Iodine Cation 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.

Iodine(I) and Silver(I) Complexes Incorporating 3-Substituted Pyridines.

Building upon the first report of a 3-acetaminopyridine-based iodine(I) complex (1b) and its unexpected reactivity toward tBuOMe, several new 3-substituted iodine(I) complexes (2b-5b) have been synthesized. The iodine(I) complexes were synthesized from their analogous silver(I) complexes (2a-5a) via a silver(I) to iodine(I) cation exchange reaction, incorporating functionally related substituents as 3-acetaminopyridine in 1b; 3-acetylpyridine (3-Acpy; 2), 3-aminopyridine (3-NH2py; 3), and 3-dimethylaminopyridine (3-NMe2py; 4), as well as the strongly electron-withdrawing 3-cyanopyridine (3-CNpy; 5), to probe the possible limitations of iodine(I) complex formation. The individual properties of these rare examples of iodine(I) complexes incorporating 3-substituted pyridines are also compared to each other and contrasted to their 4-substituted counterparts which are more prevalent in the literature. While the reactivity of 1b toward etheric solvents could not be reproduced in any of the functionally related analogues synthesized herein, the reactivity of 1b was further expanded to a second etheric solvent. Reaction of bis(3-acetaminopyridine)iodine(I) (1b) and iPr2O gave [3-acetamido-1-(3-iodo-2-methylpentan-2-yl)pyridin-1-ium]PF6 (1d), which demonstrated potentially useful C-C and C-I bond formation under ambient conditions.

Total synthesis of (+)-asperazine A: A stereoselective domino dimerization

<h2>Summary</h2> The concise total synthesis of (+)-asperazine A, bearing unsymmetrical C3–N1′ linkage, was achieved stereoselectively via an unprecedented 4<i>N</i>-based cascade linkage. Umpolung from nucleophilic aniline (N¹) to electrophilic <i>N</i>-iodoaniline was implemented via oxidant iodine cation, released steadily by Ni-catalyzed keto/enol-tautomerism ring-opening of 1,3-dicarbonyl iodomethylcyclopropane. It triggered the condensation via <i>endo</i>-attack by enamine (N²) followed by the addition of aniline (N³) for the key quaternization at C3 position. The proton generated in the first cyclization initiates the isomerism from enamine (N⁴) to iminium, followed by the addition from aniline (N¹). The unsymmetrical dimer <b>4</b> was acquired via ring-reopening (N⁴) driven by the thermodynamic stability of indole aromatization. This domino process assembles four distinct "N"s in sequence to achieve the aniline-dihydro-pyrrole dimerization-isomerization, efficiently establishing a 22-membered library of asperazine A scaffolds. Control experiments and density functional theory calculations supported the electrophilic <i>N</i>-iodoaniline pathway and elucidated the highly <i>endo</i>-selective preference.

Pressure-induced phase transition and increase of oxygen-iodine coordination in magnesium iodate

The structural and vibrational behavior of $\mathrm{Mg}{({\mathrm{IO}}_{3})}_{2}$ under compression has been investigated via a combination of high-pressure (HP) synchrotron x-ray diffraction (XRD), Raman scattering, and infrared spectroscopy experiments as well as first-principles ab initio calculations. In this paper, we reveal that $\mathrm{Mg}{({\mathrm{IO}}_{3})}_{2}$ undergoes a pressure-induced phase transition between 7.5 and 9.7 GPa at ambient temperature from a monoclinic (space group $P{2}_{1}$) to a trigonal (space group P3) structure. $\mathrm{Mg}{({\mathrm{IO}}_{3})}_{2}$ also exhibits the gradual formation of additional bonds between iodine and oxygen atoms in neighboring ${\mathrm{IO}}_{3}^{\ensuremath{-}}$ units with increasing pressure, thereby increasing the oxygen-iodine coordination from 3 to 6. The bond formation under compression is a consequence of the existence of lone electron pairs on the iodine cation. To accommodate the additional bonds, the I--O bonds within the original ${[{\mathrm{IO}}_{3}]}^{\text{--}}$ trigonal pyramids increase in length under increasing compression. The appearance of additional Raman modes at 7.7 GPa and infrared modes at 9.6 GPa supports the phase transition observed in XRD experiments. Interestingly, the lengthening of I--O bonds causes a softening of several Raman modes under compression. We provide the crystal structure of the HP phase, the pressure-volume equations of state for both low- and HP phases, and the symmetry assignment of the Raman- and infrared-active modes of both phases.

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.

Characterization and ultrasound-assisted activation of Indonesian natural zeolite from Cikalong West Java Province

Natural zeolite activation from Cikalong, Tasikmalaya Regency, West Java Province, Indonesia, has been investigated experimentally. The activation process is carried out with a solution of sodium chloride (NaCl), which is utilized by ultrasound cavitation. The purposes of this research are to determine the effect of variation of process variables on the physical-chemical characteristics of zeolites. There were two variables studied, namely; sonication time and NaCl concentration. The study was conducted with the one factor at a time (OFAT) method, which is observing responses to changes in one variable at other constant. The range of sonication time of 20 - 60 minutes, while the NaCl concentration is 0.25N - 4N. Natural zeolites and activated zeolites are then characterized using SEM, XRF, FTIR, iod number, and cation exchange capacity to test their physical-chemical characteristics. Characterization results showed that activated natural zeolite had better quality than natural zeolite. The results of the SEM analysis showed the crystal type of natural zeolite minerals in the form of elongated crystals and others, which indicate the shape of quartz and mordenite. XRF analysis results prove that the elements of Ferrum, calcium, magnesium, and potassium are cations that can be exchanged with other metal elements. The results of the volumetric analysis showed an increase in iodine number and cation exchange capacity, along with an increase in sonication time and decreased along with the increasing of NaCl concentration. Based on these properties, zeolites have excellent performance as an adsorbent.

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.

Control of Charge Recombination in Perovskites by Oxidation State of Halide Vacancy.

Advances in perovskite solar cells require development of means to control and eliminate the nonradiative charge recombination pathway. Using ab initio nonadiabatic molecular dynamics, we demonstrate that charge recombination in perovskites is extremely sensitive to the charge state of the halogen vacancy. A missing iodine anion in MAPbI3 has almost no effect on charge losses. However, when the vacancy is reduced, the recombination is accelerated by up to 2 orders of magnitude. The acceleration occurs due to formation of a deep hole trap in the singly reduced vacancy, and both deep and shallow hole traps for the doubly reduced vacancy. The shallow hole involves a significant rearrangement of the Pb-I lattice, leading to a new chemical species: a Pb-Pb dimer bound by the vacancy charge, and under-coordinated iodine bonds. Hole trapping by the singly reduced iodide vacancy operates parallel to recombination of free electron and hole, accelerating charge losses by a factor of 5. The doubly reduced vacancy acts by a sequential mechanism-free hole, to shallow trap, to deep trap, to free electron, and accelerates the recombination by a factor of 50. The study demonstrates that iodine anion vacancy can be beneficial to the performance, because it causes minor changes to the charge carrier lifetime, while increasing charge carrier concentration. However, the neutral iodine and iodine cation vacancies should be strongly avoided. The detailed insights into the charge carrier trapping and relaxation mechanisms provided by the simulation are essential for development of efficient photocatalytic, photovoltaic, optoelectronic and related devices.

A rechargeable iodine-carbon battery that exploits ion intercalation and iodine redox chemistry

Graphitic carbons have been used as conductive supports for developing rechargeable batteries. However, the classic ion intercalation in graphitic carbon has yet to be coupled with extrinsic redox reactions to develop rechargeable batteries. Herein, we demonstrate the preparation of a free-standing, flexible nitrogen and phosphorus co-doped hierarchically porous graphitic carbon for iodine loading by pyrolysis of polyaniline coated cellulose wiper. We find that heteroatoms could provide additional defect sites for encapsulating iodine while the porous carbon skeleton facilitates redox reactions of iodine and ion intercalation. The combination of ion intercalation with redox reactions of iodine allows for developing rechargeable iodine–carbon batteries free from the unsafe lithium/sodium metals, and hence eliminates the long-standing safety issue. The unique architecture of the hierarchically porous graphitic carbon with heteroatom doping not only provides suitable spaces for both iodine encapsulation and cation intercalation but also generates efficient electronic and ionic transport pathways, thus leading to enhanced performance.

A 2,2'-bipyridine coordination complex of [ICl₂]⁺.

The formation of a new class of I(III) compound is reported; an N,N' chelated iodine cation ([bpy-ICl2](+); bpy = 2,2'-bipyridine). The complex is obtained as an [ICl4](-) salt and is formed via simple reaction of bpy with ICl3. The compound is relatively unstable, but may be stored as a solid and is shown to be competent in the oxidative chlorination of Au(I)-NHC complexes.

Electrophilic Carbocyclization of Aryl Propargylic Alcohols: A Facile Synthesis of Diiodinated Carbocycles and Heterocycles

Diiodinated carbocycles and oxygen heterocycles can be readily synthesized by electrophilic carbocyclization of aryl propargylic alcohols in moderate to good yields under mild conditions. The resulting diiodide can be further exploited by subsequent oxidizing and coupling reactions. Both the iodine anion and cation generated from I(2) are used effectively. The presence of a trace amount of water is essential for this electrophilic cyclization.

Catalytic hydroxylation of [Closo-B12H12]2−—adaptation of the Periana reaction to a polyhedral borane

Per-B-hydroxylation of a polyhedral borane anion has been demonstrated by the catalytic hydroxylation of icosahedral [closo-B(12)H(12)](2-) using soft electrophiles such as platinum group metal catalysts or iodine cation. A new route to [closo-B(12)(OH)(12)](2-) from [closo-B(12)H(12)](2-) without the use of H(2)O(2) oxidant provides an alternative hydroxylation process.

A Novel Iodine‐Promoted Tandem Cyclization: An Efficient Synthesis of Substituted 3,4‐Diiodoheterocyclic Compounds

Iodine sets allenes ringing: A novel iodine-promoted tandem cyclization reaction of but-2-yne-1,4-diol and 4-aminobut-2-yn-1-ol derivatives leading to substituted 3,4-diiodoheterocyclic compounds has been developed (see scheme). In this reaction, a trace amount of water is needed. Both the iodine anion and cation generated from I2 are used in the reaction. The resulting iodides can then be used in palladium-catalyzed coupling reactions. The reaction conditions are metal-free, mild, and environmentally friendly.

Photocatalytic properties and electronic structures of iodine-doped TiO 2 nanotubes

In order to improve the photocatalytic activity, iodine cation and anion were successfully doped into TiO 2 nanotubes by using cathode reduction and anodization, as evidenced from X-ray photoelectron spectroscopy results. Field-emission scanning electron microscopy images suggest that electrochemical method is efficient to dope nonmentals and advantageous to keep the morphological integrity of TiO 2 nanotubes. I-doped TiO 2 nanotubes show the high photocurrent and photocatalytic activity under UV–vis irradiation. First-principle calculation results indicate that some new bands appear in the band gaps and are beneficial for photogenerated carriers migration. For cation-doped TiO 2, a strong interaction between the electrons in I 5p orbitals and in Ti 3d orbitals occurred and results in the CB shifting downwards. The band potentials of cation-doped TiO 2 shift downwards to a larger extent and thus the VB has a stronger oxidative power than undoped and anion-doped TiO 2.

Features of mamona oil of cultivar BRS -188 Paraguaçu

The objective of this study was to determine the physico-chemical and physical oil from the castor bean cultivar BRS - 188 Paraguacu. For characterization of the physical and chemical analyses were made of moisture, acidity, peroxide, iodine and saponifi cation. In the physical characterization were made determinations of density, viscosity at -15, -10, -5, 0, 20, 40, 60, 80 ° C and the point of freezing obtained by the curve of freezing temperature of -196 ° C. The water content was found acceptable, the acidity of the commercial classifi ed as type 1, the iodine establish that it as half-dried, the refraction presented their quality, confi rmed by the peroxide below the ceiling, presenting its potential for industry of cosmetics. The density and viscosity decreased with the increase in temperature and the freezing point occurred a little over -90 ° C.

Formation of impurity bands in iodine cation substitutionally doped TiO 2 and its effects on photoresponse and photogenerated carriers

First-principles calculations based on the plane-wave pseudopotential (PWP) method were performed to investigate the electronic structure of iodine cation substitutionally doped anatase TiO 2 (referred to as I s TiO 2). A 2 × 2 × 1 anatase supercell, in which one Ti atom was substituted by one iodine atom, was constructed for calculations. The calculated results reveal that iodine dopant contributes part of its 5 s states to form one isolated impurity band in band gap and part of its 5 p states to form some impurity bands at the bottom of conductive bands. The visible light response of I s TiO 2 should be the consequence of the excitation between the two types of impurity bands (2.77 eV, about 450 nm). According to the distribution of impurity states, iodine dopant is considered to serve as a recombination center or an efficient trap for photogenerated carriers. This deduction was partly approved by water photosplitting under visible light irradiation.

Electronic structures and reactivities of iodinating agents in the gas phase and in solutions: A density functional study

The electronic and spatial structures of a broad spectrum of neutral compounds with X-Hal (X = N, O, Cl; Hal = Cl, Br, I) bonds and their protonated forms and of different electronic states of triiodide cation, I3 +, were determined from density functional B3LYP/6 311G* quantum chemical calculations. The effects of the structure of these compounds on the parameters of electrophilic reactivity were revealed and the thermochemical characteristics of homolytic and heterolytic X-Hal bond dissociation and of iodine transfer in hydroxyl-containing solvents were calculated. Due to low homolytic bond dissociation energies of X-I, the formation of molecular iodine and triiodide cation I3 + becomes thermodynamically favorable and the cation should act as iodinating agent alternative to acylhypoiodites and N-iodoimides. The solvation effects of MeOH and CH2Cl2 on the X-Hal bond homolysis and heterolysis were determined using the PCM model.

Optical properties of bis-(2,4,6-trimethylpyridine)iodine(I) cation: absorption and emission

With regard to its electronic structure, the cation Icoll 2 + (coll = collidine or 2,4,6-trimethylpyridine) is viewed as a coordination compound of iodine(I) with a p 4 electron configuration. The lowest-energy excited state of Icoll 2 + is suggested to be a ππ * collidine intraligand (IL) triplet which appears in absorption ( λ max=332 nm, ε=250) and emission ( λ max=405 nm, φ=0.001, τ∼90 ns). Owing to the heavy-atom effect of iodine this phosphorescence occurs at r.t. The longest-wavelength pp absorption is apparently obscured by the intense spin-allowed IL band at λ max=268 nm.

Iodine and disinfection: theoretical study on mode of action, efficiency, stability, and analytical aspects in the aqueous system.

Although they have been in use for nearly 170 years, the mode of action of iodine-based disinfectants is not yet clearly understood, as is manifested, for example, in diverging judgements about the relevance of the individual iodine species. Although studies based on calculated equilibrium concentrations in pure iodine solutions have already been done, there is a lack of knowledge about iodine solutions in the presence of additional iodide which would be of intrinsic importance for disinfection practice. Therefore, a re-calculation was undertaken considering variations of this parameter in the pH range 0-14. The presented calculations concern fresh iodine solutions not affected by disproportionation (iodate formation) and provide information about the equilibrium concentrations of the species I, I2, I3, I5-, I6(2-), HOI, O1-, HI2O-, IO2- and H2OI+. Additional iodide and the pH value have a very pronounced influence on the individual equilibrium concentrations (several powers of ten); hence, conditions can be indicated where the number of species of virtual importance is drastically reduced. In the most common case with iodine in the presence of additional iodide at pH < 6, only I-, I2 and I3- play a role. In the absence of additional iodide, at pH 8-9 and at high dilution (c(I2) < 10(-5) M), on the other hand, HOI accounts for over 90% of the oxidation capacity. At high iodide concentration (e.g., Lugol's solution) the species I5- and I6(2-) make up 8.2% of the oxidation capacity. The iodine cation H2OI+, frequently quoted as an active agent in disinfection, is without any relevance under the conditions occurring in practice, as are IO- and HI2O- which become important only at pH > 10. The stability problem (i.e. rate of iodate formation) arising at pH > 6 can be reduced to hypoiodous acid, as manifested in the simple rate law d[IO3]/dt = 0.25 [HOI]3/[H+] which allows an estimation of stability under weakly alkaline conditions. The results of this study allow us to deduce general qualities of aqueous iodine solutions, such as reactivity, stability, and analytical aspects, and to estimate major disinfection-orientated properties such as microbicidal activity, irritation, and incorporation effects. Though the calculations consider primarily preparations devoid of polymeric organic compounds capable of complexing iodine species, the results can be largely transferred to iodophoric preparations.

Structural effects on the iodine cation basicity of organic bases in the gas phase

Structural effects on the iodine cation basicity of organic bases in the gas phase