Iodine Complex Research Articles

Synthesis and structure of cobalt(II) iodide bearing a bulky N-heterocyclic carbene ligand, and catalytic activation of bromoalkanes

A divalent cobalt iodine complex bearing 1,3-bis(mesityl)imidazol-2-ylidene and pyridine ligands was synthesized and its structure was determined. The cobalt center has a typical d7-tetrahedral geometry, as expected. Catalytic application of this cobalt complex with bromoalkanes and Grignard reagents demonstrated high-yield formation of alkenes as a result of β-hydrogen elimination; in sharp contrast, the activation of alkyl halides was not successful using the larger N-heterocyclic carbene ligand, 1,3-bis(2,6-diisopropyl-phenyl)imidazol-2-ylidene. In the presence of styrene, Heck reaction proceeded with trans selectivity. The reaction of a substrate containing a bromobenzyl moiety yielded a homocoupling product.

Halogen-bonded liquid crystals of 4-alkoxystilbazoles with molecular iodine: a very short halogen bond and unusual mesophase stability

Complexes of molecular iodine with alkoxystilbazoles are liquid crystals with unusually high mesophase stability, predicated on an intermolecular I···I contact. Attempts to prepare analogous complexes with bromine led to an unexpected electrophilic substitution product.

Flow Injection Spectrophotometric Analysis of Human Salivary α-Amylase Activity Using an Enzyme Degradation of Starch–Iodine Complexes in Flow Channel and Its Application to Human Stress Testing

Flow injection spectrophotometric analysis (FIA) of human salivary α-amylase was developed using an enzyme degradation reaction of starch-iodine complexes. In this proposed method, the salivary α-amylase, known as a human stress indicator, is directly and rapidly determined without any pretreatment. In this study, the optimum starch-iodine complexes (i.e., optimum molecular weight and amylase-amylopectin compounding ratio) were selected, and their rapid degradation in the flow channel was investigated to determine salivary amylase in the FIA system. The determination range of α-amylase was obtained from 0.25 to 5.0 kilo Novo unit per milliliter (KNU/mL), and these concentrations were equivalent to the real concentration of amylase in human saliva. The quantitative values obtained by this method were found to be highly reproducible with 1.6% (n=25) of the relative standard deviation for 1.0 KNU/mL. The detection limit (3σ) was 60 NU/mL. In addition, the method requires small volume of a sample (20 µL), and 30 samples was sequentially measured within one hour. Real human saliva collected before and after exercise was utilized to demonstrate the feasibility of human stress test and analytical performance of this approach.

Processing and Performance of Polymeric Transparent Conductive Composites

Recent advances in microelectronic and optoelectronic industries have spurred interest in the development of reticulate doped polymer films containing “metallic” charge transfer complexes. In this study, such reticulate doped polymer films were prepared by exposing solid solutions of bis(ethylenedioxy) tetrathiafulvalene (BEDO-TTF) in polycarbonate (PC) to iodine, forming conductive charge transfer complexes. The resulting films exhibited room temperature conductivities ranging from 6.33 to S cm−1. The colored iodine complexes in the film were reduced by cyclic voltammetry yielding conductive, colorless, transparent films. We were intrigued to examine the dielectric properties of BEDO-TTF in solid solution in PC prior to formation of the charge transfer complex as no such studies appear in the literature. Dielectric analysis (DEA) was used to probe relaxations in neat PC and BEDO-TTF/PC. BEDO-TTF plasticized the PC and decreased the glass transition temperature. Two secondary relaxations appeared in PC films, whereas the transitions merged in the BEDO-TTF/PC film. DEA also evidenced conductivity relaxations above 180°C which are characterized via electric modulus formalism and revealed that BEDO-TTF increased AC conductivity in PC.

Quantification of PVA hydrogel dissolution in water and bovine serum

Poly(vinyl alcohol) (PVA) hydrogel is a candidate biomaterial for orthopaedic applications such as cartilage resurfacing due to its viscoelastic nature, high water content, and biocompatibility. PVA is not assumed to be biodegradable; however, depending on the level of physical and/or chemical crosslinking it may illicit dissolution either during storage in water or during in vivo use when articulating against cartilage. In addition, gravimetric quantification of wear during pre-clinical wear testing of a PVA-based implant is challenging due to unpredictable changes in water content. Our aim was to develop a method to detect dissolved PVA in water and bovine serum; bovine serum is the lubricant of choice for pre-clinical wear testing of orthopaedic implants. We used iodine complexation to determine PVA concentration in solution using UV–Vis spectrophotometry. We further refined this method to determine the effects of PVA molecular weight and the presence of poly(ethylene glycol) (PEG) that may be used in the fabrication of the gel. In addition, we developed a method for determining the amount of PVA dissolved in bovine serum to quantify the extent of PVA dissolution during pre-clinical wear studies. We were able to detect PVA in solution with concentrations as low as 10−5 g/mL and created calibration curves for different solvents, i.e. water and bovine serum. Based on the calibrations, we quantified the dissolution behavior of PVA in water at 40 °C during a six month period and found that the dissolution from an untreated PVA hydrogel is 3 × 104 ppm, and could be lowered to 1 × 103 ppm by dehydration and/or annealing of the PVA hydrogel.

Ultrasound-treated starch: SEM and TEM imaging, and functional behaviour

Potato, wheat, corn and rice starch granules were suspended in water or ethanol and sonicated at frequency of 20 KHz and power 170 W for 30 min. The effect of ultrasonic treatment on starch structure was assessed on the basis of blue value (BV), A680/A545 ratio and λmax determinations. The results showed that modification of starches in both solvents led to the reduction of all parameters connected with the starch–iodine complex. However, depolymerization of starch was higher when it was sonicated in water than in ethanol (e.g. BVs for potato starch: native and sonicated in water and ethanol were equal, respectively, 0.306, 0.275, and 0.279). Starch granules were also observed under scanning and transmission electron microscopes. The main effects of ultrasonic action were cracks and depressions on the surface of granules, which were especially well seen in the case of potato and wheat starches. Ultrasonic treatment, especially in water, influenced functional properties of starch causing an increase of fat and water absorption, least gelling concentration (except potato starch), solubility and swelling power, and a decrease of starch paste viscosity. Effect of ultrasounds on clarity of pastes was rather small, except potato starch for which its value increased from 70.3 to 82.5% after sonication in water.

Spectroscopic Studies of the Complexation of Iodine with Antihistamine Drugs in Solvents of Varying Relative Permittivity

The interaction of oxatomide (OXA), azacyclonol (AZA) and chloropheniramine (ClPA) antihistamine drugs with iodine was studied spectrophotometrically in different solvents and at three different temperatures. The electronic, FT-IR, far-IR, and mass spectra of the resulting charge-transfer (CT) complexes were recorded, in addition to thermal analysis. The results obtained show that the stoichiometries of the reactions are all 1:1. The observed time dependence of the CT band and subsequent formation of \( {\text{I}}_{3}^{ - } \) in solution were related to the slow transformation of the initially formed 1:1 (donor: I2) outer complex to an inner complex (electron donor–acceptor), followed by a fast reaction of the inner complex with iodine to form a triiodide ion. The characteristic strong absorptions of \( {\text{I}}_{3}^{ - } \) are observed around 360 nm. The CT-complexes have the formulae [(OXA)I]+\( {\text{I}}_{3}^{ - } \), [(AZA)I]+\( {\text{I}}_{3}^{ - } \) and [(ClPA)I]+\( {\text{I}}_{3}^{ - } \). The formation constants (K), molar absorption coefficients (eCT), and thermodynamic parameters ΔH#, ΔS# and ΔG# of these interaction have been determined and discussed.

Cationic starch iodophores

AbstractCross‐linked cationic starches N‐(2‐hydroxyl)propyl‐3‐trimethyl ammonium starch chloride (CQS chloride), N‐(2‐hydroxyl)propyl‐3‐trimethyl ammonium starch iodide (CQS iodide), and N‐(2‐hydroxyl)propyl‐3‐trimethyl ammonium starch iodide–iodine (CQS triiodide) with the degree of substitution (DS) according to cationic groups from 0.04 to 0.62, as well as cross‐linked starch–iodine complexes were synthesized and tested as potential antibacterial agents. Cationic starch iodine derivatives were obtained during ion exchange reaction between CQS chloride and iodide or iodide–iodine anions in aqueous solutions. CQSDS≤0.3 chloride can form several types of iodine complexes, such as the blue amylose–iodine inclusion complex and ionic CQS+I−·(I2)m complex (m ≥ 1). The antibacterial activity of modified starches–iodine samples against different pathogenic bacterial cultures and contaminated water microorganisms was evaluated. CQS chloride and CQS iodide were found to be bacteriostatic. A strong antibacterial activity was characteristic of CQS triiodides in which molecular iodine is present in both ionic and inclusion complexes. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

The effect of the amphoteric properties of amino acids in the zwitterionic form on the structure of iodine complex compounds in aqueous solutions

The donor–acceptor interactions in three model systems: water–glycine (a), water–glycine–KI3 (b), water–glycine–KI3–LiCl–ethanol (c) were investigated by UV-, IR-spectroscopy, and the quantum-chemical DFT-B3PW91/midi method.UV- and IR spectrum data for the considered systems agree well with the results of calculations of the spectral characteristics of glycine cluster that consists of six molecules, and models that simulate the influence of the zwitterionic form of glycine on the structure of complex iodine compounds in the systems (b–c).Localization of a negative and a positive charge at the ends of a zwitterion makes it possible for a cluster of glycine zwitterions to be formed in water. In such cluster glycine molecules are located under each other so that the protonated group is always under (or above) the carboxy group. Glycine fragments are bound by strong hydrogen bonds and also by hydrogen bonding interactions with water molecules. In the water–glycine–KI3–LiCl–ethanol system the cluster of glycine zwitterions splits the iodide ion into I− and I2 (I− reacts with the protonated amino group, and I2 with the carboxy group). This creates conditions for the formation of an iodine complex compound, in which molecular iodine reveals the acceptor properties towards glycine, and the donor properties towards the LiCl–ethanol complex.

Functionalization of natural gum: An effective method to prepare iodine complex

To overcome the drawbacks associated with iodine e.g. insolubility in water, etc., it has been complexed with polymers that have the ability to bind it. In this study, gum arabic (GA), a natural gum was functionalized to introduce new reactive groups that can easily interact with small molecules followed by iodination in ethanol solution to prepare an iodine complex. The samples were characterized by FTIR, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The synthesized iodine complex was found reddish-brown in colour and stable at room temperature. The interaction of free available iodine with functionalized GA was also studied and established by UV–vis spectrophotometer. The amount of iodine released in water was measured by iodometric titration method and its value compared with the available iodine complex, polyvinylpyrrolidone–iodine complex. The antimicrobial activity of iodine complex was tested against Escherichia coli (Gram negative bacteria) and found to be effective against it.

Spectrophotometric determination of the formation constant of triiodide ions in aqueous-organic solvent or polymer mixed media both in absence and presence of a surfactant

The formation constant of triiodide ions from iodine–iodide equilibrium in aqueous-organic solvent or polymer mixed media have been determined spectrophotometrically at three different temperatures 20, 30 and 40°C. The organic solvents chosen for the study are ethylene glycol, 2-methoxy ethanol, and 2-ethoxy ethanol while the polymers include polyethylene glycol (PEG), hydroxypropyl cellulose (HPC) or polyethylene oxide (PEO). Effect of a surfactant on the formation of triiodide ions in the mixed media has also been investigated. Though presence of the organic solvents led to an increase in the triiodide formation except for 2-ethoxy ethanol mixed media at low percentage, the increase in presence of PEG or the other polymer mixed media even at very low percentage was much higher as compared to those in ethylene glycol or its homologues. The increase in the formation constant has been discussed in terms of changes in its solvation properties and the hydrophobic character of the mixed media besides the solvent dielectric effects. The sharp increase in triiodide formation in presence of the polymer under study suggests the possibility of iodine being present as triiodide or other higher polyiodides in the inclusion complexes of iodine with other polymers like starch or PVA. The decrease in the triiodide formation in presence of surfactant micelles may, however, be attributed to solubilization of iodine by the micelles. Iodine was found to be better solubilized in TX-100 micelles as compared to SDS micelles.

Controlled antiseptic release by alginate polymer films and beads

Biodegradable polymeric materials based on blending aqueous dispersions of natural polymer sodium alginate (NaAlg) and povidone iodine (PVPI) complex, which allow controlled antiseptic release, are presented. The developed materials are either free standing NaAlg films or Ca2+-cross-linked alginate beads, which properly combined with PVPI demonstrate antibacterial and antifungal activity, suitable for therapeutic applications, such as wound dressing. Glycerol was used as the plasticizing agent. Film morphology was studied by optical and atomic force microscopy. It was found that PVPI complex forms well dispersed circular micro-domains within the NaAlg matrix. The beads were fabricated by drop-wise immersion of NaAlg/PVPI/glycerol solutions into aqueous calcium chloride solutions to form calcium alginate beads encapsulating PVPI solution (CaAlg/PVPI). Controlled release of PVPI was possible when the composite films and beads were brought into direct contact with water or with moist media. Bactericidal and fungicidal properties of the materials were tested against Escherichia coli bacteria and Candida albicans fungi. The results indicated very efficient antibacterial and antifungal activity within 48h. Controlled release of PVPI into open wounds is highly desired in clinical applications to avoid toxic doses of iodine absorption by the wound. A wide variety of applications are envisioned such as external and internal wound dressings with controlled antiseptic release, hygienic and protective packaging films for medical devices, and polymer beads as water disinfectants.

Preparation, stability and antimicrobial activity of cationic cross-linked starch–iodine complexes

Cationic cross-linked starch (CCS)–iodine complexes containing different amounts of quaternary ammonium groups (different degrees of substitution (DS)) and iodine have been obtained by iodine adsorption on CCS from aqueous iodine potassium iodide solution. Equilibrium adsorption studies showed that with an increase of DS the amount of iodine adsorbed on CCS and the affinity of iodine to CCS increased linearly.The influences of the DS of CCS and the amount of adsorbed iodine on the stability of CCS–iodine complexes in a solution of 0.02M sodium acetate and reactivity toward l-tyrosine have been investigated. At the same DS, the stability of CCS–iodine complexes decreased with an increase of the amount of adsorbed iodine. With increasing the DS, the stability of CCS–iodine complexes increased. The iodine consumption in the reaction with l-tyrosine increased significantly with an increase of the amount of adsorbed iodine. The influence of DS on iodine consumption was lower and depended on the amount of adsorbed iodine. The antibacterial activity of CCS–iodine complexes against Bacillus cereus, Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli was determined by the broth-dilution and spread-plate methods. The obtained results have demonstrated that an appropriate selection of the CCS–iodine complex composition (the DS of CCS and the amount of adsorbed iodine) could ensure good antimicrobial properties by keeping a low concentration of free iodine in the system. The main advantage of using CCS–iodine complexes as antimicrobial agents is the biodegradability of the polymeric matrix.

Reduction of iodine complexed with sulfoxides and organophosphorus esters near 4.0 V vs. Li/Li+

It is accepted that the reduction of iodine species in non-aqueous solvents occurs through one-electron or two-electron processes below roughly 3.5 V vs. Li/Li+. In some iodine solutions, the molecular complexation of iodine with the organic solvent proceeded via a charge–transfer interaction. Reduction of iodine in non-aqueous solvents having SO or PO groups, as well as interactions of iodine molecules with these solvents, were studied. Iodine molecules associated with dimethyl sulfoxide (DMSO), tetramethylene sulfoxide (TMSO), and trimethyl phosphate (TMP) showed anomalous reduction above+1.0 V vs. NHE. We demonstrated the operation of lithium–iodine batteries using DMSO, TMSO and TMP near 4.0 V vs. Li/Li+.

Salt-independent thermophilic α-amylase from Bacillus megaterium VUMB109: An efficacy testing for preparation of maltooligosaccharides

An amylase (est. Mw 150kDa) was purified 27.39-folds from the culture broth of Bacillus megaterium VUMB109. The purified enzyme was not inhibited by p-chloromercuro benzoate and iodoacetamide (10mM), it rapidly decolorized the blue color of starch–iodine complex and produced α-anomeric products from starch hydrolysis, thus, it is an endo-attacking α-amylase. The enzymatic activity was not affected by any metal ion and EDTA, therefore, it is not in the class of metalloenzyme. The purified α-amylase showed higher affinity (Km=1.5μM; Vmax/Km=0.38 and Kcat/Km=2.5×106) to starch than other tested substrates like amylose, amylopectin and glycogen. Maltooligomer mixture with high proportion of maltopentaose (G5) and maltotriose (G3) was produced during hydrolysis of starch, amylopectin and amylose. It exhibited high degree of hydrolysis on raw potato starch than wheat, rice and corn starches. Thus the studied α-amylase could be exploited as a useful catalyst in the bioprocessing of maltooligomer mixture as food supplement for baby and aged people.

The mechanism of oxidative addition of iodine to a dimethylplatinum(II) complex

The oxidative addition of iodine to [PtMe2(bipy)], 1, occurs easily with trans stereochemistry to give trans-[PtI2Me2(bipy)], 2a, which then equilibrates slowly with cis-[PtI2Me2(bipy)], 2b. The structures of 2a and 2b were determined in a crystal containing both isomers and an additional iodine molecule. Low temperature NMR studies show that an intermediate charge transfer complex [PtMe2(I2)(bipy)], 3, or solvated iodine complex [PtMe2(I2)(S)(bipy)], S = solvent, may be formed in dichloromethane or acetone solution before formation of 2a. In dilute benzene solution, as monitored by UV–visible spectroscopy, the rearrangement of the intermediate complex to 2a followed first order kinetics, and exhibited a large negative entropy of activation, as expected if cleavage of the I–I bond to give an ionic intermediate [PtIMe2(bipy)]+I−, is rate determining. The overall reaction is slower in more polar solvents because, although the I–I bond is more easily cleaved to give [PtIMe2(bipy)(S)]+I−, the subsequent displacement of solvent, S, by iodide to give 2a is slow.

Physico‐chemical characterization of starches extracted from potatoes of the group Phureja

AbstractStarch was extracted from twenty‐four accessions of Group Phureja cultivated diploid potatoes, and from two commercial potato (Solanum tuberosum) varieties. Extracted starch samples were characterized and compared to industrial potato starch. Starch from Phureja generally exhibited smaller granule sizes and lower phosphorus content than starch from commercial potatoes. Amylose content and thermal properties (gelatinization temperature and enthalpy) were however in the same range for both groups. Starches from Phureja displayed very distinct pasting behavior from that of commercial potato. The former exhibited lower initial pasting viscosity but higher shear resistance. This may be related to lower starch granule size, causing lower swelling power and solubility. Iodine complexation results seem to indicate that phureja potatoes have higher proportion of amylopectin long chains. Phureja thus appears to be a promising new source of starch with specific physico‐chemical and functional properties intermediate between industrial potato and cereal starches.

Synthesis, spectroscopic, thermal and electrical conductivity studies of three charge transfer complexes formed between 1,3-di[(E)-1-(2-hydroxyphenyl)methylideneamino]-2-propanol Schiff base and different acceptors

Charge-transfer complexes (CTC) resulting from interactions of 1,3-di[(E)-1-(2-hydroxyphenyl) methylideneamino]-2-propanol Schiff base with some acceptors such as iodine (I2), bromine (Br2), and picric acid (PiA) have been isolated in the solid state in a chloroform solvent at room temperature. Based on elemental analysis, UV-Vis, infrared, and 1H NMR spectra, and thermogravimetric analysis (TG/DTG) of the solid CTC, [(Schiff)(I2)] (1), [(Schiff)(Br2)] complexes with a ratio of 1:1 and [(Schiff)(PiA)3] complexes with 1:3 have been prepared. In the picric acid complex, infrared and 1H NMR spectroscopic data indicate that the charge-transfer interaction is associated with a hydrogen bonding, whereas the iodine and bromine complexes were interpreted in terms of the formation of dative ion pairs [Schiff+, I 2 ∙− ] and [Schiff+, Br 2 ∙− ], respectively. Kinetic parameters were obtained for each stage of thermal degradation of the CT complexes using Coats–Redfern and Horowitz–Metzger methods. DC electrical properties as a function of temperature of these charge transfer complexes have been studied.

KINETIC STUDY OF CHARGE TRANSFER COMPLEXES OF IODINE WITH SOME CROWN ETHERS IN NONAQUEOUS SOLVENTS

ABSTRACT Charge-transfer complexation of iodine with 15-crown-5(15C5), dicyclohexyl-18-crown-6 (DC18C6), benzo-18-crown-6 (B18C6) and dibenzo-24-crown-8 (DB24C8) has been studied in chloroform (CHCl 3 ), Dichloromethane (DCM) and 1,2-dichloroethane (1,2-DCE) solutions at different time. The results indicated immediate formation of an electron donor–electron acceptor complex; which is followed by two relatively slow consecutive reactions. The pseudo-first-order rate constants for the formation of the ionic intermediate and the final product have been evaluated at 25 °C. The rate of formation of product has been measured as a function of time in different halocarbone solvents. The pseudo first order rate constants were evaluated from the absorbance- time data and found to vary in the order of 1,2-DCE >DCM >CHCl 3 . Keywords : Iodine; Charge transfer complex; Spectrophotometry; Kinetic; Crown ether. e-mail: nializadeh@yahoo.com INTRODUCTION Lariat ethers belong to special class of crown ethers with covalency linked side arm(s), which enhance the binding ability of crown ethers towards metal ions. Many investigations have been carried out on applications of crown ethers in several varieties of areas, such as: chemical analysis [1], in construction of ion-selective electrodes [2,3], solid phase in chromatography column [4]. Studies of crown ethers complexation in different solvents show that the thermodynamic and kinetic parameters and even the mechanism of the complexation processes are affected by the nature and composition of the solvent system [5,6]. Crown ethers are macrocyclic ethers known for their ability to form stable and selective inclusion complexes with many metal ions, including alkali and alkaline earth metal cations [7]. The stability of these complexes appears to be related to the macrocycles

In vitrosusceptibility ofStaphylococcus aureusstrains isolated from cows with subclinical mastitis to different antimicrobial agents

Sensitivity to commercial teat dips (nonoxinol-9 iodine complex and chlorhexidine digluconate) of 56 Staphylococcus (S.) aureus strains isolated from quarter milk samples of various German dairy herds treated with different teat dipping schemes was investigated in this study. The minimum inhibitory concentration was determined using a broth macrodilution method according to the German Veterinary Association guidelines. The main objective of the current study was to induce in vitro resistance induction of S. aureus to chemical disinfectants. Ten different strains were repeatedly passed ten times in growth media with sub-lethal concentrations of disinfectants. Nine strains showed a significant reduction in susceptibility to the nonoxinol-9 iodine complex but only one strain developed resistance to chlorhexidine digluconate. Stability of the acquired resistance was observed in all S. aureus strains adapted to the nonoxinol-9 iodine complex and chlorhexidine digluconate. In contrast, simultaneous resistance to different antibiotics was not observed in any of the ten investigated S. aureus strains. However, the isolates exhibited a high degree of resistance to penicillin G. Based on these results, resistance of S. aureus to chemical disinfectants may be more likely to develop if the chemicals are used at concentrations lower than that required for an optimal biocidal effect.