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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]

Supramolecular peptide assemblies have been widely used for the development of biomedical, catalytical, and optical materials with chiral nanostructures in view of the intrinsic chirality of peptides. However, the assembly pathway and chiral transformation behavior of various peptides remain largely elusive especially for the transient assemblies under out‐of‐equilibrium conditions. Herein, the N‐fluorenylmethoxycarbonyl‐protected phenylalanine‐tyrosine dipeptide (Fmoc‐FY) was used as a peptide assembly platform, which showed that the assembly proceeds multistep evolution. The original spheres caused by liquid‐liquid phase separation (LLPS) can nucleate and elongate into the formation of right‐handed helices which were metastable and easily converted into microribbons. Interestingly, a bipyridine derivative can be introduced to effectively control the assembly pathway and induce the formation of thermodynamically stable right‐handed or left‐handed helices at different stoichiometric ratios. In addition, the chiral assembly can also be regulated by ultrasound or enzyme catalysis. This minimalistic system not only broadens the nucleation‐elongation mechanisms of protein aggregates but also promotes the controllable design and development of chiral biomaterials. [ABSTRACT FROM AUTHOR]

Here, we present the preparation and characterization of two novel picrate salts. The 2,2′-bis(pyridinium)ketone picrate, DPK-PA (1), crystallizes in the triclinic system and centrosymmetric space group P 1 ¯ , with unit cell parameters a = 9.378(17) Å, b = 9.790(15) Å, c = 10.141(16) Å, α = 99.63(7)°, β = 99.09(8)°, and γ = 102.55(8)°, while the 4,4′-bis(tert-butyl)-2-pyridine-2-pyridinium picrate, BBBPY-PA (2), crystallizes in the non-centrosymmetric P212121 space group, orthorhombic unit cell parameters a = 6.3902(6) Å, b = 23.416(3) Å, and c = 16.7320(18) Å. Both crystal structures present an ion-pair in the asymmetric unit, one picrate anion, and one bipyridine derivative. In the DPK-PA (1) structure, the molecule of DPK presents one intramolecular N1-H ⋯ N H-bond that contributes to stabilizing the planar conformation of DPK. The absence of intramolecular H-bonding in the BBBPY-PA (2) can be explained by the steric hindrance of the tert-butyl group. For DPK-PA (1) and BBBPY-PA (2), the crystal packing is stabilized N–H ⋯ O strong hydrogen bonding interactions, which could be identified by the Hirshfeld surface analysis and fingerprint plots. The compounds were also studied by UV–Vis and infrared analyses, which may support the statement of the formation of new material. Finally, as an attempt to obtain a molecular system to act as a chemical sensor, we studied the fluorescence of both compounds, in solution and in solid state; however, no fluorescence was observed. [ABSTRACT FROM AUTHOR]

Starting from 3‐oxo‐N‐(3‐pyridyl)butanamide, as key intermediate, the title compounds were synthesized in good yields. Reaction of the pyridine‐carboxamide 1 with hydrazonoyl chlorides 3a,b and with triethyl orthoformate afforded the corresponding pyrazole‐carboxamides 6a,b, and the bis‐pyridine 7, respectively. Coupling of the pyridine‐carboxamide 1 with 3‐phenylpyrazole‐5‐diazonium chloride gave the hydrazone 10 which upon heating in pyridine afforded the pyrazolo[5,1‐c]‐1,2,4‐triazine derivative 11. Reaction of the pyridine‐carboxamide 1 with arylmethylenepropanedinitrile derivatives afforded 1,3′‐bipyridines 13a–c. Structure elucidation of the newly synthesized compounds was carried out using IR, NMR spectroscopy, and mass spectrometry. The extensive theoretical and experimental mechanical studies of the pyrazole derivative 6a were in accordance with its elemental analysis, FT‐IR, NMR, and MS spectral data. Moreover, computer analyses indicated that the pyridine derivatives 13a,b predominated over the pyran derivatives 14a,b as the adducts. In addition, the optimization of compounds utilized the HF/6‐31G(d) and DFT/B3LYP/6‐31G(d) basis sets. Furthermore, the physical descriptors of these compounds demonstrated their stability, and NMR correlation investigations were also carried out. [ABSTRACT FROM AUTHOR]

The supramolecular complex formation between donor (E)-bis(18-crown-6)azobenzene ((E)-1) and bis(ammoniopropyl) derivatives of bipyridine and dipyridylethylene acceptors (2, (E)-3) was studied in MeCN using steady-state absorption and fluorescence spectroscopy, fluorescence kinetics, and quantum-chemical (DFT, TDDFT, QDPT) calculations. The complexes are quite stable, but they undergo decomposition via substitution by alkali and alkaline-earth metal cations. The formation of 1:1 and 1:2 complexes between (E)-1 and alkali and alkaline-earth metal cations (Mn+) was confirmed. Spectral-kinetic parameters and stability constants were calculated. The determined stability constants are generally lower than those for bis(crown)stilbene complexes due to moderate electron-donor ability of azobenzene. The plot of fluorescence quantum yields of 1·(Mn+)2vs charge density of the metal cation shows two separate linear relations for unipositive and dipositive ions. The results of quantum-chemical calculations supported the conclusions derived from steady-state experiments. The most stable conformations of pseudocyclic complex (E)-1·2 and two metal complexes were found. The latter involve 4 or 6 molecules of acetonitrile per each complex: (E)-1·(Ca2+)2·(MeCN)4, (E)-1·(K+)2·(MeCN)6. Based upon quantum-chemical calculations of model species, the character of absorption bands of crowns and their complexes with actual energy conversion pathway are discussed. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: In recent years, the construction of stable multicomponent assembled structures on surfaces and the exploration of the assembled mechanism have become research hotspots. In this paper, the azobenzene‐carboxylic acid called (E)‐4',4"'‐(diazene‐1,2‐diyl) bis(([1,1'‐biphenyl]‐3,5‐dicarboxylic acid)) (H4DBBD) could self‐assemble into regular network structure at heptanoic acid/graphite via hydrogen bonding, and could be regulated into analogous kagomé network by coronene (COR) molecules. In addition, a series of bipyridine derivatives were further introduced to construct bi‐component systems with H4DBBD molecules, and successfully induced diversified structural transitions of H4DBBD on the graphite surface. Combined with scanning tunneling microscope (STM) and density functional theory (DFT) calculations, we have investigated the diversified structural transitions and analyzed the formation mechanism of the assembled systems. [ABSTRACT FROM AUTHOR]

An efficient gold [Au]‐catalyzed one‐pot synthesis has been developed for the construction of biologically interesting mono‐ and bipyridines by utilizing the commercially available cyclic ketones and propargylamine in a sealed tube. The formation of bipyridine derivative 21 a indicates that annulation followed by retro‐Diels–Alder reaction is occurring with norbornene system. However, keto‐derivatives containing bicyclo[2.2.2]octene system 25 indicate that retro‐Diels–Alder reaction is not facile. Compounds 32 a and 33 a were subjected to ring opening cross‐ metathesis to generate diversity and further functionalization of pyridine derivatives. [ABSTRACT FROM AUTHOR]

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The structural transformations of metal nanoclusters are typically quite complex processes involving the formation and breakage of several bonds, and thus are challenging to study. Herein, we report a case where two lacunary Keggin polyoxometallate templated silver single-pods [PW9O34@Ag51] (SD/Ag51b) fuse to a double-pod [(PW9O34)2@Ag72] by reacting with 4,4'-bipyridine (bipy) or 1,4-bis(4-pyridinylmethyl)piperazine (pi-bipy). Their crystal structures reveal the formation of a 2D 44-sql layer (SD/Ag72a) with bipy and a 3D pcu framework (SD/Ag72c) with pi-bipy. The PW9O349− retains its structure during the cluster fusion and cluster-based network formation. Although the two processes, stripping of an Ag-ligands interface followed by fusion, and polymerization, are difficult to envisage, electrospray ionization mass spectrometry provides enough evidences for such a proposal to be made. Through this example, we expect the structural transformation to become a powerful method for synthesizing silver nanoclusters and their infinite networks, and to evolve from trial-and-error to rational. Controlling the structural transformations of metal clusters is challenging. Here, the authors synthesize a silver nanocluster and study the structural changes that take place upon reaction with bipyridine derivatives. [ABSTRACT FROM AUTHOR]

In this work we show, using the example of a series of [Cu(Xantphos)(N^N)]+ complexes (N^N being substituted 5-phenyl-bipyridine) with different peripheral N^N ligands, that substituents distant from the main action zone can have a significant effect on the physicochemical properties of the system. By using the C≡C bond on the periphery of the coordination environment, three hybrid molecular systems with −Si(CH3)3, −Au(PR3), and −C2HN3(CH2)C10H7 fragments were produced. The Cu(I) complexes thus obtained demonstrate complicated emission behaviour, which was investigated by spectroscopic, electrochemical, and computational methods in order to understand the mechanism of energy transfer. It was found that the −Si(CH3)3 fragment connected to the peripheral C≡C bond changes luminescence to long-lived intra-ligand phosphorescence, in contrast to MLCT phosphorescence or TADF. The obtained results can be used for the design of new materials based on Cu(I) complexes with controlled optoelectronic properties on the molecular level, as well as for the production of hybrid systems. [ABSTRACT FROM AUTHOR]

Low-dimensional molecular motifs with diversity developed via the on-surface chemistry are attracting growing interest for their potential in advanced nanofabrication. In this work, scanning tunneling microscopy was employed to investigate the in situ and ex situ metal coordinations between 4,4'-ditetradecyl-2,2'-bipyridine (bpy) and Zn(II) or Cu(II) ions at a highly oriented pyrolytic graphite (HOPG)/1-phenyloctane interface under ambient conditions. The results demonstrate that the bpy adopts a flat-lying orientation with its substituted alkyl chains in a tail-to-tail arrangement in a bpy monolayer. For the in situ coordination, the bpy/Zn(II) and bpy/Cu(II) complexes are aligned in edge-on fashions, wherein the bpy stands vertically on the HOPG surface and interdigitates at the alkyl chains. In the two-dimensional arrays of ex situ coordinated complexes, metal dependent motifs have been observed with Zn(II) and Cu(II), wherein the bipyridine moieties are parallel to the graphite surface. These results suggest that the desired on-surface coordination architectures may be achieved by the intentional selection of the metal centers. [ABSTRACT FROM AUTHOR]

A series of novel cyano-substituted bipyridine derivatives were obtained in good yields (45–72%) via the reaction of malononitrile dimer with isomeric azachalcones. For all synthesized compounds, spectral-fluorescent properties were carefully investigated, and correlation thereof with chemical structure was found. The developed approach represents a novel convenient method for the preparation of functionalized bipyridines containing unique combination of structural fragments. [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]

This microreview summarizes the most frequently employed methods for the synthesis of cyano-substituted bipyridine derivatives over the past 5 years. Most of the approaches to the preparation of such compounds described in the literature are based on cross-coupling reactions, heterocyclization of pyridine-containing substrates, and various multicomponent processes. [ABSTRACT FROM AUTHOR]

Regioselective cobalt‐catalyzed [2+2+2] cycloaddition using fluorine‐containing diynes with nitriles was described. Cycloaddition of fluorinated diynes with nitriles under the influence of CoCl2(phen), zinc bromide, and zinc dust in dichloroethane at 80 °C for 3 h took place smoothly, exclusively affording the corresponding α‐fluoroalkylated pyridines in excellent yields. In addition, dinitriles as substrate were also found to be suitable for this reaction, giving the corresponding fluoroalkylated bipyridine derivatives in excellent yields. [ABSTRACT FROM AUTHOR]

The Cu(II) ion locates in a distorted octahedral geometry, defined by one O atom (O2) form one 6-phenylpyridine-2-carboxylate ligand and one N atom (N1) from 2,2'-bipyridine ligand at the axial positions (O2-Cu1-N1, 173.37(6)°), one O atom (O2') and two N atoms (N2, N2') form 6-phenylpyridine-2-carboxylate ligand, and one N atom (N1') from the 2,2'-bipyridine ligand in the equatorial plane. 8 Liu, S.-Y., Tian, J.-J., Zhu, L.-J., Tian, H.-T., Yang, M., Huang, K.-L., Xu, W.-T. 13 Wang, L.-H., Wang, Z.-J., Ouyang, J., Tai, X.-S. [Extracted from the article]

Amino acid chirality plays an important role in conveying directionality and specificity to their supramolecular organization. However, the impact of enantiopure and racemic amino acids on the favorable packing and macroscopic properties of organic cocrystals with nonchiral coformers is poorly understood. Herein, we performed a systematic study of the effect of chirality on the macroscopic properties of acetylated alanine (AcA) single crystals and cocrystals with a nonchiral photo-sensitive bipyridine derivative (BPE). Cocrystallization with BPE produced a marked morphology transition that improved the supramolecular chirality, thermal stability and mechanical strength of AcA crystals. The distinct supramolecular packing modes were analyzed by X-ray crystallography. The highest rigidity was observed for BPE/ dl -AcA, while BPE/ d -AcA and BPE/ l -AcA crystals exhibited higher efficiency of photo-induced emission for fluorescent imprinting, as well as significantly higher piezoelectricity. This work provides a striking illustration that subtle differences in amino acid stereochemistry translate into tunable macroscopic properties of organic cocrystals for future applications in rigid solids, fluorescent imprinting, and energy harvesting. [ABSTRACT FROM AUTHOR]

Herein, the syntheses, solid-state molecular structures, and characterization of two types of one-dimensional FeIII coordination polymers showing thermally induced spin crossover are reported. The reaction of [Fe(acen)Cl] (acen2 = N,N0-ethylenebis(acetylacetonylideneaminate) with 3,30-bpy or 4,40-bpy (bpy = bipyridine) produced zigzag and linear one-dimensional chain complexes, [Fe(acen)(3,30-bpy)][BPh4] (1) or [NEt3H][Fe(acen)(4,40-bpy)][BPh4]2-0.5(4,40-bpy) (2), respectively, as confirmed by single crystal X-ray diffraction analysis. Variable-temperature single crystal X-ray diffraction measurements, continuous-wave X-band electron paramagnetic resonance (EPR) spectra, 57Fe Mössßauer spectra, and DC magnetic susceptibility data revealed that complex 1 exhibited a gradual and complete spin crossover at a transition temperature of 212 K, while complex 2 undergoes an incomplete spin crossover even at 400 K. [ABSTRACT FROM AUTHOR]

A new series of pyrazole, bipyridine, N-amide derivatives and Schiff bases was synthesized using compound 2-(3-cyano-6- (thiophen-2-yl)-4,4′- bipyridin-2-yloxy) acetohydrazide (3) as a starting material. The compounds structures were confirmed depending on the spectroscopic methods and elemental analysis. Also, the compounds were evaluated as anticancer agents by the compounds screened towards adenocarcinoma breast cancer cell line (MCF-7). The compounds showed a promising cytotoxic effect against human breast cancer cells. Compound 7c showed the most effective activity compared to other compounds with (IC50 = 0.6 ± 0.01 μg mL−1) in comparison with the reference drug doxorubicin (IC50 = 1.6 ± 0.02 μg mL−1). While compound 3 is closely active with doxorubicin. Also compounds 2, 4, 6, 7a, 7b and 7d showed noticeable cytotoxic effect. Early and late apoptotic cells were detected using Acridine orange/Ethidium bromide staining technique. The results of biologically screening of the tested compounds give an idea about the importance in the compounds acting against breast cancer and may lead to the discovery of a potent anticancer agent. [ABSTRACT FROM AUTHOR]

Herein, the effects of the number (mono-PT and di-PT types) and different types of proton donors (hydroxyl (OH) and amino (NH2) groups) on the hydrogen bond strengths, electronic properties, and excited-state intramolecular single proton transfer (SPT) and double proton transfer (DPT) reactions in bipyridine derivatives were theoretically investigated using time-dependent density functional theory with both static calculations and dynamic simulations. The results of the static calculations show that the strength of the intramolecular hydrogen bond of all the studied molecules is stronger in the S1 state than that in the S0 state, which is supported by the red-shift in the corresponding vibrational mode and topology analysis. The effect of the number of proton donors causes the absorption peak of the mono-PT type to be blue-shifted, but its emission peak is red-shifted compared with that of the di-PT type. In contrast, the effect of different proton donors causes both the absorption and emission peaks in the molecules having OH groups to be blue-shifted compared with that with NH2 groups. The potential energy curves along the PT coordinates in the S1 state show that the mono-PT type has a lower PT barrier and are more exothermic than that of the di-PT type. The PT process in the molecules with an OH proton donor occurs easily than that in the molecules with an NH2 proton donor because of the lower PT barrier. Moreover, the 1st PT for SPT was found to be more favorable than the 2nd PT for DPT of the di-PT type due to its low PT barrier and exothermic reaction. Furthermore, the results of the dynamic simulations for the S1 state support that the occurrence of SPT and DPT is dependent on the PT barrier and reaction energy, in which the PT process is favorable with a low PT barrier and exothermic reaction but unfavorable with a high PT barrier and endothermic reaction. Therefore, the photophysical properties and PT processes of bipyridine derivatives can be tuned based on the number and type of proton donors. [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]

Supramolecular self-assembly is an important strategy in nanotechnology and surface science, which has attracted extensive attention in the past decades. In this field, how to obtain more diverse two-dimensional structures and make them more stable has always been a huge challenge. Scanning Tunneling Microscopy (STM), with atomic resolution, is a unique technique for exploring supramolecular self-assembly. In this review, we present the latest progress in the development of two-dimensional (2D) nanostructures using bipyridine derivatives as ligands in our laboratory. Our focus is mainly on: (1) supramolecular coordination on the HOPG surfaces; (2) synergistic interactions of H-bonding; and (3) regulation of aromatic acid derivatives. It is worth noting that the addition of bipyridine provides a new idea and method for the construction of diverse two-dimensional self-assembly structures. [ABSTRACT FROM AUTHOR]

A new complex with the formula [La(5,5′-dmbpy)2(NO3)3] (a) [where (5,5′-dmbpy = 5,5′-dimethyl-2,2′-bipyridine)] has been synthesized. The compound was characterized by cyclic voltammetry, elemental analysis and spectroscopic methods (IR, UV–Vis, 1H-NMR). Single crystals adapted for X-ray diffraction analysis were recorded by slow crystallization from a methanol solution. The complex is neutral being the lanthanum cation chelated by two bipyridine derivative neutral ligands and three bidentate nitrate groups. Electronic spectra show the transition of both ligand field and charge transfer bands. The fluorescence properties of the compound have been studied. The interactions of complex with FS-DNA (salmon sperm DNA) have been studied using UV–Vis, fluorescence spectroscopies and gel electrophoresis. The above-mentioned techniques were used in physiological buffer having pH 7.2. The binding constant (Kb) for interaction in (a) with DNA was obtained using UV–Vis spectroscopies (Kb= 1.2 × 105) and fluorescence spectroscopies (Kb= 1.50 × 105). The binding constant (Kb), the number of binding sites for each 1000 nucleotides (n) and the apparent bio molecular quenching constant (kq) for FS-DNA were obtained through Stern–Volmer equation. Thermodynamic parameters data (∆H°, ΔS° and ΔG°) showed that hydrogen bonding and van der Waals interactions have an important function in the interaction of DNA–La(III) complex, and the binding mode is the groove binding. The DNA binding of La(III) complex is spontaneous as suggested by the negative ΔG°. Moreover, the DNA cleavage has been studied using agarose gel electrophoresis. The antibacterial effects of complex (a) have also been examined in vitro against standard bacterial strains. [ABSTRACT FROM AUTHOR]

A series of [Pt(bpy)(qdt)] {bpy = 2,2′-bipyridine; qdt = quinoxaline-2,3-dithiolate} derivatives was chosen to study the effect of structural modifications on the optoelectronic and nonlinear optical (NLO) properties of the molecules. Here, this study examined eight bipyridine derivatives with different electron-donating and electron-withdrawing anchoring groups using density functional theory (DFT) and time-dependent density functional theory (TD-DFT). The results indicated that the electronic character of the [Pt(bpy)(qdt)] complex is sensitive to the type of anchoring groups connected to the bpy ligand. The considered electron-withdrawing anchors notably narrow the energy gap of the [Pt(bpy)(qdt)] complex in comparison to the electron-donating anchors. Interestingly, replacement of a hydrogen atom by electron-donating anchors in the [Pt(bpy)(qdt)] complex leads to high molar absorption coefficients, whilst complexes with electron-withdrawing anchors can be redshifted significantly. The values of light-harvesting efficiency (LHE) were also calculated and compared in both gas and solvent phases. Moreover, the results reveal that substituting H atoms of bpy ligand by electron-withdrawing anchors dramatically increases the static first hyperpolarizability (β0) value. We expect that the present study would deepen the understanding of electron-donating and -withdrawing anchoring groups in diimine–dithiolate complexes and may contribute to the development of potentially high performance NLO materials. [ABSTRACT FROM AUTHOR]

Abstract An electrochromic device, capable of three-level color switching, has been envisaged by exploiting different color switching properties of Ethyl viologen (EV) and Poly (3-hexylthiophene) (P3HT) to make them switch in congruence with each other. The device, consisting of an EV/P3HT bilayer in poly-ethylene oxide matrix, appears magenta, blue or transparent under an appropriate bias. The unbiased device shows magenta colored appearance and turns transparent at a bias of 1 V when P3HT layer is used as anode. The device turns blue on increasing the bias to 1.4 V without changing the polarity. The mechanism of multilevel switching has been identified using UV–Vis and Raman spectroscopic investigations which reveal that the 1 V bias converts the P3HT into polarons and 1.4 V converts the EV dications (EV2+) into free radical. The electrochromic device demonstrates better color contrast (~ 50%) in both the optical domains. The fabricated device shows better switching speeds of ~ 1.5 s and good stability and coloration efficiency along with three-level color switching. However the reported device uses ITO coated glass as substrate, it can be used for all-organic flexible electrochromic device. Graphical abstract fx1 Highlights • Multistage electrochromic device by exploiting electrochromism of P3HT-viologen. • Enhancement in electrochromic performance parameters. • Electrolyte free electrochromic device designed for power efficient operation. • Paving way for all-organic flexible electrochromic device. [ABSTRACT FROM AUTHOR]

Thorium chalcogenolates Th(ER)4 react with 2,2′-bipyridine (bipy) to form complexes with the stoichiometry (bipy)2Th(ER)4 (E = S, Se; R = Ph, C6F5). All four compounds have been isolated and characterized by spectroscopic methods and low-temperature single crystal X-ray diffraction. Two of the products, (bipy)2Th(SC6F5)4 and (bipy)2Th(SeC6F5)4, crystallize with lattice solvent, (bipy)2Th(SPh)4 crystallizes with no lattice solvent, and the selenolate (bipy)2Th(SePh)4 crystallizes in two phases, with and without lattice solvent. In all four compounds the available volume for coordination bounded by the two bipy ligands is large enough to allow significant conformational flexibility of thiolate or selenolate ligands. 77Se NMR confirms that the structures of the selenolate products are the same in pyridine solution and in the solid state. Attempts to prepare analogous derivatives with 2,2′,6′,2′′-terpyridine (terpy) were successful only in the isolation of (terpy)(py)Th(SPh)4, the first terpy compound of thorium. These materials are thermochromic, with color attributed to ligand-to-ligand charge transfer excitations. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • One-pot synthesis of 6-oxo-7-aryl-6,7-dihydrochromenopyrano[2,3- b ]pyridines was described. • Guanidine hydrochloride as the organocatalyst was used. • Aromatic aldehydes containing various functional groups are well tolerated in the reaction. • Double heterocyclization was carried out in the reaction. Abstract A simple and efficient protocol has been developed for the construction of novel 6-oxo-7-aryl-6,7-dihydrochromenopyrano[2,3- b ]pyridine derivatives using one-pot, three-component cyclocondensation of 4-hydroxycoumarin, various aromatic aldehydes and 2-aminoprop-1-ene-1,1,3-tricarbonitrile using 10 mol % guanidine hydrochloride as the organocatalyst under solvent-free conditions at 90 °C for the first time. The significant features of this protocol are operational simplicity, provide good to high yields, avoidance of toxic solvents, straightforward work-up, no column chromatographic purification and atom-economy which is considered to be relatively environmentally benign. [ABSTRACT FROM AUTHOR]

A convenient and efficient protocol has been developed for the preparation of aryl‐isothioureas based on the Chan–Lam C–S coupling reaction. The desired aryl‐isothioureas were synthesized in good yields (up to 95 %) in the presence of Cu(OAc)2·H2O as catalyst and bipyridine as ligand. A variety of functional groups on the aryl‐thiourea and arylboronic acid reagents are tolerated. The method features mild reaction conditions and good yields, thereby illustrating its practical synthetic value in organic synthesis. [ABSTRACT FROM AUTHOR]

A new symmetrical dinuclear complex of two tricarbonylrhenium(I) moieties, of formula [(CH 3 CN)(CO) 3 Re(4,4″-azobpy) Re(CO) 3 (CH 3 CN)](PF 6 ) 2 , with 4,4″-azobpy = 4,4″-azobis-(2,2′-bipyridine), has been synthesized and characterized by spectroscopic, electrochemical, spectroelectrochemical, photophysical and computational techniques. The bridging azo group in the bipyridyl ring decreases the emission quantum yield of the 3 MLCT lowest-lying excited state respect to similar Re(I) complexes and introduces a new emissive excited state with a longer lifetime, due to increased electronic delocalization in the bridging ligand. When reducing the azo group in CH 3 CN/H 2 O mixtures with sodium dithionite, the emission is enhanced by an order of magnitude. Therefore, this complex can be used as a “molecular switch” with electron and proton additions. Besides, changes in the absorption spectrum on addition of l -Cysteine can be applied for sensing aminoacids with reducing thiol groups. The electronic structures calculated by DFT methods agree reasonably well with experimental results. [ABSTRACT FROM AUTHOR]

We report the study of a series of Ru-bipyridine (Ru-Bpy) complexes to correlate their photophysical and electrochemical properties to their performance in [4 + 2] cycloadditions, as a model reaction for electron transfer catalysis. Redox potentials, absorption and emission spectra, quantum yields and DFT calculations are presented to understand the catalytic transformation. The study shows that complex [Ru(Bpy) 3 ](PF 6 ) 2 is the more active photocatalyst, giving complete conversion to the product after 2 h reaction under white light. Any substitution in the para position of the Bpy ring decreases the reaction conversion. The [4 + 2] cycloaddition can be performed with different substrates and dienes, using either acetonitrile or nitromethane as solvents. Mechanistic studies suggest that the active catalyst for the transformation is [Ru(Bpy) 3 ] 3+ and that the rate determining step is the oxidation of [Ru(Bpy) 3 ] 2+ to generate the corresponding Ru 3+ species. [ABSTRACT FROM AUTHOR]

In the title compound, [(tBuSiMe2O)2MoO2(2,2'-bipyridine)] or [Mo(C6H15OSi)2O2(C10H8N2)], the MoVI atom has a distorted octahedral environment with the siloxy substituents occupying the trans positions. The complex contains a rare (R3SiO)2MO2 (M = Mo, W) structural motif and was formed in a reaction between sodium molybdate and tert-butyldimethylsilyl chloride in the presence of 2,2-bipyridine. In the crystal, neighbouring molecules are linked by C-H...==Mo hydrogen bonds, forming chains propagating along the a-axis direction. [ABSTRACT FROM AUTHOR]

Manganese carbonyl complexes have become popular homogeneous catalysts for carbon dioxide electro- or photoreduction since the beginning of the 2010s. This article presents a comprehensive survey of all the Mn carbonyl systems reported during the last decade as being active catalysts for CO 2 reduction, with a comparison of their activity, stability and selectivity under electroreduction and, for some of them, photoreduction conditions. The development of in situ spectroelectrochemical techniques, often backed by DFT calculations, has enabled gaining more insight into the associated catalytic mechanisms and reaction intermediates. Though manganese tricarbonyl compounds featuring a bipyridine derivative have been by far the most studied, alternative Mn coordination spheres have recently been explored, opening a way towards new families of potential catalysts for homogeneous and heterogeneous CO 2 reduction. [ABSTRACT FROM AUTHOR]

6-Chloro-5,6-dihydro-dibenzo[c,e][1,2]azaborinine (1) reacts with pyridine derivatives to borenium or boronium ions. The boronium ion obtained from reaction with an excess of pyridine could be characterized structurally and transforms into the borenium ion in solution. The reaction of 1 with 2,2'-bipyridine (a) and derivatives (b: 6,6'-dimethyl; c: 4,4'-di-tert-butyl) results in spirocyclic boronium ions 8a-c of which 8b could be characterized by X-ray crystallography. Despite the chelate effect, the spirocyclic boronium ions readily undergo hydrolysis or alcoholysis. Treatment of the spirocyclic boronium ion 8c with potassium hexamethyl disilazide (KHMDS) results in neutral products that are monomers, dimers, or trimers of dibenzo[c,e] [1,2]azaborinine ("BN-phenanthryne") trapped with 4,4'-di-tert-butyl-2,2'-bipyridine by formation of B-C, B-N, or dative B-N bonds, indicative of deprotonation of NH and CH bonds of the boronium ion by KHMDS. [ABSTRACT FROM AUTHOR]

Two novel D-π-A-π-D structural 2,2 ′ -bipyridine derivatives based on different electron donors, namely aza-crown ether and triphenylamine groups were synthesized and characterized. One of which was characterized by single crystal X-ray diffraction determination. Their linear photophysical properties were systematically investigated in various solvents. The two-photon excited fluorescence were investigated. The two dyes both exhibited excellent one- and two-photon excited fluorescence as well as high quantum yield and large two-photon absorption cross-section ( δ ). Fluorescence microscopy imaging of them in NIH/3T3 cell line was studied. The result indicated that both of them exhibit excellent biological compatibility. [ABSTRACT FROM AUTHOR]

Extending the conjugation of viologen by a planar thiazolo[5,4-d]thiazole (TTz) framework and functionalizing the pyridinium with hydrophilic ammonium groups yielded a highly water-soluble π-conjugation extended viologen, 4,4′-(thiazolo[5,4-d]thiazole-2,5-diyl)bis(1-(3-(trimethylammonio)propyl)pyridin-1-ium) tetrachloride, [(NPr)2TTz]Cl4 , as a novel two-electron storage anolyte for aqueous organic redox flow battery (AORFB) applications. Its physical and electrochemical properties were systematically investigated. Paired with 4-trimethylammonium-TEMPO (NMe-TEMPO) as catholyte, [(NPr)2TTz]Cl4 enables a 1.44 V AORFB with a theoretical energy density of 53.7 Wh L−1. A demonstrated [(NPr)2TTz]Cl4/NMe-TEMPO AORFB delivered an energy efficiency of 70 % and 99.97 % capacity retention per cycle. [ABSTRACT FROM AUTHOR]

Transfer and inversion of supramolecular chirality from chiral calix[4]arene analogs (3D and 3L) with an alanine moiety to an achiral bipyridine derivative (1) with glycine moieties in a coassembled hydrogel are demonstrated. Molecular chirality of 3D and 3L could transfer supramolecular chirality to an achiral bipyridine derivative 1. Moreover, addition of 0.6 equiv of 3D or 3L to 1 induced supramolecular chirality inversion of 1. More interestingly, the 2D-sheet structure of the coassembled hydrogels formed with 0.2 equiv of 3D or 3L changed to a rolled-up tubular structure in the presence of 0.6 equiv of 3D or 3L. The chirality inversion and morphology change are mainly mediated by intermolecular hydrogen-bonding interactions between the achiral and chiral molecules, which might be induced by reorientations of the assembled molecules, confirmed by density functional theory calculations. [ABSTRACT FROM AUTHOR]

Complex Fe(bpyB)3 (1, bpyB = 5,5′-bis- (dimesitylboranyl)-2,2′-bipyridine) and its reduced species [(18-c-6)K(THF)2]·[Fe(bpyB)3] (2) were synthesized. Their solid state and electronic structures were investigated by single crystal X-ray crystallography, electron paramagnetic resonance and UV-vis spectroscopy, and SQUID measurements. In 1 two bpyB radical anions are fused by a diamagnetic FeII ion, whereas in 2 all three bpyB ligands are in the radical state. Complex 1 possesses an open-shell singlet ground state with a singlet-triplet gap of 0.18 kcal mol-1 and 2 features an open-shell doublet ground state with a doublet-quartet gap of 1.4 kcal mol-1, as determined by SQUID measurements. The unpairedelectrons in 1 and 2 mainly delocalize over the boron atoms and the bipyrdine moieties with negligible spin density at the iron center. Complex 2 represents the first isolable example of boron-based triradicals. [ABSTRACT FROM AUTHOR]

Six new lanthanide complexes [Ln(2-Br-5-MOBA) 3 (2,2′-DIPY)] 2 (Ln = Nd( 1 ), Eu( 2 ), Gd( 3 ), Tb( 4 ), Ho( 5 ), Er( 6 ); 2-Br-5-MOBA = 2-bromine-5-methoxybenzoate; 2,2′-DIPY = 2,2′-bipyridine) have been successfully synthesized and characterized. The complexes 1 – 5 are isostructural and nine-coordinated by the single-crystal X-ray diffraction analyses, while the complex 6 is eight-coordinated. The difference of crystal structure may be the result of the lanthanide contraction effect. The binuclear units were further assembled into 1D, 2D, 3D supramolecular structures by the π-π stacking and C H⋯O hydrogen bonding interactions. The thermal decomposition mechanism of complexes 1 – 6 was studied by TG analysis and further authenticated by TG/DSC-FTIR techniques. The solid-state luminescence properties of complexes 2 and 4 were investigated at room temperature. The results indicate that complexes 2 and 4 show characteristic emission of Eu 3+ ion and Tb 3+ ion, respectively. What's more, the title complexes have good antibacterial activities against Candida albicans . [ABSTRACT FROM AUTHOR]

The article describes the interaction of Y(III), Zr(IV), La(III), Ce(IV) and U(VI) with moxifloxacin hydrochloride and 2,2′-bipyridine. Characterization of complexes was made by elemental analyses, molar conductivity, magnetic moment measurements and spectral measurements e.g. IR, UV–Vis., 1 H NMR and mass as well as thermal analyses (TG and DTG). The molar conductivity shows that the complexes are electrolytes nature. Spectroscopic investigation of the solid complexes studied here indicate that moxifloxacin hydrochloride and 2,2′-bipyridine are coordinated to the metal ions in a neutral bidentate manner. After complete characterization, the chemical formulae of the complexes were established. The calculated bond length and force constant, F(U O), in the uranyl complex are 1.756 Å and 637.90 Nm −1 , respectively. Kinetic and thermodynamic parameters were determined using Coats–Redfern and Horowitz–Metzger equations. Establishment of hydrochloric acid that induce acute lung injury (ALI) in rats by intratracheal administration through damaging the alveolar epithelium and activation of the neutrophil and subsequent oxidative stress by increasing malondialdehyde (MDA), tumor necrosis factor (TNF-α) and neutrophil, which were confirmed by histopathological investigation while decreasing in antioxidant enzymes and lymphocytes. Whereas treatment with mixed-ligand metal complexes significantly decrease MDA, TNF-α and neutrophils and increase antioxidant and lymphocytes. [ABSTRACT FROM AUTHOR]

Organic materials have recently gained considerable attention for electronic applications, improving performance and sustainability to current technologies. Commercialized metal-based systems are generally expensive, toxic and difficult to recycle, however organic materials offer promising solutions. Viologens, N, N′ di-quaternized bipyridyl salts, are a well-studied species exhibiting three reversible redox states, possessing valuable electrochromic and electron-accepting properties. These properties can be fine-tuned through synthesis by altering the nitrogen substituents and various counteranions. Currently, viologens have become of great interest as functional materials in a wide array of applications; a few to name include electrochromic devices, molecular machines, and organic batteries. This review highlights representative recent work and advances towards utilizing viologens in practical applications that currently compete with metal-based technologies. Additionally, modified viologens that can be further fine-tuned will be discussed. [ABSTRACT FROM AUTHOR]

Retinoid X receptor alpha (RXRα) is an important therapeutic target of cancer. Recently, small molecules (e.g., XS-060 and its derivatives), which can significantly induce RXRα-dependent mitotic arrest by inhibiting p RXRα-PLK1 interaction, have been demonstrated as excellent anticancer agents. To further obtain novel RXR-targeted antimitotic agents with excellent bioactivity and drug-like properties, we herein synthesized two new series of bipyridine amide derivatives with XS-060 as the lead compound. In the reporter gene assay, most synthesized compounds showed antagonistic activity against RXRα. The most active compound, bipyridine amide B9 (BPA-B9) , showed better activity than XS-060 , with excellent RXRα-binding affinity (K D = 39.29 ± 1.12 nM) and anti-proliferative activity against MDA-MB-231 (IC 50 = 16 nM, SI > 3). Besides, a docking study revealed a proper fitting of BPA-B9 into the coactivator binding site of RXRα, rationalizing its potent antagonistic effect on RXRα transactivation. Further, the mechanism studies revealed that the anticancer activity of BPA-B9 was dependent on its cellular RXRα-targeted mechanism, such as inhibiting p RXRα-PLK1 interaction and inducing RXRα-dependent mitotic arrest. Besides, BPA-B9 displayed better pharmacokinetics than the lead XS-060. Further, animal assays indicated BPA-B9 had significant anticancer efficacy in vivo with no considerable side effects. Together, our study reveals a novel RXRα ligand BPA-B9 targeting the p RXRα-PLK1 interaction, with great potential as a promising anticancer drug candidate for further development. [Display omitted] • New bipyridine amide derivatives are synthesized as novel RXRα modulators. • Compound B9 is an excellent RXRα binder (K D = 39 nM) and selective RXRα antogonist. • B9 induces RXRα-dependent cell cycle arrest and apoptosis by hindering pRXRα-PLK1 interaction. • B9 displays more better pharmacokinetic properties than the lead XS-060. • B9 effectively inhibits tumor growth in a mice MDA-MB-231 xenograft model. [ABSTRACT FROM AUTHOR]

The electronic structure of thiazolo[3,2- a ]pyridine and some of its derivatives are investigated theoretically using B3LYB/6-311G (d, p) method. The calculations show that all the studied compounds 1 – 5 are non-planar, as indicated from the dihedral angles. The electronic absorption spectra of the studied compounds are recorded in the UV–VIS region, in both DMF and Dioxane solvents. Assignments of the observed electronic transitions are facilitated via time-dependent density functional theory (TD-DFT) computations. Band maxima ( λ max ) and intensities of the spectra are found to have solvent dependence reflected as blue and red shifts. Electronic configurations contributing to each excited state are identified and the relevant MOs are characterized. The extent of delocalization and intermolecular charge transfer are estimated and discussed in terms of natural bond orbital (NBO) analysis and second order perturbation interactions between donor and acceptor MOs. The theoretical spectra computed at “A new hybrid exchange-correlation functional using the Coulomb-attenuating method (CAM-B3LYP),” at the 6-311G (d, p) bases set in gas phase and with the Polarizable Continuum Model (PCM) in Dioxane and DMF indicate a good agreement with the observed spectra. [ABSTRACT FROM AUTHOR]

Two bis -bromo substituted imidazo-[1,5- a ]-pyridine derivatives IMPY1 and IMPY2 were synthesized from a 2:1:2 mixture of ortho / meta -bromobenzaldehyde, 2-cyanopyridine and ammonium acetate. The compounds IMPY1 and IMPY2 exhibit blue fluorescence in both THF and methanol solution and their highly fluorescent nature is revealed by the quantum yields Φ F ranging from 9.3 to 10.4%. The crystal structure of the compounds are stabilized by various weak, non-classical hydrogen bonds viz. C−H⋯N, C−H⋯Br and C−H⋯π as well as type II interhalogen and C−Br⋯π halogen bonds. The supramolecular features and electronic property of these compounds have been thoroughly analyzed with the aid of DFT, TD-DFT and molecular electrostatic potential (MEP) analyses. [ABSTRACT FROM AUTHOR]

A series of mercury(II) complexes, [Hg(N N)(SCN) 2 ] (N N is 4,4′-dimethyl-2,2′-bipyridine in 1 , 5,5′-dimethyl-2,2′-bipyridine in 2 , 6,6′-dimethyl-2,2′-bipyridine in 3 and 6-methyl-2,2′-bipyridine in 4 ), were prepared from the reactions of Hg(SCN) 2 with mentioned ligands in methanol. Suitable crystals of these complexes were obtained for X-ray diffraction measurement by methanol diffusion into a DMSO solution. The four complexes were thoroughly characterized by spectral methods (IR, UV–Vis, 13 C{ 1 H}NMR, 1 H NMR and luminescence), elemental analysis (CHNS) and single crystal X-ray diffraction. The X-ray structural analysis indicated that in the structures of these complexes, the mercury(II) cation is four-coordinated in a distorted tetrahedral configuration by two S atoms from two thiocyanate anions and two N atoms from one chelating 2,2′-bipyridine derivative ligand. Also, in these complexes intermolecular interactions, for example C H⋯N hydrogen bonds (in 1 – 4 ), C H⋯S hydrogen bonds (in 1 , 2 and 4 ), π … π interactions (in 2 – 4 ), Hg⋯N interactions (in 2 ) and S⋯S interactions (in 4 ), are effective in the stabilization of the crystal structures and the formation of the 3D supramolecular complexes. Furthermore, the luminescence spectra of the title complexes show that the intensity of their emission bands are stronger than the emission bands for the free bipyridine derivative ligands. [ABSTRACT FROM AUTHOR]

We previously reported a novel series of 1 H -pyrazolo[3,4- c ]pyridine derivatives and the identification of compound 4b as a highly potent GPR119 agonist. However, the advancement of preclinical evaluations of compound 4b is expected to be difficult because of the compound’s significantly poor aqueous solubility (0.71 μM at pH6.8). In this article, we describe the further optimization of compound 4b focusing on the improvement of its aqueous solubility. Optimization of the central spacer, left-hand aryl group and right-hand piperidine N -capping group led to the identification of a potent GPR119 agonist, 3 H -[1,2,3]triazolo[4,5- c ]pyridine derivative 32o , with improved solubility (15.9 μM at pH6.8). [ABSTRACT FROM AUTHOR]