Untersuchungen an Polyhalogeniden. XXVII. Über Tetra(n-propyl)ammoniumpolyiodide (n-Pr4N)In mit n = 3, 5, 7: Darstellung und strukturelle Charakterisierung eines Triiodids (n-Pr4N)I3, eines Pentaiodids (n-Pr4N)I5 und eines Heptaiodids (n-Pr4N)I7

Studies of Polyhalides. 27. On Tetra(n-propyl)ammonium Polyiodides (n-Pr₄N)I_n with n = 3, 5, 7: Preparation and Crystal Structures of a Triiodide (n-Pr₄N)I₃, a Pentaiodide (n-Pr₄N)I₅, and a Heptaiodide (n-Pr₄N)I₇ [(n-C₃H₇)₄N]I₃, [(n-C₃H₇)₄N]I₅ and [(n-C₃H₇)₄N]I₇ have been prepared by the reaction of tetra(n-propyl)ammoniumiodide [(n-C₃H₇)₄N]I with iodine I₂ in ethanol. Their crystal structures have been determined by single crystal X-ray diffraction methods. The triiodide is built up from layers of the quarternary ammonium ions n-Pr₄N⁺ and from two independent differently packed centrosymmetric triiodide ions I₃^? which alternate with each other along [100]. The pentaiodide ion forms slightly puckered almost squared nets perpendicular [001] of iodide ions which are connected with four iodine molecules by secondary bonds. The meshes from twelve iodine atoms include the cations. The centrosymmetric Z-shaped heptaiodide ion is built up from a linear symmetric triiodide ion and two iodine molecules forming twisted rope ladders along [001] which are separated by stacks of cations.     

Triiodide PVC Membrane Electrode Based on a Charge‐Transfer Complex of Iodine with Ditertbutyl‐Dicyclohexyl‐18‐Crown‐6

A new triiodide ion‐selective electrode based on a charge‐transfer complex of iodine with ditertbutyl‐dicyclohexyl‐18‐crown‐6 (t‐Bu)₂DC18C6 as membrane carrier was prepared. The electrode has a linear dynamic range from 6.3 × 10^?3‐5 × 10^?6 with a Nernstian response of 58.6 ± 1 mV decade^?1 and a detection limit of 1.3 × 10^?6 M. The response time of the sensor was 25 s. The membrane could be used for two months without any divergence in potentials. The electrode exhibits an anti‐Hofmeistetr selectivity sequence with a preference for triiodide at pH 2.0‐10.0. The response mechanism of the electrode was investigated by Uv‐Vis spectroscopic technique. The electrode can be used for the determination of ascorbic acid in orange juice.     

Über die Decamethylferroceniumpolyiodide [(Me5C5)2Fe]Ix mit x = 3, 5 und 6,5. Darstellung und strukturelle Charakterisierung eines Triiodids (DMFc)I3, eines Pentaiodids (DMFc)I5 und eines Hexacosaiodids (DMFc)4I26

Studies on Polyhalides. 30 On Decamethylferriciniumpolyiodides [(Me₅C₅)₂Fe]I_x with x = 3, 5, 6.5: Preparation and Crystal Structures of a Triiodide (DMFc)I₃, a Pentaiodide (DMFc)I₅ and a Hexacosaiodide (DMFc)₄I₂₆ Decamethylferrocene (DMFc) may be oxidized by iodine analogous to ferrocene (Fc) to the decamethylferrocenium ion (DMFc)⁺ and precipitated as the crystalline solids decamethylferrocenium triiodide (DMFc)I₃, decamethylferrocenium pentaiodide (DMFc)I₅ and tetracisdecamethylferrocenium hexacosaiodide (DMFc)₄I₂₆. The two compounds with higher iodine content are new. These are characterized by X-ray diffraction methods on single crystals. The structures are built up from complex cations of expected geometry and isolated or remarkably connected polyiodide ions. Decamethylferrocenium triiodide C₂₀H₃₀FeI₃ crystallizes monoclinically in C2/m with a = 1489.9(4) pm, b = 1133.0(2) pm, c = 765.9(3) pm, β = 111.76(3)° and Z = 2. The crystal structure follows the CsCl-type and contains isolated triiodide ions of the linear symmetric form. Decamethylferrocenium pentaiodide C₂₀H₃₀FeI₅ crystallizes monoclinically in P2₁/c with a = 1130.0(2) pm, b = 1442.6(1) pm, c = 1716.6(2) pm, β = 96.62(1)° and Z = 4. The crystal structure may be deduced from the primitiv quadratic bundle of alternating cationic and anionic rods. It contains exceptionally isolated somewhat opened out pentaiodide ions. Tetrakisdecamethylferrocenium hexacosaiodide (C₂₀H₃₀Fe)₄I₂₆ crystallises monoclinically in P2₁/n with a = 1331.3(8) pm, b = 1319.4(4) pm, c = 3564(2) pm, β = 90.84(5)° and Z = 2. The crystal structure of this compound with unusual composition may be described as an inclusion compound with channels for the cations. The outstanding anionic grating may be derived from the primitive cubic lattice of iodide ions with iodine bridges on all edges by removing systematically 1/12 of the iodine molecules.     

Corrosion of Au particles in air-exposed NaI-treated Au colloidal suspensions

This study examines the influence of the treatment of citrate-capped Au colloidal particles with NaI under exposure to air. Whereas in the NaI-treated centrifugate of the Au colloidal suspension the iodide-induced formation of triiodide runs spontaneously, its accumulation is found to be strongly decelerated in the Au colloidal suspension under the same conditions. In accordance with the experimental findings from electron absorption spectroscopy and transmission electron microscopy, a mechanism is proposed which describes the oxidation of the Au particles by oxygen under intermediate participation of triiodide.     

Liquid–liquid microextraction in a multicommuted flow system for direct spectrophotometric determination of iodine value in biodiesel

A flow-based procedure was developed for the direct spectrophotometric determination of the iodine value (IV) in biodiesel. The procedure was based on the microextraction/reaction of unsaturated compounds with triiodide ions in an aqueous medium by inserting the reagent solution between the aliquots of biodiesel without any pretreatment. The interaction occurred through the biodiesel film formed on the inner walls of the hydrophobic tube used as the reactor and at the aqueous/biodiesel interfaces. The spectrophotometric detection was based on the discoloration of the I₃⁻ reagent in the aqueous phase by using a glass tube coupled to a fiber-optic spectrophotometer as the detection cell. Reference solutions were prepared by dilution of biodiesel samples with previously determined IV in hexane. The analytical response was linear for IV from 13 to 135 g I₂/100 g with a detection limit of 5 g I₂/100 g. A coefficient of variation of 1.7% (n = 10) and a sampling rate of 108 determinations per hour were achieved by consuming 224 μL of the sample and 200 μg of I₂ per determination. The slopes of analytical curves obtained with three different biodiesel samples were in agreement (variations in slopes lower than 3.1%), thus indicating an absence of any matrix effects. Results for biodiesel samples from different sources agreed with the volumetric official procedure at the 95% confidence level. The proposed procedure is therefore a simple, fast, and reliable alternative for estimating the iodine value of biodiesel.     

Highly Selective and Sensitive Triiodide PVC‐Based Membrane Electrode Based on a New Charge Transfer Complex of 2‐(((2‐(((E)‐1‐(2‐Hydroxyphenyl) Methylidine) Amino) Phenyl) Imino) Methyl) Phenol for Nano‐Level Monitoring of Triiodide

Abstract

A highly selective and sensitive triiodide sensor based on a 2‐(((2‐(((E)‐1‐(2‐hydroxy phenyl) methylidine) amino) phenyl) imino) methyl) phenol with iodine (CTC) as membrane carrier was developed. The electrode revealed a Nernstian behavior over a very wide triiodide‐ion concentration range (5.0×10^?8–1.0×10^?2 M), and relatively low detection limit (3.0×10^?8 M). The potentiometric response is independent of the pH of solution in the pH range of 3.0–10.0. The electrodes manifest advantages of low resistance, very fast response (<12 s), and most importantly, good selectivities relative to a wide variety of inorganic and organic anions, including iodide, bromide, chloride, fluoride, sulfite, sulfate, cyanide, thiocyanate, and acetate. In fact, the selectivity behavior of the proposed triiodide ion‐selective electrode shows great improvements compared to the previously reported electrodes for the triiodide ion. The proposed membrane sensor can be used for at least 6 months without any significant divergences in the potential. The electrode was successfully applied as an indicator electrode in the titration of triiodide with thiosulfate ion.     

碘、碘离子和碘三离子的紫外吸收光谱

研究了碘I₂、碘离子I- 和碘三离子I-₃ 水溶液的紫外吸收光谱,测定了三种型体的摩尔吸光系数。I₂水溶液在203 nm呈现一吸收峰,摩尔吸光系数为1.96×104 L·mol-1·cm-1;I- 水溶液在193和226 nm呈现双吸收峰,摩尔吸光系数分别为1.42×104和1.34×104 L·mol-1·cm-1;当I₂水溶液与KI溶液混合时,在288和350 nm出现两个吸收峰,表明I-₃的形成。利用饱和法测得I-₃在288和350 nm处的摩尔吸光系数分别为3.52×104和2.32×104 L·mol-1·cm-1。