Search results for "PYRIDINE"
showing 10 items of 2516 documents
Stimuli-Responsive Y-Shaped Polymer Brushes Based on Junction-Point-Reactive Block Copolymers
2012
Reversibly responsive, thin or ultrathin polymer fi lms, often referred to as “smart surfaces”, can alter their properties upon application of external stimuli. [ 1 , 2 ] One particular application fi eld represents the engineering of nanostructured fi lms mimicking cell membranes. [ 3 , 4 ] Such materials offer application potential for sensors, textiles, construction materials, and smart coatings due to a rapid change in surface energy and morphology. [ 5–7 ] The surface response can be triggered by various external stimuli such as light, temperature, electrical potential, mechanical force, magnetic fi eld, pH change, or selective solvent treatment. [ 1 , 8–12 ] A variety of different thi…
Enhancement of metallo-supramolecular dissociation kinetics in telechelic terpyridine-capped poly(ethylene glycol) assemblies in the semi-dilute regi…
2019
The dynamics of supramolecular polymer assemblies is governed by that of their polymeric building blocks and that of the transient bonds between them. Entrapment of such bonds by topological crowding often causes renormalization of the bond lifetimes towards prolonging. In the present study, by contrast, we show that this effect can also be inverse in the case of telechelic metallo-supramolecular polymers in semi-dilute solution. We focus on linear poly(ethylene glycols) capped by terpyridine binding motifs at both ends that can form metal–ligand coordinative bonds with various transition metal ions, thereby creating transient metallo-supramolecular assemblies of varying length and binding …
Tandem asymmetric Michael reaction-intramolecular Michael addition. An easy entry to chiral fluorinated 1,4-dihydropyridines.
2010
A novel one-pot tandem asymmetric Hantzsch-type process has been employed to generate fluorinated 1,4-dihydropyridines (1,4-DHPs) as single diastereoisomers. It involves the condensation of (R)-(+)-allyl p-tolyl sulfoxide, fluorinated nitriles, and alkyl propiolates, giving access to a new family of enantiomerically pure fluorine-containing 1,4-DHPs.
Expanding the 3d-4f heterometallic chemistry of the (py)2CO and pyCOpyCOpy ligands: structural, magnetic and Mössbauer spectroscopic studies of two F…
2011
Complex [Fe(II)Gd(III){pyCO(OEt)pyCOH(OEt)py}(3)](ClO(4))(2) (1) crystallizes in the Cc space group and contains one hexacoordinate ferrous ion and one enneacoordinate Gd(III) ion. Complex [Fe(2)(II)Gd(III){pyCO(OEt)py}(4)(NO(3))(H(2)O)][Gd(NO(3))(5)](0.5)(ClO(4)) (2) crystallizes in the C2/c space group and contains two hexacoordinate ferrous ions and one octacoordinate Gd(III) ion. Both complexes have been prepared by the metal-assisted ethanolysis of ligands di-2,6-(2-pyridylcarbonyl)pyridine (pyCOpyCOpy, dpcp) and di-2-pyridyl ketone ((py)(2)CO, dpk), which exhibit similar structures. Mössbauer spectroscopic studies of 2 revealed the presence of two quadrupole-split doublets of equal in…
Mn(II) complexes with sulfonamides as ligands.
2012
Abstract Sulfonamides derived from 8-aminoquinoline react with Mn(II) and Mn(III) salts to form Mn(II) complexes; the Mn(III) species are reduced to the divalent state in the presence of 1,10 phenanthroline and bipyridine. Their molecular structure, determined by single crystal X‐ray diffraction, show that all the complexes present a distorted octahedral geometry, in which the deprotonated sulfonamide acts as a bidentate ligand. UV–visible spectroscopy and changes in the melting temperature (Tm) of calf thymus DNA show a strong interaction of these complexes with DNA. The significant hypochromicity of the charge transfer transition at 370 nm without an appreciable change in wavelength and t…
Chemistry and reactivity of mononuclear manganese oxamate complexes: Oxidative carbon-carbon bond cleavage of vic-diols by dioxygen and aldehydes cat…
2006
[EN] Two new mononuclear octahedral manganese(III) complexes with the tetradentate equatorial ligand o-phenylenebis(oxamate) (opba) and two aquo (1a) or two pyridine (1b) axial ligands have been synthesized and characterized structurally, magnetically, and electrochemically. The cyclovoltammogram of 1a in acetonitrile (25 degrees C, 0.1 M Bu4NPF6) shows an irreversible one-electron oxidation peak at a high anodic potential (E-ap = 1.03 V versus SCE), while that of 1b shows two well-separated one-electron oxidation peaks at moderate to high anodic potentials (E-ap = 0.92 and 1.27 V versus SCE), the first redox-wave being quasireversible in nature. The access to formally high-valent Mn-IV and…
Solid-state luminescence of Au-Cu-alkynyl complexes induced by metallophilicity-driven aggregation.
2012
A new series of homoleptic alkynyl complexes, [{Au2Cu2(C2R)4}n] (R=C3H7O (1), C6H11O (2), C9H19O (3), C13H11O (4)), were obtained from Au(SC4H8)Cl, Cu(NCMe)4PF6, and the corresponding alkyne in the presence of a base (NEt3). Complexes 1-4 aggregate upon crystallization into polymeric chains through extensive metallophilic interactions. The cluster that contains fluorenolyl functionalities, C13H9O (5), crystallizes in its molecular form as a disolvate, [Au2Cu2(C2C13H9O)4]·2THF. The substitution of weakly bound THF molecules with pyridine molecules leads to the complex [Au2Cu2(C2C13H9O)4]·2py (6), thus giving two polymorphs in the solid state. Such structural diversity is established through …
Study on the synthesis of novel 5-substituted 2-[2-(pyridyl)ethenyl]-1,3,4-oxadiazoles and their acid–base interactions
2014
Abstract A series of novel 5-substituted 2-[2-(pyridyl)ethenyl]-1,3,4-oxadiazoles were efficiently synthesized by cyclocondensation of the appropriate 3-(pyridyl)acrylohydrazides with triethyl orthoesters in the presence of glacial acetic acid. The products were identified by means of spectroscopic methods and their pKA ionization constants were determined. The influence of substituents on the basicity of the pyridine system has been discussed. Graphical Abstract
Local dynamics in supramolecular polymer networks probed by magnetic particle nanorheology
2019
Transient supramolecular polymer networks are promising candidates as soft self-healing or stimuli-sensitive materials. In this paper, we employ a novel nanorheological approach, magnetic particle nanorheology (MPN), in order to better understand the local dynamic properties of model supramolecular networks from a molecular point of view. Hence, the bond strength between four-arm star-shaped polyethylene glycol (PEG) functionalized at the four extremities with terpyridine ligands is tuned by implementing different metal ions with variable complexation affinities for the ligand. We show that MNP allows for the evaluation of the strength and connectivity of the polymer networks by the estimat…
Near Isotropic D4d Spin Qubits as Nodes of a Gd(III)-Based Metal-Organic Framework
2021
Embedding coherent spin motifs in reproducible molecular building blocks is a promising pathway for the realization of quantum technologies. Three-dimensional (3D) MOFs are a versatile platform for the rational design of extended structures employing coordination chemistry. Here, we report the synthesis and characterization of a gadolinium(III)-based MOF, [Gd(bipyNO)4](TfO)3·xMeOH (bipyNO = bipyridine,N,N′-dioxide; TfO = triflate; and MeOH = methanol) (quMOF-1), which presents a unique coordination geometry that leads to a tiny magnetic anisotropy (in terms of D, an equivalent zero-field splitting would be achieved by D = 0.006 cm–1) even compared with regular Gd(III) complexes. Pulsed elec…