Iodine Cations Research Articles

Regio- and stereoselective access to highly substituted vinylphosphine oxides via metal-free electrophilic phosphonoiodination of alkynes

In general, the P-centered ring-opening of quaternary phosphirenium salts (QPrS) predominantly leads to hydrophosphorylated products, while the C-centered ring-opening is primarily confined to intramolecular nucleophilic reactions, resulting in the formation of phosphorus-containing cyclization products instead of difunctionalized products generated through intermolecular nucleophilic processes. Here, through the promotion of ring-opening of three-member rings by iodine anions and the quenching of electronegative carbon atoms by iodine cations, we successfully synthesize β-functionalized vinylphosphine oxides by the P-addition of QPrS intermediates generated in situ. Multiple β-iodo-substituted vinylphosphine oxides can be obtained with exceptional regio- and stereo-selectivity by reacting secondary phosphine oxides with unactivated alkynes. In addition, a variety of β-functionalized vinylphosphine oxides converted from C-I bonds, especially the rapid construction of benzo[b]phospholes oxides, demonstrates the significance of this strategy.

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.

Electrochemically Generated Iodine Cations from a Glassy Carbon Electrode for Highly Selective Iodination of Anisole

The synthesis of aryl iodides from commercially available raw chemicals by simple, cheap and green strategies is of fundamental significance. Aryl iodides can undergo a series of homo-/cross-coupling reactions for the synthesis of important industrial chemicals and materials. Traditional methods require the electrophilic substitution on aromatic compounds by iodine or hypervalent iodine compounds, which suffers from the use of erosive halogens or hazardous oxidants. With the development of green chemistry in the field of electrochemical synthesis, anodic oxidation-derived I+ cations have been used for substitution reactions. However, the selectivity of the iodination by these electrochemical methods remains unsatisfactory. We believed that the anolyte is contaminated by trace platinum species from the working electrode. Herein, we report the generation of active I+ species from the anodic oxidation of I2 in acetonitrile using a glassy carbon electrode. With the presence of H+, electrolyte prepared with a glassy carbon anode can react with anisole to selectively form 4-iodoanisole with a yield as high as 97%. On contrast, the electrolytes prepared from Pt and graphite anodes finished the reaction with yields of 16% and 60% for 4-iodoanisole, respectively. This electrochemical method also applies to the iodination of toluene, benzonitrile and bromobenzene, delivering the target para-iodination products with 92%, 84%, and 73% yields, respectively. Thus, an atom-efficient and highly selective aryl iodination method was developed without the use of excessive oxidants.

A dual-site doping strategy for developing efficient perovskite oxide electrocatalysts towards oxygen evolution reaction

Perovskite-type ABO3 transition metal oxides are promising electrocatalysts for oxygen evolution reaction (OER), but still suffer from insufficient activities. Traditional efforts are mainly based on a single-site doping of heteroatom ions into either B-sites or O-sites of the ABO3 structures. Here we propose a dual-site doping strategy by simultaneous incorporation of iodine cations and anions into the B-sites and O-sites of ABO3 perovskite oxides, respectively. Consequently, both activated B-site transition metals with optimal eg orbital occupancy and large amount of active oxygen species were achieved for remarkably improved OER activities. Using this approach, significantly improved OER activities are achieved in some representative perovskite oxides, including Ba0.5Sr0.5(Co0.8Fe0.2)0.9O3–δ (BSCF), SrCo0.9O3−δ (SCO) and SrNi0.9O3−δ (SNO). Specifically, the iodine dual-site doped BSCF boosts a small overpotential of 290 mV at 10 mA cm−2 and a small Tafel slope of 53 mV dec−1, which is about 130 mV and almost half times lower than that of pristine BSCF, respectively. Besides, this general dual-site doping strategy can also realize scale-up synthesis and achieve a gram-scale production. Our findings show a unique doping strategy to design efficient perovskite oxide electrocatalysts beyond the conventional approaches.

Synthesis, crystal structure, optoelectric properties and theoretical study of three perovskite-like iodobismuthate charge-transfer salts based on butylpyridinium

Three new perovskite-like iodobismuthate hybrids with two butylpyridinium cations, namely (BPY)3(Bi2I9) (1), (BPY)5(Bi2I11) (2) and (BMPY)3(Bi2I9) (3) (BPY ​= ​1-butylpyridinium, BMPY ​= ​1-butyl-4-methylpyridinium), were synthesized by reacting of BiI3 and butylpyridinium. Single-crystal X-ray diffraction analysis revealed that these three hybrids exhibit two types of di-nuclear cluster structures, face-sharing Bi2I93− cluster for 1 and 3, and vertex-sharing Bi2I115− cluster for 2. Their optical band gaps were determined as 2.06 ​eV(1), 2.01 ​eV(2), 1.86 ​eV(3), respectively. DFT calculation reveals that their valence band tops and conduction band bottoms are composed of the states of iodine and pyridinium cations, respectively. Therefore these materials were classified as charge-transfer salts. Compared with similar iodobismuthates, their band gaps are significantly reduced. In addition, it is found that the band gaps should be affected by supramolecular interaction between cations in 2 and also by the conformational multiplicity of cations in structure 3. Photocurrent response test showed that these charge-transfer salts have rapid and consistent photocurrent response. This result indicated their potential applications as a photocatalyst or a photovoltaic absorber.

Iodine cation bridged graphene sheets with strengthened interface combination for electromagnetic wave absorption

Graphene-based metal-free aerogel is desirable for lightweight electromagnetic wave (EMW) absorbing materials. However, the weak van-der-Waals combination between graphene sheets, accompanied by the repulsion from surface oxygen-related polar groups, significantly hinder the transfer of electrons between the sheets, and lead to poor mechanical strength. These become bottlenecks for the further improvement of EMW absorption and have a huge impact on achieving multi-functions. Here, we used an iodine modification strategy to fabricate reduced graphene oxide (RGO) aerogel, in which graphene sheets are bridged by iodine cations (I+). Meanwhile, iodine promotes the conversion of epoxy groups to hydroxyl groups on graphene, thereby facilitating the adhension of I+ on the surface. These iodine cations rather than iodine anions are essential to strengthen the interconnection between graphene sheets, which enables the RGO aerogel to exhibit higher electrical conductivity, larger mechanical strength, higher thermal stability, and significantly improved EMW absorbing capability. With the improvement in conduction loss and impedance matching, the iodine-bridged RGO aerogel exhibits a maximium reflection loss of −52.8 dB and an effective absorption bandwidth of 7.2 GHz at 2 wt% filler loading, which are 3.8 and 1.5 times of pure RGO, respectively. Besides, the improved mechanical strength and resistance to temperature change benefit expanding the application fields of this aerogel.

Size‐dependent Molecular Characteristics and Possible Sources of Organic Aerosols at a Coastal New Particle Formation Hotspot of East China

AbstractWe investigated size‐dependent molecular characteristics of coastal organic aerosols from <0.032 to 3.2 μm at a new particle formation (NPF) hotspot of east China by using Fourier transform‐ion cyclotron resonance mass spectrometry (FT‐ICR‐MS). Strong connection between C20–33HhOo/C18,30HhOoNn compounds in particles smaller than 0.10 μm and the volatile organic compounds emitted from local intertidal macroalgae suggests that the organic compounds (OC) in ultrafine particles are formed probably via the gas‐phase oxidation of long‐chain fatty aldehydes or acids, followed by particle‐phase accretion reactions or imine formation during the coastal NPF events. In 0.18–0.56 μm particles, dominant C8–C20 CHO, CHON, CHOS and CHONS compounds (maximum: C10 or C15) are suggested most likely to be terpene oxidation products. Highly oxygenated compounds with 0.6 ≤ H/C ≤ 1.5 and 0.67 ≤ O/C ≤ 1.2 reside mostly in 0.18–0.56 μm particles, accounting for 5% of the OC formulas in this size range. Iodinated OC are subsequently formed via electrophilic substitution of non‐iodinated OC by iodine cations (e.g., from HOI or I2) in iodine‐rich particles. CHN and Cl/Br‐containing OC account altogether for only 0.7% and 0.9% of OC formulas, respectively. As a result of the above compound distribution, the intensity weighted unsaturation degree and carbon oxidation state of OC increase with particle size. The distribution of aromatic compounds (i.e. Aromaticity Index > 0.5) is bimodal with peaks in 0.056–0.18 μm and 1.0–3.2 μm. In addition, our study observed higher unsaturation degree, carbon oxidation state and aromaticity of OC in coastal PM2.5 than inland urban PM2.5 in the same region.

The S ⋅⋅⋅ Hal and Se ⋅⋅⋅ Hal chalcogen bonding in a series of thiourea, selenourea and their derivatives

The chalcogen bonding (ChB) in a series of thiourea, selenourea and their derivatives has been investigated in the present paper. Thus, selenourea and dimethylselenourea undergo dimerization and trimerization processes in the presence of various halogen species (1–5). Selenourea and dimethylselenourea form trimers 3–4 in the presence of lighter halogens (chlorine and bromine) through Se⋯Se chalcogen bonding. When moving to heavier halogen (iodine), the dimers 1–2 are formed. Thiourea and its derivatives also tend to make very strong S⋯S bonds and form dimers in the case of lighter halogens chlorine and bromine (compounds 6–7). However, the monomers separated by the iodine species are formed upon interaction with iodine via very strong S⋯I bonding (compounds 9–12). Furthermore, among all the crystal structures of 1–12, only iodine cations I+ in 10 and 12 act as electron density acceptors, while in the remaining compounds 1–9 and 11 halogen species act as electron density donors.

Ionic reaction products of iodine with pyridine, 4-methylpyridine, and 4-tert-butylpyridine in a polyethylene matrix. A FTIR polarization spectroscopic investigation

The ionic reaction products of the title pyridines with iodine in low-density polyethylene are identified by comparison of their IR spectra with literature data. The bis(pyridine)iodine(I), bis(4-methylpyridine)iodine(I), and bis(tert-butylpyridine)iodine(I) cations are spontaneously formed in the polymer medium. At elevated temperature, the 4-methylpyridinium cation is identified as a product of the reaction between 4-methylpyridine and iodine. In spite of their elongated molecular shape, the bis(pyridine)iodine(I) and bis(4-methylpyridine)iodine(I) cations are randomly aligned in stretched polyethylene; they probably form micro-crystalline polyiodide aggregates in the amorphous regions of the polymer. In contrast, the bis(tert-butylpyridine)iodine(I) cation is efficiently aligned in stretched polyethylene.

ChemInform Abstract: Synthesis of Polysubstituted 2‐Iodoindenes via Iodonium‐Induced Cyclization of Arylallenes.

AbstractA new chemo‐ and regioselective iodocarbocyclization of allenylarenes is presented.

Synthesis of Polysubstituted 2-Iodoindenes via Iodonium-Induced Cyclization of Arylallenes

A new chemoselective iodocarbocyclization of allenyl arenes was developed leading to the formation of 2-iodoindenes. In acetonitrile or nitromethane, electrophilic sources of iodine cations react selectively with the C2-C3 double bond of 1-arylallenes to give, after anti nucleophilic attack of the aromatic ring, 2-iodoindene products in high yields. Variations of the allenic skeletons revealed the high 5-endo selectivity and some competitive pathways of cyclization. Postfunctionalization reactions of the carbon-iodine bond, via Pd- and Cu-cross-couplings, gave rise to substituted indenes in good to excellent yields.

A guided-ion beam study of the collisions and reactions of I(+) and I2 (+) with I2.

Growing interest in developing and testing iodine Hall effect thrusters requires measurements of the cross sections of reactions that generate low energy plasma following discharge. Limited experimental and theoretical work necessitates a decisive experiment to elucidate the charge exchange and collision-induced dissociation channels. To this end, we have used guided-ion beam techniques to measure cross sections for both I(+) + I2 and I2 (+)+I2 collisions. We present total collision cross sections as well as collision-induced dissociation cross sections for center-of-mass collision energies ranging from 0.5 to 200 eV for molecular iodine cations. Similarly, we present total collision cross section and charge-exchange cross sections for atomic iodine cations for center-of-mass collision energies ranging from 0.67 to 167 eV. Time-of-flight measurements of the collision products allow determination of velocity distributions, which show evidence of complex formation of I3 (+) from the I(+) + I2 reaction at collision energies below 6 eV.

Coincidence ion imaging with a fast frame camera.

A new time- and position-sensitive particle detection system based on a fast frame CMOS (complementary metal-oxide semiconductors) camera is developed for coincidence ion imaging. The system is composed of four major components: a conventional microchannel plate/phosphor screen ion imager, a fast frame CMOS camera, a single anode photomultiplier tube (PMT), and a high-speed digitizer. The system collects the positional information of ions from a fast frame camera through real-time centroiding while the arrival times are obtained from the timing signal of a PMT processed by a high-speed digitizer. Multi-hit capability is achieved by correlating the intensity of ion spots on each camera frame with the peak heights on the corresponding time-of-flight spectrum of a PMT. Efficient computer algorithms are developed to process camera frames and digitizer traces in real-time at 1 kHz laser repetition rate. We demonstrate the capability of this system by detecting a momentum-matched co-fragments pair (methyl and iodine cations) produced from strong field dissociative double ionization of methyl iodide.

High yield conversion of methane to methyl bisulfate catalyzed by iodine cations.

Iodine in 2% oleum is an efficient catalyst for the selective, high yield oxidation of methane to methyl bisulfate.

Electrical measurements on the system tetrahydrofuran–polytetrahydrofuran–iodine

The ‘gel electrolyte’ composed of polytetrahydrofuran (POLYTHF), tetrahydrofuran (THF) and iodine has been prepared by heating near to the ceiling temperature the iodine solution in THF or by electrolyzing the iodine–THF solutions at room temperature. In both cases, the freshly prepared systems iodine–THF and POLYTHF–THF–iodine have been characterized by several electrical measurements in AC and DC current. The conductivity of these systems arises from the charge-transfer interaction between I 2 and THF, which leads to the formation of iodide ions and positively charged oxonium ions of THF. The oxonium ions could involve also the presence of complexed iodine cations, which could be responsible for THF polymerization. The electrolyzed system POLYTHF–THF–iodine acts as a concentration pile whose tension arises from the concentration gradients present in the electrolytic cell.

Purification and characterization of macrolide 2′-phosphotransferase type II from a strain ofEscherichia colihighly resistant to macrolide antibiotics

The resistance mechanism of Escherichia coli BM2506 to macrolides was found to be due to inactivation. Inactivated oleandomycin was identified as oleandomycin 2′-phosphate by thin-layer chromatography. A new type of macrolide-phosphorylating enzyme, macrolide 2′-phosphotransferase type II (MPH(2′)II), was detected, purified 95-fold and its enzymological properties investigated. MPH(2′)II was a constitutive intracellular enzyme which showed high levels of activity with both 14-member-ring and 16-member-ring macrolides. The optimum pH for the inactivation of oleandomycin was 8.2 and the optimum temperature of the reaction was 40°C. Enzyme activity was lost by heat treatment at 60°C for 1 min. The isoelectric point and Mr of the enzyme were 5.3 and 48 000, respectively. Purine nucleotides, such as ITP, GTP and ATP, were effective as cofactors in the inactivation of macrolides. An inhibitory effect of iodine, EDTA, or divalent cations on MPH(2′)II activity was observed.

Purification and characterization of macrolide 2′-phosphotransferase type II from a strain of Escherichia coli highly resistant to macrolide antibiotics

The resistance mechanism of Escherichia coli BM2506 to macrolides was found to be due to inactivation. Inactivated oleandomycin was identified as oleandomycin 2′-phosphate by thin-layer chromatography. A new type of macrolide-phosphorylating enzyme, macrolide 2′-phosphotransferase type II (MPH(2′)II), was detected, purified 95-fold and its enzymological properties investigated. MPH(2′)II was a constitutive intracellular enzyme which showed high levels of activity with both 14-member-ring and 16-member-ring macrolides. The optimum pH for the inactivation of oleandomycin was 8.2 and the optimum temperature of the reaction was 40°C. Enzyme activity was lost by heat treatment at 60°C for 1 min. The isoelectric point and M r of the enzyme were 5.3 and 48 000, respectively. Purine nucleotides, such as ITP, GTP and ATP, were effective as cofactors in the inactivation of macrolides. An inhibitory effect of iodine, EDTA, or divalent cations on MPH(2′)II activity was observed.

Polar trifluoromethylation reactions: the formation of bis(trifluoromethyl)iodine(III) compounds and trifluoromethyl iodine(III) cations and anions

IX3 (X = Cl, OCOCF3, ONO2) reacts with Cd(CF3)2 complexes or Bi(CF3)3 to yield the corresponding CF3IX2 derivatives. 19F nuclear magnetic resonance spectroscopic evidence is found for [I(CF3)2]+ and I(CF3)2X (X = Cl, OCOCF3) in the reactions of CF3IX2 with Cd(CF3)2 complexes. During the reaction of CF3IF2 and Hg(CF3)2 the new species I(CF3)2F and cis-[I(CF3)2F2]− are identified by nuclear magnetic resonance spectroscopy. The reactions proceed under polar conditions and can be accelerated by the addition of a Lewis acid such as BF3, B(OCOCF3)3, or Sb(V) compounds. Difluoromethyl compounds are formed as by-products. Key words: polar trifluoromethylations, trifluoromethyl iodine(III) compounds, difluoromethyl group formation.

Purification and characterization of macrolide 2'-phosphotransferase from a strain of Escherichia coli that is highly resistant to erythromycin

Macrolide 2'-phosphotransferase [MPH(2')] was purified 90-fold from an erythromycin-resistant strain of Escherichia coli, and its enzymatic properties were investigated. MPH(2') is an inducible intracellular enzyme which showed high levels of activity with 14-member-ring macrolides and extremely low levels with 16-member-ring macrolides. The optimum pH for inactivation of oleandomycin was 8.2, and the optimum temperature of the reaction was 40 degrees C. Enzyme activity was lost by heat treatment at 50 degrees C for 1 min. The isoelectric point and molecular weight of the enzyme were 5.3 and 34,000, respectively. Purine nucleotides, such as GTP, ITP, and ATP, were effective as cofactors in the inactivation of macrolides. Iodine, EDTA, or divalent cations inhibited MPH(2') activity.

Amide derivatives of poly(3,4-dimethylenepyrrolidine): Synthesis, characterization, and complexation studies

Improved synthesis of polydiallylamine provides ready access to an entire family of amide-functionalized polymers. Complete conversion to the acetamide derivative was attained under mild conditions. Formation of the formamide polymer required harsher conditions and did not give complete functionalization. The formamide polymer displayed typical polyelectrolyte behavior caused by residual amine units. Complexation with iodine and transition metal cations was strong as shown by UV, IR, and 13C-NMR evidence indicating potential of these polymers for trace metal recovery, waste water treatment, and antiseptic formulations.