ESR Spectra of Trifluoromethyl Radical Obtained by Radiolysis and Photolysis in Solid Matrices

The ESR spectrum of CF₃ radicals trapped at 77 K in glassy matrices of a hexafluoropropylene trimer was examined. All the anisotropic components of the spectrum were assigned. The signals from parallel and perpendicular components resulting from hyperfine coupling to fluorine nuclei in the axially symmetrical CF₃ radical were identified. The values of magnetic parameters were found to be A _|| = 25.15 mT, A = 9.1 mT, g _|| = 1.9996, and g = 2.0056. The computer simulated ESR spectrum of CF₃ radical obtained in a glassy hexafluoropropylene trimer matrix can be used to interpret the spectrum of this radical in other solid matrices. Available literature data on the ESR spectra of CF₃ radicals trapped in solid matrices are summarized.     

Transference Numbers of NaCl in Aqueous Mixtures with Organic Solvents of Moderate to Low Permittivities

Electromotive forces (emf) were measured in the transference cells: AgAgCl- Nacl (m₂) in Z NaCl (m₁) in ZAgClAg and Na_xHg_1-xNaCl (m₁) in Z NaCl (m₂) in ZNa_xHg_1-x (where Na_xHg_1-x denotes a flowing Na–amalgam electrode and Z an aqueous-organic solvent mixture) at various molalities m ₂ > m₁ of NaCl in Z = (ethylene glycol + water), (acetonitrile + water) and (1,4-dioxane + water), with mass fractions of the organic components 0.8. The transference number of Na⁺ in (ethylene glycol + water) and (1,4-dioxane + water) varies little with respect to that in pure water medium, whereas in (acetonitrile + water) it increases remarkably with increasing proportion of acetonitrile so as to approach equitransference, behavior similar to that previously found in (methanol + water) and in (ethanol + water). At acetonitrile mass fraction 0.6 NaCl is sufficiently close to equitransference to emerge as a useful salt bridge, nearly at the same level as the popular aqueous KCl.     

Simultaneous TG and TGT investigations of the decomposition of 1-Oxy-2-diazonaphthalene-5-sulphochloride under quasi-isothermal conditions

A derivatographic examination was made of the exothermic decomposition of 1-oxy-2-diazonaphthalene-5-sulphochloride. It was found that the DTA, DTG and TG curves traced under the conventional conditions could not be interpreted, since their course changed from case to case according to the experimental conditions. As a result of the combined application of the multiplate sample holder and the quasi-isothermal heating technique the course of the decomposition became unambiguous. The diazo group split off at 116°, while the sulphochloride group departed between 200 and 400°. This latter process could also be traced separately by the continuous measurement of the liberated sulphur dioxide and chlorine thermo-gas-titrimetrically.

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Zusammenfassung Die Autoren prüften mittels des Derivatographen die exotherme Zersetzung von 1-Oxy-2-Diazo-Naphtalin-5-Sulfochlorid. Sie stellten fest, daß die unter herkömmlichen Bedingungen aufgenommenen DTA, DTG und TG Kurven nicht interpretiert werden konnten, da ihr Verlauf je nach den Versuchsbedingungen von Fall zu Fall verschieden war. Als Ergebnis des gewöhnlichen Einsatzes des Vielplatten-Probenbehälters und der quasi isothermen Aufheizungstechnik wurde der Zersetzungsverlauf eindeutig. Es wurde festgestellt, daß die Diazo-Gruppe bei 116° abgespalten wurde, während sich die Sulfochlorid-Gruppe bei 200–400° abtrennte. Die Autoren konnten diesen letzten Vorgang auch gesondert verfolgen, und zwar durch kontinuierliches Messen des freigesetzten Schwefeldioxids und Chlors mittels Thermo-Gas-Titrimetrie.

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Résumé Les auteurs ont étudié à l'aide d'unDerivatograph la décomposition exothermique de l'1-oxy-2-diazo naphtalène 5-sulfochlorure. Ils ont trouvé que les courbes ATD, TG et TGD obtenues suivant les conditions habituelles ne pouvaient pas être interprétées, étant donné que leur allure changeait d'un cas à l'autre, selon les conditions d'expérience. Au contraire, sous l'effet conjugué de l'utilisation d'un support échantillon multiplaques et de l'emploi de la technique de chauffage quasi-isotherme, la décomposition s'effectue de manière univoque. On a établi ainsi que le groupe diazo se sépare à 116° et le groupe sulfochlorure à 200–400°. Les auteurs ont pu également enregistrer ce dernier processus par la mesure, en continu, de l'anhydride sulfureux et du chlore dégagés, par analyse titrimétrique des gaz émis.

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1--2- --5- . , , , , , . - , . , 116° , 200–400°. -- .

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The authors wish to thank prof. E. Pungor for valuable discussions.     

Oscillatory behavior in the oxidation of hematoxylin with bromate and sulfuric acid

Uncatalyzed and catalyzed oscillatory behavior in the redox potential in the oxidation of hematoxylin with acidic (H₂SO₄) bromate is reported.

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- (H₂SO₄) .

     

Distorted pentacoordinate copper(II) complexes containing a tridentate ligand

Summary Copper(II) complexes with a tridentate chelating ligand within the general 2N, X (X = O or S) donor class, containing abis(benzimidazolyl) donor set, were prepared and characterized. X-band e.p.r. spectra of the complexes indicateg >g and the largeg and lowA have been interpreted in terms of a distorted basal plane. Superimposed on theg component are five SHF lines withA _N = 16±2G, supporting the interaction of two nitrogen atoms with the copper nucleus. Thus, the basal plane of the complex comprises 2N atoms, with the ligand hetero atom being axially coordinated.     

Studies of the composition and catalytic properties of supported catalysts prepared through halide-substituted titanium and zirconium benzyl complexes

Composition and catalytic properties in ethylene polymerization of supported systems prepared via the interaction of Ti(CH₂C₆H₅)₃X (X=F, Cl, Br) and Zr(CH₂C₆H₅)₂Cl₂ complexes with silica and alumina have been studied. Halide addition to benzyl complexes decreases the polymer molecular mass.

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, Ti(CH₂C₆H₅)₃X (X=F, Cl, Br) Zr(CH₂C₆H₅)₂Cl₂ SiO₂ Al₂O₃. , .

     

Synthesis,crystal structure and spectroscopic characterization of a hydrogen-bonded 1D copper(II) complex

Novel 1:2 and 1:1 (M:L) copper(II) complexes have been prepared from the tridentate ligand 2-(1-methyl-2-aza-5-oxapentyl)phenol (H₂L¹). The crystal structure of [Cu(HL¹)₂] (1) exhibits a noncentrosymmetric square-planar geometry with a slightly tetrahedral distortion. The Cu^II atom is coordinated by two amino N and two phenoxo O atoms of two (HL¹)^– ligands. The phenoxo and the alkoxy groups are involved in two strong intramolecular hydrogen bonds. The coordination moieties are further connected to a 1D linear structure by the action of intermolecular hydrogen bonds between the alkoxyl and the amino groups. The importance of steric hindrance introduced by the methyl group in the molecular structure and the packing of the complex molecules has been demonstrated. The e.p.r. parameters of (1) have been obtained: g = 2.231, g = 2.005, g _iso = 2.080, A = 185.0 G, A _iso = 86.5 G, A = (3A _iso – A )/2 = 37.3 G. These results confirm a distorted square planar stereochemistry with a ( )¹ ground state.     

Ruthenium clusters containing the [2.2] paracyclophane ligand: Recent developments in arene-cluster chemistry

In this article we review the synthesis, reactivity, and characterization of a number of clusters bearing the [2.2] paracyclophane ligand with nuclearities ranging from two to eight. Particular attention is focused on the different coordination modes that paracyclophane adopts; these being µ₁- ⁶, µ₂- ³ : ³, µ₃- ¹ : ² : ², and µ₃- ² : ² : ². Structural modifications which take place within the ring system on bonding in these various modes are also discussed.     

On theC v toC p conversion for solid linear macromolecules

TheC _v toC _p conversion for solid linear macromolecules via the Nernst-Lindemann equationC _p -C _v =A ₀,C _p ² T/T_m is discussed on hand of data for 10 crystals and seven glasses. An average value ofA ₀=(5.11±2.41) · 10^–3 mol K J^–1 was calculated if the mole is assumed to refer to heavy atoms only. ThisA ₀ is numerically equal to the original Nernst—Lindemann constant.

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Zusammenfassung An Hand von sich auf 10 Kristalle und 7 Gläser beziehenden Daten wird die Umrechnung vonC _v -inC _p -Werte für feste lineare Makromoleküle mittels der Nernst-Lindemann-GleichungC _p -C _v =A ₀ C _p ² T/T _m diskutiert. Ein Durchschnittswert vonA ₀=(5.11±2.41) · 10^–3 mol K J^–1 wurde unter der Annahme berechnet, daß sich das Mol nur auf schwere Atome bezieht. DieserA ₀-Wert ist numerisch gleich der ursprünglichen Nerns-Lindemann-Konstanten.

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10 , - C _v C _p , —C _p –C _v = _{0 p} ² / . , , ₀ (5.11±2.41) · 10^–3 · ^–1. ₀ — .

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Support by the National Science Foundation, Polymers Program (Grant No. DMR 83-17097) is gratefully acknowledged.     

Fluorescent Molecular Sensing System Based on Tri-Pyrenes-Labeled γ-Cyclodextrin at the Hetero Rim

Fluorescent active host labeled at the upper and lower rims of -cyclodextrin, namely, mono-3^A-deoxy-3^A-pyrenebutylamido-6^X,Y-O-bis-pyrenebutylate-mono-altro--cyclodextrin (-3) has been synthesized as a chemosensor for steroidal guests using fluorescence spectra change upon a guest addition. The -3 shows monomer and excimer fluorescence, which results in an increase of the intensity of monomer and decrease of excimer fluorescence with a host–guest binding in the cyclodextrin cavity. The extent of monomer and excimer fluorescence variations of -3 was used as an indication for the sensing ability for the guests examined. The guest-induced fluorescence changes were measured for 10^–7 M solutions of -3. The sensing parameters (I_ex/I⁰_ex and I_mon/I⁰_mono) were used to describe the sensing ability of -3. The values of I_ex/I⁰_ex describe that -3 shows less selectivity for guests than that of mono-3^A-deoxy-3^A-pyrenebutylamido-6^X-O-mono-pyrenebutylate-mono-altro--cyclodextrin (-2), and the values of I_mon/I⁰_mono show that -3 shows higher sensitivity and selectivity than that of -2.     

Biogels of cytochrome c : Cytochrome c peroxidase complex studied by electron paramagnetic resonance spectroscopy

Cytochrome c: cytochrome c peroxidase (Cc: CcP in 1: 1 ratio) complex was successfully encapsulated in sol-gel derived glass. The electron paramagnetic resonance (e.p.r.) and optical absorption techniques were used to characterize the coordination number, spin state, charge-transfer activity and structural orientation of Cc: CcP complex and its constituents. The sol-gel encapsulation of metalloproteins allows, for the first time, the detection of e.p.r. signals of biological systems at room temperature. CcP exhibits an e.p.r. spectrum representing the high spin and purely axial symmetry with parameters at g 6 and g 2 and an electronic absorption spectrum with a descent in spectral intensity of shoulder band at 380 nm and a blue-shifted charge-transfer band at 620 nm. Cc shows an e.p.r. spectrum characterizing a mixture of high spin (g 6 and g 2) and low spin (g _x=2.7, g _y=2.2 and g _z=1.8) components. Upon complexation, Cc:CcP pair displays a single and broad e.p.r. spectrum at g 2 and a light absorption spectrum with a red-shifted Soret band at 423 nm, a blue-shifted charge-transfer band at 620 nm and an intensified charge-transfer band at 507 nm. These results suggest that the sol-gel encapsulated Cc:CcP complex has the following chemical and physical characteristics: (a) a hexa-coordination, (b) a high-spin state, (c) an active charge-transfer (or redox) pair, and (d) the direction of the g paramagnetic center of Cc : CcP complex lies nearly parallel to that of the heme normal. The structural coordinations of the sol-gel encapsulated Cc, CcP and Cc : CcP are examined. Moreover, the possible use of biogels at the sol, gelation, and xerogel stages during gel processing to control the structural rigidity and spatial separation/orientation of the encapsulated heme proteins and to study their possible routes of long-range electron transfer reactions are also discussed.     

Phase equilibria in the V2O5-Cr2O3 system

The phase equilibria in the total range of component concentrations in the V₂O₅-Cr₂O₃ system up to 1000 °C were studied by means of phase powder diffraction and DTA. Two compounds exist in the system: CrVO₄, melting incongruently at 860±5 °C, and Cr₂V₄O₁₃, which decomposes in the solid state at 640±5 °C to CrVO_4(s) and V₂O_5(s). At 645±5 °C, CrVO₄ and V₂O₅ form a eutectic mixture with the CrVO₄ content not exceeding 2% mol.

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Zusammenfassung Mittels DTA und Pulverdiffraktionsaufnahmen wurde das Phasengleichgewicht des Systems V₂O₅-Cr₂O₃ bis 1000 °C im gesamten Konzentrationsbereich untersucht. Innerhalb des Systemes existieren zwei Verbindungen: CrVO₄ mit einem inkongruentem Schmelzpunkt bei 860±5 °C und Cr₂V₄O₁₃, das sich in festem Zustand bei 640±5 °C in CrVO_4(s) und V₂O_5(s) zersetzt. Bei 645±5 °C bilden CrVO₄ und V₂O₅ ein eutektisches Gemisch mit einem maximalen CrVO₄-Gehalt von 2 mol%.

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DTA V₂₅-Cr₂₃ 1000° . : CrVO₄, 860±5° Cr₂V₄O₁₃, 640±5° CrVO₄ V₂O₅, 645±5° CrVO₄, 2 %.

     

Isomerization of 3β-acetyl-α-3,4-epoxycarane

Conclusions 3-Acetyl--3,4-epoxycarane under the influence of bases is easily rearranged to the,-unsaturated ketol, namely 3-acetyl-4-caren-3-ol, by the E₂ mechanism of the-elimination reaction.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2084–2086, September, 1971.     

Kinetics of Methyl Iodide Tribosorption on the Solid-Phase Salt KI

It was found that the tribosorption of methyl iodide from the gas phase of a closed reactor onto a matrix of KI is described by the rate equation for a reversible first-order reaction v _g – v _{, g} = mv _ts ^* exp(–_td D _sp), where v _g and v _{, g} are, respectively, the current and equilibrium amounts of methyl iodide in the gas phase; v _ts ^* is the equilibrium amount of methyl iodide tribosorbed per gram of salt; m is the mass of potassium iodide; _td is a constant, which characterizes the efficiency of tribodesorption (_td = 0.011 ± 0.005 g/J); and D _sp is the specific dose of mechanical energy absorbed by the KI powder. The value of v _ts ^* monotonically increased with increasing equilibrium partial pressure of methyl iodide and reached a maximum value of 25 mol/g. The lower limit of the constant _td, which characterizes the efficiency of tribosorption, was estimated at 0.1 g/J.     

Some Pharmaceutical Properties of a New Branched Cyclodextrin, 6-O-α-(4-O- α-D-Glucuronyl)-D-glucosylβ-cyclodextrin

Some physicochemical and biological properties of a new branched cyclodextrin, 6-O--(4-O--d-glucuronyl)-d-glucosyl--cyclodextrin GUG--CyD) were investigated. Further, theinteraction of GUG--CyD with several drugs was studied by the solubility and spectroscopic methods, and compared with those of parent -CyD and 6-O--maltosyl--CyD(₂--CyD).The hemolytic activity of GUG--CyD on rabbit erythrocytes was lower than those of -CyD and ₂--CyD. GUG--CyD and ₂--CyD showed negligible cytotoxicity on Caco-2 cells up to at least 0.1 M. The inclusion ability of GUG--CyD to neutral and acidic drugs was comparable to or slightly smaller than those of -CyD and ₂--CyD, probably because of a steric hindrance of the branched sugar. On the other hand, GUG--CyD showed greater affinity for the basic drugs, compared with -CyD and ₂--CyD, owing to the electrostatic interaction of its carboxylate anion with positive charge of basic drugs. Thus GUG--CyD may be useful as a safe solubilizing agent particularly for basic drugs.     

ESR study of99Tc/II/ complex formed by reduction of ammonium pertechnetate with ascorbic acid in concentrated hydrochloric acid

Paramagnetic⁹⁹Tc complex formed by the reduction of ammonium pertechnetate by ascorbic acid with excess sodium nitrite in concentrated hydrochloric acid was investigated by ESR technique. This complex had total electron spin S=1/2 and the obtained ESR parameters were: g_|=2.032, g=2.043, A_|=264 gauss and A=108 gauss. Based upon these data it was concluded that the formed species was low spin⁹⁹Tc/II/ complex.     

The importance of the CO 2 2− anion in the mechanism of thermal decomposition of oxalates

The effects of active (carbon dioxide and carbon monoxide) and neutral (helium, argon and nitrogen) atmospheres on the course of thermal decomposition of oxalates have been studied and compared. A mechanism of thermal decomposition has been proposed on the basis of the results obtained, the first stage of which consists in a heterolytic dissociation of the C-C bond, with the formation of carbon dioxide and the CO ₂ ^2– anion.

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Zusammenfassung Die Effekte von aktiven (Kohlendioxid und Kohlenmonoxid) und neutralen (Helium, Argon, Stickstoff) Atmosphären auf den Verlauf der thermischen Zersetzung von oxalaten wurden untersucht und miteinander verglichen. Aus den erhaltenen Ergebnissen wird ein Mechanismus der thermischen Zersetzung abgeleitet, dessen erster Schritt die heterolytische Dissoziation der C-C-Bindung unter Bildung von CO₂ und des CO ₂ ^2– -Anions ist.

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(- ) (, ) . , C-C CO ₂ ^2– .

     

Complexing equilibria and redox potentials of the Ag(II)/Ag(I) system in the presence of 2,2′:6′,2″-terpyridine in water

Summary The conditional protonation constants (=0.1) for 2,2:6,2-terpyridine, logK ₁=4.93, logK ₂=3.69, were determined by thepH-metric method. The compositions of complexes of Ag²⁺ and Ag⁺ ions with 2,2:6,2-terpyridine (tp) were studied and equilibria of the complex formation process were described. The values of conditional complex formation constants are as follows: for Ag(tp) ₂ ⁺ :log₀₁=5.79, log₀₂=9.68, for Ag(tp) ₂ ²⁺ :log₀₂=25.31, while the conditional constant of the Ag(tp)NO₃ precipitate formation is:K _SO=2.45·10⁴. Using coulometric and chronovoltamperometric measurements, the redox systems being formed in the complex solutions of Ag(II) and Ag(I) were determined and described including their formal potentials.

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Komplexibildungsgleichgewichte und Redoxpotentiale des Systems Ag(II)/Ag(I) in Gegenwart von 2,2:6,2-Terpyridin in Wasser

Zusammenfassung Mit Hilfe derpH-metrischen Methode wurden die konditionalen Protonationskonstanten (=0.1) von 2,2:6,2-Terpyridin bestimmt: logK ₁=4.93, logK ₂=3.69. Es wurde auch die Zusammensetzung der Komplexe von Ag(II) und Ag(I) mit 2,2:6,2-Terpyridin(tp) bestimmt sowie die Gleichgewichte der komplexbildung beschrieben. Die Werte der Konditionalkomplexbildungskonstanten sind: für Ag(tp) ₂ ⁺ :log₀₁=5.79, log₀₂=9.68, für Ag(tp) ₂ ²⁺ :log₀₂=25.31 und für das Löslichkeitsprodukt Ag(tp)NO₃:K _SO ^–1 =4.08·10^–5. Die in Komplexlösungen von Ag(II) und Ag(I) vorliegenden Redoxsysteme wurden mittels cyclischer Voltametrie und Coulometrie untersucht und die Formalpotentialwerte dieser Systeme in Wasser bestimmt.

     

Ab initio investigation of the electron structure in bis-Cu+ acetylene and vinylidene complexes

[Cu(-C₂H₂)₂]⁺, [Cu(-CCH₂)₂]⁺ and [Cu(-C₂H₂) (-CCH₂]⁺ complexes have been studied by the ab initio double-zeta basis set method. It has been established that all calculated compounds are stable to decomposition into two C₂H₂ molecules and Cu⁺ cation and into one C₂H₂ molecules and the respective monocomplex. Calculation results suggest the possibility of intramolecular acetylene-vinylidene rearrangement in the coordination sphere of Cu⁺.

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ab initio : [Cu(-C₂H₂)₂]⁺, [Cu(-CCH₂)₂]⁺, [Cu(-C₂H₂) (-CCH₂)]⁺. C₂H₂ Cu⁺ C₂H₂ . - Cu⁺.

     

Controlled-potential coulometric studies on fluoride and sulphate complexes of neptunium (VI)

Fluoride and sulphate complexing of Np(VI) has been studied by controlled-potential coulometry at a constant ionic strength. The values of ₁ ^* and ₂ ^* for fluoride complexes were found to be 9.4 and 8.9, respectively, at an ionic strength =0.5. At an ionic strength =1.0, ₁ ^* and ₂ ^* obtained were 6.6 and 10.5, respectively. Sulphate complexing of Np(VI) was studied only at an ionic strength =0.5. The value of ₁ ^* obtained was 5.6.