Novel dioximato-bridged chromium(III)-copper(II)-chromium(III) trinuclear complexes with ferromagnetic exchange interactions

Summary Two new dioximato-bridged trinuclear Cr^II-Cu^II-Cr^III complexes, [Cr(salen)-Cu(-BD)₂-Cr(salen)] (1) and [Cr(salen)-Cu(-FD)₂-Cr(salen)]-H₂O (2), have been prepared and characterized [salen^2– = N,N-ethylene- bis (salicylideneiminate), (-BD)^2– = -benzyldioximato and (-FD)^2– = -furildioximato]. Magnetic susceptibility measurements in the 4.2–300 K range demonstrated the operation of a ferromagnetic interaction between the adjacent Cr^III and Cu^II ions through oximato bridges in both (1) and (2). Based on spin Hamiltonians =–2J(₁₂+₂₃)(S₁=S₃=3/2,S₂=1/2) the exchange integrals (J) were evaluated as 3.19 and 5.38 cm^–1 for (1) and (2), respectively.     

Pressure dependence ofT x2113;ℓx2113;ℓx2113;ℓ

Summary For simplified analysis of PVT data to locateT and other secondary transitions, we demonstrate that series expansion of the term, lne(1 +P/b), in the Tait equation yields a number of approximations of varyine accuracy but all linear inP. The most useful ones are: (1 – V/V_o)=(C'/b)PforP/b < 0.3;P ¹ (1 - V/V_o) = (C/b) (1 – (P/2b)) forP/b < 0.6 but > 0.2 and the compressibility, /gz = (C/b)(1 -P/b) which requires a calculation of point-to-point derivatives, V,^–1 (/gDV//gDP), and hence is less satisfactory. C' andb are parameters in the Tait equation. We use C' = 0.0894.b = C' /-K, where /-K, is bulk modulus, increases with decreasing temperature but also has a step increase at each pressure-induced isothermal transition.b has a value of 1000 – 1500 bars nearT .Isothermal plots of (1 - V/V_o) againstP consist of two or more relatively straight line plots whose intersections give pressures,P ⁱ _n corresponding to each successive transition.T is usually the first transition,P ⁱ _l P ⁱ _n,moves to higher values as temperature increases.T starts at or near 1.2Tg and increases at a rate,dT /dP, which can be estimated. For iso PMMA data of Quach, Wilson and Simha, we estimateT = 110 °C atP = 0,dT /dP = 70 K/kbar. The original authors reportdTg/dP = 21.1 K/kbar.The same simplified equations apply even better to the glassy state relaxation for whichb is about 4100 bars at 26°C. We find that iso PMMA does indeed have adT at 10 °C (contrary to some authors) and adTß/dP of 70 K/kbar. These simple approximations do not work at isotherms nearTg whereb is changing; not near two close transitions for which there are insufficient data points to resolve them.Using values ofdT /dP previously determined for other polymers, and now for iso PMMA, we show thatdT /dP increases with the expansivity in free volume, /gDa, and hence, via Simha-Boyer, linearly inTg ¹.dT /dP 28 × 103/Tg (K).Finally, we present evidence which suggests that for weak secondary transitions each intersection,P ⁱ _n , gives a new origin with the new value of bn so that the effective pressure is P-Pⁱ _n-1 and (P-P ⁱ _n-1 )/b _n always remains less than about 0.5.

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Zusammenfassung Die Flüssig/Flüssig-UmwandlungT und andere sekundäre Umwandlungstemperaturen können aus PVT-Daten über eine Reihe geschlossener Ausdrücke erhalten werden, die alle durch Reihenentwicklung des Ausdrucks In (1 +P/b) der Tait-Gleichung gewinnbar sind. Die folgenden Ansätze erwiesen sich als besonders nützlich: (1 – V/V_o) = (C/b)P für Plb < 0,3 und P-(1 - V/V_o) = (Clb) (1 - (Pl2b)) fürP/b zwischen 0,2 und 0,6 wobeiC undb Parameter in der Tait-Gleichung sind. Die Verwendung der Kompressibilität ist weniger zufriedenstellend, da sie Punkt für Punkt über den Ausdruck V- (/gDVI /gDP) berechnet werden muß, bevor sie in den ebenfalls abgeleiteten Ausdruck = (C/b)(1 -P/b) eingesetzt werden kann. Gute Resultate werden mit C = 0,0894 undb = C /-Kerhalten, wobei /-K der Kompressionsmodul ist. Der Kompressionsmodul nimmt mit abnehmender Temperatur zu, weist aber auch eine stufenweise Zunahme bei jeder druckinduzierten isothermen Umwandlung auf. b hat in der Nähe vonT Werte von ca. 1000–1500 bar.Die Auftragung von (1-V/V_o) gegenP für konstante Temperatur liefert zwei oder mehr ziemlich gerade Linien, deren Schnittpunkte für jede entsprechende Umwandlung die DrückeP ⁱ _n angeben. Der erste UmwandlungsdruckP ⁱ _n, entspricht gewöhnlich der UmwandlungstemperaturT . Eine Temperaturzunahme führt zu höheren P _n ⁱ '-Werten.T weist bei Normaldruck etwa den Wert 1,2 Tg auf. Die ZunahmeT dP mit dem Druck kann aus Literaturdaten abgeschätzt werden. Aus den Daten von Quach, Wilson und Simha für isotaktisches PMMA erhalten wirT = 110 °C für P = 0 unddT /dP = 70 K/kbar. Diese Autoren berichtendTg/dP = 21,1 K/kbar.Die gleichen vereinfachten Gleichungen können sogar noch besser für die Analyse der ß-Relaxationen im Glaszustand angewendet werden. Die Konstanteb beträgt hier ca. 4100 bar bei 26 °C. Im Gegensatz zu anderen Autoren finden wir für isotaktisches PMMA eine-Umwandlung mitTß = 10 °C und dTßldP = 70 K/kbar. Diese Approximationen gelten jedoch nicht in der Nähe der Glasübergangstemperatur.Tg, da hier die Größeb nicht konstant ist. Sie können ebenfalls nicht angewendet werden, wenn zwei Übergangstemperaturen so nahe beieinander liegen, daß die Zahl der Meßpunkte nicht für eine Analyse ausreicht.Mit den zuvor für andere Polymere und nunmehr auch für isotaktisches PMMA erhaltenen Werten fürdT /dP kann gezeigt werden, daßdT /dP mit dem Unterschied /gDa der Ausdehnungskoeffizienten ansteigt. Nach der SimhaBoyer-Regel mußdT /dP daher auch linear mitTg ^-1 zunehmen. Für "dT /dP finden wir so 28 000/Tg(K).Es werden ferner Hinweise gefunden, daß die Drücke Pⁱ _n bei jeder schwachen sekundären Umwandlung einen neuen Ursprung mit einem neuen Wert vonb in der Weise geben, daß der effektive Druck (P – Pn _i ^n–1 ) beträgt und daß (P-P ⁱ _n ¹/b _n immer niedriger als ca. 0,5 bleibt.

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With 6 figures and 1 table

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Dedicated to Prof. Dr. G. Rehage on the occasion of his 60th bithday     

Thiolactame als Reagenzien in der quantitativen Analyse. IX

Zusammenfassung Thiocaprolactam (T) eignet sich zur Goldbestimmung im Konzentrationsbereich 10 bis 130 g Au/ml mit einem Fehler von ±0,5g. Thiocaprolactam bildet mit [AuCl₄]^– eine Verbindung im molaren Verhältnis TAuCl=112, mit [AuJ₄]^– im molaren Verhältnis TAuJ=213. Dagegen bilden sich im System T:Au:Br zwei verschiedene Verbindungen: Ein Bromidkomplex mit höherem Goldgehalt TAu=12, der mit Chloroform extrahierbar ist, und eine sich als Niederschlag ausscheidende Verbindung mit dem Verhältnis TAuBr=112.

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Thiolactams as reagents in quantitative analysis. IX

Summary Thiocaprolactam (T) is suitable for the determination of gold in the concentration range 10–130g Au/ml with an error of ±0.5g. Thiocaprolactam yields with [AuCl₄]^– a compound in the molar ratio TAuCl=112, with [Aul₄]^– in the molar ratio TAuI=213. On the other hand various compounds result in the system TAu Br. The molar ratio in the case of the bromide complex has a higher gold content, namely TAu=12; this product is extractable with chloroform and a compound that comes down as a precipitate shows the ratioT Au Br=112.

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Herrn Dr.K. Czerepko möchte ich hiermit meinen Dank für die Diskussion der Ergebnisse aussprechen.     

Synthesis,X-ray crystal structure and cation binding properties of a tetrahomodioxacalix[4]arene tetraester

Treatment ofp-t-butyltetrahomodioxacalix[4]arene with ethyl bromoacetate yields a tetraester derivative (4) whose crystal and molecular structure have been determined and whose ion binding properties have been assessed by phase transfer and stability constant measurements. Colorless transparent triclinic crystals (obtained from methoxyethanol) C₆₂H₈₄O₁₄,a = 10.347(2),b = 11.583(2),c = 13.448(3) Å, = 72.04(2), = 86.50(2)°, = 81.23(2)°, space group ,Z = 1, MoK radiation = 0.70930 Å. Refinement was carried out using 2221 reflections withI > 1.5(I). The complexation properties resemble those of calix[6]arene hexaester (6), although weaker, with a preference for the larger alkali cations. Ca²⁺ and Ba²⁺; though not extracted, are more strongly complexed than alkali cations. Eu³⁺ is better complexed than Na⁺.Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82106 (22 pages) and at the Cambridge Crystallographic Data Centre, University Chemical Laboratory, Lensfield Road, Cambridge CB2 9EW, U.K.     

Kinetics of enzymatic hydrolysis of sodium carboxymethylcellulose with different degrees of polymerization by cellulase

The reaction cellulase (EC 3.2.1.4)—sodium carboxymethylcellulose (Na-CMC) with different degrees of polymerization (n=140, 640 and 900) was investigated by the use of a modifiedMichaelis-Menten equation, valid for enzymatic hydrolysis of linear homopolymers. TheMichaelis-Menten constant [Km (M)=6.31·10^–2mol/dm³] and the reaction rate constant (k ₊₂=4.07·10^–6s^–1), which correspond to the enzymatic hydrolysis of a single bond in the homopolymer substrates are determined. The free energy ( =101 kJ/mol), which corresponds to the degradation and formation of a single bond in the enzyme—polymer substrate is also estimated. This energy expressed in electronvolt units is =1.39 eV. The ratio between the effective cross section of the reactive substrate bond and the active enzyme center is =1.22.

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Kinetik der enzymkatalysierten Hydrolyse von Natriumcarboxymethylcellulose mit verschiedenem Polymerisationsgrad durch Cellulase

Zusammenfassung Die modifizierte Gleichung nachMichaelis-Menten wird bei der durch Cellulase (EC 3.2.1.4) katalysierten hydrolytischen Spaltung von Natriumcarboxy-methylcellulose (Na-CMC) verschiedenen Polymerisationsgrades (n=140, 640 und 900) angewandt. Es wurde dieMichaelis-Menten-Konstante [Km (M)=6.31·10^–2mol/dm³] und die Reaktionsgeschwindigkeitskonstante (k ₊₂=4.07·10^–6s^–1), die der enzymatischen Hydrolyse einer Einfachbindung im homopolymeren Substrat entspricht, berechnet. Die freie Energie ( =101 kJ/mol), die dem Abbau und der Bildung einer Einfachbindung im Enzym—Polymer-Substrat entspricht, wurde bestimmt. Diese Energie — ausgedrückt in Elektronvolt-Einheiten — beträgt =1.39 eV. Das Verhältnis zwischen den effektiven Querschnitten der reaktiven Substratbindung ( _S ) und des aktiven Enzym-Zentrums ( _E ) beträgt =1.22.

     

Quadrupole polarizability and hyperpolarizability of carbon monoxide

Summary We report a study of the electric dipole-quadrupole (A _,,), quadrupole-quadrupole (C _,,), dipole-octopole (E _,) polarizability and the dipole-dipole-quadrupole (B _,,) hyperpolarizability of carbon monoxide. All values are obtained from finite-field self-consistent field (SCF) and fourth-order manybody perturbation theory (MP4) calculations. Our best values for the dipole-octopole polarizability areE _z,zzz=60.19 andE _x,xxx=–38.06e ² a ₀ ⁴ E _h ^–1 . For the dipole-dipole-quadrupole hyperpolarizability we reportB _zz,zz=–296,B _xz,xz=–170,B _xx,zz=88 andB _xx,xx=–178e ³ a ₀ ⁴ E _h ^–2 .     

Thermodynamics of tri- and pentabromide anions in aqueous solution

Formation constants for the tribromide and pentabromide anions were measured by a vapor partitioning method from 5 to 80°C. The molal thermodynamic parameters for these respective species at 25°C are: K ₃ –16.73, H ^o =–5.90 kJ-mol ^–1 , Cp ^o =–29 J-K ^–1 -mol ^–1 , and S ^o =3.6 J-K ^–1 -mol ^–1 ; K ₅ =37.7, H ^o =–13.0 kJ-mol ^–1 , S ^o =–13.6 J-K ^–1 -mol ^–1 , with Cp ^o assumed zero. These results are used to reevaluate published emf results for the bromine/bromide couple.     

On the asymptotic behavior of Hartree-Fock orbitals

Summary Handy et al. have shown that the asymptotic behavior of Hartree-Fock orbitals is controlled by the energy of highest occupied molecular orbital, except for the atomic case in which onlys-orbitals are occupied. However, their proof is not complete at one point. This point is clarified, and a more unified derivation is given. Further, we discuss the preexponential factorr of the leading asymptotic termr exp[–r], where =(–2_HOMO)^1/2 and _HOMO is the orbital energy of HOMO. New results are obtained for linear molecules, and the results of several authors for atoms and non-linear molecules are reproduced.     

Kinetics of the displacement of aqua ligands from cis-diaqua(ethylenediamine)-platinum(II)perchlorate by adenosine 5′-monophosphate in aqueous medium

The kinetics of the interaction of adenosine 5-monophosphate (5-AMP) with cis-[Pt(en)(H₂O)₂]²⁺ have been studied spectrophotometrically as a function of [Pt(en)(H₂O)₂]²⁺, [5-AMP] and temperature at pH 4.0, where the substrate complex exists predominantly as the diaqua species. Both N1 and N7 donor sites of 5-AMP are active for coordination to Pt at this pH. Base stacking and metal-induced macrochelate formation of 5-AMP plays a vital role in determining the concentration limit of 5-AMP during kinetics. Substitution occurs in two consecutive steps; both dependent on the 5-AMP concentration. Activation parameters for both steps have been calculated. The low H ₁ (42.76 ± 1.64 kJ mol^–1) and large negative values of S ₁ (–112.1 ± 5.1 J K^–1 mol^–1) as well as H ₂ (58.1 ± 1.4 kJ mol^–1) and S ₂ (–84.2 ± 4.4 J K^–1 mol^–1) indicate associative modes of activation for both ligand substitution processes in the two consecutive steps.     

Determination of Attogram Quantities of Silver via Quenching of the Solid Substrate Room-Temperature Phosphorescence of Rhodamine B Based on the Catalysis of its Oxidation by Potassium Persulfate

A new method of SS-RTP for the determination of trace silver has been established. This method is based on the fact that Ag⁺, when activated by ,-bipyridyl (bipy) in a media of HAc–NaAc (pH=4.9), can catalyze the reaction of Rhodamine B (RhoB) oxidized by K₂S₂O₈, thus causing the Solid Substrate Room-Temperature Phosphorescence (SS-RTP) of RhoB to be quenched. The activating efficiency of bipy is 6.7 times higher than that of o-phenanthroline (phen). The reduction of the phosphorescence intensity (I_p) of RhoB is directly proportional to the concentration of Ag⁺ ions in the range of 1.6016.0agspot^–1 (0.40µLspot^–1). The regression equation of the working curve can be expressed as I_p=18.78+5.100m_Ag+ (agspot^–1) (r=0.9994, n=6), the detection limit is 0.28agspot^–1. This rapid, accurate and sensitive method has been successfully applied to the determination of trace silver in tea and human hair samples, and the results agree well with the Atomic Absorption Spectroscopy (AAS) method. The mechanism of the catalyzing reaction is also discussed.     

Synthesis and protonation of an OS3(μ-H)(CO)10(μ-σ,η2-C≡CCMe2OMe) cluster

Triosmium cluster Os₃(-H)(CO)₁₀(--²-CCC Me₂OMe) (1) was obtained by treating OS₃(-H)(-Cl)(CO)₁₀ with LiCCCMe₂OMe. The reaction of cluster1 with HBF₄ · Et₂O at –60 °C leads to the cationic complex [Os₃(-H)(CO)₁₀(-,,²-C=C=C Me₂)]⁺BF₄ ^– (2) with an allenylidene ligand. The^s1H and¹³C NMR spectra of complex2 reveal the temperature dependence caused by migration of hydrocarbon and carbonyl ligands. Thermodynamic parameters were obtained for be exchange process of the allenylidene ligand.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp, 2990–2992, December, 1996.     

Electroconductivity and Ion Transport in Protonic Solid Electrolytes BaCe0.85R0.15O3–δ, where R is a Rare-Earth Element

The total, ionic, and protonic conductivities of solid electrolytes BaCe_0.85R_0.15O_{3 –} (BC15R), where R = Sc, Y, La, and all lanthanides bar Pm, are studied at ₂ = 2.1 × 10⁴–10^–15 Pa, ₂ = 2.1 × 10³ Pa, and temperatures of 550–1000°. The samples are synthesized in air at 1450° for two hours. In oxidizing media, all the electrolytes are mixed ion–hole conductors. In reducing environment, BC15R doped with R³⁺ exhibit oxygen–proton conduction. Ionic and protonic conductivities are independent of ₂. Protonic conductivity disobeys the Arrhenius dependence: it decreases with increasing temperature. The total and ionic conductivities of BC15R are virtually independent of the nature of cations R³⁺ in the interval from Nd to Lu.     

Atranes

The infrared absorption spectra over the range 400–1700 cm^–1 of ten organyl- and organoxysilatranes, p-CH₃C₆H₄O] are investigated. The SiN coordinate link in these compounds is largely unreflected in the fundamental vibration frequencies of the bonds of the central silicon atom or the internal vibration frequencies of the substituents X linked to that atom. However, all the IR spectra have an absorption band in the 570 cm^–1 region, related to the valence vibrations (SiN), or manifesting itself as the frequency (Si-O) of the XSi (O)₃ group, substantially lowered because of interaction between the Si-O and Si-N bonds. Evidence in favor of this bond is shift of the (Si-H) frequency in the spectrum of silatrane(X=H).For Part V see [1].     

State of copper in massive Cu?V?Mo oxide systems

ESR data for X(CuO) V₂O₅·8.3 MoO₃ system heated at 400–550 °C indicate the occurrence of a copper state with d_Z ²-ground state. Copper ions are orbitally ordered apparently in –Cu²⁺–O–Cu¹⁺–O–Cu²⁺-chains.

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B X(CuO) V₂O₅·8,3 MoO₃ , 400–550°C d_Z ²- . , , –Cu²⁺–O–Cu¹⁺–O–Cu²⁺-.

     

Magnetische Messungen im System Fe—Te

In the binary Fe–Te system six intermediate solid phases exist with varying ranges of homogeneity. With the exception of the high temperature -phase the magnetic behavior of these phases and in some cases the variation of magnetic properties with composition were investigated by susceptibility measurements in the temperature range from 100 to 300 K. Both the -phase (FeTe_1–x ) and the -phase (Fe₅Te₆) follow theCurie—Weiss law and can be designated as antiferromagnetic compounds according to the negativeWeiss constants of –192 K and –314 K, resp. The magnetic moments identify these two phases as high-spin compounds of Fe. The observed increase of the magnetic moments towards the Ferich limit of the -phase is due to the occupation of the octahedral interstices in the anion sublattice by excess iron and it was explained by a simple model. The magnetic moment of the hypothetical equiatomic compounds FeTe, obtained by extrapolation (3.87 _B), as well as the moment of the -phase (3.83 _B) are nearly identical and can be interpreted as being due to the existence of three unpaired 3d-electrons per formula unit. For the Te-rich (Fe_1–x Te)-, (Fe_1–x Te)- and (FeTe₂)-phases the transition metal is supposed to be in the low-spin state. The observedPauli paramagnetism is not temperature independent but decreases with decreasing temperature. Below 100 K FeTe₂ appears to be diamagnetic.

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Mit 7 Abbildungen     

Negativer linearer thermischer Ausdehnungskoeffizient von verstrecktem Polyäthylen

Zusammenfassung Der lineare thermische Ausdehnungskoeffizient von linearem Polyäthylen hoher Dichte wurde im Temperaturbereich –20 °C bis + 40°C bestimmt. Bei isotropen Proben besteht eine lineare Beziehung zwischen Dichte bzw. Kristallisationsgrad _v und. Die gemessenen Koeffizienten liegen fürT ₀ = 20 °C im Bereich = 110 ... 130 · 10^–6 K^–1.Kalt verstreckte Proben mit Verstreckungsgraden = 8 ... 15 haben beiT ₀ = 20 °C in Verstreckrichtung den Koeffizienten _l = –24 · 10^–6 K^–1. Der negative Zahlenwert von _tl ist unabhängig von und weiteren Herstellungsparametern. Seine Ursache ist einerseits die Orientierung derc-Achsen der Kristallite in Verstreckrichtung mit _c = –12 · 10^–6 K^–1 und andererseits der negative Koeffizient _am * –50 · 10^–6 K^–1 der verspannten amorphen Phase, der auf dem gummielastischen Verhalten der tie-molecules beruht.Beim Tempern oberhalb von +40 °C schrumpfen die Proben irreversibel, wobei _| ansteigt und nach dem Aufschmelzen der Proben wieder den Wert des isotropen Materials annimmt. Nach dem Tempern wenig unterhalb der Schmelztemperatur der Kristallite wurden überhöhte Koeffizienten _| gemessen, die eine Rotation der Kristallite um dieb-Achsen erkennen lassen.

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Summary The linear thermal coefficient of expansion,, of high density linear polyethylene has been determined in the temperature range of –20 ° ... + 40 °C. For isotropic samples a linear relationship between density or crystallinity _v and is valid. Measured values of forT ₀ = 20 °C amount to = 110 ... 130 · 10^–6 K^–1.Cold drawn samples of draw ratios = 8 ... 15 yield _| = –24 · 10^–6 K^–1 atT ₀ = 20 °C parallel to the draw axis. The negative value of _| does not depend on draw ratio or other parameters of sample processing. It is caused byc-axis orientation of the crystallites in draw direction with _c = –12 · 10^–6 K^–1 and by a negative coefficient _am * = –50 · 10^–6 K^–1 of the stressed amorphous phase, which is due to rubber elastic behaviour of the tie molecules.When annealed above 40 °C the samples shrink irreversibly and _| is augmented. After melting the samples the value of isotropic material is restored. Annealing the samples little below the melting temperature of the crystallites leads to superelevated values all which reflect| rotation of the crystallites around theb-axis.

     

Kinetic and mechanistic studies on the interaction of thymidine with the hydroxopentaaquarhodium(III) ion

The interaction of thymidine, a nucleoside, with hydroxopentaaquarhodium(III), [Rh(H₂O)₅(OH)]²⁺ ion in aqueous medium is reported and the possible mode of binding is discussed. The kinetics of interaction between thymidine and [Rh(H₂O)₅OH]²⁺ has been studied spectrophotometrically as a function of [Rh(H₂O)₅OH²⁺], [thymidine], pH and temperature. The reaction has been monitored at 298 nm, the _max of the substituted complex, and where the spectral difference between the reactant and product is a maximum. The reaction rate increases with [thymidine] and reaches a limiting value at a higher ligand concentration. From the experimental findings an associative interchange mechanism for the substitution process is suggested. The activation parameters (H=47.8 ± 5.7 kJ mol^–1, S=–173 ± 17 J K^–1 mol^–1) supports our proposition. The negative G⁰ (–13.8 kJ mol^–1) for the first equilibrium step also supports the spontaneous formation of the outer sphere association complex.