Molecular Iodine Research Articles

Reaction mechanism of decomposition of phosphine-bridged Pd(I)-Pd(I) dimers into Pd(II) monomers by molecular iodine

Mechanistic studies on decomposition of Pd(I)-Pd(I) dimers via Pd(II)-Pd(II) intermediates into Pd(II) monomers were performed by the reaction of [Pd2I2(dppm)2] (1) (dppm = bis(diphenylphosphino)methane) and [Pd2(p3)2](BF4)2 (2) (p3 = bis(diphenylphosphinoethyl)phenylphosphine) with molecular iodine, where dppm and p3 are bridging “short-bite” bidentate and “regular-bite” tridentate phosphine ligands, respectively. It was previously reported that the decomposition rate constant for the Pd(II)-Pd(II) intermediate of 1, [Pd2I4(dppm)2], to give the monomeric [PdI2(dppm)] was independent of the I2 concentration under the pseudo-first-order conditions with excess I2. On the other hand, we have found that the decomposition was retarded by an addition of I2, which reduces the nucleophilicity and donating ability of the iodido ligand by association of I2 to give the I-–I2 interaction. The activation parameters of the decomposition with a large negative ΔS‡ value similar to substitution reactions of usual four-coordinate squarer-planar palladium(II) complexes suggested the associative intramolecular substitution mechanism. The oxidation of 2 to the Pd(II)-Pd(II) intermediate, [Pd2I2(p3)2]2+, and its decomposition into the monomeric [PdI(p3)]+ by I2 were also investigated kinetically and both reactions were also retarded with an increase in the I2 concentration. From the activation parameters of the intramolecular decomposition, it was indicated that the associative character was reduced because of breakdown of the sterically restricted framework. Such different properties in solution of 1 and 2 were applied complementarily to Heck-type C–C coupling reaction and dehalogenation reaction of aryl halide, respectively.

Precision spectroscopy of iodine absorption lines near the 1S0-3P2 transition of Yb atoms at 507 nm

We performed Doppler-free spectroscopy on the P(40)52-0 and P(52)53-0 lines of molecular iodine (127I2) near the 1S0-3P2 metastable transition of Yb at 507 nm. The frequency instability of an external-cavity diode laser locked to the observed hyperfine transitions of the 127I2 lines reached a level below 1.0 × 10−12, at the average time τ of the measurement of >10 s. The absolute frequency of the laser locked to the hyperfine transitions was measured with an uncertainty of 8 kHz (fractionally 1.4 × 10−11) using an optical frequency comb. The hyperfine transition intervals were fitted to a four-term Hamiltonian to validate the measurements and calculate the hyperfine constants of the iodine lines. The observed 30 hyperfine transitions of the P(40)52-0 and P(52)53-0 lines of 127I2 can be used as optical frequency references to investigate the 1S0-3P2 transition of Yb atoms.

Numerical and experimental research on the performance of an iodine-fed Hall thruster

The development of space technology brings about an increasing demand for electric thrusters. Iodine has been considered a feasible alternative to resource-critical xenon. Numerical and experimental methods are used to study the performance of the iodine-fed Hall thruster. The ionization and acceleration characteristics are investigated in the simulation with a particle-in-cell/Monte Carlo collision model. Different from previous simulations of noble gas, the dissociation equation of molecular iodine is added to the code for propulsive performance evaluation. A dissociation region in the discharge chamber is presented and described in detail. The propulsive performances of the iodine-fed Hall thruster are calculated by the plasma parameters. Meanwhile, the experimental measurements are finished for model verification and performance comparison at nominal conditions. The measured data is slightly lower than the simulated data. The error between them is about 1.65%. The reasons are analyzed and discussed. Then, the performance is predicted and measured using this simulated and experimental method within 20% mass flow rate and 10% anode voltage fluctuations relative to the nominal condition. Further optimizations of the simulation and experiment are in progress.

Synthesis of [1]Benzothieno[3,2-b][1]benzothiophenes through Iodine-Mediated Sulfur Insertion Reaction.

[1]Benzothieno[3,2-b][1]benzothiophenes (BTBTs) are important molecules that have been extensively studied as high-performance organic field-effect transistors (OFETs). Therefore, it is important to develop a simple synthetic method for these molecules. In this paper, a synthetic method to obtain the BTBTs from 2-arylbenzo[b]thiophenes and elemental sulfur, in which two C-S bonds are formed at once, is described. In this method, molecular iodine plays a very important role as an additive. The role of iodine is discussed in the presumed reaction pathways.

Iodine-Mediated δ-Amination of sp3 C-H Bonds.

We present a direct δ-amination reaction of sp3 C-H bonds, employing molecular iodine (I2) as the sole oxidant under transition-metal-free conditions. This remote C-H functionalization approach is operationally simple and provides facile, efficient access to pyrrolidines and related heterocyclic derivatives from readily accessible substrates.

An emerging strategy towards the iodine catalyzed synthesis of Streptindole and its derivatives in water medium.

In this study, we propose an alternative metal‐free methodology for the synthesis of Streptindole and its derivatives. This approach employs economically viable and easily handled molecular iodine (I2) as the catalyst in an aqueous medium. The method demonstrates remarkable tolerance towards a diverse array of functional groups. The versatility of the developed protocol is highlighted by its application in the efficient total syntheses of the alkaloid natural products, Streptindole and Arsindoline B accomplished in a single step from indole. Furthermore, the methodology is also useful for the synthesis of pharmaceutically significant compounds, specifically anti‐TMV agents (5c, 5d, and 5e) and an anticancer agent (5f). Control experiments have been carried out to study the plausible catalytic cycle by finding the key intermediates. The experimental findings support the mechanistic pathway involving halogen bond activation in molecular iodine catalysis

Iodide manipulation using zinc additives for efficient perovskite solar minimodules

Interstitial iodides are the most critical type of defects in perovskite solar cells that limits efficiency and stability. They can be generated during solution, film, and device processing, further accelerating degradation. Herein, we find that introducing a small amount of a zinc salt- zinc trifluoromethane sulfonate (Zn(OOSCF3)2) in the perovskite solution can control the iodide defects in resultant perovskites ink and films. CF3SOO̶ vigorously suppresses molecular iodine formation in the perovskites by reducing it to iodide. At the same time, zinc cations can precipitate excess iodide by forming a Zn-Amine complex so that the iodide interstitials in the resultant perovskite films can be suppressed. The perovskite films using these additives show improved photoluminescence quantum efficiency and reduce deep trap density, despite zinc cations reducing the perovskite grain size and iodide interstitials. The zinc additives facilitate the formation of more uniform perovskite films on large-area substrates (78-108 cm2) in the blade-coating process. Fabricated minimodules show power conversion efficiencies of 19.60% and 19.21% with aperture areas of 84 and 108 cm2, respectively, as certified by National Renewable Energy Laboratory (NREL), the highest efficiency certified for minimodules of these sizes.

Laser frequency stabilization by modulation transfer spectroscopy and balanced detection of molecular iodine for laser cooling of 174Yb.

We report laser frequency stabilization by the combination of modulation transfer spectroscopy and balanced detection of a relatively weak hyperfine transition of the R(158)25-0 line of molecular iodine (127I2), which is used as a new frequency reference for laser trapping and cooling of 174Yb on the 1S0 - 3P1 transition. The atomic cloud is characterized by time-of-flight measurements, and an on-resonance optical depth of up to 47 is obtained. We show laser noise reduction and characterize the short-term laser frequency instability by the Allan deviation of the laser fractional frequency. The minimum measured value is 3.9 ×10-13 at 0.17 s of averaging time.

Adsorption of molecular iodine and alkyl iodides from spent-nuclear-fuel-reprocessing off-gas using reduced silver mordenite

Radioactive iodine is a hazardous byproduct of spent-nuclear-fuel reprocessing that must be removed from the off-gas stream before it can be discharged. Reduced silver mordenite (Ag0Z) is currently the baseline material for iodine capture in the U.S. Although the performance characteristics and capture mechanisms of I2 and CH3I have been established, similar investigations into long-chain organic iodides have yet to be performed. In this study, thin beds of Ag0Z were loaded with I2, CH3I, C4H9I, and C12H25I (5 ppm to 50 ppm) carried in a dry air stream at 150 °C. The maximum iodine capacity was 105 ± 5 mg I/g Ag0Z for all species. Saturated Ag0Z samples were characterized using scanning electron microscopy, X-ray fluorescence, X-ray photoelectron spectroscopy, diffuse reflectance UV–visible spectroscopy, pair distribution function analysis, and thermogravimetric analysis. Near-complete Ag utilization and similar physical/chemical properties were observed for all samples. Through a comparison with previous studies and an investigation of aged Ag0Z, we propose that iodine species react with Ag+ at exchange sites, forming α-AgI within the mordenite channels, and with surface Ag0 nanoparticles, yielding β-/γ-AgI. The available Ag sites in the interior (Ag+) and exterior (Ag0) of mordenite determine the adsorption capacity since α-AgI formation is limited by the total pore volume. Potential iodine uptake routes were summarized for aging and non-aging environments. A scalable predictive model was implemented for deep-bed iodine removal, and predictions were in good agreement with experimental data. Sensitivity analysis suggests that iodine uptake kinetics is governed by pore diffusion.

A facile double moving redox boundary model for visual electrophoresis titration of ascorbic acid.

In this work, we proposed a double moving redox boundary (MROB) model to realize the colorless analyte electrophoresis titration (ET) by the two steps of the redox reaction. Single MROB has been proposed for the development of ET sensing (Analyst, 2013, 138, 1137. ACS Sensor, 2019, 4, 126.), and faces great challenges in detecting the analyte without color change during redox reaction. Herein, a novel model of double-MROB electrophoresis, including its mechanisms, equations, and procedures, was developed for titration by using ascorbic acid as a model analyte. The first MROB was created with ferric iron (Fe3+) and iodide ion (I-) in which Fe3+ was reduced as Fe2+ and I- was oxidized as molecular iodine (I2) used as an indicator of visible MROB due to blue starch-iodine complex. The second boundary was then formed between the molecular iodine and model analyte of ascorbic acid. Under given conditions, there was a quantitative relationship between velocity of MROB (VMROB(ii)) and ascorbic acid concentration (CVit C) in the double-MROB system (1/VMROB(ii)=0.6502CVit C+4.5165, and R=0.9939). The relevant relative standard deviation values of intraday and inter-day were less than ∼5.55% and ∼6.64%, respectively. Finally, the titration of ascorbic acid in chewable vitamin C tablets was performed by the developed method, the titration results agreed with those via the classic iodometric titration. All the results briefly demonstrated the validity of the double MROB model, in which Vit C was used as a model analyte. The developed method had potential use in quantitative analysis of redox-active species in biomedical samples.

Tunable Regioselective Allylic Alkylation/Iodination of Imidazoheterocycles in Water.

The switchable roles of allylic alcohol and molecular iodine as reagents and catalysts have been demonstrated in the regioselective allylic alkylation and iodination of imidazoheterocycles employing the mixture of allylic alcohol-I2. First, we have explored the catalytic activity of iodine for the allylation of imidazoheterocycles using allylic alcohol in an aqueous medium. The allylation of a library of imidazoheterocycles and other electron-rich heterocycles like indole, pyrazole, 4-hydroxy coumarin, and 6-amino uracil has been achieved by employing this methodology. The efficiency of the I2 catalyst for N-allylation of azoles has also been demonstrated. Next, we have shown that this mixture of allylic alcohol and I2 could be beneficial for the iodination of imidazoheterocycles under room temperature. Mechanistic studies indicate that the activation of allylic alcohol by molecular iodine took place probably through halogen bonding, and NMR studies show that the reaction did not proceed through allylic ether formation.

Structures and stability of I2 and ICl complexes with pyridine: Ab initio and DFT study.

Theoretical investigation of thermodynamic stability and bonding features of possible isomers of the molecular and ionic complexes of pyridine with molecular iodine and iodine monochloride IX (X = I,Cl) is presented. M06-2X DFT functional is found to provide bond distances and dissociation energies which are close to those obtained at high-level ab initio CCSD(T)/aug-cc-pvtz//CCSD/aug-cc-pvtz benchmark computations for the most stable isomers, formed via donation of a lone pair of nitrogen atom of pyridine to the iodine atom. These isomers are by 23-33 kJ mol-1 (in case of I2) and by 39-56 kJ mol-1 (in case of ICl) more stable than other molecular complexes. T-shaped π-σ* bonded isomers turn out to be energetically comparable with van der Waals bound compounds. Among the ionic isomers, structures featuring [IPy2]+ cation with I3 - or ICl2 - counterions are more stable. Oligomerization favors ionic isomers starting from the tetrameric clusters of the composition (IX)4Py4.

Luminescent monitoring the state of dichroic complexes in polaroids based on polyvinyl alcohol

In this work, to control the content of dichroic complexes in film polarizers based on polyvinyl alcohol, a luminescent technique is proposed that allows us to estimate: the ratio of molecular and paired iodine centers in H-type polarizers at T = 4.2 K; of dichroic complexes caused by molecular and aggregated forms of the dye in L-type polarizers at T = 300 K. The use of this technique will make it possible in the future to establish the dependence of the properties of polarizers on the structure of dichroic complexes, not only in H-type or L-type film polarizers but also in mixed (H + L)-type polarizers, to create polarizers of various spectral ranges.

The CCL-K11 ongoing key comparison. Final report for 2023

Main textSix lasers from six national metrological institutes (NMIs) were compared in the year 2023 as part of the CCL-K11 ongoing key comparison, initiated by the 13th meeting of the Comité Consultative des Longueurs (CCL) in 2007. The absolute frequency of theses lasers was measured in three different node laboratories following the technical protocol for CCL-K11. All are practical realisations of the definition of the metre according to the MeP for the definition of the metre.Five standards are He-Ne-lasers stabilized on the f component of the R(127) 11-5 transitions of molecular iodine 127I2 with a wavelength of approximately 633 nm.The sixth standard is a fibre laser stabilized to the P(16) (ν1+ν3) transition of molecular acetylene 13C2H2 with a wavelength of approximately 1542 nm. The technical protocol was deliberately designed to accommodate artefacts of different wavelengths in a common framework.The results of these measurements are compiled in the present report. The comparison reports, as communicated by each participant, are included in the main document.This document constitutes the thirteenth final report for the ongoing key comparison CCL-K11.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCL, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

The crucial and versatile roles of bacteria in global biogeochemical cycling of iodine

Abstract Iodine (I) is a trace element with health and environmental significance. Iodate (IO3-), iodide (I-) and organic iodine (org-I) are the major species of iodine that exist in the environment. Dissimilatory IO3--reducing bacteria reduce IO3- to I- directly under anoxic conditions via their IO3- reductases that include periplasmic iodate reductase IdrABP1P2, extracellular DMSO reductase DmsEFAB and metal reductase MtrCAB. IdrAB and DmsEFAB reduce IO3- to hypoiodous acid (HIO) and H2O2. The reaction intermediate HIO is proposed to be disproportionated abiotically into I- and IO3- at a ratio of 2:1. The H2O2 is reduced to H2O by IdrP1P2 and MtrCAB as a detoxification mechanism. Additionally, dissimilatory Fe(III)- and sulfate-reducing bacteria reduce IO3- to I- directly via their IO3- reductases and indirectly via the reduction products Fe(II) and sulfide in the presence of Fe(III) and sulfate, respectively. I--oxidizing bacteria oxidize I- to molecular iodine (I2) directly under oxic conditions via their extracellular multicopper iodide oxidases IoxAC. In addition to I2, a variety of org-I compounds are also produced by the I--oxidizing bacteria during I- oxidation. Furthermore, ammonia-oxidizing bacteria oxidize I- to IO3- directly under oxic conditions, probably via their intracellular ammonia-oxidizing enzymes. Many bacteria produce extracellular reactive oxygen species that can oxidize I- to triiodide (I3-). Bacteria also accumulate I- during which I- is oxidized to HIO by their extracellular vanadium iodoperoxidases. The HIO is then transported into the bacterial cells. Finally, bacteria methylate I- to org-I CH3I, probably via their methyltransferases. Thus, bacteria play crucial and versatile roles in the global biogeochemical cycling of iodine via IO3- reduction, I- oxidation and accumulation and org-I formation.

Real-time dynamics of vibronic wavepackets within Rydberg and ion-pair states of molecular iodine.

Real-time dynamics of vibrationally and electronically excited I2 molecules has been investigated experimentally using the pump-probe technique. A 2-photon excitation was performed either at 269 nm or 266 nm. An electronic and vibrational wavepacket was built as coherent superposition of a few (269 nm excitation) or many (266 nm excitation) Rydberg states of the and series partly coupled with ion-pair states. The probe operated by ionisation or photodetachement. The energy and angular distribution of the resulting photoelectrons, I+ photocations and I- photoanions were monitored. During the dynamics that is turned on by the pump excitation, the wavepacket splits and explores a variety of electronic states of Rydberg and ion-pair character. The experimental results were complemented by molecular dynamics calculations. This provided invaluable information to identify wavepacket motion along ion-pair potential energy curves.

Investigating the processes and rate of iodide ion and compound oxidation in subterranean hydrothermal waters

Studies using physico-chemical methods have been conducted to evaluate the oxidative characteristics of various reagents for the technological extraction of iodine from groundwater and sufficient data have been obtained. According to the research results, iodine is predominantly present in the form of molecular iodine (85.6%), iodide ions (3.2%), iodate (9.1%) and iodine chloride (2.1%) were detected. Preserving all forms of iodine in solution at the same time is possible only in an alkaline environment, where the oxidizing properties of iodates are sharply reduced. This information is important for choosing a method for purifying iodine paste using various physical and chemical methods. From experiments in research, the beginning of the release of elemental iodine was noted at a voltage above 0.250 V and a pH of 5-3 or less. In this case, the solution usually becomes dark red with a reddish or brownish tint, which indicates the formation of complex compounds of iodine with other ions in the solution.

A comparison of molecular iodine evolution on the chemistry of lead and tin perovskites

The development of new strategies which target simultaneous adsorption of corrosive iodine (I2), facilitate reduction into I− and reintroduction within the crystal lattice are highly promising for addressing the longevity of perovskite-based devices.

Unveiling the significance of adduct formation between thiocarbonyl Lewis donors and diiodine for the structural organization of rhodanine-based small molecule semiconductors

Rhodanine vinyl bithiophene was reacted with molecular iodine to give a 1 : 1 stoichiometric charge-transfer adduct whose crystals, structurally and spectroscopically characterized, exhibited remarkable stability and enhanced conductivity.

Iodine Promotes Glucose Uptake through Akt Phosphorylation and Glut-4 in Adipocytes, but Higher Doses Induce Cytotoxic Effects in Pancreatic Beta Cells.

Epidemiological clinical reports have shown an association between iodine excess with diabetes mellitus type 2 and higher blood glucose. However, the relationship between iodine, the pancreas, adipose tissue, and glucose transport is unclear. The goal of this study was to analyze the effect of iodine concentrations (in Lugol solution) on glucose transport, insulin secretion, and its cytotoxic effects in mature 3T3-L1 adipocytes and pancreatic beta-TC-6 cells. Fibroblast 3T3-L1, mature adipocytes, and pancreatic beta-TC-6 cells were treated with 1 to 1000 µM of Lugol (molecular iodine dissolved in potassium iodide) for 30 min to 24 h for an MTT proliferation assay. Then, glucose uptake was measured with the fluorescent analog 2-NBDG, insulin receptor, Akt protein, p-Akt (ser-473), PPAR-gamma, and Glut4 by immunoblot; furthermore, insulin, alpha-amylase, oxidative stress, and caspase-3 activation were measured by colorimetric methods and the expression of markers of the apoptotic pathway at the RNAm level by real-time PCR. Low concentrations of Lugol significantly induce insulin secretion and glucose uptake in pancreatic beta-TC-6 cells, and in adipose cells, iodine-induced glucose uptake depends on the serine-473 phosphorylation of Akt (p-Akt) and Glut4. Higher doses of Lugol lead to cell growth inhibition, oxidative stress, and cellular apoptosis dependent on PPAR-gamma, Bax mRNA expression, and caspase-3 activation in pancreatic beta-TC-6 cells. Iodine could influence glucose metabolism in mature adipocytes and insulin secretion in pancreatic beta cells, but excessive levels may cause cytotoxic damage to pancreatic beta cells.