Home About us Contact
|
Home About us Contact | ||
|
|
||
Pyridine Ring (pyridine + ring)
Selected AbstractsDye-Sensitized Solar Cells Based on a Novel Fluorescent Dye with a Pyridine Ring and a Pyridinium Dye with the Pyridinium Ring Forming Strong Interactions with Nanocrystalline TiO2 FilmsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 1 2010Yousuke Ooyama Abstract As new-type donor,acceptor ,-conjugated dyes capable of forming a strong interaction between the electron-acceptor moiety of the sensitizers and a TiO2 surface, fluorescent dye OH11 and pyridinum dye OH12 with a pyridine and pyridinium ring as the electron-accepting group, respectively, have been designed and synthesized as photosensitizers for use in dye-sensitized solar cells (DSSCs). The fluorescent dye OH11 exhibits an absorption band at around 410 nm and a fluorescence band at around 530 nm. On the other hand, the pyridinum dye OH12 shows an absorption maximum at around 560 nm, assigned to a strong intramolecular charge-transfer excitation from the dibutylamino group to the pyridinium ring. The short-circuit photocurrent densities of the DSSCs prepared by using OH11 and OH12 are 4.33 and 1.74mA cm,2, and the solar energy-to-electricity conversion yields are 1.33 and 0.51,%, respectively, under simulated solar light [AM (air mass) 1.5, 100 mW,cm,2]. The open-circuit photovoltage for OH11 (525 mV) is higher than that of OH12 (444 mV). The effects of the configuration of the dyes on the TiO2 surface and of their chemical structures on the photovoltaic performances are discussed on the basis of semi-empirical molecular orbital calculations (AM1 and INDO/S), spectral analyses and cyclic voltammetry. [source] ChemInform Abstract: The Syntheses of Nitrogen-Oxygen Donor Macrocycles Containing Pyridine Ring.CHEMINFORM, Issue 44 2001Bin Zhao Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Crystal structures of two acridinedione derivativesCRYSTAL RESEARCH AND TECHNOLOGY, Issue 3 2005K. Palani Abstract The crystal structures of two acridinedione derivatives, namely 10-(3,4-Dichloro-5-hydroxyphenyl)-3,4,6,7,9,10-hexahydro-1,8(2H, 5H) acridinedione (DHHA, CCDC 206440) and 10-(3,5-Dihydroxy-4-nitrophenyl)-3,4,6,7,9,10-hexahydro-1,8(2H, 5H) acridinedione (DHNA, CCDC206441) are reported here. Both the structures were solved by direct methods and refined by full-matrix least-squares procedures to final R- values of 0.073 and 0.076 respectively. In both the crystal structures, the central pyridine ring in the acridinedione moiety tends to be planar while the outer two rings adopt half-chair (sofa) conformation. The buckling angles 2.2(2)° and 11.0(1)° for DHHA and DHNA show the degree of planarity of the acridinedione moiety. The C-H,O types of hydrogen bonds help to stabilize the molecules in the unit cell in addition to van der Waals forces. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Palladium-Catalysed Amination of Electron-Deficient or Relatively Electron-Rich Benzo[b]thienyl Bromides , Preliminary Studies of Antimicrobial Activity and SARsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 17 2004Maria-João R. P. Queiroz Abstract Several diarylamines in the benzo[b]thiophene series were prepared in good to high yields by palladium-catalysed amination of ethyl 3-bromobenzo[b]thiophene-2-carboxylate with anilines and 5-aminoindole in the presence of Pd(OAc)2, BINAP and Cs2CO3 in toluene. The presence of the ester group at the 2-position of the benzo[b]thiophene moiety increases the yields and lowers the heating times relative to the reactions performed with 3-bromobenzo[b]thiophene. When aminopyridines were used instead of anilines, the ligand and the solvent need to be changed to XANTHPHOS and dioxane in the amination reaction. With 2-aminopyridine a one-pot C,N coupling and intramolecular cyclization involving the nitrogen atom of the pyridine ring occurred, with loss of ethanol, giving an interesting fluorescent tetracyclic heteroaromatic compound. The antimicrobial activity, the minimal inhibitory concentrations (MICs) and the structure-activity relationships (SARs) were evaluated. A selectivity with low MICs was observed against Bacillus Cereus, and good results were also obtained against Candida albicans. The acids obtained by hydrolysis of the ester group, as non-proteinogenic ,,,-unsaturated ,-amino acids, can be incorporated into peptide chains to induce conformational constraints. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Structure,Property Relationship of Pyridine-Containing Triphenyl Benzene Electron-Transport Materials for Highly Efficient Blue Phosphorescent OLEDsADVANCED FUNCTIONAL MATERIALS, Issue 8 2009Shi-Jian Su Abstract Three triphenyl benzene derivatives of 1,3,5-tri(m -pyrid-2-yl-phenyl)benzene (Tm2PyPB), 1,3,5-tri(m -pyrid-3-yl-phenyl)benzene (Tm3PyPB) and 1,3,5-tri(m -pyrid-4-yl-phenyl)benzene (Tm4PyPB), containing pyridine rings at the periphery, are developed as electron-transport and hole/exciton-blocking materials for iridium(III) bis(4,6-(di-fluorophenyl)pyridinato- N,C2,)picolinate (FIrpic)-based blue phosphorescent organic light-emitting devices. Their highest occupied molecular orbital and lowest unoccupied molecular orbital (LUMO) energy levels decrease as the nitrogen atom of the pyridine ring moves from position 2 to 3 and 4; this is supported by both experimental results and density functional theory calculations, and gives improved electron-injection and hole-blocking properties. They exhibit a high electron mobility of 10,4,10,3,cm2,V,1,s,1 and a high triplet energy level of 2.75,eV. Confinement of FIrpic triplet excitons is strongly dependent on the nitrogen atom position of the pyridine ring. The second exponential decay component in the transient photoluminescence decays of Firpic-doped films also decreases when the position of the nitrogen atom in the pyridine ring changes. Reduced driving voltages are obtained when the nitrogen atom position changes because of improved electron injection as a result of the reduced LUMO level, but a better carrier balance is achieved for the Tm3PyPB-based device. An external quantum efficiency (EQE) over 93% of maximum EQE was achieved for the Tm4PyPB-based device at an illumination-relevant luminance of 1000,cd,m,2, indicating reduced efficiency roll-off due to better confinement of FIrpic triplet excitons by Tm4PyPB in contrast to Tm2PyPB and Tm3PyPB. [source] Absolute Conformations of the (,)-[9](2,5)Pyridinophane MoleculeHELVETICA CHIMICA ACTA, Issue 8 2009Maxim Fedorovsky Abstract [9](2,5)Pyridinophane was first synthesized, and its enantiomers were separated, more than 40 years ago, but the molecule's absolute conformations could not be determined up to now. We show here, by the comparison of measured and computed vibrational optical activity (VOA), that the CIP descriptor (P) applies to the (,)-enantiomer. This assignment is based on the VOA of bands from vibrations localized on the pyridine ring bent by the tense (CH2)9 chain extending from position 2 to 5. The VOA of vibrations localized on the chain is in agreement with this assignment. Its behavior differs from the VOA of the bent pyridine ring, and conclusions drawn from the chain's VOA alone would not be sufficient, because the close-to-enantiomorphic geometries of the chain present in some of the 14 conformers of (,)-[9](2,5)pyridinophane lead to VOA with an opposite sign. Understanding of how VOA is generated is crucial for the unambiguous assignment of the molecule's absolute conformations. [source] Metallo-Supramolecular Polymers Based on Functionalized Bis-terpyridines as Novel Electrochromic Materials,ADVANCED MATERIALS, Issue 22 2007S. Han Self-assembly of various metallo-supramolecular coordination polyelectrolytes (MEPEs) based on pyridine ring functionalized ditopic bis-terpyridines, as well as the electrochromic property is presented. MEPEs derived from electron-donating OMe functionalized ligands exhibit rapid switching rates, good reversibility, high stability, and an optical memory. The first structure-property relationships are proposed, which are needed for the de novo design and fabrication of new materials. [source] Highly Enantio- and Diastereoselective Inverse Electron Demand Hetero-Diels,Alder Reaction using 2-Alkenoylpyridine N -Oxides as Oxo -HeterodienesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009Santiago Barroso Abstract A general catalytic inverse electron demand hetero-Diels Alder reaction for 2-alkenoylpyridine N -oxides is presented. 2-Alkenoylpyridine N -oxides react very efficiently with alkenes in the presence of bisoxazolidine-copper(II) [BOX-Cu(II)] complexes to give chiral dihydropyrans bearing a pyridine ring at the 6-position with very high yields and excellent diastereo- and enantioselectivity. These heterodienes exhibited higher reactivity and enantioselectivity than the corresponding non-oxidized 2-alkenoylpyridines. [source] Synthesis of new proton-ionizable crown ether compounds containing substituted lh-pyridin-4-one subcyclic unitsJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 6 2001Peter Huszthy Five novel pyridono-18-crown-6 (10-14) and two new benzyloxy-substituted pyridino-18-crown-6 (15 and 16) ligands have been prepared. By the catalytic hydrogenative removal of the benzyl group from the benzyloxy moiety at position 4 of the pyridine ring of 15 and 16, pyridono-18-crown-6 ethers 5 and 12 were obtained. These ligands were transformed to their 3,5-dibromo (10 and 13) and 3,5-dinitro derivatives (11 and 14) by treatment with bromine in methylene chloride and nitric acid in acetic anhydride, respectively. The latter proton-ionizable crown ethers have pKavalues of about 7.5 for 10 and 13 and 4.5 for 11 and 14. Thus, they are good candidates for complexation and proton-coupled transport of selected cations. [source] The syntheses of nitrogen-oxygen donor macrocycles containing pyridine ringJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 3 2001Bin Zhao Five new nitrogen-oxygen mixed donor macrocycles have been prepared by condensation of 2,6-bis [(2-formylphenyl)oxymethyl]pyridine with different diamino compounds in hot methanol, followed by a one-pot reduction of the intermediate bis-Schiff base. All the macrocycles were identified by elemental analysis, and ir, uv, and nmr spectroscopy. [source] Studies on deprotection of cysteine and selenocysteine side-chain protecting groupsJOURNAL OF PEPTIDE SCIENCE, Issue 2 2007Katharine M. Harris Abstract We present here a simple method for deprotecting p -methoxybenzyl groups and acetamidomethyl groups from the side-chains of cysteine and selenocysteine. This method uses the highly elecrophilic, aromatic disulfides 2,2,-dithiobis(5-nitropyridine) (DTNP) and 2,2,-dithiodipyridine (DTP) dissolved in TFA to effect removal of these heretofore difficult-to-remove protecting groups. The dissolution of these reagents in TFA, in fact, serves to ,activate' them for the deprotection reaction because protonation of the nitrogen atom of the pyridine ring makes the disulfide bond more electrophilic. Thus, these reagents can be added to any standard cleavage cocktail used in peptide synthesis. The p -methoxybenzyl group of selenocysteine is easily removed by DTNP. Only sub-stoichiometric amounts of DTNP are required to cause full removal of the p -methoxybenzyl group, with as little as 0.2 equivalents necessary to effect 70% removal of the protecting group. In order to remove the p -methoxybenzyl group from cysteine, 2 equivalents of DTNP and the addition of thioanisole was required to effect removal. Thioanisole was absolutely required for the reaction in the case of the sulfur-containing amino acids, while it was not required for selenocysteine. The results were consistent with thioanisole acting as a catalyst. The acetamidomethyl group of cysteine could also be removed using DTNP, but required the addition of > 15 equivalents to be effective. DTP was less robust as a deprotection reagent. We also demonstrate that this chemistry can be used in a simultaneous cyclization/deprotection reaction between selenocysteine and cysteine residues protected by p -methoxybenzyl groups to form a selenylsulfide bond, demonstrating future high utility of the deprotection method. Copyright © 2006 European Peptide Society and John Wiley & Sons, Ltd. [source] Piroxicam/2-hydroxypropyl-,-cyclodextrin inclusion complex prepared by a new fluid-bed coating techniqueJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 2 2009Xingwang Zhang Abstract This work was aimed at investigating the feasibility of fluid-bed coating as a new method to prepare cyclodextrin inclusion complex. The inclusion complex of the model drug piroxicam (PIX) and 2-hydroxypropyl-,-cyclodextrin (HPCD) in aqueous ethanol solution was sprayed and deposited onto the surface of the pellet substrate upon removal of the solvent. The coating process was fluent with high coating efficiency. Scanning electron microscopy revealed a coarse pellet surface, and a loosely packed coating structure. Significantly enhanced dissolution, over 90% at 5 min, was observed at stoichiometric PIX/HPCD molar ratio (1/1) and at a ratio with excessive HPCD (1/2). Differential scanning calorimetry and powder X-ray diffractometry confirmed absence of crystallinity of PIX at PIX/HPCD molar ratio of 1/1 and 1/2. Fourier transform-infrared spectrometry and Raman spectrometry revealed interaction between PIX and HPCD adding evidence on inclusion of PIX moieties into HPCD cavities. Solid-state 13C NMR spectrometry indicated possible inclusion of PIX through the pyridine ring. It is concluded that fluid-bed coating has potential to be used as a new technique to prepare cyclodextrin inclusion complex. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:665,675, 2009 [source] Crystal structure and polarized vibrational spectra of 2-bromo-4-nitropyridine N -oxide single crystalJOURNAL OF RAMAN SPECTROSCOPY, Issue 4 2002J. Hanuza 2-Bromo-4-nitropyridine N -oxide is orthorhombic, space group Pbca, with eight molecules per unit cell of dimensions a = 5.979(1), b = 9.899(1), c = 23.249(5) Å. The Br ion is nearly coplanar with the pyridine ring, while the two oxygen atoms of the nitro group are displaced above and below the ring by (,0.214 Å) and (+0.053 Å). The hydrogen bond of the type C,H···O links the molecules into pairs around centers of symmetry. These dimers, arranged into layers related by glide planes, are held together solely by contacts of the van der Waals type. The polarized Fourier transform IR and Raman spectra, measured in the regions 30,3500 and 80,3500 cm,1, respectively, are correlated with x-ray structural data. Comparison of the spectrum of the dissolved sample with the spectra obtained from the polycrystalline sample and single crystals shows the attractive character of the intermolecular C,H···O contacts for these molecules. The temperature-dependent IR spectra suggest the presence of orientational disorder at higher temperatures. Copyright © 2002 John Wiley & Sons, Ltd. [source] Cytotoxic and antimitotic effects of N -containing Monascus metabolites studied using immortalized human kidney epithelial cellsMOLECULAR NUTRITION & FOOD RESEARCH (FORMERLY NAHRUNG/FOOD), Issue 4-5 2006Anja Knecht Abstract Recently the first Monascus metabolites with a pyridine ring were detected, the monascopyridines A and B. They are formally dehydrogenated derivatives of the red rice pigments rubropunctamine and monascorubramine. Because of their structural similarity, the toxicological effects of these secondary metabolites were studied using immortalized human kidney epithelial cells. The cytotoxicity was determined with the following different endpoint detection methods: metabolic activity, trypan blue exclusion, and electronic cell counting. The compounds led to EC50 values between 11 and 31 ,mol/L but the pigments caused a stronger reduction of the cell viability. Also, the apoptotic potential was examined by measuring caspase 3 activity and detecting apoptotic bodies, but none of the tested compounds induced apoptosis. All four substances caused a rise of the mitotic index to about 9% (100 ,mol/L monascopyridine A and B) and 20% (25 ,mol/L rubropunctamine and monascorubramine). The significant decrease of the ratio of cells in the ana- and telophase to cells in the prometa- and metaphase proved a stop of the mitosis at the meta- to anaphase control point. The compounds caused mitotic arrest and the formation of structural damages like c-mitosis through interaction with the mitotic spindle. These effects point to an aneuploidy inducing potential, which is linked to cancer formation. [source] X-ray crystallographic structures of enamine and amine Schiff bases of pyridoxal and its 1:1 hydrogen-bonded complexes with benzoic acid derivatives: evidence for coupled inter- and intramolecular proton transferACTA CRYSTALLOGRAPHICA SECTION B, Issue 3 2006Shasad Sharif Crystal structures of Schiff bases containing pyridoxal (PL), N -(pyridoxylidene)-tolylamine, C15H16N2O2 (I), N -(pyridoxylidene)-methylamine, C9H12N2O2 (III), and their 1:1 adduct with 2-nitrobenzoic acid, (I)+ C7H4NO (II), and 4-nitrobenzoic acid, (III)+ C7H4NO (IV), serve as models for the coenzyme pyridoxal-5,-phosphate (PLP) in its PLP-dependent enzymes. These models allow the study of the intramolecular OHN hydrogen bond of PL/PLP Schiff bases and the H-acceptor properties of their pyridine rings. The free base (I) forms hydrogen-bonded chains involving the hydroxyl side groups and the rings of adjacent molecules, whereas (III) forms related hydrogen-bonded cyclic dimers. The adducts (II)/(IV) consist of 1:1 hydrogen-bonded complexes, exhibiting strong intermolecular bonds between the carboxylic groups of the acids and the pyridine rings of (I)/(III). In conclusion, the proton in the intramolecular O,H,N hydrogen bond of (I)/(III) is located close to oxygen (enolamine form). The added acids protonate the pyridine ring in (II)/(IV), but only in the latter case does this protonation lead to a shift of the intramolecular proton towards the nitrogen (ketoimine form). All crystallographic structures were observed in the open form. In contrast, the formation of the pyridinium salt by dissolving (IV) leads to the cyclic aminal form. [source] Green chemistry synthesis: 2-amino-3-[(E)-(2-pyridyl)methylideneamino]but-2-enedinitrile monohydrate and 5-cyano-2-(2-pyridyl)-1-(2-pyridylmethyl)-1H -imidazole-4-carboxamideACTA CRYSTALLOGRAPHICA SECTION C, Issue 9 2010Muhammad Altaf The title compounds, C10H9N5O·H2O (L1·H2O) and C16H12N6O (L2), were synthesized by solvent-free aldol condensation at room temperature. L1, prepared by grinding picolinaldehyde with 2,3-diamino-3-isocyanoacrylonitrile in a 1:1 molar ratio, crystallized as a monohydrate. L2 was prepared by grinding picolinaldehyde with 2,3-diamino-3-isocyanoacrylonitrile in a 2:1 molar ratio. By varying the conditions of crystallization it was possible to obtain two polymorphs, viz. L2-I and L2-II; both crystallized in the monoclinic space group P21/c. They differ in the orientation of one pyridine ring with respect to the plane of the imidazole ring. In L2-I, this ring is oriented towards and above the imidazole ring, while in L2-II it is rotated away from and below the imidazole ring. In all three molecules, there is a short intramolecular N,H...N contact inherent to the planarity of the systems. In L1·H2O, this involves an amino H atom and the C=N N atom, while in L2 it involves an amino H atom and an imidazole N atom. In the crystal structure of L1·H2O, there are N,H...O and O,H...O intermolecular hydrogen bonds which link the molecules to form two-dimensional networks which stack along [001]. These networks are further linked via intermolecular N,H...N(cyano) hydrogen bonds to form an extended three-dimensional network. In the crystal structure of L2-I, symmetry-related molecules are linked via N,H...N hydrogen bonds, leading to the formation of dimers centred about inversion centres. These dimers are further linked via N,H...O hydrogen bonds involving the amide group, also centred about inversion centres, to form a one-dimensional arrangement propagating in [100]. In the crystal structure of L2-II, the presence of intermolecular N,H...O hydrogen bonds involving the amide group results in the formation of dimers centred about inversion centres. These are linked via N,H...N hydrogen bonds involving the second amide H atom and the cyano N atom, to form two-dimensional networks in the bc plane. In L2-I and L2-II, C,H..., and ,,, interactions are also present. [source] 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...,(pyridine) hydrogen bonds in 3-(4-nitrophenyl)-4-phenyl-1H -pyrazolo[3,4- b]pyridineACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2010Jairo Quiroga In 6-(4-bromophenyl)-3-methyl-1-phenyl-4,5-dihydro-1H -pyrazolo[3,4- b]pyridine, C19H16BrN3, 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...,(arene) hydrogen bonds into cyclic centrosymmetric dimers. Molecules of 3-(4-nitrophenyl)-4-phenyl-1H -pyrazolo[3,4- b]pyridine, C18H12N4O2, are linked into centrosymmetric R22(8) dimers by pairs of symmetry-related N,H...N hydrogen bonds, and these dimers are linked by pairs of C,H...,(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. [source] Di-,-chlorido-bis[chlorido(4,- p -tolyl-2,2,:6,,2,,-terpyridine-,3N,N,,N,,)nickel(II)]: a supramolecular system constructed by C,H...Cl interactionsACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2009Ying-Lin Chen The title complex, [Ni2Cl4(C22H17N3)2], was synthesized solvothermally. The molecule is a centrosymmetric dimer with the unique NiII centre in a distorted octahedral N3Cl3 coordination environment. The chloride bridges are highly asymmetric. In the 4,- p -tolyl-2,2,:6,,2,,-terpyridine ligand, the p -tolyl group is perfectly coplanar with the attached pyridine ring, and this differs from the situation found in previously reported compounds; however, there are no ,,, interactions between the ligands. The terminal Cl atom forms four intermolecular C,H...Cl hydrogen bonds with one methyl and three methine groups. The methyl group also forms intermolecular C,H..., interactions with a pyridine ring. These nonclassical hydrogen bonds extend the molecule into a three-dimensional network. [source] Synthesis, characterization and hydroformylation activity of 7-azaindolate-bridged dinuclear rhodium(I)phosphines with pendant polar-groupsAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 11 2009Chandra Sekhar Vasam Abstract New dinuclear Rh(I),Phosphines of the types [Rh(µ-azi)(CO)(L)]2 (1,3,7) and [Rh(µ-azi)(L)]2 (8) with pendant polar groups, and a chealated mononuclear compound [Rh(azi-H)(CO)(L)] (2) (where azi = 7-azaindolate, L = polar phosphine) were isolated from the reaction of [Rh(µ-Cl)(CO)2]2 with 7-azaindolate followed by some polar mono - and bis -phosphines (L1,L8). A relationship between ,,31P-NMR and ,(CO) values was considered to define the impact of polar-groups on ,-donor properties of the phosphines. These compounds were evaluated as catalyst precursors in the hydroformylation of 1-hexene and 1-dodecene both in mono- and biphasic aqueous organic systems. While the biphasic hydroformylations (water + toluene) gave exclusively the aldehydes, the monophasic one (aqueous ethanol) showed propensity to form both aldehydes and alcohols. The influence of bimetallic cooperative effects, and ,-donor and hydrophilic properties of the phosphines with pendant polar-groups in enhancing the yields and selectivity of hydroformylation products was emphasized. In addition, when strong ,-donor phosphine was used, the ,-acceptor nature of pyridine ring of 7-azaindolate spacer was found to be a considerable factor in facilitating the facile cleavage of CO group during hydroformylation and in supplementing the cooperative effects. Copyright © 2009 John Wiley & Sons, Ltd. [source] 2-Bromo-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyridine, a new unexpected bifunctional building block for combinatorial chemistryACTA CRYSTALLOGRAPHICA SECTION C, Issue 10 2003Jana Sopková-de Oliveira Santos The first reported structure of a pyridin-2-ylboron derivative, viz. the title compound, C11H15BBrNO2, (I), is compared with its regioisomer 2-bromo-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyridine, (II) [Sopková-de Oliveira Santos, Lancelot, Bouillon & Rault (2003). Acta Cryst. C59, o111o113]. Structural differences are observed, firstly in the orientation of the dioxaborolane ring with respect to the pyridine ring and secondly in the bond angles of the BO2 group. These differences do not explain the experimentally observed differences in chemical reactivity between (I) and (II) but do confirm the relatively lower stability of (I). However, ab initio calculations of the HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital), based on the known crystal structures of the two compounds, show different distributions, which correspond to the differences observed during chemical reactions. [source] 4-[N,N -Bis(2-cyanoethyl)amino]pyridineACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2003Jun Ni The title compound, 3,3,-(4-pyridylimino)dipropanenitrile, C11H12N4, has a twofold axis and consists of a pyridine ring head and two cyanoethyl tails, the three groups being linked by an N atom. The planar geometry around the amino N atom suggests conjugation with the ,-system of the pyridine ring. The molecules are stacked in a layer structure via relatively weak to very weak intermolecular C,H,, and C,H,N hydrogen-bond interactions. [source] Di-2-pyridyl ketone p -aminobenzoylhydrazone hydrateACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2002Mohammed Bakir The title compound [systematic name: 4-amino-2,-(di-2-pyridylmethylene)benzohydrazide hydrate], C18H15N5O·H2O, crystallizes in the triclinic space group P. Structural analysis shows one pyridine ring and the p -aminobenzoylhydrazone moiety to be coplanar and orthogonal to the second pyridine ring. The packing reveals infinite molecular units interlocked via a network of hydrogen bonds. [source] cis -Dichloro(dimethyl sulfoxide- S)(2-methoxypyridine- N)platinum(II)ACTA CRYSTALLOGRAPHICA SECTION C, Issue 11 2000Georgia M. Arvanitis The title complex, [PtCl2(C6H7NO)(C2H6OS)], exhibits square-planar geometry. The plane of the pyridine ring makes a dihedral angle of 67.2,(3)° with the square plane of the metal center. The S,O bond is nearly aligned with the adjacent Pt,N bond, leaving the methyl groups of the dimethyl sulfoxide ligand to stagger the Pt,Cl bond. [source] Pyridine-4-carbaldehyde azineACTA CRYSTALLOGRAPHICA SECTION C, Issue 6 2000S. Shanmuga Sundara Raj In the crystal structure of the title compound, C12H10N4, the pyridine ring makes a dihedral angle of 1.12,(9)° with the mean plane of the complete almost planar and crystallographically centrosymmetric molecule. There are stacks of parallel molecules along the a -axis direction, with alternate stacks having a herring-bone arrangement relative to each other and an interplanar spacing of 3.551,Å. [source] Xylogranatins F,R: Antifeedants from the Chinese Mangrove, Xylocarpus granatum, A New Biogenetic Pathway to TetranortriterpenoidsCHEMISTRY - A EUROPEAN JOURNAL, Issue 4 2008Jun Wu Dr. Abstract Thirteen limonoids with a new carbon skeleton, the xylogranatins,F,R (1,13), have been isolated from the seeds of a Chinese mangrove, Xylocarpus granatum; two recently reported compounds, xylogranatins,C and,D were also isolated. Their structures were elucidated on the basis of spectroscopic data and chemical methods. The absolute configurations of these compounds were determined by using the modified Mosher MTPA ester method and by quantum chemical circular dichroism (CD) calculations. Xylogranatins,F,Q are the first aromatic B-ring limonoids found in nature. They belong to two substructural classes, of which one (1,3) contains a pyridine ring while the other one (4,12) contains a central furan core. Xylogranatins,C and,R can be considered to be key biosynthetic intermediates, while xylogranatin,D, the only limonoid found so far with a carbon skeleton that conatains a C30C9 linkage, is apparently an artifact. The structures of these compounds suggest a new biogenetic pathway to tetranortriterpenoids. Xylogranatins,F, G and R were found to exhibit marked antifeedant activity against the third instar larvae of Mythimna separata (Walker) at a concentration of 1,mg,mL,1. The most potent compound tested was xylogranatin,G. Its AFC50 (concentration for 50,% antifeedant activity) values at the exposure times of 24 and 48,h were 0.31 and 0.30,mg,mL,1, respectively. [source] Methylazacalixpyridines: Remarkable Bridging Nitrogen-Tuned Conformations and Cavities with Unique Recognition PropertiesCHEMISTRY - A EUROPEAN JOURNAL, Issue 36 2006Han-Yuan Gong Abstract Methylazacalix[n]pyridines (n = 4, 8) and methylazacalix[m]arene[n]pyridines (m = n = 2, 4) have been synthesized by a convenient fragment coupling approach starting from 2,6-dibromopyridine, 2,6-diaminopyridine, and benzene-1,3-diamine. Thanks to the intrinsic electronic nature of nitrogen, which can adopt mainly sp2 hybridization, allowing it variously to conjugate, partially conjugate, or not conjugate with the adjacent one or two pyridine rings, the resulting nitrogen-bridged calixpyridine derivatives act as a unique class of macrocyclic host molecules with intriguing conformational structures offering fine-tunable cavities and versatile recognition properties. Whilst in solution it is fluxional, in the solid state methylazacalix[4]pyridine adopts a 1,3-alternate conformation with a C2v symmetry in which every two bridging nitrogen atoms conjugate with one pyridine ring. After protonation, the methylazacalix[4]pyridinium species has a different conjugation system of its four bridging nitrogen atoms, yielding the similar twisted 1,3-alternate conformations with an approximate S4 symmetry. The cavity of each protonated methylazacalix[4]pyridine, however, varies finely to accommodate guest species of different size and geometry, such as planar DMF or HO2CCO2, ion, a twisted HO2CCO2, ion, and a tetrahedral ClO4, ion. As giant macrocyclic hosts, both methylazacalix[8]pyridine and methylazacalix[4]arene[4]pyridine interact efficiently with fullerenes C60 and C70 through van der Waals forces. Their ease of preparation, versatile conformational structures, and recognition properties make these multinitrogen-containing calixarenes or cyclophanes unique and powerful macrocyclic hosts in supramolecular chemistry. [source] Conformational spaces of the gastrointestinal antisecretory chiral drug omeprazole: Stereochemistry and tautomerismCHIRALITY, Issue 1 2006Hava Caner Abstract A study of the conformational spaces of the chiral proton pump inhibitor (PPI) drug omeprazole by semiempirical, ab-initio, and DFT methods is described. In addition to the chiral center at the sulfinyl sulfur atom, the chiral axis at the pyridine ring (due to the hindered rotation of the 4-methoxy substituents) was considered. The results were analyzed in terms of the 5-methoxy and 6-methoxy tautomers and the two pairs of enantiomers (R,P)/(S,M) and (R,M)/(S,P). Five torsion angles were systematically explored: the backbone rotations defined by D1 (N3,C2,S10,O11), D2 (C2,S10,C12,C13), and D3 (S10,C12,C13,N14) and two methoxy rotations defined by D4 (C6,C5,O8,C9) and D5 (C16,C17,O19,C20). Significant energy differences were revealed between the 5- and 6-methoxy tautomers, the extended and folded conformations, and the (S,M) and (S,P) diastereomers. The "extended M" conformation of the 6-methoxy tautomer of (S)-omeprazole was found to be the most stable conformer. © 2005 Wiley-Liss, Inc. Chirality [source] Dinuclear Iridium(III) Complexes Linked by a Bis(,-diketonato) Bridging Ligand: Energy Convergence versus Aggregation-Induced EmissionEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2010Chang Hwan Shin Abstract Novel iridium(III)/iridium(III) and iridium(III)/platinum(II) dinuclear complexes, [{Ir(ppyFF)2}2(,2 - L)] (4) and [{Ir(ppyFF)2}(,2 - L){Pt(ppy)}] (5) [ppyFF = 2-(2,4-difluorophenyl)pyridine, ppy = 2-phenylpyridine, L = 1,3-bis(3-phenyl-3-oxopropanoyl)benzene], linked by an L bridging ligand were prepared, and their photophysical properties were investigated in solution and in the solid state. The photophysical properties of mononuclear iridium(III) and platinum(II) complexes, [Ir(ppyFF)2(dbm)] (1) and [Pt(ppy)(dbm)] (2) bearing a dibenzoylmethane (dbm) ligand were also compared. Whereas the UV/Vis absorption spectra of 4 and 5 show independent light absorption at each metal-centered moiety, the photoluminescence spectra of 4 and 5 display almost identical features, but very weak emissions in solution at both room temperature and 77 K. The weak emission in solution is found to mainly originate from a 3LX state of the L bridging ligand, which reflects the occurrence of efficient energy convergence from the triplet states of the Pt(ppy) and Ir(ppyFF) moieties to the 3LX state of L. By contrast, intense orange-red emission, that is, aggregation-induced emission, is produced in the solid state of 4 and 5. Inspection of the crystal-packing structures of 5 reveals that strong intermolecular ,,, interactions between the adjacent pyridine rings of ppyFF ligands in the Ir-centered moieties are responsible for the emissive metal-to-ligand,ligand charge-transfer [3M(LL)CT] state of the solid-state dinuclear systems. The electrochemical properties of 4 and 5 further indicate that the first two reductions occur at the dbm moieties of the L bridging ligand linked to each metal center, which is consistent with the fact that the lowest-energy excited state of the L bridging ligand dominates the excited-state properties of 4 and 5 in solution. [source] Structural, Spectroscopic, and Proton-Coupled Electron-transfer Behavior of Pyrazolyl-3,5-bis(benzimidazole)-Bridged Homo- and Heterochiral RuIIRuII, OsIIOsII, and OsIIRuII 2,2,-Bipyridine ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 4 2010Sujoy Baitalik Abstract The homo- and heterobimetallic complexes [(bpy)2MII(H2pzbzim)M,II(bpy)2](ClO4)3·nH2O (1, 3, 5) and their corresponding deprotonated complexes [(bpy)2MII(pzbzim)M,II(bpy)2](ClO4)·nH2O (2, 4, 6) [where MII, M,II = Ru (1, 2) = Os (3, 4); MII = Os and M,II = Ru (3, 5); bpy = 2,2,-bipyridine; H3pzbzim = pyrazole-3,5-bis(benzimidazole)] were synthesized, separated to their heterochiral (a, ,,/,,) and homochiral (b, ,,/,,) diastereoisomers, and characterized by elemental analyses, ESI-MS, and 1H NMR spectroscopy. The X-ray structures of 1a, 3a, and 5a show the involvement of two pyridine rings of two bpy ligands in strong intramolecular nonbonded ,,, interaction. The occurrence of a C,H···, interaction between an aromatic C,H and the ,-cloud of a pyridine ring leads to strong electronic shielding of this proton (1H NMR). In all cases, the two diastereoisomers show practically no differences in their absorption spectra, redox potentials, and pK values. The large shifts in the E1/2 values to less positive potentials and substantial redshifts in the MLCT bands that occur on deprotonation of 1, 3, and 5 are energetically correlated. From the profiles of E1/2(1), (2) vs. pH over the pH range 1,12, the equilibrium constants and standard redox potentials for all the complex species in the metal oxidation states II·II, II·III, and III·III and the bridged ligand in the protonation states H2pzbzim,, Hpzbzim2,, and pzbzim3, have been evaluated. Using these values the bond dissociation free energies for the benzimidazole N,H bonds have been estimated. Spectroelectrochemical studies have been carried out for 1a, 3a, and 5a in the range 400,1100 nm. With stepwise oxidation of the metal centers replacement of MLCT bands by LMCT bands occur gradually with the observation of sharp isosbestic points. In the case of 1a, a band observed at ,max = 910 nm for the RuIIRuIII species has been ascribed to intervalence charge transfer (IVCT) transition. [source] One-Dimensional Coordination Polymers of MnII, CuII, and ZnII Supported by Carboxylate-Appended (2-Pyridyl)alkylamine Ligands , Structure and MagnetismEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 22 2009Himanshu Arora Abstract Four new complexes [MnII(L1OO)(H2O)][ClO4]·2H2O (1), [ZnII(L1OO)][ClO4]·2H2O (2), [CuII(L3OO)][CF3SO3]·H2O (3), and [ZnII(L3OO)][ClO4] (4) (L1OO, = 3-[(2-(pyridine-2-yl)ethyl){2-(pyridine-2-yl)methyl}amino]propionate; L3OO, = 3-[(2-(pyridine-2-yl)ethyl){(dimethylamino)ethyl}amino]propionate) have been synthesized and characterized by elemental analysis, IR, and UV/Vis spectroscopy. Structural analysis revealed that 1, 3, and 4 are one-dimensional chain-like coordination polymers. In 1 distorted octahedral MnN3O3 and in 3 square-pyramidal CuN3O2 coordination is satisfied by three nitrogen atoms and an appended carboxylate oxygen atom of the ligand, and an oxygen atom belonging to the carboxylate group of an adjacent molecule. In 4 trigonal bipyramidal ZnN3O2 coordination environment is provided by two nitrogen atoms and an appended carboxylate oxygen atom of the ligand in the equatorial plane, and the two axial positions are satisfied by a tertiary amine nitrogen and an oxygen atom belonging to the carboxylate group of an adjacent molecule. In 1 the MnII center is coordinated by an additional water molecule. In these complexes each monomeric unit is sequentially connected by syn - anti carboxylate bridges. Temperature-dependent magnetic susceptibilities for 1 and 3 are measured, revealing antiferromagnetic interactions through syn - anti carboxylate bridges between the MII centers. Analysis of the crystal packing diagram reveals that in 1 extensive ,,, stacking involving alternate pyridine rings of adjacent 1D chain exists, which eventually lead to the formation of a 2D network structure. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] | ||||||||||||||||||||||||||||||||||