPLC analysis of pharmaceuticals and biomolecules.

Palladium-catalyzed coupling reactions are versatile and powerful tools for the construction of carbon-carbon bonds in organic synthesis. Although these reactions have favorable features that proceed selectively in mild reaction conditions using aqueous organic solvents, no attention has been given to their application in the field of biomedical analysis. Therefore, we focused on these reactions and evaluated the scope and limitations of their analytical performance. In this review, we describe the pros and cons and future trends of fluorescence derivatization of pharmaceuticals and biomolecules based on palladium-catalyzed coupling reactions such as Suzuki-Miyaura coupling, Mizoroki-Heck coupling, and Sonogashira coupling reactions for HPLC analysis.

Acenaphthylene-Based Chromophores for Dye-Sensitized Solar Cells: Synthesis, Spectroscopic Properties, and Theoretical Calculations.

A set of acenaphthylene dyes with arylethynyl π-bridges was tested for dye-sensitized solar cells (DSSCs). Crucial steps for the extension of the conjugated system from the acenaphylene core involved Sonogashira coupling reactions. Phenyl, thiophene, benzotriazole, and thieno-[3,2-b]thiophene moieties were employed to extend the conjugation of the π-bridges. The systems were characterized by cyclic voltammetry and by UV-vis absorption and emission. The spectroscopic characterization showed that the last three bridges resulted in red-shifted absorption and emission spectra relative to the parent phenyl-bridged compound, in accordance with TD-DFT calculations. The phenylethynyl derivative 6a achieved a conversion efficiency of 2.51% with Voc, Jsc, and FF values of 0.365 V, 13.32 mA/cm2, and 0.52, respectively. The efficiency of this compound improved to 3.15% with the addition of CDCA (10 mM), representing the best efficiency result in this study. The overall conversion efficiency of the other aryl derivatives 6b-d proved to be significantly inferior (14-40%) to that of 6a due to a significant decrease of Jsc.

Solvothermal single‐pot synthesis of Pd‐Fe3O4@GO catalyst: Enhanced catalytic performance in Sonogashira coupling reactions

In this study, we present a new approach to synthesizing a magnetically separable Pd‐Fe3O4@GO catalyst using a simple single‐pot method. The catalyst was employed in Sonogashira coupling reactions, demonstrating excellent results. The catalyst was studied using a various characterization method, including X‐ray photoelectron spectroscopy (XPS), scanning electron microscope–energy‐dispersive X‐ray spectroscopy (SEM‐EDS) mapping, TEM, X‐ray diffraction (XRD), FTIR, and inductively coupled plasma mass spectrometry (ICP‐MS). Pd‐Fe3O4@GO exhibited superior catalytic activity compared with its conventional counterparts in phenylacetylene‐iodobenzene coupling reactions under copper co‐catalyzed‐free and ligand‐free conditions, with a higher turnover frequency (TOF) of 118.3 h−1. Optimized conditions yielded high yields for various substrates, including inactive aryl chloride and bromide substrates, emphasizing its versatility. Also, a reaction mechanism was proposed and a kinetic model was developed. The catalyst's green chemistry potential was highlighted because of its high efficiency, purity of products, recoverability, and ease of preparation. Moreover, Pd‐Fe3O4@GO demonstrated impressive stability through multiple recycling rounds without loss of functionality, making it a promising tool for sustainable chemical processes.

Late-Stage Diversification of Pyrazoles as Antileishmanial Agents.

N-Pyrazolylcarboxamides and N-pyrazolylureas represent promising lead compounds for the development of novel antileishmanial drugs. Herein, we report the late-stage diversification of 3-bromopyrazoles 10 A/B and 14 A by Pd-catalyzed Sonogashira and Suzuki-Miyaura cross coupling reactions. The electron-withdrawing properties of the cyano moiety in 4-position of the pyrazole ring limited the acylation of the primary amino moiety in 5-position. A large set of pyrazoles bearing diverse aryl and alkynyl substituents in 3-position was prepared and the antileishmanial and antitrypanosomal activity was recorded. The urea 38 lacking the electron withdrawing cyano moiety in 4-position and containing the large 4-benzylpiperidinoo moiety exhibited a modest antileishmanial (IC50=19 μM) and antitrypanosomal activity (IC50=7.9 μM)). However, its considerable toxicity against the PMM and MRC-5 cells indicates low selectivity, i. e. a small gap between the desired antiparasitic activity and undesired cytotoxicity of <2- to 4-fold.

Synthesis, acid-base responsive fluorescence, and ion-selectivity of novel π-conjugated polymers containing coumarin unit in the main chain

A two-step synthetic method for four dibromocoumarin monomers (3,7-dibromo-4-methylcoumarin, 3, 6-dibromo-4-methylcoumarin, 3,7-dibromocoumarin, and 3,6-dibromocoumarin) containing von Pechmann reaction for the formation of coumarin ring followed by regioselective bromination at C3 position at monobrominated coumarins was developed. A series of novel coumarin-fluorene π-conjugated copolymers was synthesized by Sonogashira coupling reaction. The polymers exhibited absorption maxima at longer wavelength due to π-π* transition of the main chain, which indicates the expansion of π-conjugated system along the polymer main chain. The polymers showed acid-base responsive fluorescence due to the lactone ring opening-closing property in the main chain accompanied by the addition of alkali and acid. The polymers also exhibited ion selectivity between Na+ and K+ ion.

Bifunctional imidazolium linked tetraphenylethene based conjugated microporous polymers for dynamic antibacterial properties and supercapacitor electrodes

Using Sonogashira coupling reactions and a postmodification approach, we successfully synthesized TPET-Im CMP incorporating an imidazolium unit to enhance antibacterial properties and optimize its performance as a supercapacitor electrode.

PdII Triazolylidene Complexes: Ancillary Ligand Dependent Catalytic Applications in Sonogashira Coupling and α‐Arylation Reactions under Copper‐Free Conditions

AbstractComplexes ofN‐heterocyclic carbenes have become an irrefutable class of molecules for the researchers in the field of organocatalysis. They rank as one of the potent tools in organic chemistry, which have a wide range of uses in various commercially important processes. Palladium(II) mesoionic carbene (MIC) complexes embedded with PPh3 as an ancillary ligand appeared to be efficient catalysts for the aforementioned purpose. Two new triazolylidene‐based palladium(II) complexes bearing either Py or PPh3 as an ancillary ligand were synthesized, with chirality present at one of the nitrogen atoms of the triazolylidene moiety. The MIC unit in these complexes possesses a mesityl group at the C‐wingtip and 1‐(1‐naphthyl)ethyl substitution at the N‐wingtip. NMR spectroscopy and ESI mass spectrometry were utilized to analyze these complexes. For the determination of the structure of the palladium(II) complex possessing mixed MIC and PPh3 donor ligands, single crystal X‐ray diffraction was utilized. The new complexes were employed in α‐arylation reaction and Sonogashira coupling reactions under copper‐free conditions. While studying their catalytic activity, it was brought to the conclusion that the PdII MIC complex having PPh3 as an ancillary ligand surpassed the complex with Py as an ancillary ligand.The catalytic results of these complexes are also correlated with cyclic voltammetric (CV) data.

ZrO2 Supported Cu Nanoparticles for Sonogashira and Ullmann Coupling Reactions Under Palladium-Free Conditions

ZrO2 Supported Cu Nanoparticles for Sonogashira and Ullmann Coupling Reactions Under Palladium-Free Conditions

Tuning emission of luminescent 2-7 disubstituted sila-and germafluorenes with –(trifluoromethyl)phenyl, -(malononitrile)phenyl, and -nitrobenzene substituents

2,7-Disubstitution and DFT-guided design have been used to tune emission wavelengths for three new fluorescent 2,7-alkynyl(aryl)-3,6-dimethoxy-9,9-diphenyl-sila- and germafluorenes. Two germafluorenes with trifluoromethyl phenyl and nitrobenzene substituents were prepared using a Pd-catalyzed Sonogashira coupling reaction to incorporate alkynyl(aryl) groups at the 2,7-positions of the ring. Another new silafluorene was prepared by modifying a benzaldehyde-substituted silafluorene to incorporate a malononitrile group. These compounds were characterized utilizing multinuclear NMR, UV–Vis, and fluorescence spectroscopic techniques. The germafluorene with the trifluoromethyl phenyl substituent was also characterized via elemental analysis and X-ray crystallography. These metallafluorenes (MFs), which are yellow or red-orange crystals in the solid state, showed a wide range of quantum yields and spectroscopic features, with the malononitrile-containing MF exhibiting significantly red-shifted emission relative to other MFs. These data demonstrate the value in applying DFT to MF design and the dramatic impact the 2,7-substituent has on the optical properties of this class of compounds.

Aromatic systems with two and three pyridine-2,6-dicarbazolyl-3,5-dicarbonitrile fragments as electron-transporting organic semiconductors exhibiting long-lived emissions.

The pyridine-3,5-dicarbonitrile moiety has gained significant attention in the field of materials chemistry, particularly in the development of heavy-metal-free pure organic light-emitting diodes (OLEDs). Extensive research on organic compounds exhibiting thermally activated delayed fluorescence (TADF) has led to numerous patents and research articles. This study focuses on the synthesis and investigation of the semiconducting properties of polyaromatic π-systems containing two and three fragments of pyridine-2,6-dicarbazolyl-3,5-dicarbonitrile. The compounds are synthesized by Sonogashira coupling reactions and characterized by steady-state and time-resolved luminescence spectroscopy. The compounds show efficient intramolecular charge transfer (ICT) from the donor to the acceptor. The photoluminescence (PL) spectra of the solutions of the compounds showed non-structured emission peaks in the visible region, which are attributed to ICT emission. The PL intensities of the solutions of the compounds are enhanced after deoxygenation, which is indicative of TADF. The photoluminescence quantum yields and TADF properties of the compounds are sensitive to the medium. Cyclic voltammetry measurements indicate good hole-blocking and electron-injecting properties due to their high ionization potentials. Photoelectron spectroscopy and time-of-flight measurements reveal good electron-transporting properties for one of the compounds. In general, polyaromatic π-systems with pyridine-3,5-dicarbonitrile fragments demonstrate promising potential for use in organic electronic devices, such as OLEDs.

Controlling the light-induced structural isomerism of lipophilic azo-bridged porphyrin dimer via steric hindrance modulated functional linkers

Herein, two azo-bridged porphyrin dimers were synthesized via Sonogashira and Suzuki coupling reactions. The relationship between molecular structures and electronic structures was investigated by spectroscopic and electrochemical characterizations. In addition, the light-induced structural isomerism of lipophilic azo-Bridged porphyrin dimer could be controlled via steric hindrance modulated functional linkers, and it can only be succeeded in the case of expanded azo-bridged porphyrin dimer.