Polyiodide Chains Research Articles

Simultane Funktionalisierung von Einwandigen Kohlenstoff‐Nanoröhren von Innen und Außen

AbstractDie Funktionalisierung einwandiger Kohlenstoff‐Nanoröhren (SWCNTs) auf eine robuste Weise, die das sp2 Kohlenstoffgerüst nicht beeinträchtigt ist in der aktuellen Forschung eine große Herausforderung. Hier beschreiben wir, wie Triiodidsalze von positiv geladenen Makrozyklen verwendet werden können, um SWCNTs nicht nur von außen, sondern auch gleichzeitig von innen zu funktionalisieren. Wir setzten den Disulfidaustausch in wässrigem Lösungsmittel ein, um den solvophoben Effekt zu maximieren und so einen hohen Grad an Makrozyklus Immobilisierung zu erreichen. Die Charakterisierung mittels Raman‐Spektroskopie, EDX‐STEM und HR‐TEM zeigte deutlich, dass dieses nasschemische Funktionalisierungsprotokoll auch zur Verkapselung von Polyiodidketten im Inneren der Nanoröhren führte. Die resultierenden dreischaligen Kompositmaterialien sind redoxaktiv und weisen ein faszinierendes Zusammenspiel von elektrostatischen, solvophoben und mechanischen Effekten auf, was für Anwendungen in der Energiespeicherung von Interesse sein könnte.

Simultaneous Inside and Outside Functionalization of Single-Walled Carbon Nanotubes.

Functionalizing single-walled carbon nanotubes (SWCNTs) in a robust way that does not affect the sp2 carbon framework is a considerable research challenge. Here we describe how triiodide salts of positively charged macrocycles can be used not only to functionalize SWCNTs from the outside, but simultaneously from the inside. We employed disulfide exchange in aqueous solvent to maximize the solvophobic effect and therefore achieve a high degree of macrocycle immobilization. Characterization by Raman spectroscopy, EDX-STEM and HR-TEM clearly showed that serendipitously this wet-chemical functionalization procedure also led to the encapsulation of polyiodide chains inside the nanotubes. The resulting three-shell composite materials are redox-active and experience an intriguing interplay of electrostatic, solvophobic and mechanical effects that could be of interest for applications in energy storage.

1D IODINE FORMED INSIDE A PRE-ORIENTED MATRIX OF CARBON NANOTUBES

1D iodine nanostructures encapsulated inside a matrix of pre-aligned single-wall carbon nanotubes were synthesized by sublimation of a crystalline iodine phase. Liquid phase self-assembly method has been used for alignment of nanotube thin film. Since the orien-tation of the iodine structure was naturally determined by the orientation of the host nanotube matrix, the anisotropic optical and electronic properties of the inner structure at the macroscopic scale were obtained. Polarized Raman spectroscopy measurements con-firmed the presence of 1D polyiodide species oriented along the axis of nanotubes. The DFT calculations of polarized Raman spectra of polyiodide chains shown that the polari-zation dependences of the longitudinal modes for chains oriented along the nanotube axis and for helical twisted chains were significantly different.

Gold Polyiodide Hybrid Perovskite Solar Cells

In this work, we present the ionic liquid (IL) synthesis of two novel pseudo-2D perovskite-type gold(III)polyiodide compounds, [DodMe2S][AuI4][I3] (1) and [Et3S][AuI4][I5] (2), and their application as active layers in monolithic solar cells. The compounds are composed of tetraiodoaurate anions and polyiodide entities, infinite polyiodide chains in 1 and pentaiodides in 2, which display short intermolecular contacts resulting in relatively small electronic bandgaps. This work represents the first demonstration of film deposition of gold iodide/polyiodide compounds onto porous monolithic substrates with subsequent solar cell characterization. The devices show promising photovoltaic performance and could unlock new materials design possibilities, ultimately moving away from lead-based photovoltaic materials. These findings further highlight the use of simple polyiodide entities to increase the structural and electronic dimensionality of gold perovskite-type anions.

Molecular self-assembly of 1D infinite polyiodide helices in a phenanthrolinium salt.

A new linear polymeric polyiodide, catena-poly[tris(1,10-phenanthrolin-1-ium)tris(1,10-phenanthroline)heptaiodide], was prepared by one-step synthesis. Its formation is driven by hydrogen-bond assisted supramolecular assembly in the presence of chromium(iii) acetate. Its structure has been characterized by the means of single-crystal X-ray diffraction. To date, this is only one of the few examples of organized linear infinite polyiodides with a known structure. The interplay between the interactions within the hypervalent iodine chain and its supramolecular environment is elucidated. The electrical, thermal, and spectroscopic properties of the studied compound were investigated and associated with the structural features. The infinite character of the polyiodide chain and its similarity to the blue starch-iodine complex has been additionally confirmed by Raman spectroscopy. Despite the apparent structural and spectroscopic similarities with the previously reported 1D polymeric polyiodide, its physical properties, i.e. electrical conductivity and thermal stability, differ significantly. This can be rationalized by the differences in the orbital overlap within the iodine chain, as well as the distinct interactions with the cation.

Synthesis and crystal structure of rare-earth biuret complexes with linear pentaiodide ions: Infinite polyiodide chains in a cationic framework

Isostructural compounds [Ln(BU)4][I5][I]2 (Ln = La, Nd, Gd) were prepared by reactions of rare-earth iodides with biuret (BU) and iodine. Their crystals contain [Ln(BU)4]3+ complex cations and non-coordinated iodide and pentaiodide ions. Complex cations and isolated iodide ions form a 3-D framework with infinite square channels via weak bonds of the N–H...O and N–H...I types. In the channels, infinite chains of almost linear pentaiodide ions are arranged. Calculated distribution of the charge in the pentaiodide ion explains the absence of weak interactions of its iodine atoms with other atoms of a coordinate compound. The energies of the inner I–I bonds correspond to formation of the anion from two iodine molecules and central iodide ion. Distances between iodine atoms and charge distribution in the polyiodide anion support Grotthuss-like charge transfer mechanism. Band gaps for polyiodide chains correspond to semi-conducting character of conductivity.

Temperature dependences of electric properties of tetramethylammonium mono- and pentaiodide

The dielectric properties of tetramethylammonium monoiodide and pentaiodide were investigated in broad temperature range ([Formula: see text]C till [Formula: see text]C). It was demonstrated that the structural organization of the polyiodide chain containing I[Formula: see text][Formula: see text][Formula: see text]I charge-assisted halogen bonds influenced the parameters and the mechanism of electric conductivity of considered compound. The impedance spectroscopic measurements revealed that the direct current electric conductivity of pentaiodide salt is around four orders of magnitude higher than that of corresponding monoiodide. Moreover, pentaiodide demonstrates the hopping mechanism of conductivity.

The features of iodine loss at high temperatures

A series of crystalline thiazoloquinolinium iodides has been studied using a combination of thermal analysis, mass and Raman spectroscopy techniques. The influence of composition and polyiodide anion stoichiometry on the features of iodine loss has been revealed. It has been shown that the existence of a bound diiodine molecule in a polyiodide chain leads to significant decrease in melting point and decomposition temperatures in comparison with corresponding mono- and triiodide salts. The loss of the diiodine molecule from the complex polyiodide proceeds independently, without decomposition of the organic cation, while the release of diiodine from the triiodide anion goes simultaneously with thermal decomposition of the cation. In addition, the decomposition processes on the surface of the thiazoloquinolinium polyiodide crystal have been investigated during sample storage. Iodine loss and formation of more stable triiodide have been proved using Raman spectroscopy data.

Iodine in Metal-Organic Frameworks at High Pressure.

Capture of highly volatile radioactive iodine is a promising application of metal-organic frameworks (MOFs), thanks to their high porosity with flexible chemical architecture. Specifically, strong charge-transfer binding of iodine to the framework enables efficient and selective iodine uptake as well as its long-term storage. As such, precise knowledge of the electronic structure of iodine is essential for a detailed modeling of the iodine sorption process, which will allow for rational design of iodophilic MOFs in the future. Here we probe the electronic structure of iodine in MOFs at variable iodine···framework interaction by Raman and optical absorption spectroscopy at high pressure ( P). The electronic structure of iodine in the straight channels of SBMOF-1 (Ca- sdb, sdb = 4,4'-sulfonyldibenzoate) is modified irreversibly at P > 3.4 GPa by charge transfer, marking a polymerization of iodine molecules into a 1D polyiodide chain. In contrast, iodine in the sinusoidal channels of SBMOF-3 (Cd- sdb) retains its molecular (I2) character up to at least 8.4 GPa. Such divergent high-pressure behavior of iodine in the MOFs with similar port size and chemistry illustrates adaptations of the electronic structure of iodine to channel topology and strength of the iodine···framework interaction, which can be used to tailor iodine-immobilizing MOFs.

Iodine nanoparticle-enhancing electrical and thermal transport for carbon nanotube fibers

The excellent electrical and thermal transport properties of individual carbon nanotubes (CNTs) have allowed them to stand out in nanoenergy and nanoelectronics applications. However, scaling them up from nanometer-sized tubes to micrometer assembled fibers generally leads to considerable electrical and thermal transport deterioration. In pursuit of a new strategy for boosting thermal and electrical transport, we experimentally confirmed that the intercalation of iodine (I) molecules can significantly raise the inter-tube interfacial electrical and thermal transport (IET and ITT), and thus boost the overall electrical and thermal transport performance of the fibers. The underlying mechanisms from an energy carrier standpoint are also explored and discussed. It is demonstrated that the introduced I molecules can invoke electron extraction from CNTs, which enhances the IET. The formed (I3)− and (I5)− polyiodide chains act as additional heat transfer channels and induce low-frequency phonons of the interfacial carbon atoms, and the intercalation also improves the matching level of the vibrational density of states at the inter-tube interface. These three-fold effects contribute to the ITT. Our findings are one step forward on the path towards advanced CNT-based functional materials with high electrical and thermal transport.

Electrically Activated Conductivity and White Light Emission of a Hydrocarbon Nanoring-Iodine Assembly.

Numerous otherwise difficult applications have been realized with materials, the chemical/physical properties of which can be controlled by external stimuli such as heat, pressure, photo-irradiation, and voltage bias. However, the complexity of design and the lack of easy-to-conduct synthetic methods make the creation of on-demand stimuli responsive materials a formidable task. Here we report an electric-stimuli-responsive multifunctional material, [10]CPP-I: crystalline assembly of a hydrocarbon nanoring ([10]cycloparaphenylene: [10]CPP) as an "electro-responsive porous host" and iodine as a "potentially functional molecule". Through applying electric stimulus, [10]CPP-I turned to exhibit two attractive properties: electronic conductivity and white light emission. We revealed that electric stimuli trigger the cascade formation of polyiodide chains inside the [10]CPP assembly through charge transfer, leading to the emergence of these properties. This "responsive porous host" approach is expected to be applicable for different stimuli, and opens the path for devising a generic strategy to the development of stimuli-responsive materials.

Electrically Activated Conductivity and White Light Emission of a Hydrocarbon Nanoring–Iodine Assembly

AbstractNumerous otherwise difficult applications have been realized with materials, the chemical/physical properties of which can be controlled by external stimuli such as heat, pressure, photo‐irradiation, and voltage bias. However, the complexity of design and the lack of easy‐to‐conduct synthetic methods make the creation of on‐demand stimuli responsive materials a formidable task. Here we report an electric‐stimuli‐responsive multifunctional material, [10]CPP‐I: crystalline assembly of a hydrocarbon nanoring ([10]cycloparaphenylene: [10]CPP) as an “electro‐responsive porous host” and iodine as a “potentially functional molecule”. Through applying electric stimulus, [10]CPP‐I turned to exhibit two attractive properties: electronic conductivity and white light emission. We revealed that electric stimuli trigger the cascade formation of polyiodide chains inside the [10]CPP assembly through charge transfer, leading to the emergence of these properties. This “responsive porous host” approach is expected to be applicable for different stimuli, and opens the path for devising a generic strategy to the development of stimuli‐responsive materials.

Polyiodide-Doped Graphene

Iodine-doped graphene has recently attracted significant interest as a result of its enhanced conductivity and improved catalytic activity. Using density functional theory calculations, we obtain the formation energy, desorption rate, and electronic properties for graphene systems doped with polyiodide chains consisting of 1–6 iodine atoms in the low-concentration limit. We find that I3 and I5 act as p-type surface dopants that shift the Fermi level 0.46 and 0.57 eV below the Dirac point, respectively. For these two molecules, molecular orbital theory and analysis of the charge density show that doping transfers electronic charge to iodine π* molecular orbitals oriented perpendicular to the graphene sheet. For even-length polyiodides, we find that I6 and I4 decompose to I2, which readily desorbs at 300 K. Adsorption energy calculations further show that I3 acts as an effective catalyst for the oxygen reduction reaction on graphene by stabilizing the rate-limiting OOH intermediate.

Effect of selectively intercalated polyiodide on the electric transports of metallic- and semiconducting-enriched single-wall carbon nanotube networks

We report the selective intercalation of polyiodide chains (I5−) inside the interstitial sites of single-wall carbon nanotube (SWCNT) bundles of which internal sites are pre-encapsulated with monatomic sulfur chains. By using metallic- and semiconducting-enriched SWCNTs with diameter of ∼1 nm, our direct-current electric transport measurements reveal that the I5− intercalation on the metallic- and semiconducting-enriched SWCNT networks exhibits an opposite trend on the temperature dependence of the electric resistance at cryogenic temperature. Based on our analysis using the fluctuation-induced tunneling conduction model, the intercalation of I5− chains into the semiconducting-SWCNTs leads to the increase in energy barriers required for tunneling processes. Since the charge transfer is negligible between I5− chains and the semiconducting-SWCNTs, the main effect of the intercalated I5− on the semiconducting-SWCNTs is to behave as a scattering center below 50 K. In contrast to the semiconducting-SWCNTs, the intercalation of I5− chains into the metallic-SWCNTs results in the suppression of tunneling barriers due to the charge transfer interaction. The energy barrier is further reduced by the encapsulation of I5− chains inside the metallic-SWCNT, implying that the doping effect could be more effectively enhanced by the interaction through the inner spaces of SWCNTs.

Inside Back Cover: Infinite Polyiodide Chains in the Pyrroloperylene–Iodine Complex: Insights into the Starch–Iodine and Perylene–Iodine Complexes (Angew. Chem. Int. Ed. 28/2016)

Inside Back Cover: Infinite Polyiodide Chains in the Pyrroloperylene–Iodine Complex: Insights into the Starch–Iodine and Perylene–Iodine Complexes (Angew. Chem. Int. Ed. 28/2016)

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.

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

AbstractWe 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.

Stabilization of polyiodide chains via anion⋯anion interactions: experiment and theory

In tyrosinium polyiodide hydrate, cations and anions aggregate in layers. The cation layers are stabilized by classical hydrogen bonds. The anionic part of the structure consists of parallel infinite polyiodide strands; the distance pattern along these chains suggests the presence of smaller subunits I3−, I2 and I−. Comparative calculations for small fragments and longer chains in frozen geometries indicate that this unexpected arrangement is favoured by local stabilizing anion⋯anion interactions and partial charge transfer between the subunits. The topological analyses of the electron density ρ, its negative Laplacian L = −∇2ρ and the electrostatic potential φ functions have been used to study the intrachain I–I and I⋯I interactions. Thorough analysis carried out with L indicates the successive arrangement of generalized charge concentration and charge depletion sites (for either L > 0 or L < 0 regions) along bond paths, and permits to distinguish iodides from iodine atoms even when they are involved in intermediate situations where interatomic distances and net charges are not conclusive.

I5–polymers with a layered arrangement: synthesis, spectroscopy, and structure of a new polyiodide salt in the nicotine/HI/I2system

AbstractThe reaction ofS-nicotine with hydroiodic acid in the presence of iodine gave the new polyiodide-containing salt nicotine-1,1′-diium bis(triiodide)-diiodine (1/1) (C10H16N2) [I3]2·I2(1). The title compound has been characterised by spectroscopic methods (Raman and IR) and single-crystal X-ray diffraction. The asymmetric unit of the title structure consists of one dication, two triiodide anions, and one iodine molecule, all located in general positions in the non-centrosymmetric space groupP1. One of the two crystallographically independent triiodide anions and the doubly protonated nicotinium dication form hydrogen-bonded chains alongb, which are arranged parallel to each other in the ½bcplane. The second crystallographically independent triiodide anion and the iodine molecule form an I5–moiety, which is end-on connected to two symmetry-related anions resulting in polyiode zig–zag chains along the [0 1 1̅] direction. These polyiodide chains are stacked parallel to each other in the 0bcplane. The Raman spectrum of the title compound shows characteristic lines in the 50–200 cm–1range, which are in excellent agreement with the findings derived from the crystal structure.

ChemInform Abstract: Iodine‐Templated Assembly of Unprecedented 3d—4f Metal—Organic Frameworks as Photocatalysts for Hydrogen Generation.

AbstractThe isotypic compounds (III) crystallize in the monoclinic space group P21/c with Z = 2 (single crystal XRD) and exhibit three‐dimensional frameworks with triangular helical channels, which accomodate linear polyiodide chains.