Iodine Adducts Research Articles

Structural studies on diaryl selenide dihalides in solution: molecular complex formation of substituted diphenyl selenides with bromine

Diaryl selenides that yield molecular complexes (MC) with bromine are prepared by modulating the effective electronegativity of the selenium atom and the steric environment around the atom in diphenyl selenide (1) with various substituents at the 2-, 3- and/or 4-positions. Halogen induced 1H and 13C NMR chemical shifts of the diaryl selenides are examined. The chlorine and iodine adducts of the selenides are shown to be trigonal bipyramidal adducts (TB) and MC, respectively. In the case of bromine adducts, the structures of (3- and 4-YC6H4)2SeBr2 are demonstrated to be MC if Y is CN and NO2, contrary to the general rule: they are TB if Y is less electron-withdrawing than the ethoxycarbonyl group. The CN and NO2 groups increase the effective electronegativity of the Se atom in (3- and 4-YC6H4)2Se and do not give TB with bromine. The four chloro groups at all meta-positions in 1 are also effective for MC formation. However, 3,5-(O2N)2C6H3SeBr2Ph is TB. Ab initio MO calculations show that the structures of (3-O2NC6H4)2Se and 3,5-(O2N)2C6H3SePh are close to the C2 and Cs symmetries, respectively, which reveals that the conformational change is also important when the structures of the bromine adducts are determined. The steric congestion must be more severe for TB formation than for MC formation. The structures of 2,6-Cl2C6H3SeBr2C6H4Y-p (Y = H and Br) are MC, which shows that the steric effect of 2,6-Cl2C6H3 group is effective for MC formation. (2-MeC6H4)2SeBr2 and (2-ClC6H4)2SeBr2 are TB and MC, respectively: the electronic effect of the Cl group must play an additional role in the MC formation since the bulkiness of the Me and Cl groups are expected to be similar. The bromine adduct of (2,4,6-Me3C6H2)2Se is also concluded to be MC: the steric effect of the four Me groups at the ortho-positions is large enough to give MC with bromine. The oxidation potentials (Eox) of the diaryl selenides explain well the structures of the bromine adducts: the electronic effect is directly correlated with Eox and the importance of the steric effect has been brought into sharp relief by Eox. Results of MO calculations support the outline of the observations. The structural behavior of some halogen adducts such as 2,6-Cl2C6H3SeCl2C6H4Y-p (TB: Y = H and Br) is also discussed in some detail.

Die Struktur des Iod-Adduktes von 2,3-Dihydro-1,3,4,5-tetramethyl-2-methylenimidazol: Schwache Wechselwirkungen in einem linearen CI2-Fragment [1

The Structure of the Iodine Adduct of 2,3-Dihydro-1,3,4,5-tetramethyl-2-methylenimidazole: Weak Interactions in a Linear CI2-Fragment [1] Crystals of C36H69Cl2I7N8 (7) consisting of 3 equivalents of 6, one equivalent of pentamethylimidazolium iodide and one equivalent of dichloromethane are obtained through the crystallisation of the iodine adduct of 2,3-dihydro-1,3,4,5-tetramethyl-2-methylenimidazole (C8H14I2N2, 6). The crystal structure analysis of 7 reveals the presence of weak I–I bond and a nearly linear C–I–I arrangement for 6 indicating an interionic charge transfer interaction between iodomethylimidazolium and iodide ions.

Control of electrochemical reactions at the capillary electrophoresis outlet/electrospray emitter electrode under CE/ESI-MS through the application of redox buffers.

It was found that combining capillary electrophoresis (CE) and electrospray ionization mass spectrometry (ESI-MS) overlays two controlled current techniques to form a three-electrode system (CE inlet, CE outlet/ES emitter, and MS inlet electrodes) in which the CE outlet electrode and the ES emitter electrode were shared between the CE and the ESI-MS circuits. Depending on the polarities and magnitudes of the voltages at the CE inlet, CE outlet/ES emitter, and MS inlet electrodes, the nature of the two redox reactions at the shared electrode was the same or different (both reduction, both oxidation, or one oxidation and the other reduction). Several redox buffers were introduced for controlling electrochemical reactions at the shared electrode. By reacting at this electrode, redox buffers were able to maintain electrode potentials below the onset of water electrolysis, thereby eliminating gas bubble formation and/or pH drift. The volume of the gas generated due to water electrolysis was used to quantitate water oxidation or reduction at this electrode. Two types of redox buffers were used. A reactive electrode with an oxidation potential below that of water was used as the electrode under anodic conditions. Also, a reactive compound with a redox potential below that of water was added to the CE and/or ESI running buffer. When the shared electrode was the anode of both CE and ESI-MS circuits, the use of iron or etched and sanded stainless steel (ss) wire, instead of platinum wire, suppressed bubble formation at the shared electrode. Under these conditions, corrosion of the Fe wire and formation of Fe2+ replaced oxidation of water, eliminating O2 gas bubble and H+ formation. When mixtures of peptides were analyzed, iron adducts of peptides were observed. For a fresh wire, however, the intensities of adduct ions were less than 3% of the protonated molecules. After a few days of operation, the intensities of the adduct ions increased to approximately 50%, due to rust formation on the Fe wire. On-column rinsing with a 40% solution of citric acid rejuvenated the Fe wire and reduced the adduct peak intensities to less than 3%. Unmodified ss wire did not quench bubble formation, which was attributed to its passivated surface. When Fe, ss, and Pt wires were used as the shared electrode under forward polarity CE and positive ESI mode, where the shared electrode acted as a cathode with respect to CE inlet and as an anode with respect to MS inlet, reduction of water at the cathodic end of the electrode and, in the case of ss and Pt wires, oxidation of water at the anodic end of the shared electrode produced a significant amount of bubbles. Under these conditions, however, a buffer containing 50 mM p-benzoquinone completely suppressed both cathodic reduction and anodic oxidation of water for CE currents up to 4 microA. Reduction of p-benzoquinone at the cathodic end of the shared electrode to hydroquinone, and oxidation of this hydroquinone at the anodic end of the electrode, replaced reduction and oxidation of water, eliminating bubble formation. A 0.1% acetic acid solution saturated with I2 was also found to suppress bubble formation at the cathode for CE currents up to 3 microA; however, strong iodine adduct ions were observed under CE/ESI-MS when a mixture of peptides was analyzed. The application of iron as an in-capillary electrode for the analysis of a peptide mixture and a protein digest demonstrated a high separation efficiency similar to when hydroquinone was used as a redox buffer.

A new assay for lipiodol in a tumor using a combination of m-chloroperbenzoic acid-mediated oxidation and the iodo-starch reaction

Lipiodol, an iodine adduct lipid, has been used as a targeting carrier of anticancer drugs in experimental animals and humans. In most studies, the concentrations of the anticancer drugs in tissues and organs have been monitored, but not of the carrier because a simple method for measuring lipiodol in biological organs did not exist. Here we present an analytical method for the quantitative determination of lipiodol in tissue. This method is based on the measurement of iodine released from lipiodol by an oxidative reaction. The released iodine was measured spectrophotometrically by monitoring the iodo-starch reaction. Using this method, we were able to demonstrate the tumor specificity of lipiodol using rabbits bearing VX2 tumors in the liver. The present method is also expected to be applicable to human cancers, such as hepatic and colon cancer.

Sulfur Site Iodine Adduct of a Nickel Thiolate Complex.

The interaction of I2 with the nickel dithiolate Ni-1* yields a charge-transfer complex of I2 in which the nucleophilic metal thiolate donates electron density into the I2 σ* LUMO. In the solid-state structure, the I−I bond is elongated from that of free I2 (3.03 A vs 2.72 A), and conductance measurements indicate that the I−I bond is heterolytically cleaved in solution. The new molecular iodine adduct is compared to I2 adducts of PPh3 and R2S.

New type of polymer containing 1,1′-ferrocenediyl unit in π-conjugated main chain. Preparation and redox behavior

New ferrocenic polymers formulated as (-FcC≡CArC≡C-)n (Fc=1,1′-ferrocenylene; Ar=p-C6H4, 2,5-pyridinediyl, and 2,5-didodecyl-p-phenylene) have been prepared by a Pd-catalyzed CC coupling polymerization. Electrochemical oxidation of the polymers requires a higher potential than those of ferrocene and poly(ferrocene) owing to bonding to the electron withdrawing -C≡C- group, and their broadened cyclic voltammograms suggest an exchange of electron between the Fc units along the π-conjugated main chain. Mössbauer spectra of iodine adducts of the polymers reveal that the polymer with the p-C6H4 unit (as the Ar unit) is oxidized with iodine whereas the polymer with the 2,5-pyridinediyl is not; the difference is accounted for by the electronic effect and reactivity of the Ar units.

Tracing Gluconeogenesis with Deuterated Water: Measurement of Low Deuterium Enrichments on Carbons 6 and 2 of Glucose

The contribution of gluconeogenesis to glucose productionin vivocan be measured by enriching body water with 0.5%2H2O and measuring the glucose labeling ratio C6/C2 (Landauet al., J. Clin. Invest.95, 172–178, 1995). We present further refinements of the measurements of the2H enrichments on C6 and C2 of glucose. The transfer of2H from C6 of glucose to hexamethylenetetramine (HMT) and extraction in preparation for gas chromatography–mass spectrometry can be done in a single test tube, without distillation of the intermediate formaldehyde. In addition, extraction of small amounts of HMT is greatly improved by making a HMT–iodine adduct. For C2, glucose is reduced to sorbitol, and2H on C2 is transferred enzymatically to [U-13C3]pyruvate, forming [U-13C3,2-2H]lactate. The latter is assayed by negative chemical ionization gas chromatography–mass spectrometry of the pentafluorobenzyl derivative. The natural enrichment of the [U-13C3]lactyl ion is only 0.4%, allowing measurements of2H enrichment down to 0.1%. These techniques were used in dogs infused with2H2O and in isolated rat livers perfused with buffer containing 1 to 5%2H2O. Our data reveal a difference in the rate of labeling of C6 and C2 of glucosein vivo.Lastly, in cows infused with [6,6-2H2]glucose, we show that the turnover of glucose can be economically measured by assaying low tracer enrichment (down to 0.1%) via hexamethylenetetramine.

Thermal Behaviour of Metal Biguanides and their Iodine Adducts

Thermal Behaviour of Metal Biguanides and their Iodine Adducts

Iodine-Incorporated Copolymer of Methyl Methacrylate andN-Vinylpyrrolidone. I. Synthesis and Characterization

Abstract Methyl methacrylate and N-vinylpyrrolidone were copolymerized in an organic solvent using peroxide initiator and gamma radiation. The copolymers were treated with different weight percentages of molecular iodine in a homogeneous solution of dichloromethane. Iodine was found to be strongly attached to the polymer backbone, and only a negligible amount of free iodine could be extracted from the sample with as high as 40% iodine content. The copolymers of methyl methacrylate and N-vinylpyrrolidone prepared under different conditions showed a marked difference in their swelling behavior and thermal stability. The percent swelling and overall thermal stability of the samples decreased after incorporation of iodine into the polymer. The FT-IR, 1H-NMR, thermogravimetric data, and intrinsic viscosity of the copolymers and their iodine adducts are discussed. The results suggest the presence of specific interactions between the pyrrolidone group and iodine.

129I Mössbauer spectroscopic study of metallocene-iodine adducts

A129I Mossbauer spectroscopic study of iodine adducts of [2]ferrocenophane, biruthenocene, and osmocene is reported. The spectra show the existence of iodine bonded to the central metals of metallocenes in addition to triiodide anions. The valence state of iron in the [2]ferrocenophane-iodine adduct is the same as those of ruthenium and osmium in their adducts.

Synthesis of poly‐yne polymer containing platinum and silicon atoms in the main chain by oxidative coupling and its reactions with transition‐metal carbonyl complexes

AbstractThe platinum poly‐yne polymer, [CCSiMe2CCPt(PBu3)2CCSiMe2CC]n (2), was synthesized by the oxidative coupling of a silicon–platinum monomer, trans‐(PBu3)2Pt(CCSiMe2–CCH)2 (1). The reaction of platinum poly‐yne polymer 2 with dicobaltoctacarbonyl gave μ‐coordinated complexes, {[CCSiMe2CCPt(PBu3)2CCSiMe2CC] [Co2(Co)6]2}n (4). the electric conductivity of iodine adducts of the polymer complexes 4 was 3.0×10−5 S cm−1. As an aid to spectroscopic characterization of the polymer complex 4, a model complex, {trans‐[(PBu3)2Pt(CCSiMe2CCH)2]} {[Co2(CO)6]2} (3), was also prepared by the reaction of 1 with dicobaltocatacarbonyl. Selective coordination of Co2(CO)6 groups to SiMe2CC CCSi(Me)2 Moieties and coordinative inertness of the PtCC moieties were confirmed by comparison of the NMR spectra of 3 with those of 4. All new compounds have been characterized by analytical and spectral analysis (IR, 1H NMR).

A stable carbene iodine adduct: secondary bonding in 1,3-diethyl-2-iodo-4,5-dimethylimidazolium iodide

The stable carbene iodine adduct 2 is formed by the reaction of the imidazol-2-ylidene 1 with iodine; the X-ray structure of 2 is reported.

Structural studies of halogen adducts of diorganyl chalcogenides in solutions by 1H, 13C, 77Se and 125Te NMR

Abstract1H, 13C, 77Se and 125Te NMR spectra were measured for several sulphides, selenides, tellurides and their halogen adducts to establish the criteria for distinguishing trigonal bipyramidal (TB) adducts from molecular complexes (MCs). TB formation caused large downfield shifts for methyl protons and methyl, ipso and para carbons of methyl and phenyl selenides and tellurides. Large downfield shifts (> 100 ppm) were also observed for selenium and tellurium by the formation of TB from the parent selenides or tellurides. The plots of the 125Te vs 77Se chemical shifts for a set of corresponding compounds gave a straight line with a slope of 1·74, showing that the linear relationship holds well for tellurides and selenides and their TB adducts examined in this work. Upfield shifts of the ipso carbons were characteristic of MC formation. The para carbon signals of MC appeared downfield relative to those of the parent selenides, although the shift values were not so large. The 77Se signals for MC shifted slightly downfield (⩽ 10 ppm). The dissociation constants for iodine adducts of dimethyl selenide and selenoanisole were determined. The MC structure of bromine adducts of sulphides is well demonstrated on the basis of the criteria set out. 1H and 13C NMR spectra of ethylbenzene and ethers were also recorded in the presence of iodine or bromine. However, their chemical shifts were the same as those in the absence of iodine or bromine, within experimental errors.

Polymers and oligomers with substituted 2,5‐thienylene units. Preparation and electrical conductivity properties

AbstractNi‐catalyzed dehalogenation polycondensation of 3‐formyl‐, 3‐hydroxyiminomethyl‐ and 3‐cyano‐2,5‐dibromothiophene with zinc affords oligo(3‐formyl‐2,5‐thienylene) (2a), oligo‐(3‐hydroxyiminomethyl‐2,5‐thienylene) (2b), and oligo(3‐cyano‐2,5‐thienylene) (2c). Electrochemical polymerization of 3‐methoxythiophene and 3,4‐dimethoxythiophene give blueblack films of oligo(3‐methoxy‐2,5‐thienylene) (2d) and poly(3,4‐dimethoxy‐2,5‐thienylene) (2e). Iodine adducts of 2a–2c show electrical conductivity values between 1,8 · 10−11 and 8,8 · 10−8 S · cm−1. Doped 2d shows electrical conductivity of 2 · 10−1 S · cm−1, whereas doped 2e exhibits an electrical conductivity between 1,5 and 30 S · cm−1. Doping of undoped 2d and 2e causes profound changes in their IR and NMR spectra, colour, and electrical conductivity properties.

Charge transfer adducts of metal complexes of π-donor ligands with I 2 and TCNQ

Copper(II) and nickel(II) biguanides and O-alkyl-1-amidinourea can act as donors for the formation of charge transfer (CT) adducts with I 2 and tetracyanoquinodimethane (TNCQ) as acceptors. Iodine adducts are characterized both in solid and solution states whereas TCNQ adducts obtain only in solution. Appearance of a broad band at 355 nm for iodine adducts and at 335 nm for TNCQ adducts and shifting of i.r. frequencies support the formation of donor acceptor associates. Elemental analysis establishes 1:1 stoichiometry of the solid adducts. The K and ε values determined by modified Benesi—Hildebrand, Scott and Rose—Drago equations are found to be of the order of 10 4 and 10 3 respectively at 298 K in methanol. The solvent effect on the K values is discussed in terms of coupled solute-solute and solute-solvent equilibria.

Li|LiI|iodine primary galvanic cell and Zn|ZnI 2|iodine secondary galvanic cell using poly(2,5-thienylene), poly(2,5-pyrrolylene), and their analogues as positive electrodes

Iodine adducts of chemically prepared poly(2,5- thienylene) show good electrical conductivity over a range of iodine content of 10–90 wt.%. The adducts serve as good active materials of positive electrodes of Li|LiI|iodine galvanic cells. Discharge curves of the galvanic cell at 500 kgω load show stable voltage (2.8–2.3 V) until about 85% of added iodine is consumed in the cell reaction. Poly(2,5-thienylene), poly(2,5-pyrrolylene), and their derivatives prepared both chemically and electrochemically are useful as materials for positive electrodes of Zn|ZnI 2|cation- exchange membrane|ZnI 2|iodine secondary cells. The cells using the polymers show about 100% current efficiency and 85% energy efficiency, and are rechargeable more than 200 times. Utilization of electric conducting π-conjugated polymers as electrodes of primary and secondary cells is a subject of recent interest [1–7]. Among the electric conducting polymers, those constituted of recurring 5-membered heterocycles have high stabilities against air and heat. They show good electric conductivity when doped with electron acceptor or donor ▪ and are suitable as electrodes of the cells. Two methods have been developed for the preparation of the polymers. Method 1: Transition metal catalyzed dehalogenation polycondensation of dihalo-compounds with magnesium or zinc [8–13]. e.g., ▪ Method 2: Anodic oxidation of thiophene, pyrrole, or their derivatives [14–21]. e.g., ▪ We now report utilization of the polymer as positive electrodes of Li|LiI|iodine primary and Zn|ZnI 2|- cation-exchange membrane|ZnI 2|iodine (abbreviated as Zn|ZnI 2|iodine) secondary cells.

Electrical conductivity of iodine adducts of nylon 6 and other non-conjugated polymers

Iodine-nylon 6 adducts containing 70 to 90wt% iodine have been prepared by heating iodine and nylon 6 at 115 and 145° C. The electrical conductivity (σ) of the adduct increases with increase in the iodine content and the iodine-nylon 6 adduct containing 90wt% iodine and prepared at 145° C gives σ = 10−3 S cm−1 at 25° C. Infrared, nuclear magnetic resonance (1H and13C{1 H}), and powder X-ray diffraction analysis of the adduct show a profound change of the structure around the amide group of nylon 6 and suggest the formation of a-C=NH+-group in the reaction of nylon 6 with iodine. The temperature dependences of σ of the idoinenylon 6 adducts prepared at 115° C give activation energies of 51 to 92 kJ mol−1 depending on the iodine content. Addition of carbon powder to the iodine-nylon 6 adduct causes an increase in electrical conductivity. Other polymers (aliphatic and aromatic nylons, poly(vinyl alcohol), poly (tetrahydrofuran), poly(N-vinylpyrrolidone), poly (4-vi nylpyridine), and poly(acrylonitrile)) which have lone pair or π-electrons also form iodine adducts containing 70 to 95 wt % iodine and the adducts show an electrical conductivity in the range of 10−5 to 10−2 S cm−1. Among the iodine adducts, those of poly(vinyl alcohol) and poly (tetra hydrofuran) show electrical conductivities as high as 1.5 X 10−2 S cm−1 when the adducts contain about 90 wt% iodine.

Zn|ZnI 2| iodine secondary galvanic cells using iodine adducts of nylon-6 and other polymers as positive electrodes

Zn|ZnI 2| iodine galvanic cells using carbon plate electrodes coated with polymer + carbon powder mixtures are rechargeable with minor self-discharge when a positive ion exchanging film is used as the separator. Among the polymers tested (nylon-6, Poly(tetrahydrofuran), poly(acrylonitrile), poly(methly methacrylate), poly(vinly Alcohol), poly( N-vinylpyrrolidone), and poly(4-vinylpridine)), nylon-6 and poly(tetrahydrofuran) have the highest ability to absorb iodine and afford secondary galvanic cells showing the best rechargeability: the secondary galvanic cells are rechargeable more than 500 times with about 100% current efficiency and 81–83% energy efficiency when charged and discharged at 2 mA/cm 2 at 25°C. The average charging and discharging voltages of the secondary cell using nylon-6 are 1.42 and 1.18 V, respectively. The cell prepared by using nylon-6 generates about 80 mA/cm 2 of an initial short-circuit current and 0.3–80 mA/cm 2 of a steady-state short-circuit current when the cell is dipped into a aqueous solution containing I − 3. The steady-state short-circuit current increases with increasing I − 3 concentration and a linear correlation holds between the logarithm of the steady-state short-circuit current and the logarithm of [I − 3] in the range of [I − 3] = 0.05–0.5 mol/1.

Lithium-iodine solid electrolyte galvanic cells using iodine adducts of nylon-6 as active materials of positive electrodes

Iodine and nylon-6 form adducts containing 70–90 wt-% of iodine on heating at 115–145°C. The adducts have electrical conductivities ranging from 10 −7 to 10 −3 S cm −1 at 25°C, and the electrical conductivity increases with increasing content of iodine of the adduct. The activation energies of the electrical conduction for the adducts prepared at 115°C and containing 69.2, 81.8, 87.1, and 90.0 wt-% of iodine are 94.6, 67.0, 52.9, and 46.1 kJ/mol, respectively. Polyamides other than nylon-6 also form similar semiconducting adducts with iodine. IR and NMR spectroscopic analyses of the iodine—nylon-6 adducts indicate profound changes in the structure of nylon-6 on adduct formation and suggest the formation of a −CN +H species. The iodine-nylon-6 adducts prepared at 115°C and containing more than 82 wt-% of iodine serve as good active materials of positive electrodes in lithium-iodine solid electrolyte galvanic cells (outer diameter = 11.6 mm; outer thickness = 2.0 mm). The current efficiencies of the galvanic cells at 500 kΩ load are about 50% based on the iodine added. Discharge at 100 kΩ load gives lower current efficiencies. The galvanic cell has an internal resistance of about 5 kΩ at 25°C before discharge, and the internal resistance increases to about 100 kΩ at about 40% discharge. The dependence of the internal resistance during discharge have been determined.

Studies of solution dynamics of poly(N‐vinyl pyrrolidone) and its iodine adduct

AbstractCarbon‐13 NMR spin‐lattice relaxation times T1 of poly(N‐vinyl pyrrolidone) (PVP) and PVP‐iodine have been studied in several solvents and at different temperatures. Three kinds of motion can be identified from the T1 data: segmental motion, ring rotation, and ring puckering. The effective correlation time for segmental motion is calculated to be 1 × 10−9s, in good agreement with published proton NMR data. Another solvent, 1,1,2,2‐tetrachloroethane, behaves like D2O, the segmental correlation time being 3 × 10−9s. In benzene, however, the linewidths are very broad and tend to narrow with increasing temperature, but the T1s are not very different from those of PVP in D2O. The results suggest association of pyrrolidone rings in benzene that reduces chain dimensions and also restricts chain mobility. As for PVP‐iodine in water, again broad resonances are observed which sharpen considerably at higher temperatures. The result agrees with previous suggestions of specific interactions between the pyrrolidone group and iodine.