Crystal and molecular structure of diphenyliodonium triiodide

A new salt diphenyliodonium triiodide (C₁₂H₁₀I₄) was obtained. The [C₁₂H₁₀I⁺][I₃⁻] compound was isolated as red brown crystals and studied by single-crystal X-ray diffraction. The structure of diphenyliodonium triiodide consists of separate, virtually linear I₃⁻ anions and C₁₂H₁₀I⁺ cations. Strong intermolecular anion-anion (I₃⁻…I₃⁻) and anion-cation (I₃⁻…I⁺) interactions in the crystal structure leads to a change in the symmetry of triiodide ions. The complex formation in the system organic cation iodide-elementary iodine was studied by spectrophotometry. The complex composition was found (1: 1), and the stability constant of the complex in chloroform was determined (loggB = 3.91).     

Nontypical iodine–halogen bonds in the crystal structure of (3E)‐8‐chloro‐3‐iodomethylidene‐2,3‐dihydro‐1,4‐oxazino[2,3,4‐ij]quinolin‐4‐ium triiodide

Two kinds of iodine–iodine halogen bonds are the focus of our attention in the crystal structure of the title salt, C₁₂H₈ClINO⁺·I₃⁻, described by X‐ray diffraction. The first kind is a halogen bond, reinforced by charges, between the I atom of the heterocyclic cation and the triiodide anion. The second kind is the rare case of a halogen bond between the terminal atoms of neighbouring triiodide anions. The influence of relatively weakly bound iodine inside an asymmetric triiodide anion on the thermal and Raman spectroscopic properties has been demonstrated.     

Electrochemical studies of iodine in an aluminium chloride-butylpyridinium chloride ionic liquid part II. Neutral and basic solvent composition

The electrochemical behavior of iodine in an ambient temperature molten salt system, aluminum chloride-N-(1-butyl)pyridinium chloride (BuPyCl), have been studied in basic (excess BuPyCl) and neutral (1.0:1.0 AlCl₃: BuPyCI mole ratio) melt compositions. Acid-base interactions of iodine in different oxidation states with the ionic solvent are observed. High stability of triiodide ion in neutral butylpyridinium tetrachloroaluminate indicates relatively weak intermolecular interactions in this solvent. In basic solutions polyhalogen equilibria involving iodine in different oxidation states and chloride ions are established. In iodine and tetraethylammonium triiodide solutions a mixture of ICI₂^?, I₂Cl^?, I₃^? and I^? ions forms. The formation constants of I₂Cl^? and I₃^? and the equilibrium constant for I₂Cl^? disproportionation are estimated.     

Mechanism and reaction rate of the karl-fischer titration reaction: Part I. Potentiometric measurements

The reaction rate of the coulometric variant of the Karl-Fischer titration reaction (in which electrolytically generated triiodide is used as oxidant instead of iodine) has been measured in methanol. The reaction is first order in water, sulfur dioxide and triiodide, respectively. For pH<5 the reaction rate constant decreases logarithmically with decreasing pH. Addition of pyridine solely influences the pH (by fixing it to a value of about 6) and has no direct influence on the reaction rate. A linear relation exists between the reaction rate constant and the reciprocal value of the iodide concentration, from which we can calculate the individual reaction rates for the oxidation by iodine and triiodide, respectively. While the reaction rate constant for triiodide is relatively small (k₃≈350 l² mol^?2s^?1), the reaction rate constant for iodine is much larger (k₃≈1.5×10⁷ l² mol^?2 s^?1.     

Bis(2‐chloro‐N‐methyl­pyridinium) iodide triiodide

The title compound, 2C₆H₇ClN⁺·I^?·I₃^?, crystallizes with undulating layers of chains containing alternate iodide and triiodide anions formed from iodine and the heterocyclic iodide salt.     

Thermodynamic study on salt effects on complex formation of α-, β- and γ-cyclodextrins with p-aminobenzoic acid

The aim of this work was to gain a deeper understanding of salt effects in the inclusion complex formation of cyclodextrins. For this purpose, thermodynamic study of complex formation of α-, β- and γ-cyclodextrins with p-aminobenzoic acid was carried out in water and solutions of KCl, KBr, KH₂PO₄ and K₂SO₄ (0.2 mol/kg). Stability constants were calculated from the binding isotherms obtained on the basis of ¹H NMR measurements. Enthalpy and entropy of complex formation were estimated from the van’t Hoff plots. It was found that effects of KCl, KH₂PO₄ and K₂SO₄ are insignificant, while the influence of KBr on complex formation of cyclodextrins with p-aminobenzoic acid is more pronounced and results in a decrease of the stability constants. Specific action of Br⁻ is caused by the ability of these anions to penetrate into macrocyclic cavity. Coexistence of two complexation equilibria in KBr solution is accompanied by significant solvent reorganization originated from more intensive dehydration of the interacting species. This results in an increase of the enthalpy and entropy of complex formation. Manifestation of Br⁻ effect was found to be the same in the binding of p-aminobenzoic acid with α-, β- and γ-cyclodextrins.     

Spectrophotometric study of the complexation of iodine with 1,7-diaza-15-crown-5 in chloroform solution

The complex formation reaction between iodine and 1,7-diaza-15-crown-5 (DA15C5) has been studied spectrophotometrically in chloroform at 25°C. The resulting 1:2 (DA15C5:I₂) molecular complex was formulated as (DA15C5...;I⁺)I ₃ ^– . The spectrophotometric results, as well as the conductivity measurements, revealed that the gradual release of triiodide ion from its contact ion paired form in the molecular complex into the solution is the rate determining step of the reaction. The rate constant was calculated ask=(8.8±0.2)×10^–3 min^–1. The formation constant of the molecular complex was evaluated from the computer fitting of the absorbance-mole ratio data as logK _f=6.89±0.09.     

A Spectrophotometric Investigation of the Interaction of Iodine with Dibenzyldiaza‐18‐crown‐6, Aza‐15‐crown‐5 and N‐phenylaza‐15‐crown‐5 in Chloroform Solution

The complex formation reactions between iodine and DBzDA18C6, A15C5 and N‐phenylA15C5 have been studied spectrophotometrically in chloroform solution. In the case of DBzDA18C6 is the resulting 1:2 (ligand…I⁺)I₃^?, while, in the case of A15C5 and N‐phenylA15C5 a 2:2 molecular complex of [(ligand)₂…I⁺]I₃^? type was formed. The spectrophotometric results indicate that gradual release of triiodide ion from its contact ion paired form in the molecular complex into the solution is the rate‐determining step of the reaction. The kinetic rate constants for the complexation reactions were determined at different temperatures, and activation parameters were calculated from Arrhenius and Eyring equations.     

Iron complex redox system as a mediator for a dye-sensitized solar cell

Photoelectric parameters of a dye-sensitized solar cell (DSSC) based on nanocrystalline titania with an adsorbed commercial sensitizer Ruthenizer 505 and a redox system based on the [FeL₂] · 2Otf complex (where L = 4′-(4-bipyridyl)-2,2′:6′,2″-tert-pyridine and Otf^? =CF₃SO ₃ ^? ) as the mediator are studied. When illuminated with a power of 100 mW/cm2, the DSSC voltage with the mediator under study and the iodide/triiodide redox pair have close values of 470 and 480 mV, respectively. The current-voltage characteristics of the DSSC with the iron complex mediator are far lower than for the iodide/triiodide redox pair. Our data indicate the slower reduction kinetics of the oxidized sensitizer species for the iron complex. The reason for this may be associated with the shift of the redox potential toward positive values in going from the iodide/triiodide redox pair to the iron complex, and thereby a reduced driving force for the reduction of the oxidized sensitizer species. We also cannot rule out that the DSSC characteristics are affected by the reduction on the photoanode of the oxidized mediator species as a result of the high reversibility of the iron complex mediator redox system.     

Kinetics and Mechanism of Reaction between N-Polyfluorophenylcarbonimidoyl Dichlorides and Tertiary Amines in Acetonitrile

The reaction of N-polyfluorophenylcarbonimidoyl dichlorides with tertiary amines in acetonitrile afforded chloroamidines R²NC(Cl) = NAr_F and alkyl chloride. The precursor of the products is the corresponding quaternary ammonium salt [R³N+C(Cl) = NAr_F]-Cl^-. The rate of the salt formation is described by a second order equation; however with some amines a saturation effect was observed for the reaction rate with the growing amine concentration. This fact and also the influence of the amine and the substrate structure on the reaction rate suggests that reaction proceeds by addition-elimination mechanism with formation of a tetrahedral intermediate. The latter in the rate-limiting stage undergoes a stereomutation into an intermediate of a configuration favorable for conversion into a quaternary salt.     

The effect of a low-molecular-mass salt on stoichiometric polyelectrolyte complexes composed of oppositely charged macromolecules with different solvent affinities

The effect of a low-molecular-mass salt on the thermodynamic stability of stoichiometric interpolymer complexes composed of oppositely charged macromolecules with different solvent affinities has been theoretically studied. It has been shown that the dissociation of such complexes with an increase in the concentration of the salt proceeds via several stages. At a low concentration of the salt, complexes retain their structure and dimensions. When a certain critical concentration of the salt n _s^cr is achieved, the dimensions of the complex increase abruptly. At this concentration, macromolecules involved in the complex begin to separate, and at concentration n _s^*, they fully move apart but remain soluble owing to the polyelectrolyte effect. Upon a further increase in the concentration of the salt, the polyelectrolyte effect is shielded and the dimensions of macromolecules decrease. The critical concentration of the low-molecular-mass salt, n _s^cr, increases with an increase in the degree of ionization of macromolecules and a decrease in the affinity of the hydrophilic component for water and diminishes with the degree of polymerization of macromolecules and the degree of hydrophobicity of a polycation. Because of the easy formation of soluble complexes from oppositely charged macromolecules differing in solvent affinities and their high stability in solutions of a low-molecularmass salt, such complexes are promising for wide use in medicine and pharmaceutical practice.     

Spectroscopic studies of charge-transfer complexation of iodine with a new benzo-substituted macrocyclic diamide in chloroform, dichloromethane and their 1:1 mixture

Charge-transfer complexation of iodine with a new benzo-substituted macrocyclic diamide 5,6,7,8,9,10-hexahydro-2H-1,13,4,7,10-benzodioxatriazacyclopentadecine-3,11(4H,12H)-dione (L) with iodine was studied spectrophotometrically in chloroform, dichloromethane and their 1:1 (v/v) mixture. The observed time dependence of the charge-transfer band and subsequent formation of I₃ ^- ion are related to the slow formation of the initially formed 1:1 L.I₂ 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, as follows: L + I₂ → L.I₂ (outer complex), fast L.I₂ (outer complex) → (L.I⁺)I^- (inner complex), slow (L.I⁺)I^- (inner complex) + I₂ → (L.I⁺)I₃ ^-, fast The pseudo-first-order rate constants for the transformation process were evaluated in different solvent systems. The stability constants of the resulting EDAr complexes were also evaluated and the solvent effect on their stability is discussed. The resulting complexes were isolated and characterized by FTIR and ¹H NMR spectroscopy.     

Spectroscopic studies on the interaction of cimetidine drug with biologically significant σ- and π-acceptors

Spectroscopic studies revealed that the interaction of cimetidine drug with electron acceptors iodine and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) resulted through the initial formation of ionic intermediate to charge transfer (CT) complex. The CT-complexes of the interactions have been characterized using UV–vis, ¹H NMR, FT-IR and GC–MS techniques. The formation of triiodide ion, I₃^?, is further confirmed by the observation of the characteristic bands in the far IR spectrum for non-linear I₃^? ion with C_s symmetry at 156 and 131 cm^?1 assigned to ν_as(I–I) and ν_s(I–I) of the I–I bond and at 73 cm^?1 due to bending δ(I₃^?). The rate of formation of the CT-complexes has been measured and discussed as a function of relative permittivity of solvent and temperature. The influence of relative permittivity of the medium on the rate indicated that the intermediate is more polar than the reactants and this observation was further supported by spectral studies. Based on the spectroscopic results plausible mechanisms for the interaction of the drug with the chosen acceptors were proposed and discussed and the point of attachment of the multifunctional cimetidine drug with these acceptors during the formation of CT-complex has been established.     

Triiodide Ion‐Selective Electrode Based on Charge‐Transfer Complex of 4,7,13,16,21,24‐Hexaoxa‐1,10‐diazabicyclo‐[8.8.8]hexacosane

Two new highly selective triiodide electrodes have been prepared using charge‐transfer complex of iodine with cryptand 222 as an electroactive ionophore and nitrophenyl octyl ether as a plasticizing agent. The electrodes showed Nernstian response to triiodide ions over a concentration range from 1.0 × 10^?;2 — 7.9 × 10^?;7 M and from 1.0 × 10^?;2 — 1 × 10^?;6 M with detection limits of 6.3 × 10^?;7 and 7.9 × 10^?;7 M for cryptand and its charge‐transfer complex with iodine, respectively. The response times (t_95%) of the sensors were 10 and 5 s. The membrane could be used for more than 1 month without any divergence in potentials. The proposed sensors exhibited very high selectivity for triiodide ion over other anions, and could be used in a wide pH range ?2–10. These electrodes were successfully applied as an indicator electrode in potentiometric titration of copper in ore samples.     

Complex structure tri- and polyiodides of iodocyclization products of 2-allylthioquinoline

Iodocyclization products of 2-allylthioquinoline are obtained in the form of polyiodides with different stoichiometric compositions. X-ray crystallography data are analyzed for two different crystal structures of 1-iodomethyl-1,2-dihydro[1,3]thiazolo[3,2-a]quinolinium polyiodides: triiodide C₁₂H₁₁INS⁺I ₃ ^? and complex polyiodide 2(C₁₂H₁₁INS⁺I ₃ ^? )·I₂. A comparison is made of the nonbonding interactions of dihydrothiazoloquinolinium with atoms of the triiodide anion and complex polyiodide to show the crystal structure features attributed to the participation of molecular iodine.     

Synthesis of new chiral organosulfur donors with hydrogen bonding functionality and their first charge transfer salts

The syntheses of a range of enantiopure organosulfur donors with hydrogen bonding groups are described including TTF related materials with two, four, six and eight hydroxyl groups and multiple stereogenic centres and a pair of chiral N-substituted BEDT-TTF acetamides. Three charge transfer salts of enantiopure poly-hydroxy-substituted donors are reported, including a 4:1 salt with the meso stereoisomer of the dinuclear [Fe₂(oxalate)₅]⁴⁻ anion in which both cation and anion have chiral components linked together by hydrogen bonding, and a semiconducting salt with triiodide.     

The Coordination Chemistry of the Versatile Ligand Bis(2‐pyridylthio)methane

Bis(2‐pyridylthio)methane [bpytm, (pyS)₂CH₂] and complexes of this ligand with Zn^II, Hg^II, Cu^I, and Ag^I have been prepared and characterised by elemental analysis, by IR, Raman and ¹H and ¹³C NMR spectroscopy, and by X‐ray diffractometry. The ligand is N, N′‐didentate in the Zn^II complexes; N‐monodentate in one Hg^II complex and N, N′‐bis(monodentate) in the other; N‐mono‐N′, S‐didentate in the Cu^I complex; and N, S′‐bis(mono)‐N′, S‐didentate in the Ag^I complex. The structural parameters of the ligand in each coordination mode are compared with those of the free ligand and those of the triiodide salt of the protonated ligand.     

The enthalpies of formation of copper(II) complexes with nicotinamide in aqueous ethanol and DMSO

The enthalpies of complex formation between nicotinamide and copper(II) perchlorate in aqueous ethanol and dimethylsulfoxide (DMSO) were determined calorimetrically. The maximum exothermic effect was observed in a solvent with ～0.1 mole fractions of DMSO. The exothermic effect of complex formation increased as the concentration of ethanol grew. The role played by solvation in the thermodynamic characteristics of monoligand complex formation was considered. The influence of solvent composition on Δ_r H ^o was largely related to the resolvation of the ligand donor atom.     

Alkylation of 1,2,3-benzotriazole with iodomethyl ketones

Solvent-free reactions of 1,2,3-benzotriazole with 1-iodopropan-2-one and 1,3-diiodopropan-2-one in the absence of a catalyst involved alkylation of the heteroring at the N¹ atom and subsequent quaternization at the N³ atom with formation of 1,3-bis(2-oxopropyl)-1H-1,2,3-benzotriazolium triiodide which is a new conducting ionic liquid. The reaction of 1,2,3-benzotriazole with 1,3-diiodopropan-2-one was accompanied by reductive deiodination of the iodomethyl groups in the initial ketone with hydrogen iodide liberated by N¹-alkylation. Triiodide ion readily exchanges for nitrate ion by the action of AgNO₃ to produce 1,3-bis(2-oxopropyl)-1H-1,2,3-benzotriazolium nitrate. The reaction of 1,2,3-benzotriazole with 2-iodo-1-phenylethan-1-one in melt resulted in the formation of 1,3-bis(2-oxo-2-phenylethyl)-1H-1,2,3-benzotriazolium triiodide.     

Highly Selective and Sensitive Triiodide PVC‐Membrane Electrode Based on a New Charge‐Transfer Complex of Bis(2,4‐Dimethoxybenzaldehyde)butane‐2,3‐Dihydrazone with Iodine

In this work, a highly selective membrane triiodide sensor based on a new charge‐transfer complex of bis(2,4‐dimethoxybenzaldehyde)butane‐2,3‐dihydrazone with iodine (Iodide Charge Transfer complex: ICT) as membrane carrier is introduced. The influences of five different solvent mediators on sensitivity and selectivity of the proposed sensor were considered. The best performance was obtained with the membrane composition containing 30% poly (vinyl chloride), 63% DBP, 5% ICT and 2% HTAB. The electrode shows a Nernstian behavior over a very wide triiodide ion concentration range (1.0 × 10^?7‐1.0 × 10^?2 M), and a detection limit value of 8.0 × 10^?8 M. The effect of pH on the potentiometric response of the sensor was also studied, and it was found that the response of the electrode is independent of the pH of the solution in the pH range of 4.0–10. The proposed sensor has a very fast response time (< 12 s), and good selectivities relative to a wide variety of common inorganic and organic anions, including iodide, acetate, bromide, chloride, fluoride, nitrite, nitrate, sulfite, sulfate, cyanide and thiocyanate. In fact the selectivity behavior of the proposed triiodide ion‐selective electrode shows great improvements compared to the previously reported electrodes for triiodide ion. The proposed membrane sensor can be used for at least 6 months without any divergence in the potentials. The electrode was successfully applied as an indicator electrode in the titration of triiodide with thiosulfate ion.