Inorganic interferences in the 2,4-xylenol spectro-photometric method for nitrate and their elimination

A study of inorganic interferences with the 2,4-xylenol spectrophotometric method for nitrate and their elimination is reported. Fifty-three substances do not interfere with the original method. Nitrite interferes somewhat by producing a faint yellow color. Certain reducing agents (Fe²⁺, S^2-, S₂O₃^2-, and SCN^-) cause low results by reducing the nitrate in the strong sulfuric acid solution, while some oxidizing agents (Mn⁷⁺, Cr⁶⁺, V⁵⁺, and ClO₃^-) cause low results by inactivating or destroying the 2,4-xylenol. Persulfate and small amounts of H₂O₂ produce a slight deepening of the color; larger amounts of H₂O₂; cause low results, as do Cl^-, Br^-, I^-, and metals. The recommended maximum permissible limits (mg per 10-ml aliquot) for the original method are NO₂^--N, Fe²⁺, S^2-, SCN^-, V⁵⁺, ClO₃^-, Cl^-, I^-, 0.2; Mn⁷⁺, Cr⁶⁺, S₂O₈^2-, 5; H₂O₂, 0.02; S₂O₃^2-, Br^-, 0.1; metals, none. Procedures for the elimination of most of the interferences are described. Nitrite is destroyed with sulfamic acid. The interferences of reductants (Fe²⁺, S^2-, S₂O₃^2-, and SCN^-) and oxidants (Mn⁷⁺ and Cr⁶⁺) are eliminated with hydrogen peroxide, the excess of which (and S₂O₈^2-) is destroyed by boiling in the presence of Fe³⁺. The interference of Cl^-, Br^-, and I^- is eliminated by precipitation with silver sulfate. An alternative to the sulfamic acid procedure is to oxidize nitrite to nitrate with peroxide and deduct NO₂^--N from the total NO₃^--N. After elimination of interferences, a 10-ml aliquot of sample solution is treated with 17.0 ml of sulfuric acid and 2,4-xylenol, the 6-nitro-2,4-xylenol is steam-distilled into an ammonia—water—isopropanol mixture, and the yellow color is measured.     

Organic interferences and their elimination in the 2,4-xylenol spectrophotometric method for nitrate

The 2,4-xylenol spectrophotometric method for nitrate involves formation of 6-nitro-2,4-xylenol, which is steam-distilled into an ammonia—water—isopropanol mixture. The yellow color of the ammonium salt of 6-nitro-2,4-xylenol is measured at 455 nm. A detailed study of the possible interferences from 123 representative organic compounds is described; 61 compounds interfered (when present in amounts of 0.1 g in the original sample). The interfering compounds can be classified according to their mode of interference: (1) compounds that are readily nitrated or oxidized by nitrate in the sulfuric acid medium used cause low results; (2) compounds containing the ONO₂ group that hydrolyze to nitrate cause high results; (3) compounds that steam-distil to produce colored solutions; (4) compounds that steam-distil to produce turbid solutions; (5) compounds that hydrolyze, either in water or sulfuric acid solution, to produce inorganic ions or compounds (e.g. Cl^-, S^2-, and H₂O₂) that repress the color development. Three procedures are described for the elimination of the interferences: (1) oxidation of the organic compound with permanganate, reduction of the excess of permanganate with hydrogen peroxide, and destruction of the peroxide by boiling in the presence of Fe(III) catalyst (this is unsuitable for organic compounds containing nitrogen, as there is invariably some oxidation to nitrate); (2) extraction of interfering organic compounds with methyl isobutyl ketone; (3) precipitation—adsorption method involving treatment with zinc sulfate and sufficient sodium hydroxide to precipitate most of the zinc as zinc hydroxide, addition of 3 g of activated carbon, digestion at 55–65°C for 20 min. cooling, dilution, and filtration. Method (3) is applicable to all organic compounds tested except formaldehyde. The amount of organic compound used to test the methods was normally 0.25 g in the solution being treated.     

An improved technique for the spectrophotometric determination of nitrate with 2,4-xylenol

An improved method is proposed for the spectrophotometric determination of nitrate with 2,4-xylenol. The sample in aqueous (1.7 + 1 ) sulfuric acid is treated with 2,4-xylenol to produce 6-nitro-2,4-xylenol which is distilled into an ammoniacal water—isopropanol mixture. The intense yellow color of the ammonium salt of 6-nitro-2,4-xylenol is measured at 455 nm. The distillation is done in a Parnas—Wagner Kjeldahl Semimicro distillation apparatus. The isopropanol keeps the excess of 2,4-xylenol in solution. Two procedures are described. In the first (applicable to samples containing alkali nitrates but no chloride, alkaline earth, or ammonium salts), the solution is evaporated to dryness, and (1.7 + 1) sulfuric acid and 2,4-xylenol in acetone are added. In the second (applicable to samples containing chloride, alkaline earth, or ammonium salts), concentrated sulfuric acid is added dropwise to a cooled aliquot and the 2,4-xylenol reagent is then added; if chloride is present, it must be removed by prior precipitation with silver sulfate. Nitrite shows a slight interference which depends on the amount of nitrate and nitrite present.     

Azothia- and Azoxythiacrown Ethers as Ion Carriers. Part II. Anionic Response of Membrane Electrodes

Ion-selective electrodes with plasticized poly(vinyl chloride) membranes containing 13-membered azothia- and azoxythiacrown ether complexes with silver, mercury or copper ions have been investigated. The potentiometric response towards various anions was studied. For membranes based on azothiacrown ether (B) complexes the following selectivity patterns were found:I^- > SCN^-, Br^- > Cl^- ClO₄ ^- > salicylate, NO₃ ^- (complex B with silver), I^- > ClO₄ ^- > SCN^-, Br^- > salicylate > Cl^-, NO₃ ^- (complex B with mercury) and SCN^- > I^- > Br^- > ClO₄ ^- > Cl^- > salicylate > NO₃ ^- (complex B with copper). For azoxythiacrown ether (A) only membranes containing its complex with mercury exhibited pronounced anion response and the selectivity pattern was similar to that observed for complex B with mercury. The origin of the anion response has been discussed.     

Synthesis and Crystal Structure of Bis(tetraethylammonium) Octabromo‐triselenate(II)‐{dibromodiselenate(I)}, [NEt4]2[Se3Br8(Se2Br2)], the Salt of a Mixed‐valence Bromoselenate(II,I) Anion

The brown crystals of [NEt₄]₂[Se₃Br₈(Se₂Br₂)] ( 1 ) were obtained when selenium and bromine reacted in the solution of acetonitrile in the presence of tetraethylammonium bromide. The crystal structure of 1 has been determined by the X‐ray methods and refined to R = 0.0308 for 10433 reflections. The crystals are monoclinic, space group P2₁ with Z = 2 and a = 12.0393(3) Å, b = 11.8746(3) Å, c = 13.1946(3) Å, β = 96.561(1)° (123 K). In the solid state structure the anion of 1 is built up of Se₃Br₈ unit which consists of a triangular arrangement of three planar SeBr₄ units sharing a common edge through two μ₃‐bridging Br atoms, and one Se₂Br₂ molecule which is linked to one of μ₃‐bridging Br atoms. The three Se^II atoms form a triangle which is almost perpendicular to the planes given by three SeBr₄ moieties. The contact between the μ₃Br and the Se^I atom of the Se₂Br₂ molecule is 3.1711(8) Å and can be interpreted as a bond of the donor‐acceptor type with the μ₃Br as donor and the Se₂Br₂ molecule as acceptor. The terminal Se^II‐Br and μ₃Br‐Se^II bond lengths are in the ranges 2.3537(7)–2.4737(7) Å and 2.7628(7)–3.1701(7) Å, respectively. The bond lengths in coordinated Se₂Br₂ molecule are: Se^I‐Se^I = 2.2636(9) Å, Se^I‐Br = 2.3387(11) and 2.3936(8) Å.     

Synthesis and Crystal Structure of Bis(tetraphenylphosphonium) Hexabromo‐diselenate(II)‐bis{dibromodiselenate(I)}, [PPh4]2[Se2Br6(Se2Br2)2], the Salt of a Mixed‐valence Bromoselenate(II,I) Anion

The Red crystals of [PPh₄]₂[Se₂Br₆(Se₂Br₂)₂] ( 1 ) were obtained when selenium and bromine reacted in the solution of acetonitrile in the presence of tetraphenylphosphonium bromide. The crystal structure of 1 has been determined by X‐ray diffraction and refined to R = 0.0201 for 4024 reflections. The crystals are triclinic, space group with Z = 2 and a = 11.2757(4) Å, b = 12.3347(5) Å, c = 12.4948(5) Å, α = 113.152(4)°, β = 114.745(4)°, γ = 91.208(3)° (120(2) K). In the solid state the anion of 1 is built up of the Se₂Br₆ core and two Se₂Br₂ molecules each of which is linked to one of the trans‐positioned terminal Br_t atoms of the Se₂Br₆ core. The central Se₂Br₆ part consists of a nearly planar arrangement of two planar SeBr₄ units sharing a common edge through two μ₂‐bridging Br atoms. The contact between the Br_t and the Se^I atom of the Se₂Br₂ molecule is 3.0872(5) Å and can be interpreted as a bond of the donor‐acceptor type with the Br_t as donor and the Se₂Br₂ molecule as acceptor. The terminal Se^II–Br and μ₂Br–Se^II bond lengths are 2.3654(4), 2.6699(5) Å and 2.5482(5), 3.0265(5) Å, respectively. The bond lengths in the coordinated Se₂Br₂ molecule are: Se^I–Se^I = 2.2686(5) Å, Se^I–Br = 2.3779(5) and 2.3810(5) Å.     

Synthesis and Crystal Structure of Bis(methyltriethylammonium) Hexabromotellurate(IV)‐tris{dibromodiselenate(I)}, [NMeEt3]2n[TeBr6(Se2Br2)3]n,Containing a Chain‐Polymeric Mixed‐valence Bromotellurate(IV)‐Selenate(I) Anion

Red crystals of [NMeEt₃]_2n[TeBr₆(Se₂Br₂)₃]n ( 1 ) were isolated when selenium and bromine (1:1) were allowed to react in acetonitrile solution in the presence of tellurium(IV) bromide and methyltriethylammonium bromide (1:2). The salt 1 crystallizes in the monoclinic space group C2/c with the cell dimensions a = 27.676(6) Å, b = 9.665(2) Å, c = 18.796(4) Å and ß = 124.96(3)° (120 K). The [TeBr₆(Se₂Br₂)₃]^2— anions contain nearly regular octahedral [TeBr₆]^2— ions which are incorporated into a polymeric chain by bonding contacts between 3 facial bromo ligands and 3 Se₂Br₂ molecules, one of which is situated on the twofold symmetry axis. The distances between the μBr ligands and the Se^I atoms of the Se₂Br₂ molecules are observed in the range 3.308(2) — 3.408(2) Å and can tentatively be interpreted as donor‐acceptor bonds with μBr as donors and Se₂Br₂ as acceptors. The Te^IV—Br distances are in the range 2.669(1) — 2.687(1) Å. The bond lengths in the connecting Se₂Br₂ molecules are: Se^I—Se^I = 2.267(2) and 2.281(2) Å, Se^I—Br = 2.340(1), 2.353(1) and 2.337(1) Å.     

Electrochemiluminescence Quenching by Halide Ions at Bipolar Electrodes

Quenching of Ru(bpy)₃²⁺ electrochemiluminescence (ECL) by Cl^?, Br^?, and I^? ions was studied as a function of halide concentration in a bipolar electrochemical cell. All of the halides investigated showed similar qualitative behavior: above a critical concentration, ECL intensity was found to decrease linearly as the halide ion concentration was increased, due to dynamic quenching of Ru(bpy)₃²⁺ ECL. Stern‐Volmer slopes (K_SV) of 0.111±0.003, 4.2±0.3, and 6.2±0.3 mM^?1 were measured for Cl^?, Br^? and I^?, respectively. The magnitude of K_SV correlates with halide ion oxidation potential, consistent with an electron transfer quenching mechanism. Using the bipolar platform described herein, aqueous, halide‐containing solutions could be quantified rapidly using the sequential standard addition method. The lower detection limit is determined by a complex mechanism involving the competitive electrooxidation of halide ions and the ECL co‐reactants, as well as the passivation of the surface of the bipolar electrode, and was found to be 0.20±0.01, 0.08±0.01 and 10±1 mM, respectively, for I^?, Br^?, and Cl^?. The performance of the bipolar ECL quenching assay is comparable to previously published fluorescence quenching methods for the determination of halide ions, while being much simpler and less expensive to implement.     

环境友好型无铅卤化物钙钛矿太阳能电池研究进展

ABX_3(A为甲胺、甲脒等有机离子或铯离子,B为铅或锡等金属离子,X为溴、碘等卤化物离子)卤化物钙钛矿材料具有优异的光电特性,是当前太阳能电池研究的前沿和热点之一。然而,这类太阳能电池普遍面临含毒性元素铅和稳定性差等问题,极大地阻碍了钙钛矿太阳能电池商业化应用进程。因此,发展新型高效无铅钙钛矿太阳能电池势在必行。本文评述了环境友好型无铅卤化物钙钛矿太阳能电池的最新研究动态和进展,探讨了该类太阳能电池的制备、性能及其稳定性等问题,展望了其未来发展趋势。     

基于含偶氮酚羟基席夫碱新型简单比色传感器

A novel N-(2-hydroxy-5-chlorodibenzophenone)-N0-[2-hydroxy-5-azophenyl-benzaldehyde]-1,2-diaminobenzene receptor has been synthesized by simple steps with good yields. The anion recognition properties were studied by ultraviolet-visible spectroscopy. The resultsshowed that the receptor had a higher affinity to F^-, AcO^-, and H₂PO₄^-, but no evident binding with Cl^-, Br^-, and I^-. Upon addition of the three former anions to the receptors in DMSO, the solution exhibited an obvious color change from colorless to yellow, which could be observed by the naked eye, thus the receptor could act as a fluoride ion sensor even in the presence of other halide ions. The UV-Vis data indicates that a 1:1 stoichiometric complex is formed through hydrogen bonding interactions between receptor and anions.     

Synthesis and Crystal Structure of Tetrakis(tetramethylammonium) Bis[decabromotetraselenate(II)]‐bis[dibromodiselenate(I)], [(CH3)4N]4[(Se4Br10)2(Se2Br2)2], the Salt of a Mixed‐Valence Bromoselenate(II/I) Anion

Brown crystals of [NMe₄]₄[(Se₄Br₁₀)₂(Se₂Br₂)₂] ( 1 ) were obtained from the reaction of selenium and bromine in acetonitrile in the presence of tetramethylammonium bromide. The crystal structure of 1 was determined by X‐ray diffraction and refined to R = 0.0297 for 8401 reflections. The crystals are monoclinic, space group P2₁/c with Z = 4 and a = 12.646(3) Å, b = 16.499(3) Å, c = 16.844(3) Å, β = 101.70(3)° (123 K). In the solid‐state structure, the anion of 1 is built up of two [Se₄Br₁₀]^2– ions. Each shows a triangular arrangement of three planar SeBr₄ units sharing a common edge through two μ₃‐bridging bromine atoms, and one SeBr₂ molecule, which is linked to the Se^II atoms of two SeBr₄ units; between the Se₄Br₁₀^2– ions a dimerized Se₂Br₂ molecule (Se₄Br₄) is situated and one Se^I atom of each Se₂Br₂ molecule has two weak contacts [3.3514(14) Å and 3.3952(11) Å] to two bromine atoms of one SeBr₄ unit. Four Se^I atoms of a dimerized Se₂Br₂ molecule are in a almost regular planar tetraangular arrangement. Contacts between the Se^II atom of the SeBr₂ molecule and the Se^II atoms of two SeBr₄ units are 3.035(1) Å and 3.115(1) Å, and can be interpreted as donor‐acceptor type bonds with the Se^II atoms of SeBr₄ units as donors and the SeBr₂ molecule as acceptor. The terminal Se^II–Br and μ₃‐Br–Se^II bond lengths are in the ranges 2.3376(10) to 2.4384(8) Å and 2.8036(9) to 3.3183(13) Å, respectively. The bond lengths in the dimerized Se₂Br₂ molecule are: Se^I–Se^I = 2.2945(8) Å and 3.1398(12), Se^I–Br = 2.3659(11) and 2.3689(10) Å.     

2,4′-Bipyridyl complexes with silver(I) and copper(II)

Summary Ag^I and Cu^II complexes with 2,4-bipyridyl (2,4-bipy or L) with the general formulae AgL₂X (where X = NO _inf3 ^sup– or ClO₄ ^-), CuL₂X₂·2H₂O (X = Cl^- or Br^-), CuL₄SO₄·4H₂O, CuL₄(NO₃)₂·2H₂O and CuL₄(ClO₄)₂·H₂O have been isolated pure and characterized by analytical, spectral and magnetic measurements. The thermal decomposition of these complexes was studied under non-isothermal conditions in air.     

Carrier dynamics in CsPbI3 perovskite microcrystals synthesized in solution phase

Carrier diffusion and recombination kinetics in all-inorganic CsPbI₃ perovskite microcrystals directly synthesized in solution phase are reported.     

Negative ion chemical ionization mass spectrometry—binding of molecules to bromide and iodide anions

The analytical potential of negative ion chemical ionization (NICI) mass spectrometry utilizing dibromodifluoro-methane (CF₂Br₂) and iodomethane (CH₃I)/methane (CH₄) as reagent gases is examined. The NICI mass spectrum of CF₂Br₂ contains Br^?, [HBr₂]^? and [CF₂Br₃]^? anions. Weak acids (i.e. those acids with approximately ΔH°_(acid) values between 1674 and 1464 kJ mol^?1) react with Br^? to produce minor yields of the hydrogen?bonded bromide attachment [MH + Br]^? anion or are unreactive. Strong acids (i.e. those acids with approximately ΔH°_(acid) > 1464 kJ mol^?1) produce primarily [MH + Br]^? anions with a minor yield of proton transfer [M ? H]^? anion. The NICI spectrum of CH₃I/CH₄ is dominated by I^?. Weak acids react with I^? to yield minor amounts of [MH + 1]^? or are unreactive. Strong acids produce only [MH + l]^? anions. From a consideration of the gas-phase basicity of the halide anion and the binding energy of the hydrogen-bonded halide attachment adduct, thermochemical data are used as a potential guide to rationalize or predict the ions observed in NICI mass spectra.     

Cobalt(II) complexes of 1,2-(diimino-4′-antipyrinyl)ethane and 4-N-(4′-antipyrylmethylidene)aminoantipyrine

Cobalt(II) complexes of the Schiff bases 1,2-(diimino-4-antipyrinyl)ethane (GA) and 4-N-(4-antipyrylmethylidene)aminoantipyrine (AA) have been prepared and characterised by elemental analysis, electrical conductance in non-aqueous solvents, i.r. and electronic spectra, as well as by magnetic susceptibility measurements. The complexes have the general formulae [Co(GA)X]X (X = ClO^– ₄ or NO₃ ^–), [Co(GA)X₂] (X = Cl^–, Br^– or I^–), [Co(AA)₂]X₂ (X = ClO₄ ^–, NO₃ ^–, Br^– or I^–) and [Co(AA)Cl₂]. GA acts as a neutral tetradentate ligand, coordinating through both carbonyl oxygens and both azomethine nitrogens. In the perchlorate and nitrate complexes of GA one anion is coordinated in a bidentate fashion, whereas in the halide complexes both anions are coordinated to the metal, generating an octahedral geometry around the Co ion. AA acts as a neutral bidentate ligand, coordinating through the carbonyl oxygen derived from the aldehydic moiety and the azomethine nitrogen. Both anions remain ionic in the perchlorate, nitrate, bromide and iodide complexes of AA, whereas both anions are coordinated to the metal ion in the chloride complex, resulting tetrahedral geometry around the Co ion.     

Hg (II) extraction in a PEG-based aqueous two-phase system in the presence of halide ions. I. Liquid phase analysis

The partition behaviour of Hg (II) was studied in an aqueous polyethylene glycol (PEG) — (NH₄)₂SO₄ two-phase system as a function of halide, halide concentration, and pH. For a system prepared by mixing equal volumes of 40 % (w/w) PEG (1550) with 40 % (w/w) (NH₄)₂SO₄, Hg(II) remains almost exclusively in the salt-rich phase. The addition of NaX (X = Cl⁻, Br⁻, I⁻) enhances Hg (II) partition into the PEG-rich phase due to the formation of halide complexes. The efficiency of halide extractants increases in the order: Cl⁻ < Br⁻ < I⁻. Mercury extraction is improved at lower halide ion concentration by higher stock salt solution acidity. From the distribution coefficients determined as a function of halide ion concentration, the extracted species were identified. The Hg (II) extractability is determined by the type and stability of the Hg (II) halide species, and depends on the stock salt solution acidity. The observed behaviour is discussed and a possible extraction mechanism is proposed.     

Pulse radiolysis study of redox reactions of safranine T in aqueous solutions: One electron oxidation

One electron oxidation of safranine T by specific oxidizing radicals such as Cl^-₂, Tl²⁺, Tl(OH)⁺, N^.₃, Br^-₂ etc. has been studied using the nanosecond pulse radiolysis technique. Reaction of free Br^. atom has also been investigated at neutral pH. The semioxidized safranine species formed by these reactions have been shown to exist in two conjugate acid-base forms with pK_a=4.0. Their spectral and kinetic parameters have been evaluated. Using N^.₃/N^-₃ and I^-₂/2I^- as reference couples, the one electron reduction potential of the semioxidized safranine has been determined to be 1.13±0.02 V vs NHE. The absorption spectra, second order decay rate constant and the pK_a of the OH-reaction product revealed features quite different from that of the semioxidized species suggesting that the mode of OH reaction is not via electron abstraction.     

ECE mechanism as a tool for the investigation of unstable metal complexes: Part I. Electrochemical reduction of trans-[CoBr2(N)4]+-type complexes on the mercury electrode

A polarographic investigation of trans-[CoBr₂(N)₄]⁺-type complexe where (N)₄ represents (NH₃)₄, (ethylenediamine)₂ and (propylenediamine)₂, has been carried out in acetate buffer solutions. These complexes gave two polarographic waves; the first wave corresponds to the reduction of Co(III) to Co(II) and the second to the reduction of Co(II) to Co(0). The relation between current and time of the first wave in a positive potential is dependent on the dissolution wave due to bromide ions produced by acid hydrolysis and parallel ECE mechanism. Overall reaction is as follows: at the electrode surface, [Co(III)Br₂(N)₄]⁺+e^-→[Co(II)Br₂(N)₄] [Co(II)Br₂(N)₄]+6H₂O→[Co(II)(H₂O₆]²⁺+2Br^-+(N)₄ 2Br^-+2Hg→Hg₂Br₂+2e and in the solution, [Co(III)Br₂(N)₄]⁺+2H₂O→[Co(III)(H₂O₂(N)₄]³⁺+2Br^-The effects of the acid hydrolysis of a tervalent cobalt complex on the current—potential curve were simulated.     

Neue Kronenether‐stabilisierte Oxoniumhalogenochalkogenate: [H3O(Dibromo‐benzo‐18‐Krone‐6)]2[Se3Br10] und [H5O2(Bis‐dibromo‐dibenzo‐24‐Krone‐8]2[Se3Br8]

Novel Oxonium Halogenochalcogenates Stabilized by Crown Ethers: [H₃O(Dibromo‐benzo‐18‐crown‐6)]₂[Se₃Br₁₀] and [H₅O₂(Bis‐dibromo‐dibenzo‐24‐crown‐8]₂[Se₃Br₈] Two novel complex oxonium bromoselenates(II,IV) and –(II) are reported containing [H₃O]⁺ and [H₅O₂]⁺ cations coordinated by crown ether ligands. [H₃O(dibromo‐benzo‐18‐crown‐6)]₂[Se₃Br₁₀] ( 1 ) and [H₅O₂(bis‐dibromo‐dibenzo‐24‐crown‐8]₂[Se₃Br₈] ( 2 ) were prepared as dark red crystals from dichloromethane or acetonitrile solutions of selenium tetrabromide, the corresponding unsubstituted crown ethers, and aqueous hydrogen bromide. The products were characterized by their crystal structures and by vibrational spectra. 1 is triclinic, space group (Nr. 2) with a = 8.609(2) Å, b = 13.391(3) Å, c = 13.928(3) Å, α = 64.60(2)°, β = 76.18(2)°, γ = 87.78(2)°, V = 1404.7(5) ų, Z = 1. 2 is also triclinic, space group with a = 10.499(2) Å, b = 13.033(3) Å, c = 14.756(3) Å, α = 113.77(3)°, β = 98.17(3)°, γ = 93.55(3)°. V = 1813.2(7) ų, Z = 1. In the reaction mixture complex redox reactions take place, resulting in (partial) reduction of selenium and bromination of the crown ether molecules. In 1 the centrosymmetric trinuclear [Se₃Br₁₀]^2? consists of a central Se^IVBr₆ octahedron sharing trans edges with two square planar Se^IIBr₄ groups. The novel [Se₃Br₈]^2? in 2 is composed of three planar trans‐edge sharing Se^IIBr₄ squares in a linear arrangement. The internal structure of the oxonium‐crown ether complexes is largely determined by the steric restrictions imposed by the aromatic rings in the crown ether molecules, as compared to complexes with more flexible unsubstituted crown ether ligands.     

Estimation of the specific adsorption of I−, Br−, and Cl− ions in systems (Tl-Ga)/[N-methylformamide + 0.1m M KA + 0.1(1 − m) M KClO4] (KA is KCl, KBr, and KI) based on the analysis of two-dimensional pressure curves obtained by integration of differential capacitance

By means of an ac bridge, the differential capacitance vs. potential curves are measured in systems (Tl-Ga)/[N-MF + 0.1m M KI + 0.1(1 ? m) M KClO₄], (Tl-Ga)/[N-MF + 0.1m M KBr + 0.1(1 ? m) M KClO₄], and (Tl-Ga)/[N-MF + 0.1m M KCl + 0.1(1 ? m) M KClO₄] for the following fractions m of the surfaceactive anion: 0, 0.02, 0.05, 0.1, 0.2, 0.5, and 1. Based on the analysis of curves of two-dimensional pressure found by integrating the differential capacitance, it is shown that the data on the specific adsorption of anions I^?, Br^?, and Cl^? in the mentioned systems can be quantitatively described by the Frumkin isotherm. The main adsorption parameters of I^?, Br^?, and Cl^? anions at the (Tl-Ga)/N-MF interface are determined. It is found that on the (Tl-Ga)/N-MF interface, the same as on the (In-Ga)/N-MF interface, the adsorption energy of ions increases in the sequence Cl^? < Br^? < I^?, in contrast to the Ga/N-MF interface, where the energy increases in the reverse sequence: I^? ≈ Br^? < I^?. For all halide ions (Hal^?), the adsorption energy and the energy of metal-Halinteraction increase in the sequence (Tl-Ga) < (In-Ga) < Ga.