Charge Transfer Complexes Of Iodine Research Articles

A comparison of charge-transfer complexes of iodine with some antibiotics formed through two different approaches (liquid-liquid vs solid-solid)

In this work, we compare CT complexes obtained from liquid starting materials to those generated in solid form. Specifically, iodine was complexed with four pharmaceutical compounds: trimethoprim (TMP), moxifloxacin (MOX), ceftriaxone (CTX), and sulfamethoxazole (SMZ). The synthesis approaches differed only by the phase of the starting materials (liquid-liquid vs solid-solid). The solid-solid approach successfully yielded the remaining three iodine CT complexes, which formed via a tri-iodide complex formulated as [D·I+]I3− (D: investigated pharmaceutical compound). Comparing the two approaches, we found that the solid-solid approach is faster, simpler, doesn't require a purification process, and does not consume large amounts of solvent or time relative to its liquid-liquid counterpart. More interesting, the solid-solid approach can generate iodine CT complexes with compounds that are very poorly soluble in a suitable organic solvent, which cannot be produced using the liquid-liquid approach.

Adsorption of P-Aminodiphenylamine with Iodine Charge Transfer Complex on Surface Arundo Plant

A charge transfer complex formed by interaction between the p- aminodiphenylamine (PADPA) as electron donor with iodine as electron acceptor in ethanol at 250C as evidenced by color change and absorption. The spectrum obtained from complex PADPA – Iodine shows absorptions bands at 586 nm. All the variables which affected on the stability of complex were studies such as temperature, pH, time and concentration of acceptor. The linearity of the method was observed within a concentration rang (10–165) mg.L-1 and with a correlation coefficient (0.9996), while the molar absorbitivity and sandell sensitivity were (4643.32) L.mol-1.cm-1 and (0.0943) µg.cm-2, respectively. The adsorption of complex PADPA–I2 was studied using adsorbent surfaces arundo plant. The dynamics of isotherm were studied according to experimental conditions of contact time, adsorbent weight, pH and particle size. The results showed the adsorption isotherm according to the Gils classification indicated L1, when the temperature (10,25)0C of plant, but S2 at (37.5,50) 0C for plant. Analytical techniques including UV-Vis. & FTIR were applied to characterize arundo. The values of Gibbs free energy, enthalpy ,entropy calculated from the thermodynamics of the process.

Experimental and theoretical analysis of substituent effect on charge transfer complexes of iodine and some alkylbenzenes in n-hexane solution at 303 K

Abstract The charge transfer (CT) interactions in n-hexane solutions containing iodine (acceptor) and aromatic compounds, benzene (BEN), toluene (TOL), o -xylene (OXYL), m -xylene (MXYL) and mesitylene (MESI) were investigated by ultrasonic, UV-Visible spectroscopic methods and DFT analysis. The trend in acoustical and excess properties with molar concentration in these systems established the existence of strong solute–solute interaction and formation of CT complex between iodine and the five aromatic compounds. Computed interaction energy values in the present investigation confirmed the formation of CT complex in these systems. Both the experimental methods and theoretical investigation of these systems indicated that tendency for formation of CT complex increases with increase in the number of methyl substituent in the aromatic ring. Our computed results are in good agreement with the experimental observations.

A spectrophotometric and thermodynamic study of the charge-transfer complexes of iodine with nortriptyline and imipramine drugs in chloroform and dichloromethane solutions

The interaction of iodine as electron acceptor with nortriptyline and imipramine drugs as electron donors has been investigated spectrophotometrically at various temperatures in chloroform and dichloromethane solutions. The observed time dependence of the charge–transfer band and subsequent formation of in solution were related to the slow transformation of the initially formed iodine: drug outer complex to an inner electron donor–acceptor (EDA) complex, followed by fast reaction of the inner complex with iodine to form a triiodide ion. The pseudo-first-order rate constants and activation parameters for the transformation process were evaluated from the absorbance-time data. Stoichiometrices of the complexes were defined by the Job’s method of the continuos variation and obtaind 2: 1 for iodine: drug complexes. The formation constants and molar absorptivities were evaluated from the absorbance-mole ratio data. Thermodynamic parameters of the complexes have been determined from the temperature dependence of the stability constant by Van’t Hoff equation.

Synthesis of amino acid iodine charge transfer complexes in situ methanolic medium: Chemical and physical investigations

New procedure for preparation of glycine and alanine triiodide charge transfer complexes by solid-solid interactions were investigated using different spectroscopic tools. The triiodide charge transfer complexes were prepared by grinding of potassium iodide, iodine and amino acid with 1:1:1 molar ratio in the presence of few drops of methanol solvent. The formulas of two solid amino acid charge transfer complexes were discussed using the infrared, Raman laser, UV–Vis. and electronic spectra, and thermal analyses. The structural changes of both complexes were probed using the positron annihilation lifetime (PAL) and positron annihilation Doppler broadening (PADB) techniques. The results reveal that most of PAL and PADB parameters are strongly correlated with the molecular weight of the prepared CT complexes.

고분자 전해질 막 연료전지에서의 아이오딘이 코팅된 분리판의 성능 효과

Polymer exchange membrane (PEM) fuel cells have multifunctional properties, and bipolar plates are one of the key components in these fuel cells. Generally, a bipolar plate has a gas flow path for hydrogen and oxygen liberated at the anode and cathode, respectively. In this study, the influence of iodine applied to a bipolar plate was investigated. Accordingly, we compared bipolar plates with and without iodine coating, and the performances of these plates were evaluated under operating conditions of <TEX>$75^{\circ}C$</TEX> and 100% relative humidity. The membrane and platinum-carbon layer were affected by the iodine-coated bipolar plate. Bipolar plates coated with iodine and a membrane-electrode assembly (MEA) were investigated by electron probe microanalyzer (EPMA) and energy-dispersive x-ray spectroscopy (EDS) analysis. Polarization curves showed that the performance of a coated bipolar plate is approximately 19% higher than that of a plate without coating. Moreover, electrochemical impedance spectroscopy (EIS) analysis revealed that charge transfer resistance and membrane resistance decreased with the influence of the iodine charge transfer complex for fuel cells on the performance.

Self-Assembly of Alkali Lignin in Tetrahydrofuran

Alkali lignin (AL) was used as a polyanion to form layer-by-layer self-assembled film with PDAC as a polycation. The effects of temperature and concentration on the adsorption characteristics of AL were investigated. Iodine was added into AL solutions to study the role of π-π interaction in self-assembly of AL and PDAC. Results show that the self-assembly of AL/PDAC is mainly driven by π-π interaction and electrostatic interaction. A higher temperature or a larger concentration can enhance the aggregation of lignin. I2 can form lignin–iodine charge–transfer complexes with AL to reduce the degree of aggregation of AL, so the adsorbed amount of AL decreases significantly with increasing iodine contents.

Spectral, Thermal and DC Electrical Conductivity of Charge Transfer Complex Formed Between 5,7-Dimethyl-1-oxo-2-phenyl-1H-pyrazolo [1,2-α]pyrazol-4-ium-3-olate and Iodine

Reaction of phenylmalonic acid dihydrazide with 2,4-pentanedione proceeded through a novel rearrangement to give 5,7-dimethyl-1-oxo-2-phenyl-1H-pyrazolo[1,2-α]pyrazol-4-ium-3-olate (DPO). This peculiar structure had a positive charge (cation) localized on the pyrazolium ring and a negative charge localized on the other ring. The intermolecular charge-transfer complexes (CTC) formed between DPO as donor and iodine as an acceptor have been studied spectrophotometrically. Doping was done in two ways: by mixing and chemically using different ratios of I2. The suggested structures of the solid iodine charge-transfer complexes were investigated by several techniques using electronic spectra, FTIR spectroscopy and thermal analysis (TGA and DTA). DC electrical conductivity variation with temperature in the range 300–500 K after annealing for 24 h at 100°C and after doping with different ratios of I2 through the two ways of doping is determined for comparison. The activation energies were calculated and the results were interpreted using the band energy model. DC electrical conductivity of the iodine CTC increased with increasing temperature. The iodine CTC are only one or two orders of magnitude higher in DC electrical conductivity than the undoped material, however the energy gap is very small in addition to its thermal stability which suggests the use of these materials in applications like photovoltaic cells.

New PVC-membrane electrode based on charge-transfer inclusion complex between I2 and 1,4,8,11-tetraazacyclotetracdecane for selective determination of I3 − ions

A new triiodide ion-selective electrode based on charge-transfer complex of iodine with 1,4,8,11-tetraazacyclotetracdecane as membrane carrier was prepared. The best performance of electrode observed with the membrane having the ligand–PVC–NPOE–NaTPB composition 3.0:33:66:0.5 mg which worked well over a wide concentration range 2.8 × 10−6–1.4 × 10−1 M with a Nernstian slope of 59.6 ± 0.3 mV per decade and a detection limit of 1.2 × 10−6 M. This electrode showed a response time of 25 s and was used over a period of 2 months. The electrode exhibits an anti-Hofmeister selectivity sequence with a performance for triiodide at pH 1.5–10.2. The response mechanism of the electrode was investigated by UV–Vis spectroscopic technique. The electrode was successfully applied as an indicator electrode in the potentiometric titration of ascorbic acid and hydroquinone in drugs.

&lt;b&gt;Thermodynamic study of charge-transfer complex of iodine with HT18C6 in

A spectrophotometric study concerning the interaction between HT18C6 as n-donor and I 2 as s -acceptor has been performed in chloroform solution at different temperatures. The results are indicative of the formation 1:1 complex through equilibrium reaction. The stability constant of the complex at 7, 13, 19 and 25 o C is obtained by the computer-fitting of absorbance-mole ratio data in MATLAB software. The ΔH o and ΔS o values are obtained by the Vant Hoff method. The obtained data show that the complex is enthalpy stabilized and entropy destabilized. The entropy destabilitization is attributed to the decrease of the entropy of the free donor upon complexation. Comparison of the data from this work with those of previous works done on 18C6-I 2 and HA18C6-I 2 is indicative of different stability, stoichiometry and products. The possible reasons for such differences are discussed. KEY WORDS: Charge-transfer complex, Iodine, HT18C6, Stability constant, Thermodynamic data, Spectrophotometry, Chloroform Bull. Chem. Soc. Ethiop. 2008 , 22(2), 287-294.

Spectrophotometric study of the charge-transfer complexes of iodine with antipyrine in organic solvents

The charge-transfer complex formation of iodine with antipyrine has been studied spectrophotometrically in chloroform, dichloromethane (DCM) and 1,2-dichloroethane (DCE) solutions at 25 °C. The results indicate the formation of 1:1 charge-transfer complexes. The observed time dependence of the charge-transfer band and subsequent formation of I 3 − in solution were related to the slow transformation of the initially formed 1:1 antipyrine:I 2 outer complex to an inner electron donor–acceptor (EDA) complex, followed by fast reaction of the inner complex with iodine to form a triiodide ion. The values of the equilibrium constant, K, are calculated for each complex and the influence of the solvent properties on the formation of EDA complexes and the rates of subsequent reaction is evaluated.

UV–vis, IR spectra and thermal studies of charge transfer complex formed between poly(amidoamine) dendrimers and iodine

The intermolecular charge-transfer (CT) complexes formed between two poly(amidoamine) dendrimers (PAMAM) from zero (D1) and second generation (D2) as donor and iodine as σ-acceptor have been studied spectrophotometrically in the chloroform medium. The suggested structures of the solid iodine charge-transfer complexes investigated by several techniques using elemental analysis, mid infrared spectra, and thermal analysis (TGA and DTG) of the solid CT-complexes along with the photometric titration curves for the reactions. The results indicate the formation of two CT-complexes [(D1)]–I 2 and [(D2)]–2I 2 with acceptor:donor molar ratios of 1:1 and 1:2, respectively. The kinetic parameters (non-isothermal method) for their decomposition have been evaluated by graphical methods using the equations of Horowitz–Metzger (HM) and Coats–Redfern (CR).

A spectrophotometric and thermodynamic study of the charge-transfer complexes of iodine with 2-aminomethyl-15-crown-5 in chloroform and 1,2-dichloroethane solutions

Interaction of 2-aminomethyl-15-crown-5 (AM15C5) with iodine has been investigated spectrophotometrically in chloroform and 1,2-dichloroethane (1,2-DCE) solutions. The observed time dependence of the charge-transfer band and subsequent formation of I 3 − in solution were related to the slow transformation of the initially formed 1:1 AM15C5·I 2 outer complex to an inner electron donor-acceptor (EDA) complex, followed by fast reaction of the inner complex with iodine to form a triiodide ion. The pseudo-first-order rate constants were evaluated from the absorbance– and conductivity–time data. The stoichiometry and formation constants of the resulting EDA complexes have also been determined. Thermodynamic parameters, Δ H° and Δ S°, of the complexes have been determined from the temperature dependence of stability constants by Van’t Hoff equation. The results indicate that iodine complexes of AM15C5 in both solvents are enthalpy stabilized but entropy destabilized. The influence of solvent properties on the kinetics and stability of the resulting charge-transfer complexes are discussed.

Novel Triiodide PVC-Based Membrane Sensor Based on a Charge Transfer Complex of Iodine and Bis(2-hydroxyacetophenone)butane-2,3-dihydrazone

In this study a novel triiodide ion-selective electrode based on a charge transfer complex of iodine and Bis(2-hydroxyacetophenone)butane-2,3-dihydrazone (ICT), as a membrane carrier was prepared. The electrode has a linear dynamic range between 1.0 <TEX>${\times}$</TEX> <TEX>$10^{-2}$</TEX> and 5.0 <TEX>${\times}$</TEX> <TEX>$10^{-7}$</TEX> M, with a Nernstian slope of 58. 99 <TEX>${\pm}$</TEX> 0.3 mV <TEX>$decade^{-1}$</TEX> and detection limit of 3.0 <TEX>${\times}$</TEX> <TEX>$10 ^{-7}$</TEX> M. The potentiometric response of the proposed sensor is independent of the pH of the solution in the pH range of 3.0-10.0. The electrode possesses the advantages of short conditioning time, fast response time, and especially, very good selectivity over a large number of common organic and inorganic anions. The electrode can be used for at least 6 months without any considerable divergences in the potentials. It was used as an indicator electrode in potentiometric titration of triiodide ion with thiosulfate.

Charge-Transfer Triiodide Ion-Selective Electrode Based on 7,16-Dibenzyl-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane

A new PVC membrane electrode for the triiodide ion based on a charge-transfer complex of iodine with 7,16-dibenzyl-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane as a membrane carrier was prepared. The electrode exhibits a Nernstian response for triiodide ions over a wide concentration range (1.0 x 10(-1)-1.0 x 10(-5) M) with a slope of 59.3 +/- 0.9 mV decade(-1) and a detection limit of 6.3 x 10(-6) M. It has a response time of 30 s and can be used for at least 3 months without any divergence in the potential. The potentiometric response is independent of the pH, in the pH range 1.6 - 10.0. The proposed electrode has shown very high selectivity for the triiodide ion over a wide variety of other anions. This electrode was successfully applied as an indicator electrode in the potentiometric titration of ascorbic acid and hydroquinone from pharmaceutical preparations as well as ascorbic acid in orange juice and dissolved O2 in tap water.

Flexible alteration of optical nonlinearities of iodine charge-transfer complexes in solutions.

The type of donor used is found to influence greatly the optical nonlinearities of iodine charge-transfer (CT) complexes in solutions for several solvents. The magnitude and sign changes of nonlinear absorption of iodine CT complexes for different solvents as donors are observed, which implies the transition from saturable absorption to reverse saturable absorption. Compared with C60 in toluene, iodine CT complexes with toluene and benzene demonstrate larger reverse saturable absorption. Meanwhile, flexible alteration of optical nonlinearities is easily obtained by adjusting the mixture ratio of different solvents, yielding a prospective means of constructing a nonlinear medium with a large nonlinear coefficient.

Triiodide PVC Membrane Electrode Based on a Charge-Transfer Complex of Iodine with 2,4,6,8- Tetraphenyl-2,4,6,8-tetraazabicyclo[3.3.0]octane

A novel triiodide ion-selective electrode based on a charge-transfer complex of iodine with 2,4,6,8-tetraphenyl-2,4,6,8-tetraazabicyclo[3.3.0]octane as membrane carrier was prepared. The electrode has a linear dynamic range between 5.0 × 10(-)(2) and 3.5 × 10(-)(6) M, with a near-Nernstian slope of 54.7 ± 0.8 mV decade(-)(1) and a detection limit of 2.0 × 10(-)(6) M. The potentiometric response is independent of the pH of the solution in the pH range 4.0-10.5. The electrode possesses the advantages of low resistance, short conditioning time, fast response, and, especially, very good selectivities over a wide variety of other anions. The electrode can be used for at least 10 months without any considerable divergence in potentials. It was used as an indicator electrode in potentiometric titration of triiodide ions.

Spectroscopic and Conductive Properties of Some Charge Transfer Complexes of Iodine

The interaction of iodine with donor bases such as neutral red (NR) and 1, 10 -phenanthroline (Ph) have been studied spectrophotometrically in C2H5OH. The results indicate the formation of 2:3 charge transfer complexes of the type (base)23I2. Mass, Raman and 1H NMR spectra have been recorded for each complex. I3 − and I2 species are observed in these complexes. In addition, the d.c. conductivity is measured in the range (300–400) K°. The energy gap of the ionic conduction has been calculated. The conduction process is thought to involve iodide transfer between polyanions.

Thioether–iodine charge-transfer complexes. Synthesis and low-temperature single-crystal structures of complexes of penta-, hexa- and octa-dentate homoleptic thioether macrocycles

Charge-transfer complexes 2([15]aneS5)·7I2 1 ([15]aneS5 = 1,4,7,10,13-pentathiacyclopentadecane), [18]aneS6·I2 2, [18]aneS6·4I2 3 ([18]aneS6 = 1,4,7,10,13,16-hexathiacyclooctadecane), [24]aneS8·I2 4 and [24]aneS8·6I2 5 ([24]aneS8 = 1,4,7,10,13,16,19,22-octathiacyclotetracosane) have been prepared and their structures and solution properties investigated. The compounds were prepared by slow evaporation of solutions containing I2 and the appropriate thioether macrocycle in CH2Cl2. The single-crystal structure determination of 1 shows three I2 molecules co-ordinated to three exo oriented S donors [S(1)–I(1) 2.797(3), I(1)–I(1′) 2.798(2), S(4)–I(4) 2.885(4), I(4)–I(4′) 2.764(2), S(7)–I(7) 2.828(3) and I(7)–I(7′) 2.779(2) A; S(1)–I(1)–I(1′) 178.39(8), S(4)–I(4)–I(4′) 171.12(8), S(7)–I(7)–I(7′) 178.80(8)°]. The fourth I2 molecule (with a site occupancy of 0.5) lies close to S(10) [I(10)–S(10) 2.839(5) A], the bond distance I(10)–I(10′) 2.674(3) A being unusually short. Compound 2 is an example of a 1∶1 I2∶macrocycle adduct and shows symmetrically bridging I2 molecules [S(1)–I(1) 3.099(2), I(1)–I(1i) 2.7881(10) A; S(1)–I(1)–I(1i) 178.68(4)°; i 1 – x, 1 – y, 1 – z] between [18]aneS6 macrocycles. Compound 3 is the first example of an adduct between I2 and a homoleptic thioether macrocycle which shows both exo [S(1)–I(1) 2.838(2), I(1)–I(1′) 2.7875(6) A; S(1)–I(1)–I(1′) 174.95(4)°] and endo [S(4)–I(4) 2.792(2), I(4)–I(4′) 2.8067(7) A; S(4)–I(4)–I(4′) 174.43(4)°] co-ordination of I2 molecules. The endo-oriented I2 molecules occupy space above and below the macrocyclic plane with the macrocycle adopting a sigmoid conformation. The single-crystal structure determination of the 1∶1 adduct 4 shows symmetrically bridging I2 molecules [S(1)–I(1) 3.215(2) and I(1)–I(1i) 2.758(2) A; S(1)–I(1)–I(1i) 172.75(3)°; i –x, –y, –z] which are a characteristic of this stoichiometry. Compound 5 contains endo- and exo-oriented S donors within the same adduct [I(1)–I(1′) 2.7861(8), I(4)–I(4′) 2.7937(8), I(7)–I(7′) 2.8345(8), S(1)–I(1) 2.821(2), S(4)–I(4) 2.815(2), S(7)–I(7) 2.741(2) A; S(1)–I(1)–I(1′) 170.15(5), S(4)–I(4)–I(4′) 177.41(5), S(7)–I(7)–I(7′) 177.24(5)°]. These results are discussed in the context of the stability and characteristics of thioether crown–iodine charge-transfer complexes, and a qualitative MO diagram is proposed to account for the shorter I–I distances in bridging I2 fragments compared to those in terminally bound I2.

Synthesis, structure and thermal decomposition of nitrogen–iodine charge-transfer complexes

Dipyridylquinoxaline (dpq), 4-cyanopyridine (4-CNpy), 4,4′-bipyridine (4,4′-bpy) and quinoxaline form n→σ* charge-transfer complexes with iodine (I2), in which the N· · ·I distance [2.532(3) A for dpq·I2; 2.543(9) and 2.555(9) A for 4-CNpy·I2; 2.406(7) A for 4,4′-bpy·2I2; 2.92(1) and 2.95(1) A for quinox·I2] is shorter than the sum of the van der Waals radii for nitrogen (1.55 A) and iodine (1.98 A). Donation of electron density into the antibonding orbital of iodine weakens the I–I bond resulting in elongation relative to the value observed in elemental iodine (2.715 A). Dpq, 4-CNpy and 4,4′-bpy form molecular adducts, while quinoxaline forms a polymeric species in which there are interactions at both ends of the I2 molecule. The type of complex which forms depends on the nucleophilic character of the donor (and its corresponding effect of the I2 molecule) and on the lattice energy of the complex. The strength of the N· · ·I interaction in each of the reported complexes has been investigated by X-ray crystallographic analysis and vibrational spectroscopy (far-IR). All of the complexes undergo thermal decomposition involving loss of I2, and their lattice energy, as a function of thermal stability, has been explored.