2,6-Bis(2-benzimidazolyl)pyridine as a chemosensor for fluoride ions

2,6-Bis(2-benzimidazolyl)pyridine, a neutral tridentate ligand, is employed as a chemosensor for the detection of fluoride ions. The binding of anionic guest species with this ligand is studied using UV-vis spectroscopy, fluorescence spectroscopy, and ¹H NMR techniques. The results indicate that 2,6-bis(2-benzimidazolyl)pyridine can be used as a chemical shift and optical modification based sensor for the detection of fluoride ions.     

新型2,6-双(3,5-二取代吡唑基-1-羰基)吡啶的合成

报道了四种吡唑衍生物和它们四种新型的杂环酰胺衍生物的合成 ,它们是 3 ,5 二甲基吡唑 (1) ,5 甲基 3 苯基吡唑(2 ) ,3 ,5 二苯基吡唑 (3 ) ,5 甲基 3 二茂铁基吡唑 (4 ) ,2 ,6 双 (3 ,5 二甲基吡唑基 1 羰基 )吡啶 (5 ) ,2 ,6 双 (5 甲基 3 苯基吡唑基 1 羰基 )吡啶 (6) ,2 ,6 双 (3 ,5 二苯基吡唑基 1 羰基 )吡啶 (7)和 2 ,6 双 (5 甲基 3 二茂铁基吡唑基 1 羰基 )吡啶 (8) .并对它们进行了元素分析 ,FT IR ,1HNMR和13 CNMR等波谱分析 .     

2,6-Diacetyl- and 2,6-diformylpyridine bis(N4-substituted thiosemicarbazones) and their copper(II) and nickel(II) complexes

2,6-Diformylpyridine bis(N4-methylthiosemicarbazone) and bis(N4-dimethylthiosemicarbazone), H₂2,6Fo4M and H₂2,6Fo4DM, respectively, and 2,6-diacetylpyridine bis(N4-methylthiosemicarbazone) and bis(N4-dimethylthiosemicarbazone), H₂2,6Ac4M and H₂2,6Ac4DM, and their copper(II) and nickel(II) complexes have been synthesized. The ¹H-n.m.r. spectra of the free bis(thiosemicarbazones) show that, most often, one of the thiosemicarbazone moieties is hydrogen bonded to the pyridine nitrogen, and in [²H₆]-DMSO there is interaction with solvent oxygen. Golden yellow H₂2,6Ac4DM has a bifurcated hydrogen bonding interaction by one of the thiosemicarbazone moieties resulting in conjugation. Coordination to copper(II) and nickel(II) centers is via the pyridine nitrogen, amine nitrogen and thiolato sulfur and most of the complexes formed are polynuclear with thiosemicarbazone moieties from the same ligand coordinating to different metal centers.     

Anion-directed self-assembly of a 2,6-bis(2-anilinoethynyl)pyridine bis(amide) scaffold

Bis(sulfonamide) receptors based on the 2,6-bis(2-anilinoethynyl)pyridine scaffold form persistent dimers with water and halides in solution and in the solid-state. The structurally related bis(amide) receptor derived from 3,5-dinitrobenzoyl chloride is a dimer in the solid-state with two HCl molecules directing the self-assembly. The 2+2 dimer, with a twisted ‘S’-shaped backbone, is held together by six hydrogen bonds. Dissolution of the (H2⁺√Cl ^? )₂ adduct in CHCl₃ results, however, in a monomeric structure. DOSY and ¹H NMR experiments were used to identify the dominance of monomer in solution for both 2 and H2⁺√Cl ^? . The ‘OFF–ON’ fluorescence response of 2,6-bis(2-anilinoethynyl)pyridine is retained with amide arms.     

Stereospecific Formation of Pentaamine Complexes of Co(III) with Terdentate 2,6-Bis(aminomethyl)pyridine

Some pentaamine complexes of Co(III) with 2,6-bis(aminomethyl)pyridine (bamp), a diamine ligand (or two ammonia ligands) and one unidentate ligand have been prepared (Table 1). In all these species, bamp remains coordinated meridionally under a variety of conditions as shown by ¹H- and ¹³C-NMR. spectroscopy and correlations by stereoretentive reaction cycles. The rates of amine proton exchange and of spontaneous aquation, Hg²⁺-induced aquation and base hydrolysis of some chloropentaamine complexes have been determined. They essentially follow the patterns observed for complexes with purely aliphatic amine ligands; the presence of a pyridine donor in these complexes does not suggest deviations from the mechanistic schemes usually proposed for the solvolytic reactions investigated.     

2,6-Di(1H-tetrazol-1-yl)pyridine and its cupric chloride complex

2,6-Di(1H-tetrazol-1-yl)pyridine (DTP) was prepared by a four-stage procedure, including step-by-step heterocyclization of both amino groups of 2,6-diaminopyridine with triethyl orthoformate and sodium azide. According to quantum-chemical calculations and single crystal X-ray diffraction data, DTP crystallizes in the form of the thermodynamically most stable conformer and has an almost flat molecular geometry. DTP was found to react with CuCl₂ ⋅ 2H₂O in ethanol to give the [Cu(DTP)Cl₂(H₂O)]_n complex, which is a 1D coordination polymer, formed at the expense of bridging DTP ligand via the tetrazole ring nitrogen atoms N⁴. Possible coordination cites in DTP molecule are discussed using the data of quantum chemical calculations. The pyridine ring nitrogen atom of DTP does not participate in the formation of either coordination or intermolecular hydrogen bonds. This is explained by the results of quantum chemical calculations showing that this atom is less basic than N3 and N4 atoms of DTP molecule.     

Theoretical study of bifurcated hydrogen bonding effects on the 1J(N,H), 1hJ(N,H), 2hJ(N,N) couplings and 1H, 15N shieldings in model pyrroles

According to the density functional theory calculations, the X···H···N (X?N, O) intramolecular bifurcated (three‐centered) hydrogen bond with one hydrogen donor and two hydrogen acceptors causes a significant decrease of the ^1hJ(N,H) and ^2hJ(N,N) coupling constants across the N? H···N hydrogen bond and an increase of the ¹J(N,H) coupling constant across the N? H covalent bond in the 2,5‐disubsituted pyrroles. This occurs due to a weakening of the N? H···N hydrogen bridge resulting in a lengthening of the N···H distance and a decrease of the hydrogen bond angle at the bifurcated hydrogen bond formation. The gauge‐independent atomic orbital calculations of the shielding constants suggest that a weakening of the N? H···N hydrogen bridge in case of the three‐centered hydrogen bond yields a shielding of the bridge proton and deshielding of the acceptor nitrogen atom. The atoms‐in‐molecules analysis shows that an attenuation of the ^1hJ(N,H) and ^2hJ(N,N) couplings in the compounds with bifurcated hydrogen bond is connected with a decrease of the electron density ρ_H···N at the hydrogen bond critical point and Laplacian of this electron density ?²ρ_H···N. The natural bond orbital analysis suggests that the additional N? H···X interaction partly inhibits the charge transfer from the nitrogen lone pair to the σ*_{N? H} antibonding orbital across hydrogen bond weakening of the ^1hJ(N,H) and ^2hJ(N,N) trans‐hydrogen bond couplings through Fermi‐contact mechanism. An increase of the nitrogen s‐character percentage of the N? H bond in consequence of the bifurcated hydrogen bonding leads to an increase of the ¹J(N,H) coupling constant across the N? H covalent bond and deshielding of the hydrogen donor nitrogen atom. Copyright © 2010 John Wiley & Sons, Ltd.     

Crystal structure and spectroscopic properties of isothiocyanato[(3,14-dimethyl-2,6,13,17-tetraazatricyclo(16.4.0.0<Superscript>7,12</Superscript>)docosane)]copper(II) thiocyanate

A new complex [Cu(L¹)(NCS)]SCN, where L¹ = 3,14-dimethyl-2,6,13,17-tetraazatricyclo( 16.4.0.0^7,12)docosane is prepared and characterized by single crystal X-ray crystallographic analysis. The complex crystallizes in the triclinic space group P1? with two mononuclear formula units in a cell of dimensions a = 7.9681(2) Å, b = 8.8644(2) Å, c = 18.8165(5) Å, α = 76.758(70)°, β = 78.490(2)° and γ = 77.679(2)°. The Cu(II) ion is five-coordinate in an axially elongated square pyramidal environment, with the four amine N atoms at the equatorial positions and the N atom of one thiocyanate at an apical site. The macrocyclic cyclam moiety adopts a stable trans-III configuration. The Cu–N basal plane bond length has a mean value of 2.037(2) Å. The coordinated Cu–NCS bond length is 2.322(3) Å. The N atom of the thiocyanate anion is connected to the macrocyclic ligand of the cation via an NH…N(CS) hydrogen bond. The UV-visible absorption and IR spectral properties are also discussed.     

Synthesis, structure, electrochemical and magnetic properties of 2,6-bis(5-trifluoromethylpyrazol-3-yl)pyridine and its NiII complexes

2,6-Bis(5-trifluoromethylpyrazol-3-yl)pyridine (H₂L) and its mono-, tri-, and tetranuclear NiII complexes were synthesized for the first time. All the obtained compounds were characterized by single-crystal X-ray diffraction analysis. In the complexes, 2,6-bis(5-trifluoromethylpyrazol-3-yl)pyridine exists in the neutral and dianionic forms and exhibits different coordination modes (??³-, ??²-??³:??¹-, and ??³-??³:??¹:??¹). The electrochemical and magnetic properties of all compounds were studied. The tetranuclear Ni^II complex with the L^2? dianion is reduced in two sequential reversible one-electron steps.     

A New Diiminopyridyl Cobalt Complex [CoCl2L] (L = 2,6-Bis(N,N'-bis(2,6-diisopropyl-4-(2,3-dimethyoxylbenzoylamide)phenylimino))pyridine)

The reaction of CoCl2·6H2O with 2,6-bis(N,N'-bis(2,6-diisopropyl-4-(2,3-dimethy-oxyl-benzoylamide)phenylimino))pyridine (L) afforded the complex [CoCl2L], which was fully characterized by elemental analysis, UV-vis, IR spectroscopy, fluorescence, and X-ray diffraction analysis. The compound is oftriclinie system, space group P1- with a = 13.058(3), b = 13.798(3), c =16.695(3) (A), α = 98.191(3),β = 102.792(3), γ = 101.820(3)°,V= 2815.0(9) (A)3, Z= 2, F(000) = 1122,μ = 0.45 mm-1, R = 0.061 and wR= 0.1349 for 9842 observed reflections (1 2σ(Ⅰ)). The Co(Ⅱ center adopts a distorted square-pyramidal coordination geometry. The extended structure shows a one-dimensional zigzag double chain linked by hydrogen bonds and π-π stacking interactions.     

Synthesis and crystal structure of 2-{5-[2-(2,6-dichlorophenylamino)benzyl]-4-p-tolyl-4H-1,2,4-triazol-3-ylthio}acetate

The compound 2-{5-[2-(2,6-dichlorophenylamino)benzyl]-4-p-tolyl-4H-1,2,4-triazol-3-ylthio}acetate has been prepared and characterized by IR, ¹H NMR, ¹³C NMR and mass spectra. The crystal and molecular structure were further confirmed using single crystal X-ray diffraction. The crystal structure has been found to be stabilized by intermolecular C–H···O interaction generating bifurcated hydrogen bonds whereas the C–H···N interactions generate chain of molecules. The intramolecular N–H···N hydrogen bond forms a ring with S(7) graph-set motif.     

Novel poly(amide-imide)s from 2,6-bis(5-amino-1-naphthoxy) pyridine

Reaction of 5-amino-1-naphthol with 2,6-dichloropyridine resulted in preparation of 2,6-bis(5-amino-1-naphthoxy) pyridine (AN). This pyridine-based ether diamine was reacted with two moles of trimellitic anhydride (TMA) to synthesize related diimide-diacid (DIDA). Direct polycondensation reaction of DIDA with different diamines in the presence of triphenyl phosphite (TPP) afforded seven different poly(amide-imide)s. All the polymers were characterized and their physical and thermal properties were studied. The inherent viscosity of the polymers was about 0.44-0.50 dl g⁻¹ and they showed high thermal stability.     

Derivatives of azacalix[3](2,6)pyridine are strong neutral organic superbases: a DFT study

The gas phase basicities and pKa values in acetonitrile of azacalix[3](2,6)pyridine and its derivatives are determined by the B3LYP DFT method. It is found that all compounds of this series are neutral organic superbases. The proton attacks the inner pyridine N(sp2) atom, thus forming a bifurcated intramolecular hydrogen bond. The most powerful superbase is provided by the hexakis(dimethylamino) derivative of the title compound. Its gas phase proton affinity is 296.6 kcal mol-1, its basicity is 291.3 kcal mol-1, and its pKa(MeCN) is 30.9 units. [structure: see text]     

Ruthenium(II) and palladium(II) complexes with 2,6-(bispyrazol-1-yl)pyridines

Ruthenium(II) and palladium(II) complexes [Ru(DMSO)(L)Cl₂] and [Pd(L)Cl]Cl, where L = 2,6-bis(pyrazol-1-yl)pyridine (bpp) or 2,6-bis(3,5-dimethylpyrazol-1-yl)pyridine (bdmpp) have been synthesized. All complexes were characterized by elemental analysis, IR, ¹H NMR, UV-Vis, and cyclic voltammetry measurements.     

(Aceto­nitrile)­[2,6‐bis­(pyrazol‐1‐yl)­pyridine](isonicotin­amide)copper(II)–tetra­fluoro­borate–aceto­nitrile (1/2/2)

Molecules of the title compound, [Cu(C₂H₃N)(C₁₁H₉N₅)(C₆H₆N₂O)](BF₄)₂·2C₂H₃N, comprise (aceto­nitrile)[2,6‐bis(pyrazol‐1‐yl)­pyridine](isonicotin­amide)copper(II) cations, tetra­fluoro­borate anions and lattice aceto­nitrile mol­ecules. The cations have distorted square‐pyramidal geometries in which the N₃‐donor, viz. 2,6‐bis­(pyrazol‐1‐yl)­pyridine, and the N‐donor, viz. the isonicotin­amide ligand, occupy the four basal positions, with the coordinated aceto­nitrile N‐donor atom occupying the apical position. Pairs of cations are linked by N—H?F hydrogen bonds through tetra­fluoro­borate anions, forming centrosymmetric dimers, which are further linked by C—H?O hydrogen bonds into two‐dimensional undulating sheets, three of which interpenetrate to generate a two‐dimensional network.     

Dichloro­[(1E,1′E)‐1,1′‐(pyridine‐2,6‐diyl)diethanone bis­(O‐methyl­oxime)‐κ3N1,N2,N6]copper(II)

In the title compound, [CuCl₂(C₁₁H₁₅N₃O₂)], the Cu^II ion is five‐coordinated in a strongly distorted trigonal–bipyramidal arrangement, with the two methyl­oxime N atoms located in the apical positions, and the pyridine N and the Cl atoms located in the basal plane. The two axial Cu—N distances are almost equal (mean 2.098 Å) and are substantially longer than the equatorial Cu—N bond [1.9757 (15) Å]. It is observed that the N(oxime)—M—N(pyridine) bond angle for five‐membered chelate rings of 2,6‐diacetyl­pyridine dioxime complexes is inversely related to the magnitude of the M—N(pyridine) bond. The structure is stabilized by intra‐ and inter­molecular C—H⋯Cl hydrogen bonds which involve the methyl H atoms, except for one of the two acetyl­methyl groups.     

Experimental and computational investigations of a cadmium(II) mononuclear complex with 2,6-Bis(3,5-dimethyl-N-pyrazolyl)pyridine (bdmpp) and selenocyanate as ligands

A new cadmium (II) complex, [Cd(bdmpp)(SeCN)₂(H₂O)] (1) (where bdmpp = 2,6-bis(3,5-dimethyl-N-pyrazolyl)pyridine), has been synthesized and characterized by elemental and spectral (IR, ¹H-NMR and ¹³C-NMR, UV-Vis) analyses, differential scanning calorimetry, and single crystal X-ray diffraction studies. X-ray analysis showed that the structure was crystallized in the monoclinic space group Cc with a = 9.031(2), b = 13.884(3), c = 16.910(3) Å, and Z = 4. The geometry around the cadmium atom is distorted octahedral with a CdN₃Se₂O setup. The N atoms of the SeCN are engaged in two strong intermolecular H-bonding interactions forming a 3D supramolecular polymeric network. The geometry and vibrational frequencies of complex 1 computed with the DFT methods (BLYP, B3LYP, B3PW91, MPW1PW91) are in better agreement with experiment than those obtained with the ab-initio method except for the bond angles. The molecular orbital diagram has been also calculated and visualized at the B3LYP/LanL2DZ level of theory.      

2,6-Bis(2-benzimidazolyl)pyridine receptor for urea recognition

The use of 2,6-bis(2-benzimidazolyl)pyridine as a neutral receptor enables the formation of highly stable supramolecular complexes with urea via self-assembly and which were characterized by spectroscopy and X-ray diffraction analysis. This receptor utilizes the imine nitrogen located on its outer core in addition to the cavity to form hydrogen-bonded adducts with high binding affinity, thus providing a unique design for chemical and biological recognition.     

Utilization of 2,6-bis(2-benzimidazolyl)pyridine to detect toxic benzene metabolites

The tridentate ligand 2,6-bis(2-benzimidazolyl)pyridine has the ability to detect toxic benzene metabolites such as phenol, hydroquinone, resorcinol, catechol and p-benzoquinone by simple techniques like UV/vis and fluorescence spectroscopy. The formation of a stable supramolecular complex between 2,6-bis(2-benzimidazolyl)pyridine and hydroquinone was confirmed by X-ray analysis.