Search

The oxygen reduction reaction (ORR) has a crucial impact on the energy conversion efficiency and the performance of fuel cells, it is urgent to deliver low‐cost efficient ORR catalysts for the aim to scale up the utilization of fuel cells. In this study, three oxamidate copper(II) complexes [Cu2(trans‐L)(H2O)2(ClO4)2]·2H2O (Cuox), [Cu2(cis‐L)(bpy)(ClO4)2]·CH3OH (Cuoxbpy), and [Cu2(cis‐L)(mebpy)(ClO4)](ClO4) (Cuoxmebpy) (L = N,N–bis(2–pyridylmethyl)oxamide, bpy = 2,2′–bipyridine, and mebpy = 4,4′–dimethyl–2,2′–bipyridine) were prepared and characterized. The configuration of L varied from the trans form to the cis form as the bipyridines were introduced to the dicopper complex. The redox properties of three oxamidate copper(II) complexes and their catalytic activities for the ORR were studied in neutral aqueous solutions. The ORR onset potentials by Cuox, Cuoxbpy, and Cuoxmebpy were 0.417, 0.502, and 0.481 versus RHE, respectively. Three complexes homogeneously catalyzed the ORR to predominantly generate H2O2. A bimolecular catalytic pathway was proposed for the ORR mediated by Cuox, whereas a single‐molecular pathway was by Cuoxbpy and Cuoxmebpy. This work demonstrated that oxamidate metal complexes are promising ORR catalyst candidates provided that their electronic structures are appropriately tuned by altering the substituent on the organic ligands. [ABSTRACT FROM AUTHOR]

[Display omitted] The covalent bonding of a ruthenium bipyridine complex derivative with the aromatic network of single walled carbon nanotubes (SWNT) through a stepwise protocol is presented, thus yielding the sample SWNT-Ru. To do that, an-amino decorated phenanthroline is bonded to the nanotube by means of the diazonium chemistry protocol, providing anchoring points for discrete organometallic units as depicted by the solid characterization techniques employed. The hybrid material, able to emit upon excitation, is active in the visible light-driven photocatalytic oxidation of organic sulfides to sulfoxides. SWNT-Ru presents a wide scope being able to convert more than 10 substrates with different characteristics, including added-value chemicals, with a stable performance over more than 6 cycles without metal leaching and enhanced activity compared to related homogeneous complexes. A versatile character is also demonstrated since this hybrid catalyst follows both possible photooxidation mechanisms. [ABSTRACT FROM AUTHOR]

New bipyridine derivatives were synthesized using 2-oxo-4-(pyridin-3-yl)-6-(thiophen-2- yl)-1,2-dihydropyridine-3-carbonitrile 1a. Terpyridine derivatives were synthesized using 2-oxo-4- (pyridin-3-yl)-6-(pyridin-4-yl)-1,2-dihydropyridine-3-carbonitrile 1b as the starting material. Alkylation of compounds 1a, b gave the alkyl derivatives 2a, b which converted into acetohydrazides 3a,b. Treating the acetohydrazides with ethyl cyanoacetate obtained 2'-[2-(3,5-dioxopyrazolidin-1-yl)-2-oxoethoxy]-6'- (thiophen-2-yl)-3,4'-bipyridine-3'-carbonitrile 4a and 6'-[2-(3,5-dioxopyrazolidin-1-yl)-2-oxoethoxy]- (3,4':2',4''-terpyridine)-5'-carbonitrile 4b. While treatment of 3a, b with ethyl benzoylacetate obtained the carbonitrile derivatives 2'-(2-oxo-2-(5-oxo-3-phenyl-4,5-dihydropyrazol-1-yl)ethoxy)-6'-(thiophen-2- yl)-3,4'-bipyridine-3'-carbonitrile 5a and 6'-[2-oxo-2-(5-oxo-3-phenyl-4,5-dihydropyrazol-1-yl)ethoxy]- (3,4':2',4''-terpyridine)-5' carbonitrile 5b. Treating compounds 3a, b with two aromatic aldehydes (3,4-dihydroxy benzaldehyde, 4-chlorobenzaldehyde) obtained Schiff bases 6a-d. Finally, the treatment of 3a, b with p-toluenesulfonyl chloride (Tosyl chloride) obtained the corresponding benzene sulfonohydrazide 7a, b. IR, 1HNMR, 13CNMR, MS, and elemental analysis confirmed the of the synthesized compounds. The anticancer activity of the compounds was investigated against breast cancer MCF-7 cell line. Compound 6b demonstrated the strongest cytotoxic activity among the tested compounds and was more active than the reference drug 5-fluorouracil (5-FU). Thus, it was subjected to further investigations, where its effect on the cell cycle distribution in the MCF-7 cell line, its ability to inhibit topoisomerase II, the level of caspase-3/7 green flow cytometry assay was investigated. Also, molecular operating environmental docking (MOE) was studied and found that the inhibition efficiency could be organized as follows (S, Kcal/mol) values: 5b > 6d > 3a > 3b > 6b; while compound 5a did not show any interaction data belonging to the shaped complex with 1cca. Hence, most of the synthesized compounds can be used as anticancer and anti-oxidant agents. [ABSTRACT FROM AUTHOR]

Two molecular structures of a complex C26H16Cl2N2Pd (1) with a benzene hemisolvate (1•0.5C6H6) and a complex C34H20Cl2N2Pd (2) revealed similar conformations: one side of the arylethynyl group is flat to the bipyridine plane while the other side of the arylethynyl group is highly twisted to the plane because rhomb-like dimer fragments are formed between respective two complexes through CH⋯π interactions. The Hirshfeld surface analysis indicates that the most important contributions for the crystal packing of 1 are from H⋯H (33.6%), C⋯H/H⋯C (28.3%), Cl⋯H/H⋯Cl (17.8%), and C⋯C (10.6%) interactions and those of 2 are from H⋯H (36.5%), C⋯H/H⋯C (26.0%), Cl⋯H/H⋯Cl (15.7%), and C⋯C (12.3%) interactions, indicating the remarkable CH⋯π and electron distribution of molecules by Cl ions. The benzene solvate molecule of 1•0.5C6H6 performs to fill the internal space instead of the naphthyl group. Detailed crystallographic and DFT studies were performed to understand the molecular structures and the corresponding supramolecular associations. [ABSTRACT FROM AUTHOR]

Bipyridine and related compounds are starting materials or precursors for a variety of valuable substances such as biologically active molecules, ligands for catalysts, photosensitizers, viologens, and supramolecular architectures. Thus, it is important to classify their synthesis methods and understand their characteristics. Representative examples include methods using homo and heterocoupling of pyridine derivatives in the presence of a catalyst. Because bipyridine compounds strongly coordinate with metal centers, a decrease in catalytic activity and yield is often observed in the reaction system. To address this issue, this review provides insights into advances over the last ~30 years in bipyridine synthesis using metal complexes under both homogeneous and heterogeneous conditions. Moreover, strategies for bipyridine synthesis involving sulfur and phosphorous compounds are examined. These alternative pathways offer promising avenues for overcoming the challenges associated with traditional catalysis methods, providing a more comprehensive understanding of the synthesis landscape. [ABSTRACT FROM AUTHOR]

In this current study, we have synthesized four europium(III) complexes utilizing a tri-fluorinated β-diketone moiety: 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione (TFDH) with auxiliary ligand: 2,2′- bipyridine and its derivatives. FTIR, UV–Vis and luminescence spectroscopic characterizations were implemented for evaluation of the bonding and luminous characteristics in synthesized europium(III) complexes. Eight-coordination environment around Eu3+ ion has been demonstrated by 1H NMR spectral data. Photoluminescence (PL) study of these complexes has been carried out in powdered form. Characteristic red emitting behavior of Eu(III) ion was observed corresponds to the transition of 5D 0 →7F 2 in PL spectra of Eu(III) complexes. The CIE (Commission Internationale de l'Eclairage) chroma coordinates 1931 and CCT (Correlated Color Temperature) values were derived from the information obtained from the emission spectra. The Judd-Ofelt intensity parameters (Ω τ ) and excited state deactivation time ( τ ) in solid state have also been estimated. In the synthesized Eu(III) complexes, the europium ion was present in a highly polarizable ligand field, as demonstrated by the higher values of Ω 2. Values of band gap i.e. optical and electronic as well as the red luminous nature of prepared complexes showed up their utilization in display devices. [Display omitted] • Octa coordinated Eu(III) complexes were synthesized using 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione and N -donor ancillary ligand. • Most intense peak at ∼612 nm relative to 5D 0.→7F 2 transition was responsible for the characteristic red emission of europium complexes. • Computational analyses were performed with the help of JOES, Avogadro interface and ORCA. • The band gap as well as the red luminous behavior suggests the utilization of Eu(III) complexes in lighting and display applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Investigating new types of β-diketonate based europium complexes. • Incorporation of Eu complexes into PMMA films to comprehensively investigate their long-term photoluminescence stability. • Eu-films were subjected to light, indoor, and dark storage conditions for a duration of 720 h. • the FAC-based europium complexes demonstrated good stability under light, indoor, and dark conditions. • β-diketonate ligands structure impact directly on the photostability of the Eu-films. In this work, two β-diketonate ligands: dibenzoylmethane (DBM) and Hexafluoroacetone (hfac) have been selected to synthesize a series of β-diketonate europium complexes based on bipyridine and terpyridine derivatives. These complexes were then incorporated into PMMA films to comprehensively investigate their thermal and long-term photoluminescence stability. Comparatively, Eu(hfac) 3 L 1-5 demonstrated higher heat resistance than Eu(DBM) 3 L 1-5 , as indicated by their respective initial decomposition temperatures. Various aspects including absorbance, excitation, and emission were examined in solution, powder, and within the PMMA-doped films. Notably, the complexes exhibited a remarkable red emission peak at 613nm and a high photoluminescence quantum yield. To assess their stability, the films were subjected to light, indoor, and dark storage conditions for 720h, with photoluminescence measurements recorded at both 0h and 720h. The results revealed that the hfac-based europium complexes (Eu(hfac) 3 L 1-5) demonstrated good stability under light, indoor, and dark conditions compared to the DBM-based europium complexes (Eu(DBM) 3 L 1-5). This study highlights the direct impact of the β-diketonate ligand structure on the stability of such complexes in films, thus showcasing their potential for future applications in stable optoelectronic devices. [ABSTRACT FROM AUTHOR]