Pyridyl Moiety Research Articles

Pyridyl-Amides as a Multimode Self-Assembly Driver for the Design of a Stimuli-Responsive π-Gelator.

An oligo(p-phenylenevinylene) (OPV) derivative connected to pyridyl end groups through an amide linkage (OPV-Py) resulted in a multistimuli-responsive π-gelator. When compared to the corresponding OPV π-gelator terminated by a phenyl-amide (OPV-Ph), the aggregation properties of OPV-Py were found to be significantly different, leading to multistimuli gelation and other morphological properties. The pyridyl moiety in OPV-Py initially interferes with the amide H-bonded assembly and gelation, however, protonation of the pyridyl moiety with trifluoroacetic acid (TFA) facilitated the formation of amide H-bonded assembly leading to gelation, which is reversible by the addition of N,N-diisopropyethylamine (DiPEA). Interestingly, addition of Ag(+) ions to a solution of OPV-Py facilitated the formation of a metallo-supramolecular assembly leading to gelation. Surprisingly, ultrasound-induced gelation was observed when OPV-Py was mixed with a dicarboxylic acid (A1). A detailed study using different spectroscopic and microscopic experimental techniques revealed the difference in the mode of assembly in the two molecules and the multistimuli-responsive nature of the OPV-Py gelation.

ChemInform Abstract: Convenient Synthesis of 2‐[2‐Aryl‐2‐oxo‐1‐(2‐oxoindolin‐3‐ylidene)ethyl]fumarates via a One‐Pot, Two‐Step Reaction.

AbstractThe reaction proceeds via sequential formation of Huisgens 1,4‐dipole, Michael addition, and loss of the pyridyl moiety.

1,2,4,6-Thiatriazinyl Radicals and Dimers: Structural and Electronic Tuning through Heteroaromatic Substituent Modification

The functionalization of thiatriazinyl (TTA) radicals with pyridyl and thienyl moieties is described, and their influence at both the molecular and solid-state level has been investigated. Comparative electron paramagnetic resonance studies of 3,5-bis-(2-pyridyl)-1,2,4,6-thiatriazinyl (Py2TTA) and 3,5-bis-(2-thienyl)-1,2,4,6-thiatriazinyl (Th2TTA) reveal the impact of heteroaromatic substitution on the electronic structure, which is supported by density functional theory calculations. Single crystal X-ray analysis emphasizes the importance of intermolecular contacts on the crystal packing and demonstrates the potential for structural control through S---N′ and N---HC′ interactions, which are enhanced in Py2TTA and Th2TTA by the presence of the pyridyl and thienyl groups, respectively. This work represents a fundamental study of heterocyclic aromatic substitution in thiazyl-based radicals and investigates how varying these functional groups influences the molecular properties and long-range order within the supramolecular structure.

ChemInform Abstract: Ruthenium(II)‐Catalyzed Direct Addition of Indole/Pyrrole C2—H Bonds to Alkynes.

A ruthenium-catalyzed C2-hydroindolation of alkynes has been achieved. This protocol provides a rapid and concise access to kinds of 2-alkenyl-substituted N-(2-pyridyl)indoles in which the pyridyl moiety can be easily removed to afford free (N–H) indoles under mild conditions. Various arenes and alkynes, including electron-deficient and electron-rich internal alkynes and terminal alkynes, allow for this transformation.

Synthesis, optical properties and protonation of chlorophyll derivatives appending a pyridyl group in the C3-substituent

Chlorophyll(Chl)-a derivatives possessing a 2-(2/3/4-pyridyl)ethenyl group at the C3 position were synthesized by Wittig reaction of the 3-formyl group in methyl pyropheophorbide-d. The catalytic hydrogenation of the resulting 3-CC double bond afforded the corresponding regioisomers of Chls bearing the 3-(2-pyridylethyl) group. Comparing their visible absorption spectra in dichloromethane, the longest wavelength (Qy) maxima were shifted bathochromically in the following order: C–C < CC as the linker between the chlorin and pyridyl moieties. The red shifts are ascribable to their intramolecular π-conjugation through the 3-vinylene moiety. All the Chl derivatives in a diluted solution gave an intense fluorescence emission band at the red-side region of Qy band and their fluorescence quantum yields were about 20%. The synthetic Chl–pyridine conjugates were titrated with trifluoroacetic acid in chloroform. Their visible spectral changes indicated that the appended pyridyl group was first protonated, followed by protonation of the chlorin π-system at the inner nitrogen atoms in a molecule.

SYNTHESIS AND ANTI-MICROBIAL ACTIVITIES OF 1,3,5-TRISUBSTITUTED-PYRAZOLE DERIVATIVES CONTAINING A PYRIDYL MOIETY

Claisen condensation of ethyl isonicotinate with different acetophenones gave the corresponding pyridyl-s-diketones, while the treatment with hydrazine hydrate yielded 3,5-disubstituted-1H-pyrazoles, which then converted 1,3,5-trisubstituted-pyrazole derivatives containing a pyridyl moiety by N-acylation with acyl chloride. The structures of all newly synthesized compounds are established by FTIR, 1H NMR, mass spectroscopy and elemental analysis, and in the case of compound 2e, analyzed by single-crystal X-ray diffraction further. The anti-microbial activities of the title compounds have been tested by disc diffusion method against Escherichia coli, Staphylococcus aureus, Pyricularia oryzae and Rhizoctnia solani. The results showed that compounds 3c and 4c exhibited good inhibitory activity against all the tested organisms.

Assembly, disassembly, and reassembly: conversion of homometallic coordination networks into mixed metal-organic frameworks.

A strategy for the conversion of homometallic coordination networks into mixed metal-organic frameworks (MM'MOFs) is proposed. Ni(II) complexes of dipyrrin (dpm) ligands bearing peripheral pyridyl or imidazolyl units have been shown to self-assemble into coordination polymers with the metal cation in an octahedral environment coordinated to two bis-pyrrolic chelates and two neutral monodentate coordinating units such as pyridyl or imidazolyl moieties. Taking advantage of the chelate effect, the two monodentate units may be replaced by a diimine ligand leading to the disassembly of the networks by the formation of discrete soluble complexes. The latter can be employed as metallatectons for the construction of heterometallic architectures upon reaction with a secondary metal salt. This approach was applied using either 1,10-phenanthroline (phen) or 2,2'-bipyrimidine (bpm) as chelates leading to a series of mono- and binuclear metallatectons of the (phen)Ni(dpm)2 and (bpm)[Ni(dpm)2]2 type. Subsequent assembly with CdCl2 afforded either interpenetrated 2D grid-type architectures or 3D MM'MOFs.

Iridium-catalyzed asymmetric hydrogenation of 2-pyridyl cyclic imines: a highly enantioselective approach to nicotine derivatives.

A highly efficient asymmetric hydrogenation of cyclic imines containing a pyridyl moiety was established by using iridium catalysts with chiral spiro phosphine-oxazoline ligands. This process will facilitate the development of new nicotine-related pharmaceuticals. The introduction of a substituent at the ortho position of the pyridyl ring to reduce its coordinating ability ensures the success of the hydrogenation and excellent enantioselectivity.

Synthesis, Luminescence Properties of Eu (III) and Tb (III) Complexes with a Polyamine Polycarboxylic Ligand as well as Their Binding Characteristics with Bovine Serum Albumin (BSA)

A novel polyamine polycarboxylic ligand (L) with imidazole and pyridyl moieties and its corresponding complexes Na3EuLCl3·6H2O and Na3TbLCl3·6H2O, on to which Eu(III) and Tb(III) were bound via coordination, were prepared and characterized by FT-IR, 1HNMR, TG-DTA and CHN elemental analysis. The thermogravimetric analysis shows the Eu (III) and Tb(III) complexes have good thermal stabilities with decomposition temperatures 380 and 398°C, respectively. The luminescence properties of the complexes show the ligand has excellent antenna effect to sensitize the lanthanide ions while using ethyl p-dimethylaminobenzoate in ethanol as reference sample, the quantum efficiency of the Eu(III) and Tb(III) complexes are 0.264 and 0.280 in the DMSO at room temperature, respectively. The interactions of the complexes with bovine serum albumin (BSA) were analyzed by fluorescence measurements under physiological conditions. The UV–vis absorbance and the Stern-Volmer analysis indicate that the main quenching mechanism of BSA by the complexes is a static quenching procedure. The binding constants, binding site number at different temperatures were calculated by Van't Hoff equation, which confirms that the Van der Waals and hydrogen bond interactions are mainly impulse to the formation of complexes BSA-L coordination compound. Furthermore, the effect of complex on the conformation of BSA was analyzed according to synchronous fluorescence and circular dichroism (CD) spectra.

Synthesis and acid–base properties of a proton-bridged biaryl compound based on pyridylazulene

We report the synthesis and acid–base properties of 1,1′-bi(2-pyridylazulene) and the crystal structure of its mono-protonated form in which pyridyl moieties are interacted by an intramolecular hydrogen bond.

Amino-functionalized carbon nanofibres as an efficient metal free catalyst for the synthesis of quinazoline-2,4(1H,3H)-diones from CO2and 2-aminobenzonitriles

Carbon nanofibres functionalized with pyridyl moieties were used as an efficient metal free catalyst for the synthesis of quinazoline-2,4(1H,3H)-diones from CO2and 2-aminobenzonitriles.

Ratiometric fluorescent and chromogenic chemodosimeter for cyanide detection in water and its application in bioimaging

An indole conjugated thiophene–pyridyl moiety, ITP, has been synthesized and characterized for the selective detection of cyanide with a low detection limit.

Photophysical and electroluminescence properties of bis(2′,6′-difluoro-2,3′-bipyridinato-N,C4′)iridium(picolinate) complexes: effect of electron-withdrawing and electron-donating group substituents at the 4′ position of the pyridyl moiety of the cyclometalated ligand

Electronic effects on the photophysics of Ir3+ compounds.

Theoretical study on the electronic structures and phosphorescent properties of a series of iridium(III) complexes with the different positional N-substitution in the pyridyl moiety

The geometry structures, electronic structures, absorption and phosphorescent properties of a series of iridium(III) complexes with the different N-substitution cyclometalating ligand and the same benzyldiphenylphosphine auxiliary ligand have been theoretically investigated by using the density functional theory method. The lowest energy absorption wavelengths are located at 378nm for A, 430nm for B, 411nm for C, 436nm for D, and 394nm for E. The introduction of N atom substitution at 1-, 2-, 3-, and 4-positions on the pyridyl moiety of complex A leads to an obvious redshifted absorption. The lowest energy emissions for complexes A–E are localized at 450, 409, 438, 483, and 429nm, respectively, simulated in CH2Cl2 medium at M052X level. Ionization potential and electron affinity have been calculated to evaluate the injection abilities of holes and electrons into these complexes. For complex C, the calculated results showed that it can possibly possess the larger radiative decay rate (kr) value than those of other four complexes. It is anticipated that the theoretical studies can provide valuable information for designing new phosphorescent metal complexes of organic light-emitting diodes.

Polymer-coated palladium nanoparticle catalysts for Suzuki coupling reactions

A set of seven different palladium nanoparticle (PdNP) systems stabilized by small amounts (1.0mg/mL) of structurally related macromolecular capping agents were comparatively tested as catalyst in p-nitrophenol (Nip) reduction and Suzuki cross-coupling reactions. The observed rate constants (kobs) for Nip reduction were in the range of 0.052–3.120×10−2s−1, and the variation reflected the effects of polymer chain conformation, ionic strength and palladium–polymer complex coordination. Macromolecules featuring pendant pyridyl moieties or inverse temperature-dependent solubility were found to be unsuitable capping agents for PdNPs catalysts, despite being active. The catalytic activity in Suzuki cross-coupling reactions followed the same behavior; the most active particles in the Nip reaction also mediated the cross-coupling reaction providing the expected products in quantitative yields under relatively mild conditions after only 4h at 50°C. Experiments involving the successive addition of reactants and catalyst recovery/re-use indicated that the recycling potential was comparable to those of the standards used in this field.

Convenient Synthesis of 2-[2-Aryl-2-oxo-1-(2-oxoindolin-3-ylidene)ethyl]fumarates via a One-Pot, Two-Step Reaction

The one-pot, two-step reactions of 4-picoline, a dialkyl acetylenedicarboxylate, and a 2-oxoindolin-3-ylidene derivative in 1,2-dimethoxyethane at elevated temperatures afford polyfunctionalized 2-[2-aryl-2-oxo-1-(2-oxoindolin-3-ylidene)ethyl]fumarates in moderate to good yields. The reaction mechanism involves the sequential formation of Huisgen’s 1,4-dipole, Michael addition, and loss of the pyridyl moiety.

Protonation of a biologically relevant Cu(II) μ-thiolate complex: ligand dissociation or formation of a protonated Cu(I) disulfide species?

The proton-induced electron-transfer reaction of a Cu(II) μ-thiolate complex to a Cu(I) -containing species has been investigated, both experimentally and computationally. The Cu(II) μ-thiolate complex [Cu(II) 2 (L(Me) S)2 ](2+) is isolated with the new pyridyl-containing ligand L(Me) SSL(Me) , which can form both Cu(II) thiolate and Cu(I) disulfide complexes, depending on the solvent. Both the Cu(II) and the Cu(I) complexes show reactivity upon addition of protons. The multivalent tetranuclear complex [Cu(I) 2 Cu(II) 2 (LS)2 (CH3 CN)6 ](4+) crystallizes after addition of two equivalents of strong acid to a solution containing the μ-thiolate complex [Cu(II) 2 (LS)2 ](2+) and is further analyzed in solution. This study shows that, upon addition of protons to the Cu(II) thiolate compound, the ligand dissociates from the copper centers, in contrast to an earlier report describing redox isomerization to a Cu(I) disulfide species that is protonated at the pyridyl moieties. Computational studies of the protonated Cu(II) μ-thiolate and Cu(I) disulfide species with LSSL show that already upon addition of two equivalents of protons, ligand dissociation forming [Cu(I) (CH3 CN)4 ](+) and protonated ligand is energetically favored over conversion to a protonated Cu(I) disulfide complex.

Diastereoselective Nitroaldol Reaction Catalyzed by Binuclear Copper(II) Complexes in Aqueous Medium

AbstractPolydentate ligands 1 and 2, which incorporate a terminal pyridyl moiety and an oxygen‐rich oxalate dihydrizide/malonic dihydrizide spacer moiety, as well as their binuclear metal complexes [Cu212] and [Cu222], which adopt a 1:1 metal/ligand ratio, were synthesized and characterized. Both complexes were screened for their catalytic activity in the nitroaldol reaction, in which [Cu212] worked efficiently as catalyst for both substituted benzaldehyde and pyridinecarboxaldehyde, whereas [Cu222] is highly substrate specific and showed activity towards nitro‐substituted aldehydes and pyridinecarboxaldehyde. Furthermore, as helicates are intrinsically chiral, the stereochemical architecture in the binuclear double‐stranded Cu2 helicates as catalyst favored the diastereoselective syn product with nitroethane and nitropropane and their respective diastereoselectivities were determined by using 1H NMR spectroscopy.

Ruthenium(II)-catalyzed direct addition of indole/pyrrole C2-H bonds to alkynes.

A ruthenium-catalyzed C2-hydroindolation of alkynes has been achieved. This protocol provides a rapid and concise access to kinds of 2-alkenyl-substituted N-(2-pyridyl)indoles in which the pyridyl moiety can be easily removed to afford free (N-H) indoles under mild conditions. Various arenes and alkynes, including electron-deficient and electron-rich internal alkynes and terminal alkynes, allow for this transformation.

Preparation and characterization of 4-amino-2-anilinopyridine and its chlorodiruthenium(III,II) complex

A new bridging agent, 4-amino-2-anilinopyridine (aap), was synthesized and used as an equatorial ligand in the preparation of a diruthenium complex (4,0) Ru2(aap)4Cl. Both the ligand and the diruthenium complex were characterized by thermal analysis, MALDI-TOF mass spectrometry, IR and NMR (1H and 13C) spectroscopy, and X-ray crystallography. The structural analysis revealed that the complex existed as a (4,0) isomer, in which the amino group on the pyridyl moiety was not involved in chemical bonding.