Pyridine Iodine Research Articles

Pyridine Iodine(I) Cations: Kinetic Trapping as a Sulfonate Complexes.

Seven pyridine iodine(I) sulfonate complexes were prepared and isolated at low temperatures and characterized by X-ray diffraction analysis. The inherently instable pyridine iodine(I) cations are stabilized by an oxygen of sulfonate anions via the I⋅⋅⋅O halogen bond. In these complexes, the iodine atom of the pyridine iodine(I) cation acts as an electron acceptor and the sulfonate oxygen as the electron donor. These complexes are stable enough in the crystalline state, yet decompose rapidly under ambient conditions, also being unstable in solution. The (pyridine)N-I bond lengths [2.140(3)-2.197(2) Å] and the I⋅⋅⋅O halogen bonds [2.345(6)-2.227(3) Å] are analogous to (imide)N-I⋅⋅⋅O-N-pyridine uncharged halogen-bonded complexes formed from N-haloimides and pyridine N-oxides, thus confirming the existence of elusive pyridine iodine(I) cation.

On spin-lattice relaxation of nuclear quadrupole resonance in polycrystalline solids

The analysis of spin–lattice relaxation in nuclear quadrupole resonance (NQR) of spin-52 reported by Okubo and Igarashi (Z. Naturforsch. A. 56 (2001) 777) is extended to take account of the distribution of the initial non-equilibrium populations created by a resonant radio-frequency pulse in powder. The proposed theory is applicable to axially symmetric electric field gradient tensor and is examined for spin–lattice relaxation of 127I NQR in polycrystalline pyridine iodine monochloride measured at 469 MHz at 77 K.

Halogen Bonding in N-Alkyl-3-halogenopyridinium Salts

We performed a structural study of N-alkylated halogenopyridinium cations to examine whether choice of the N-substituent has any considerable effect on the halogen bonding capability of the cations. For that purpose, we prepared a series of N-ethyl-3-halopyridinium iodides and compared them with their N-methyl-3-halopyridinium analogues. Structural analysis revealed that N-ethylated halogenopyridinium cations form slightly shorter C−X⋯I− halogen bonds with iodide anion. We have also attempted synthesis of ditopic symmetric bis-(3-iodopyridinium) dications. Although successful in only one case, the syntheses have afforded two novel ditopic asymmetric monocations with an iodine atom bonded to the pyridine ring and another on the aliphatic N-substituent. Here, the C−I⋯I− halogen bond lengths involving pyridine iodine atom were notably shorter than those involving an aliphatic iodine atom as a halogen bond donor. This trend in halogen bond lengths is in line with the charge distribution on the Hirshfeld surfaces of the cations—the positive charge is predominantly located in the pyridine ring making the pyridine iodine atom σ-hole more positive than the one on the alkyl chan.

Construction of Acyclic All-Carbon Quaternary Stereocenter Based on Asymmetric Michael Addition of Chiral Amine.

Acyclic asymmetric quaternary stereocenters, which are composed of four carbon-carbon bonds, were finely constructed by utilizing a face-selective alkylation of enolate intermediates derived from an asymmetric Michael addition reaction of a chiral lithium amide with trisubstituted (E)-α,β-unsaturated esters. The present face-selective alkylation was able to employ diverse alkyl halides as an electrophile to afford various Michael adducts having an all-carbon quaternary stereocenter. With regard to the deprotection of the chiral auxiliary, N-iodosuccinimide used in our previous study did not work in the present cases; however, we found that pyridine iodine monochloride in the presence of H2O was effective to remove the bornyl group and the benzyl group on the amino group to provide the β-amino ester derivative.

Convenient but powerful method to dope single-walled carbon nanotube films with iodonium salts

Single-walled carbon nanotubes (SWCNTs) demonstrate unique properties of both electrical and thermal conductivity, but at the moment of producing a network composed of multiple nanotubes, these values sharply decrease. It is associated with the presence of defects in the nanotube network structure, as well as with the dissipation phenomena at the junctions between SWCNTs. One of the methods to alleviate this problem is doping. In our study, we obtained a film made of high-quality SWCNTs doped with three types of iodonium salts: Barluenga’s reagent (bispyridineiodonium tetrafluoroborate, IPy2BF4), pyridine iodine monochloride (IPyCl) and diphenyliodonium chloride (DPIC). We recorded a significant improvement in electrical properties after doping with IPy2BF4 and IPyCl, by as much as 224% and 322%, respectively. What is more, we noted improvement in thermal conductivity, which amounted to over 50% when the material was doped with IPyCl. Our research indicates that permanent doping of CNT-based ensembles is possible with iodonium salts. The process significantly improves electrical conductivity, and the compounds themselves are more convenient to work with rather than when other halogen-based dopants are used commonly for this purpose.

An alternative electrolyte based on acetylacetone–pyridine–iodine for dye-sensitized solar cells

We prepared a new organic electrolyte by the reaction among acetylacetone, pyridine and iodine in 3-methoxypropionitrile. The UV–Visible spectra, conductivity measurement and ESI mass spectra were used to study this electrolyte. It was suggested that the quaternization reaction of pyridine took place in this electrolyte solution and two kinds of pyridinium iodide were formed. The efficiency of dye-sensitized solar cells (DSCs) using this electrolyte reaches 6.72%, which is higher than that of DSCs using LiI electrolyte and methylpropylimidazolium iodide electrolyte. It implies that these pyridinium iodides are effective alternative component of iodide for the electrolytes of DSCs. As this organic iodide electrolyte was in situ synthesized based on iodine instead of alkyl iodide, it will be cost-effective and facilitative for the production of DSCs.

U(IV) Chalcogenolates Synthesized via Oxidation of Uranium Metal by Dichalcogenides

Treatment of uranium metal with dichalcogenides in the presence of a catalytic amount of iodine in pyridine affords molecular U(IV) chalcogenolates that do not require stabilizing ancillary ligands. Oxidation of U(0) by PhEEPh yields monomeric seven-coordinate U(EPh)4(py)3 (E = S(1), Se(2)). The dimeric eight-coordinate complexes [U(EPh)2(mu2-EPh)2(CH3CN)2]2 (E = S(3), Se(4)) are obtained by crystallization from solutions of 1 and 2 dissolved in acetonitrile. Oxidation of U(0) by pySSpy and crystallization from thf yields nine-coordinate U(Spy)4(thf) (5). Incorporation of elemental selenium into the oxidation of U(0) by PhSeSePh results in the isolation of [U(py)2(SePh)(mu3-Se)(mu2-SePh)]4.4py (6), a tetrameric cluster in which each U(IV) ion is eight-coordinate and the U4Se4 core forms a distorted cube. The compounds were analyzed spectroscopically and the single-crystal X-ray structures of 1 and 3-6 were determined. The isolation of 1-6 represents six new examples of actinide chalcogenolates and allows insight into the nature of "hard" actinide ion-"soft" chalcogen donor interactions.

Improved synthesis of oligonucleotides containing 2-thiouridine derivatives by use of diluted iodine solution

It is known that the 2-thiocarbonyl group of 2-thiouridine (s 2U) derivatives reacts easily with various oxidizing agents used in oligonucleotide synthesis to give a complex mixture. In this letter, we report an improved method for the synthesis of oligonucleotides containing s 2U derivatives. It turned out that the 2-thiocarbonyl group of oligonucleotides containing s 2U derivatives was stable in a 0.02 M solution of iodine in pyridine–THF–H 2O. These conditions were successfully applied to the synthesis of oligonucleotides containing s 2U derivatives on an automated DNA/RNA synthesizer. Moreover, no undesirable side reactions were detected so that these modified oligonucleotides could be obtained in markedly improved yields.

Stereoselective Chloro‐Deboronation Reactions Induced by Substituted Pyridine–Iodine Chloride Complexes

AbstractA novel class of charge‐transfer complexes based on iodine chloride and substituted pyridines, which possess a number of interesting and unique structural features, can be employed to bring about a stereocontrolled chloro‐deboronation of certain vinyl boronates to generate the (1Z)‐alkenyl chlorides in good yields. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

The Development of a Manufacturing Route for the GPIIb/IIIa Receptor Antagonist SB-214857-A. Part 2: Conversion of the Key Intermediate SB-235349 to SB-214857-A

The process development to the manufacturing route to (2S)-7-([4,4‘-bipiperidin]-1-ylcarbonyl)-2,3,4,5-tetrahydro-4-methyl-3-oxo-1H-1,4-benzodiazepine-2-acetic acid hydrochloride (SB-214857-A, lotrafiban) is described. The starting point is the previously reported intermediate (2RS)-2,3,4,5-tetrahydro-4-methyl-3-oxo-1H-1,4-benzodiazepine-2-acetic acid methyl ester. The first stage is a lipase-catalysed resolution of the racemic ester to (2S)-2,3,4,5-tetrahydro-4-methyl-3-oxo-1H-1,4-benzodiazepine-2-acetic acid and subsequent iodination using a pyridine iodine monochloride complex to give (2S)-2,3,4,5-tetrahydro-7-iodo-4-methyl-3-oxo-1H-1,4-benzodiazepine-2-acetic acid. The unreacted (R)-enantiomer of the starting ester is recovered and recycled to the racemate by treatment with sodium methoxide. The next stage describes the palladium-catalysed aminocarbonylation of the aryl iodide with 4,4‘-pyridylpiperidine to give (2S)-2,3,4,5-tetrahydro-4-methyl-3-oxo-7-[[4-(4-pyridinyl)-1-piperidinyl]carbonyl]-1H-1,4-...

Mild and Efficient Iodination of Aromatic Compounds with Pyridine–Iodine Monochloride Complex (PyICI)

A wide range of aromatic compounds has been effectively iodinated with pyridine-iodine monochloride complex, PylCl.

A facile access to nucleoside phosphorofluoridate, nucleoside phosphorofluoridothioate, and nucleoside phosphorofluoridodithioate monoesters

Oxidation of H-phosphonate, H-phosphonothioate, or H-phosphonodithioate monoesters with iodine in pyridine in the presence of trimethylsilyl chloride, followed by addition of triethylamine trishydrofluoride (TAF) furnished rapid and quantitative formation of the corresponding phosphorofluoridate, phosphorofluoridothioate, or phosphorofluoridodithioate monoesters.

Surface enhanced Raman study of the pyridine—iodine charge transfer complex on the silver electrode

The surface enhanced Raman spectra (SERS) of the pyridine—iodine charge transfer complex on the Ag electrode were identified. As compared with the well known SERS of pyridine, the ν 1, ν 6a and ν 12 modes are blue-shifted. This is also confirmed from the comparison of the infrared absorption spectra of pyridine—iodine crystalline complex and pyridine. The origin of the blue shift and other characteristics of the SERS spectra of the complex are discussed. An attempt to observe the SERS spectra of the iodine moiety of the complex was unsuccessful. This is attributed to the short range effect of the charge transfer mechanism of SERS.

Weak molecular complexes as studied by NMR spectroscopy of oriented molecules

Abstract Weak molecular interactions such as those in pyridine—iodine, benzene—iodine and benzene—chloroform systems oriented in thermotropic liquid crystals have been studied from the changes of the order parameters as a result of complex formation. The results indicate the formation of at least two types of charge transfer complexes in pyridine—iodine solutions. The pi-complexes in benzene—chloroform and benzene—iodine mixtures have also been detected. No detectable changes in the inter-proton distances in these systems were observed.

Investigation of charge-transfer complexes by computer simulation. II. Iodine in pyridine solution

In this article we report molecular-dynamics (MD) simulation results for the thermodynamic, structural, and dynamic properties of a dilute solution of iodine in liquid pyridine (Py). The molecules of the simulated solution (10I2+246Py) interact through site–site intermolecular potentials for which the pyridine molecules are modeled by 12 sites (11 atomic sites plus a lone-pair site on the nitrogen atom) and the iodine molecules by four sites (two sites coinciding with the iodine atoms plus two extra sites). The site–site potentials contain isotropic terms to describe the electrostatic, dispersion and repulsion interactions between molecules. The potential parameters are determined from a Monte Carlo (MC) simulation of the iodine–pyridine complex in the gaseous phase where it appears that the most stable conformation is realized when iodine and pyridine are in a linear arrangement (the iodine molecule interacting with the nitrogen atom of the pyridine molecule). The MC study also shows that the complex becomes unstable near room temperature. On the contrary, in liquid pyridine our molecular-dynamics simulation predicts that iodine and pyridine molecules associate to form long-lasting (1:2) complexes, the latter ones (Py–I2–Py) adopting a nearly linear conformation. Concerning the intermolecular motions the simulation indicates that the stretching mode of the I–I⋅⋅⋅N bonds produces the predominant contribution to the far-infrared absorption spectrum of the iodine solution and is responsible of the sharp band observed on the experimental spectra reported in the literature.

Molecular orbital calculations for iodine complexes 2. Ammonium iodine and pyridine iodine

Calculations of H3N·I2 and PY·I2 using the INDO method with single and double-zeta Slater atomic orbital basis are reported. It is found that polarization and charge transfer play a fundamental role in stabilizing the complex. Interaction between donor and acceptor molecules involves the highest occupied as well as the inner molecular orbitals of the constituent molecules. A detailed description of the complex molecular orbitals is presented.

Nucleoside phosphonates: part 7. Studies on the oxidation of nucleoside phosphonate esters

Oxidation of phosphonate mono- and di-esters with various oxidizing agents including diaryl disulphides, hexachloroacetone, and iodine, has been investigated under various reaction conditions. The most efficient oxidation procedure consists of treatment of phosphonate esters with iodine in pyridine–water. When the phosphonate esters were presilylated by treatment with trimethylsilyl chloride, the subsequent oxidation with aqueous iodine was faster. 31P N.m.r. spectroscopic studies have enabled us to propose the most likely pathway for the majority of the oxidations.

Ionic dissociation in pyridine–iodine solutions

An electrochemical technique has been employed to study the ionization of the pyridine–iodine complex in pure pyridine and in 1,2-dichloroethane. A mechanism for the ionization in accord with the experimental data is proposed. The results indicate that, for wide ranges of iodine and pyridine concentration, one quarter of the I2 is dissociated into ionic species.

Solute–solute interaction in liquid crystal solvents: a nuclear magnetic resonance study of pyridine–iodine molecular complex in the nematic phase

1 H N.m.r. spectra of [14N]- and [15N]-pyridine partially oriented in nematic phase IV in the presence of iodine show dipolar couplings (Dij) increasing linearly as a function of iodine concentration. The spectral changes induced by iodine can be rationalized, to a first approximation, by assuming that the pyridine molecule is in equilibrium, in the oriented phase, with the pyridine–iodine charge transfer complex so that a considerable variation in the mean orientation of the pyridine moiety occurs. Attempts to reproduce the measured dipolar couplings of the exchanging complex on the basis of an average geometry and orientation afforded only dramatic distortion effects on the apparent geometry. Looking, moreover, at the geometry of [15N]pyridine in phase IV and in other liquid crystals geometrical distortions were also found, probably due to solute–solvent interactions, except for the ZLI 1167 phase, where an rα structure in close agreement with gas-phase microwave measurements was observed. The results suggest that, for pyridine in the nematic phase in the presence of iodine, at least a three-site mechanism is operating, one of the sites being the complexed pyridine.

Mössbauer effect of 129I in n–σ and π–σ charge-transfer complexes of iodine in the frozen solution

The Mössbauer effect of 129I was applied to investigate charge-transfer complexes of the n–σ and π–σ types in the carbon disulfide frozen solution at 16 K. In the case of n–σ type complexes such as triethylamine–iodine and pyridine–iodine, two chemical species of iodine, which correspond to the bridging and terminal iodines, were observed in the Mössbauer spectra. It is elucidated that a charge-transfer bond is described as a mixture of a four-electron three-center bond and a covalent bond involving dσpσ hybrid orbitals in the bridging iodine. On the other hand, for the π–σ type complexes such as benzene–iodine and methylated benzene–iodine the Mössbauer spectra show only one chemical species of iodine. The acceptor orbital of iodine is thought to be described by an spd hybrid orbital. That is, a small amount of s and d characters contributes to the formation of the charge-transfer bond. From the Mössbauer parameters the charge densities and the charge distributions of iodine in these complexes were obtained.