Structure of iodide ion arrays in iodinated nylon 6 and the chain orientation induced by iodine in nylon 6 films

Two species of iodide ions (I₃^? and I₅^?) are found in iodine—nylon 6 complexes. Orientation of I₅^? arrays (most likely I₂/I₃^? complex) along the polymer chain and I₃^? ions perpendicular to the chain axis in uniaxially drawn films and in films with planar orientation suggests that there is and intrinsic relation between the direction of iodide ion arrays and nylon 6 chains. When an unoriented film of nylon 6 in the amorphous or the α crystalline form is treated with an aqueous solution of iodine—potassium iodide, the I₃^? species in the resulting iodine—nylon complex lie in planes parallel to the surface of the film, and I₂/I₃^? units are oriented normal to the surface of the film. The γ form obtained by desorbing the iodine from this complex shows considerable uniaxial rientation with the nylon chains oriented perpendicular to the plane of the film; this orientation is maintained during the γ to α transition. It is proposed that the iodine-induced orientation of the nylon 6 chains is due to the nucleating effects of the iodide ion species as the iodine diffuses unidirectionally into the film.     

Infinite Polyiodide Chains in the Pyrroloperylene–Iodine Complex: Insights into the Starch–Iodine and Perylene–Iodine Complexes

We report the preparation and X‐ray crystallographic characterization of the first crystalline homoatomic polymer chain, which is part of a semiconducting pyrroloperylene–iodine complex. The crystal structure contains infinite polyiodide I_∞^δ?. Interestingly, the structure of iodine within the insoluble, blue starch–iodine complex has long remained elusive, but has been speculated as having infinite chains of iodine. Close similarities in the low‐wavenumber Raman spectra of the title compound and starch–iodine point to such infinite polyiodide chains in the latter as well.     

The Photochemistry of Ch3I in Various Matrices at Low Temperature

The photodissociation of methyl iodide in various matrices at low temperature was studied. The observed Raman spectra excited by 514.5 nm laser radiation showed that there were two different photolytically produced iodine species isolated in the matrices after illumination by a medium pressure mercury lamp. One species which was dominant at lower iodine concentrations and exhibited a progression with an ωe of 201 cm^?1, belonged to the matrix isolated iodine monomer (I₂). The other species, which was dominant at higher iodine concentrations with an ω_e of approximately 180 cm^?1, belonged to the iodine aggregate ((I₂)_n). Five progressions of resonance Raman or resonance fluorescence of these two species were also observed in the other matrices. The iodine aggregate in the methyl iodide matrix at 77 K was formed in a crystalline structure, while the photolytically generated iodine aggregate from CH₃I/Ar (2/3) matrix at 10 K, after illumination with a mercury lamp, was in amorphous form. The rearrangement of photolytically produced iodine aggregate in methyl iodide matrix was observed as a function of the duration of illumination. Local heating effects of the laser radiation might induce the iodine monomer to aggregate in matrices. The photodissociation mechanism of methyl iodide in matrices is also proposed.     

Complex structure tri- and polyiodides of iodocyclization products of 2-allylthioquinoline

Iodocyclization products of 2-allylthioquinoline are obtained in the form of polyiodides with different stoichiometric compositions. X-ray crystallography data are analyzed for two different crystal structures of 1-iodomethyl-1,2-dihydro[1,3]thiazolo[3,2-a]quinolinium polyiodides: triiodide C₁₂H₁₁INS⁺I ₃ ^? and complex polyiodide 2(C₁₂H₁₁INS⁺I ₃ ^? )·I₂. A comparison is made of the nonbonding interactions of dihydrothiazoloquinolinium with atoms of the triiodide anion and complex polyiodide to show the crystal structure features attributed to the participation of molecular iodine.     

Conducting Polymers: Partially Oxidized Bridge-Stacked Metallophthalocyanines

The synthesis and characterization of a novel class of polymeric phthalocyanines (Pc), (PcMX)_n (M-Al, Ga, Cr; X?F and M-Si, Ge, Sn; X?0) of exceptional thermal stability are summarized. These materials possess a linear MX backbone surrounded by a sheath of cofacial M-centered Pc rings.

(PcAlF)_n and (PcGaF)_n are sublimable (10^?3mmHg,540°C and 430°C, respectively) allowing for thin film formation. Iodine-doping leading to compositions (PcMXI_y)_n with y ranging from 0.06 to 5.5 is reported. Thermogravimetric analysis has proven useful for iodine analyses and has revealed that the order of thermal stability with regard to loss of iodine is (PcCrFI_y)_n < (PcGaFI_y)_n< (PcAlFI_y)_n

< (PcSioI_y)_n. Raman spectra point to I₃-and I₅-as the principle polyiodide species, though their relative proportions vary depending on M and doping level. Increases in the electrical conductivity by as much as 10⁹ with maximum conductivities in the range of 0.01–1 ohm^?1cm^?1 result from iodine doping. Conduction appears to be thermally activated (77–300K) with an apparent activation energy of 0.04eV. It is likely that electron transport is primarily ligand based and is metal-like in character.     

Ein Netzwerk aus Iodid-Ionen und Iod-Molekülen in der Kristallstruktur von [Pr(Benzo-15-Krone-5)2]I21

A Three Dimensional Network of Iodide Ions and Iodine Molecules in the Crystal Structure of [Pr(Benzo-15-Crown-5)₂]I₂₁ Black polyhedra of [Pr(benzo-15-crown-5)₂]I₂₁ were grown from an ethanol / dichlormethane solution of PrI₃, benzo-15-crown-5 and I₂. The crystal structure (orthorhombic, P2₁cn, a = 1201.1(1), b = 2168.3(1), c = 2571.1(1) pm, Z = 4) is built up from sandwich like cations [Pr(benzo-15-crown-5)₂]³⁺ and polyiodide anions I₂₁^3-. This unique polyiodide anion exhibits a complex connection pattern of iodide ions and iodine molecules with variable bond lengths forming a complicated network.     

From an Icosahedron to a Plane: Flattening Dodecaiodo‐dodecaborate by Successive Stripping of Iodine

It has been shown by electrospray ionization–ion‐trap mass spectrometry that B₁₂I₁₂^2? converts to an intact B₁₂ cluster as a result of successive stripping of single iodine radicals or ions. Herein, the structure and stability of all intermediate B₁₂I_n^? species (n=11 to 1) determined by means of first‐principles calculations are reported. The initial predominant loss of an iodine radical occurs most probably via the triplet state of B₁₂I₁₂^2?, and the reaction path for loss of an iodide ion from the singlet state crosses that from the triplet state. Experimentally, the boron clusters resulting from B₁₂I₁₂^2? through loss of either iodide or iodine occur at the same excitation energy in the ion trap. It is shown that the icosahedral B₁₂ unit commonly observed in dodecaborate compounds is destabilized while losing iodine. The boron framework opens to nonicosahedral structures with five to seven iodine atoms left. The temperature of the ions has a considerable influence on the relative stability near the opening of the clusters. The most stable structures with five to seven iodine atoms are neither planar nor icosahedral.     

(β-Cyclodextrin)2·KI7·9 H2O. Spatial fitting of a polyiodide chain to a given matrix

α-Cyclodextrin, a torus shaped molecule with a 5 Å wide central cavity, forms a number of deep green, blue and black crystals when complexed with iodine/metal iodide. In contrast, β-cyclodextrin, having a 6 Å cavity produces only one type of reddish-brown crystal, no matter what metal iodide is used. The complex (β-cyclodextrin)₂ ·KI₇·9H₂O displays space groupP2₁ (pseudo-C2) with cell constantsa=19.609(5),b=24.513(7),c=15.795(6)Å, β=109.50(2)°,Z=4. The crystal structure was solved inC2 on the basis of 3022 absorption corrected CuKα (Ni-filter) X-ray intensities and refined by full matrix least squares toR=17%. This relatively highR-factor is due to many weak reflections (pseudo-C2) and considerable disorder exhibited by water and iodine. In the complex, β-cyclodextrin adopts a ‘round’ shape with O(2)...O(3) interglucose hydrogen bonds formed and all O(6) hydroxyls pointing away from the cavity. Two molecules are arranged head-to-head to produce a dimer, and dimers are stacked such that a slightly zigzagged cylinder with a 6 Å-wide cavity is formed. In the cavity described by each dimer, an I ₇ ^? ion composed of I₂·I ₃ ^? ·I₂ units is located, with I₂ and I ₃ ^? perpendicular to each other. K⁺ ions and 9 H₂O molecules are found in interstices between the β-cyclodextrin cylinders. This zigzag polyiodide contrasts with the linear form observed in the 5 Å wide α-cyclodextrin channels. It explains differences in color of the crystals and suggests that β-cyclodextrin polyiodide is not a good model for blue starch-iodine.     

Ternary diffusion with charged-complex formation in aqueous I2+NaI and I2+KI solutions

Diaphragm cells have been used to measure ternary diffusion coefficients for I₂+NaI and I₂+KI in aqueous solution at 25°C. Although most of the iodine molecules are bound to iodide ions and are transported as the triiodide species [I₂(aq)+I^–(aq)=I ₃ ^– (aq)], diffusion of the iodide salts produces relatively small countercurrent coupled flows of the iodine component. The ternary diffusivity of the iodine component in the solutions is 10 to 20% larger than the diffusivity of the triiodide species. This behavior can be understood by considering electrostatic coupling of the ionic flows. The diffusion equations for I₂+NaI and I₂+KI components are reformulated in terns of NaI₃+NaI and KI₃+KI mixed electrolyte components.     

Comparison of non-covalent interactions and spectral properties in 1-methyl-3-methylthio-5-phenyl-1,2,4-triazinium mono- and tetraiodide crystals

The reaction of 1-methyl-3-methylthio-5-phenyl-1,2,4-triazinium (MTPT) iodide with diiodine in a solution leads to monoiodide crystal structure that in excess of iodine gives the unusual tetraiodide anion with two central iodine atoms in disorder. The bonding within the anion has been characterized as I^–…I₂…I^–; the existence of the bound iodine molecule inside has been proven by the characteristic band in experimental and calculated Raman spectra. Non-covalent interactions of MTPT in considered crystal structures are different. Monoiodide anion as a strong electron donor allows the formation of the S…I chalcogen bonds that are absent in tetraiodide structure. The features of halogen bonds within the I₄^2– anion are also performed.

     

A Janus Separator based on Cation Exchange Resin and Fe Nanoparticles-decorated Single-wall Carbon Nanotubes with Triply Synergistic Effects for High-areal Capacity Zn−I2 Batteries

Zn−I₂ batteries stand out in the family of aqueous Zn-metal batteries (AZMBs) due to their low-cost and immanent safety. However, Zn dendrite growth, polyiodide shuttle effect and sluggish I₂ redox kinetics result in dramatically capacity decay of Zn−I₂ batteries. Herein, a Janus separator composed of functional layers on anode/cathode sides is designed to resolve these issues simultaneously. The cathode layer of Fe nanoparticles-decorated single-wall carbon nanotubes can effectively anchor polyiodide and catalyze the redox kinetics of iodine species, while the anode layer of cation exchange resin rich in −SO₃⁻ groups is beneficial to attract Zn²⁺ ions and repel detrimental SO₄²⁻/polyiodide, improving the stability of cathode/anode interfaces synergistically. Consequently, the Janus separator endows outstanding cycling stability of symmetrical cells and high-areal-capacity Zn−I₂ batteries with a lifespan over 2500 h and a high-areal capacity of 3.6 mAh cm⁻².     

A Dual Plating Battery with the Iodine/[ZnIx(OH2)4−x]2−x Cathode

Plating battery electrodes typically deliver higher specific capacity values than insertion or conversion electrodes because the ion charge carriers represent the sole electrode active mass, and a host electrode is unnecessary. However, reversible plating electrodes are rare for electronically insulating nonmetals. Now, a highly reversible iodine plating cathode is presented that operates on the redox couples of I₂/[ZnI_x(OH₂)_4?x]^2?x in a water‐in‐salt electrolyte. The iodine plating cathode with the theoretical capacity of 211 mAh g^?1 plates on carbon fiber paper as the current collector, delivering a large areal capacity of 4 mAh cm^?2. Tunable femtosecond stimulated Raman spectroscopy coupled with DFT calculations elucidate a series of [ZnI_x(OH₂)_4?x]^2?x superhalide ions serving as iodide vehicles in the electrolyte, which eliminates most free iodide ions, thus preventing the consequent dissolution of the cathode‐plated iodine as triiodides.     

An insight into the disorder properties of the α-cyclodextrin polyiodide inclusion complex with Sr2+ ion: dielectric,DSC and FT-Raman spectroscopy studies

At T < 250 K, the polyiodide inclusion complex (α-cyclodextrin)₂·Sr_0.5·I₅·17H₂O displays two separate relaxation processes due to both the frozen-in proton motions in an otherwise ordered H-bonding network and the order–disorder transition of some normal H-bonds to flip-flop ones. At T>250 K, the AC-conductivity is dominated by the combinational contributions of the disordered water network, the mobile Sr²⁺ ions, the polyiodide charge-transfer interactions and the dehydration process. The evolution of the Raman spectroscopic data with temperature reveals the coexistence of four discrete pentaiodide forms. In form (I) (I^?  ₃·I₂ ? I₂·I^?  ₃), the occupancy ratio (x/y) of the central I^?  ion differs from 50/50. In form (IIa) (I₂·I^? ·I₂) x/y = 50/50, whereas in its equivalent form (IIb) (I₂·I^? ·I₂) ^* as well as in form (III) (I^?  ₃·I₂), x/y = 100/0 (indicative of full occupancy). Through slow cooling and heating, the inverse transformations (I) → (IIa) and (IIa) → (I) occur, respectively.

     

Zur Struktur zweier Isothiazolium‐Polyiodide (C19H16FeNS)I5 und (C15H12NS)2I8

On the Structure of Two Isothiazolium Polyiodides (C₁₉H₁₆FeNS)I₅ and (C₁₅H₁₂NS)₂I₈ By oxidation of 3‐phenylamino thiopropenones with iodine two isothiazolium polyiodides were obtained, whose structures have been determined by X‐ray structure analysis. 2‐Phenyl‐5‐ferrocenyl‐isothiazolium pentaiodide(C₁₉H₁₆FeNS)I₅ forms a layer structure with isothiazolium cations and polyiodide anions. The polyiodide layers contain pentaiodide ions I₅^–, triiodide ions I₃^– and iodine molecules I₂. Bis(2,5‐diphenyl‐isothiazolium) octaiodide (C₁₅H₁₂NS)₂I₈ also forms a layer structure with isothiazolium cations and polyiodide anions. The polyiodide layers are built up by octaiodide ions I₈^2–, pentaiodide ions I₅^– and triiodide ions I₃^–.     

Ring-disk electrode studies of the open-circuit dissolution of iodine films formed during the anodic oxidation of iodide on platinum

The open-circuit behavior of iodine films formed on platinum by electrooxidation of iodide was studied at rotating disk and rotating ring-disk electrodes. The potential transient and ring current transient at open circuit for c_I^?>0.012 M can be explained by assuming: (1) convective-diffusion controlled dissolution of the film; (2) establishment of the I₂+I^?→ I₃^? equilibrium; (3) establishment of the I₂ (solid) →I₂ (solution) equilibrium. The behavior at lower concentrations of c_I^? suggests that convective-diffusion control is absent.     

Bis(2‐chloro‐N‐methyl­pyridinium) iodide triiodide

The title compound, 2C₆H₇ClN⁺·I^?·I₃^?, crystallizes with undulating layers of chains containing alternate iodide and triiodide anions formed from iodine and the heterocyclic iodide salt.     

Electrochemistry of iodine and iodide in chloroaluminate melts

The electrochemical behavior of iodine and iodide has been studied in AlCl₃+NaCl mixtures with compositions ranging from NaCl saturated melts to AlCl₃+NaCl (63+37 mol %) at platinum and tungsten electrodes. Iodide is oxidized in two steps to iodine and I(I); a reduction wave to iodide and an oxidation wave to I(I) are obtained in iodine solutions. The equilibrium constant for the reaction, I^?+I(I)=I₂, is 6×10⁸ l mol^?1 in molten chloroaluminate melts at 175°C.     

Ionic Liquid Based Electrolyte with Mesoporous Silica SBA-15 as Framework for Quasi-solid-state Dye-sensitized Solar Cells

Quasi-solid-state electrolytes were fabricated with mesoporous silica SBA-15 as a framework material. Ionic conductivity measurements revealed that SBA-15 can enhance the conductivity of the quasi-solid-state electrolyte. The diffusion coefficients of polyiodide ions such as Ⅰ3ˉ and Ⅰ5ˉ which were confirmed by Raman spectroscopic measurement, were about twice larger than that of I-. The optimized photoenergy conversion efficiency of dye-sensitized solar cells （DSSC） with the quasi-solid-state electrolyte was 4.3% under AM 1.5 irradiation at 75 mW·cm^-2 light intensity.     

Global Minimum‐Energy Structure and Spectroscopic Properties of I2.−⋅n H2O Clusters: A Monte Carlo Simulated Annealing Study

The vibrational (IR and Raman) and photoelectron spectral properties of hydrated iodine‐dimer radical‐anion clusters, I₂^.? ? n H₂O (n=1–10), are presented. Several initial guess structures are considered for each size of cluster to locate the global minimum‐energy structure by applying a Monte Carlo simulated annealing procedure including spin–orbit interaction. In the Raman spectrum, hydration reduces the intensity of the I? I stretching band but enhances the intensity of the O? H stretching band of water. Raman spectra of more highly hydrated clusters appear to be simpler than the corresponding IR spectra. Vibrational bands due to simultaneous stretching vibrations of O? H bonds in a cyclic water network are observed for I₂^.? ? n H₂O clusters with n≥3. The vertical detachment energy (VDE) profile shows stepwise saturation that indicates closing of the geometrical shell in the hydrated clusters on addition of every four water molecules. The calculated VDE of finite‐size small hydrated clusters is extrapolated to evaluate the bulk VDE value of I₂^.? in aqueous solution as 7.6 eV at the CCSD(T) level of theory. Structure and spectroscopic properties of these hydrated clusters are compared with those of hydrated clusters of Cl₂^.? and Br₂^.?.