Pyridine Hydrogen Research Articles

4-Nitro-6-[(8-quinolylamino)methylidene]cyclohexa-2,4-dien-1-one

The mol­ecule of the title compound, C16H11N3O3, exists in the keto form and the C=O and N—H bonds are mutually cis in the crystal structure. There are two crystallographically independent mol­ecules per asymmetric unit with broadly similar structural data. The only noticeable difference between the two is the dihedral angles between the benzene and the quinoline rings: 1.04 (4) and 3.07 (4)°. In the structure, intra­molecular N—H⋯O(carbon­yl) and N—H⋯N(pyridine) hydrogen bonds exist but there is no evidence of formal inter­molecular hydrogen-bonding associations.

A hydrogen-bonded dimer in 6-(4-bromophenyl)-3-methyl-1-phenyl-4,5-dihydro-1H-pyrazolo[3,4-b]pyridine and a chain of rings built from N—H...N and C—H...π(pyridine) hydrogen bonds in 3-(4-nitrophenyl)-4-phenyl-1H-pyrazolo[3,4-b]pyridine

In 6-(4-bromophenyl)-3-methyl-1-phenyl-4,5-dihydro-1H-pyrazolo[3,4-b]pyridine, C(19)H(16)BrN(3), the reduced pyridine ring adopts a conformation that is close to a screw-boat form. Molecules are linked by pairs of symmetry-related C-H...pi(arene) hydrogen bonds into cyclic centrosymmetric dimers. Molecules of 3-(4-nitrophenyl)-4-phenyl-1H-pyrazolo[3,4-b]pyridine, C(18)H(12)N(4)O(2), are linked into centrosymmetric R(2)(2)(8) dimers by pairs of symmetry-related N-H...N hydrogen bonds, and these dimers are linked by pairs of C-H...pi(pyridine) hydrogen bonds to form a chain of edge-fused rings, or a molecular ladder, along [100]. The molecular aggregation in this compound is completed by two weak C-H...O hydrogen bonds, one of which links the chains along [100] into sheets.

Design and stabilization of block copolymer micelles via phenol–pyridine hydrogen-bonding interactions

A new approach for the preparation of block copolymer micelles in non-selective solvent is introduced. Phenol–pyridine hydrogen-bonding interactions are used for the first time to prepare core–shell micelles in non-selective solvents using block copolymers and bifunctional low-molecular-weight hydrogen-bonding crosslinkers. Poly(styrene- b-4-vinylphenol)/Bis-pyridyl ethane and poly(styrene- b-4-vinylpyridine)/Bisphenol A were investigated as micelle formation due to phenol–pyridine hydrogen bond crosslinking. The influence of several factors such as temperature, concentration, solvent and pH in micellization–demicellization process was analyzed by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), dynamic light scattering (DLS) and atomic force microscopy (AFM). This method opens new possibilities to the generation of block copolymer micelles in non-selective solvents.

Order‐disorder transitions in self‐assembled polymers: A positron annihilation study

AbstractWe report here the first results of order‐disorder transition (ODT) in a self‐assembled comb‐like polymer‐amphiphile supramolecular system as identified from the change in positron lifetime parameters. We have used poly(4‐vinyl pyridine) hydrogen bonded with 3‐pentadecyl phenol, which upon heating showed a stepwise reduction in o ‐Ps intensity at the ODT from lamellar self‐assembled state to the disordered state. The ODT temperature was confirmed by differential scanning calorimetry and small angle X‐ray scattering. The free volume “holes” in this polymer‐amphiphile system are proposed to be near the chain ends of the polymer backbones. We suggest that positron lifetime spectroscopy can serve as a technique to identify ODTs in self‐assembled lamellar structured supramolecular systems. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Thermal and FTIR analysis of the miscibility and phase behaviour of poly (isobutyl methacrylate-co-4-vinylpyridine)/poly (styrene-co-acrylic acid) systems

The miscibility and phase behaviour of poly (isobutyl methacrylate-co-4-vinylpyridine) containing 20 mol% of 4-vinylpyridine (IBM4VP20) and poly (styrene-co-acrylic acid) containing 27 or 32 mol% of acrylic acid (SAA27 or SAA32) mixtures were investigated by DSC, TGA and FTIR spectroscopy in the 25–180 °C temperature range. The results showed that sufficient specific carboxyl–pyridine hydrogen bonding interactions occurred between these copolymers and led to miscible blends as cast from THF and to inter-polymer complexes of significantly improved thermal stability when butan-2-one is the common solvent. The self-association effect on the inter-polymer interactions was evidenced by the decrease of complexation yields, observed when the carboxylic content is increased above 27 mol% as with SAA32. The trend of phase behaviour predicted by a thermodynamic analysis of the specific interactions of hydrogen bonding type that occurred between the two components of the SAA27/IBM4VP20 blends, neglecting the weak carboxyl–ester interactions and the functional group accessibility effect, carried out using the Painter–Coleman association model that considers the screening effects, is in a fair agreement with the experimental results. Moreover an LCST is predicted to occur at relatively high temperature.

Nanostructured polystyrene-block-poly(4-vinyl pyridine)(pentadecylphenol) thin films as templates for polypyrrole synthesis

Abstract Polypyrrole has been chemically synthesized on thin film nanostructures obtained from comb-shaped supramolecules of polystyrene-block-poly(4-vinyl pyridine) (PS-b-P4VP) hydrogen bonded with pentadecylphenol (PDP). PDP was washed from thin films of cylindrical and lamellar self-assembled comb-copolymer systems, which resulted in removal of the upper layers of microdomains, leaving single cylindrical and lamellar layers covering a substrate, with P4VP segregated at the bottom as well as at the free air interface. This P4VP was complexed with Cu2+ ions, after which chemical oxidation polymerization of pyrrole resulted in a thin polypyrrole layer covering the nanostructured block copolymer. The use of a catalytic amount of bipyrrole greatly improved the quality of the obtained product. The conductivity was measured to be ∼0.7 S cm−1.

Copolymerization of vinyl chloride with 1-vinyl-4,5,6,7-tetrahydroindole and 2-methyl-5-vinylpyridine

The radical copolymerization of vinyl chloride with 2-methyl-5-vinylpyridine and 1-vinyl-4,5,6,7-tetrahydroindole is accompanied by dehydrochlorination. In the vinyl chloride-2-methyl-5-vinylpyridine system, the evolved hydrogen chloride interacts with a pyridine hydrogen atom to give charged units of a heterocycle. In the vinyl chloride-1-vinyl-4,5,6,7-tetrahydroindole system, the hydrogen chloride being formed initiates the cationic dimerization of a nitrogen-containing monomer. The synthesized copolymers based on vinyl chloride surpass the commercial poly(vinyl chloride) in terms of thermal stability and solubility in organic solvents.

Hierarchy of Supramolecular Synthons: Persistent Carboxylic Acid···Pyridine Hydrogen Bonds in Cocrystals That also Contain a Hydroxyl Moiety

A Cambridge Structural Database (CSD) analysis was conducted in order to evaluate the hierarchy of supramolecular heterosynthons that involve two of the most relevant functional groups in the context of active pharmaceutical ingredients, carboxylic acids and alcohols, in competitive environments. The study revealed that 34% of the 5690 molecular carboxylic acid entries and 26% of the 25 035 molecular alcohol entries form supramolecular homosynthons, whereas the remaining entries form supramolecular heterosynthons with other functional groups, in particular Narom, CONH2, C−O−C, C═O, and chloride anions. Further refinement of this raw data revealed the following: 98% occurrence of the COOH···Narom supramolecular heterosynthon in the 126 crystal structures that contain acid and pyridine moieties in the absence of other hydrogen bond donors or acceptors; and 78% occurrence of the OH···Narom supramolecular heterosynthon in 228 crystal structures that contain hydroxyl and pyridine moieties (excluding intramolec...

Hydrogen-Bonded Helices for Anion Binding and Separation

Herein we report the competitive crystallization of urea-functionalized hydrogen-bonded helical frameworks as a new approach to separating anions from aqueous mixtures. N,N′-Bis( m-pyridylurea) ( 1) containing orthogonal pyridine and urea hydrogen-bonding functionalities forms upon monoprotonation with 1 equiv of HX acids (X = Cl −, Br −, I −, NO 3 −, and ClO 4 −) an isomorphous series of crystalline hydrogen-bonded helices assembled by pyridinium···pyridine hydrogen bonds, with the urea functional groups binding the anions through chelate hydrogen bonding. The helices are further connected in the crystals by CH···X − and pyridinium···X − interactions, as well as π-stacking interactions. Competitive crystallization experiments and lattice energy calculations of the 1·HX crystals showed the solvation-based Hofmeister bias that typically dominates anion separation selectivities from water was attenuated, but not completely overturned. The observed selectivity is apparently a result of the relatively soft and unspecific hydrogen-bonding environment around the anions in the crystals, combined with the high flexibility of the helices, which expand or contract as necessary to accommodate each anion.

Synthesis and structural characteristics of lithocholate triads: steroid-type channels occupied by spacer fragments

Reported in this paper are the syntheses and X-ray investigations of C(2) symmetrical molecular A-B-A triads consisting of two steroid units (lithocholic acid or its methyl ester) joined together by linkers derived from bifunctional molecules such as terephthalic acid or N,N'-dicarboxypiperazine. Unlike their monomeric analogues, some of these compounds form inclusion complexes. All steroidal triads form crystals that are highly pseudo-centrosymmetric, in which the constituting molecules are held together either exclusively by van der Waals forces or form lattice inclusion complexes, with guest molecules hydrogen bonded to the host. The presence of carboxyl groups promotes the inclusion of pyridine molecules and the formation of the well known carboxylic acid...pyridine hydrogen bonds. Combined with pairwise face-to-face pi-stacking between pyridine rings, these hydrogen-bond interactions lead to the formation of extended supramolecular tapes, analogous to polymers. The co-crystals of pyridine and a lithocholic acid triad undergo a symmetry-lowering phase transition from a P1 cell with Z = 1 to a P1 cell with Z = 2. The two structures are virtually the same, the two independent molecules in the larger cell being related by pseudo-translation. Changes in the type of spacer between two methyl lithocholate units from planar aromatic (terephthalic acid) to highly puckered aliphatic six-membered ring (N,N'-dicarboxypiperazine) bring about inclusion properties and changes in side-chain conformation in a crystal. Although the efficient packing of these highly elongated molecules is hindered, as indicated by low values of crystal density, ranging from 1.16 to 1.19 g cm(-3), several very short C...O and H...H contacts are present in the crystals.

Bis(2-amino-6-methylpyridinium) tetrabromidocuprate(II)

In the crystal structure of the title compound, (C6H9N2)2[CuBr4], the geometry around the Cu atom is inter­mediate between tetra­hedral (Td) and square planar (D4h). Each [CuBr4]2− anion is connected non-symmetrically to four surrounding cations through N—H⋯X (pyridine and amine proton) hydrogen bonds, forming chains of the ladder-type running parallel to the crystallographic b axis. These layers are further connected by means of offset face-to-face inter­actions (parallel to the a axis), giving a three-dimensional network. Cation π–π stacking [centroid separations of 3.69 (9) and 3.71 (1) Å] and Br⋯aryl inter­actions [3.72 (2) and 4.04 (6) Å] are present in the crystal structure. There are no inter­molecular Br⋯Br inter­actions.

(Acetato-κ2O,O′)(aqua-κO)[1-(2-pyridylmethylidene-κN)semicarbazide-κ2N1,O](thiocyanato-κS)cadmium(II) monohydrate

The Cd atom in the title complex, [Cd(C2H3O2)(NCS)(C7H8N4O)(H2O)]·H2O, is coordinated by one neutral Schiff base ligand, one acetate anion, one thio­cyanate anion and one water mol­ecule, forming a distorted penta­gonal–bipyramidal geometry. The thio­cyanate S atom and the coordinated water ligand occupy the apical positions of the coordination polyhedron. The acetate acts as a bidentate ligand through the carboxylate O atoms. The Schiff base, derived from the condensation of pyridine-2-carbaldehyde and semicarbazone, acts as a tridentate ligand, coordinating the metal through the amide, imine and pyridyl N atoms in a meridional fashion. The crystal packing is stabilized by π–π stacking inter­actions between the neighboring pyridine rings and hydrogen bonds involving the Schiff base, thio­cyanate, water mol­ecules and uncoordinated solvent water mol­ecules.

Effects of Hydrogen Bonding on the Ring Stretching Modes of Pyridine

The effects of hydrogen bonding on the ring stretching modes (both ring breathing and triangle) of pyridine are experimentally investigated using noisy light based coherent Raman scattering spectroscopy. Three systems, pyridine/formamide, pyridine/water, and pyridine/acetic acid, provide varying degrees of strength for the diluent-pyridine hydrogen bond complex. Formamide forms a relatively weaker hydrogen bond, while acetic acid essentially fully transfers a proton to pyridine. Both dilution studies and temperature studies are performed on the three systems. Together, these provide a broad context in which a very simple model for the electronic behavior of pyridine is formulated. This model is based on a molecular orbital picture and electrostatic arguments, and it well explains the observed experimental results. Additionally, a new mechanism for the line broadening of the ring breathing mode for the pyridine-water hydrogen bonded complex is proposed.

2-{[N-(Pyridinium-2-ylmethyl)-N-(pyridin-2-ylmethyl)amino]methyl}-1-(pyridin-2-ylmethyl)pyridinium diperchlorate

The cation of the title salt, C24H25N52+·2ClO4−, contains a tris­(2-pyridylmeth­yl)amine core in which one of the pyridine N atoms is protonated and a second pyridine N atom forms an additional C—N bond to another 2-pyridylmeth­yl group, resulting in a second pyridinium center. The protonated pyridinium hydrogen bonds to a pyridine ring of a neighboring dication. The hydrogen-bonded H atom is disordered between the two N atoms.

Theoretical ONIOM2 Study on Pyridine Adsorption in the Channels and Intersection of ZSM-5

The structures of the acid sites in the channels and intersections of H-, Li-, and Na-ZSM-5 (ZSM = zeolite socony mobil) and their interactions with pyridine molecule have been computed by using three corresponding models containing 22 tetrahedral sites. The calculated adsorption energies of pyridine in the intersection regions of H-, Li-, and Na-ZSM-5 are 197.0, 172.5, and 122.3 kJ/mol, respectively, in good agreement with the respective experimental values of 200 +/- 5, 155-195, and 120 kJ/mol, while those in the straight and sinusoidal channels are much smaller (157.9 and 127.6, 152.2 and 149.4, and 150.4 and 109.9 kJ/mol, respectively). These indicate that the most probable adsorption site for pyridine in ZSM-5 is the acidic site located in the intersection region. The structural parameters of the adsorption complexes show that the acidic proton in the three models of H-ZSM-5 has been transferred to the nitrogen of pyridine, while in alkali cation-exchanged ZSM-5, the coordination of the alkali cation to the nitrogen atom of pyridine dominates the overall interaction. In addition, the adsorption complexes were further stabilized by the long-range electrostatic interaction between the positively charged pyridine hydrogen atoms and the negatively charged lattice oxygen atoms of the zeolite framework. In the intersection regions of H-, Li-, and Na-ZSM-5, the coordination energy of the charge-compensating cation to the pyridine nitrogen amounts to 58, 60, and 68% of the total adsorption energy, respectively, while another 42, 40, and 32%, respectively, is due to long-range electrostatic interactions. This indicates that the zeolite lattice framework surrounding the adsorption site has important contributions to the adsorption energy of the pyridine molecule.

The co-crystallisation of pyridine with benzenepolycarboxylic acids: The interplay of strong and weak hydrogen bonding motifs

Co-crystallisation of pyridine with terephthalic, trimesic, phthalic, isophthalic and pyromellitic acids has been investigated via single crystal X-ray diffraction and thermogravimetric analysis, concentrating on the nature of the intermolecular interactions. The five new compounds are terephthalic acid bis(pyridine) solvate, trimesic acid tris(pyridine) solvate, pyridinium hydrogen phthalate, isophthalic acid pyridine solvate and pyridinium trihydrogen pyromellitate. A variety of supramolecular hydrogen bonded motifs involving interactions between pyridine molecules and carboxylic acid groups are observed rather than just the R22(7) O–H⋯N/C–H⋯O motif; while the common carboxylic acid head-to-tail ring motif is absent in all of the examples investigated. TGA analysis of pyridine loss from two of the compounds has been shown to correlate with the strength of hydrogen bonds in the crystal structures.

Molecular Complexes of Homologous Alkanedicarboxylic Acids with Isonicotinamide: X-ray Crystal Structures, Hydrogen Bond Synthons, and Melting Point Alternation

Crystallization of α,ω-alkanedicarboxylic acids (HOOC−(CH2)n-2−COOH, n = 2−6) with isonicotinamide (IN) is carried out in 1:2 and 1:1 stoichiometry. Five cocrystals of (diacid)·(IN)2 composition (diacid = oxalic acid, malonic acid, succinic acid, glutaric acid, and adipic acid) are characterized by X-ray diffraction at 153(2) K. Tapes of acid−pyridine O−H···N and amide−amide N−H···O hydrogen bond synthons stabilize these five crystal structures as predicted by the hierarchic model: the best donor (COOH) and best acceptor group (pyridine N) hydrogen bond as acid−pyridine and the second best donor−acceptor group (CONH2) aggregates as an amide dimer. Glutaric acid and adipic acid cocrystallize in 1:1 stoichiometry also, (diacid)·(IN), with acid−pyridine and acid−amide hydrogen bonds. Synthon energy calculations (ΔEsynthon, RHF/6-31G**) explain the observed hydrogen bond preferences in 1:2 (five examples) and 1:1 (two examples) cocrystals. The acid−pyridine hydrogen bond is favored over the acid−amide dimer ...

Cocrystals of 1,3,5-Cyclohexanetricarboxylic Acid with 4,4‘-Bipyridine Homologues: Acid···Pyridine Hydrogen Bonding in Neutral and Ionic Complexes

cis,cis-1,3,5-Cyclohexanetricarboxylic acid (H3CTA) is crystallized with bipyridine bases 1,2-bis(4-pyridyl)ethane (bipy-eta), 1,4-bis(4-pyridyl-2-ethyl)benzene (bipy-etabz), 1,2-bis(4-pyridyl)ethylene (bipy-ete), and 1,4-bis(2-(4-pyridyl)ethenyl)benzene (bipy-etebz) to afford molecular complexes (H3CTA)·(bipy-eta)1.5 1, (H3CTA)·(bipy-etabz) 2, (H2CTA-)·(bipy-ete2H+)0.5 3, and (H2CTA-)·(bipy-etebz2H+)0.5 4. Cocrystal 1 has a super honeycomb hydrogen bond network stabilized by carboxylic acid-bipyridine O−H···N synthon Va. The hexagonal cavity of 34.1 × 36.7 A is filled by parallel triple interpenetration of independent networks. 2 has zigzag chains of synthon Va connected via O−H···O hydrogen bonds. Carboxylic acid to pyridine proton transfer occurs in 3 and 4. These structures have undulated and flat 2D layers of O−H···O- and O−H···O hydrogen bonds that are connected to bipyridinium via N+−H···O- hydrogen bond Vb. H2CTA- anions in 4 form a porous parquet grid of 14.5 × 7.5 A with the channels accommodati...

Five (1H-pyrrol-2-yl)pyridines.

The title (1H-pyrrol-2-yl)pyridines, C(9)H(8)N(2), substituted at the ortho, meta, and para positions of the pyridine ring all have hydrogen-bonded arrangements with geometrically similar, nearly linear, N(pyrrole)-H...N(pyridine) hydrogen bonds of average length. The graph sets for the ortho, meta, and three para polymorphs are R(2)(2)(10), C(6), C(7), C(7), and R(4)(4)(28), respectively.

Supramolecular synthons in phenol–isonicotinamide adducts

Molecular complexes of four phenols (hydroquinone, resorcinol, phloroglucinol and 4-hydroxybenzoic acid) with isonicotinamide are characterized by X-ray diffraction. (Hydroquinone)0.5·(isonicotinamide) 1 and (resorcinol)·(isonicotinamide)22 have tapes of O–H⋯N and amide N–H⋯O dimer synthons. In (phloroglucinol)·(isonicotinamide)2·(H2O)23, six component self-assembly results in stacked dimers with four O–H⋯N and four amide N–H⋯O hydrogen bonds and the third phenol OH aggregates with two water molecules in a supramolecular chair cyclohexane array. Phenol⋯pyridine and amide N–H⋯O dimers are robust synthons in 1–3 for the self-assembly of 0D discrete aggregates and infinite 1D chains. Hydrogen bonding of amide dimers via N–H⋯Ophenol/water is ascribed to cooperative effects. The crystal structure of (4-hydroxybenzoic acid)·(isonicotinamide) 4 establishes the robustness of phenol⋯pyridine hydrogen bonding in the presence of carboxylic acid groups. Molecular components in 4 are arranged as zigzag tapes of O–H⋯N hydrogen bonds and acid⋯amide heterodimers. Supramolecular synthesis with phenol–isonicotinamide adducts expands the versatility of isonicotinamide as a co-crystallizing agent in crystal engineering.