Substituent dependence of the d-d transition band in the electronic absorption spectra of arylferrocenes and the corresponding arylferricenium salts

The electronic absorption spectra of 22 arylferrocenes and their arylferricenium salts with pentacyanopropenide (PCNP) were recorded. The attemptedHammett correlation of _max of the d-d transition bands of arylferrocenes revealed that this band is substituent dependent only for strong electron-withdrawing substituents. Excellent correlation of _max of the d-d transition bands with ⁺ constants was found in the case of arylferricenium cations. Good correlations of _max was also found with theE _1/2 oxidation potentials measured by cyclic voltametry.

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Substituentenabhängigkeit des d-d-Überganges in den Elektronenabsorptions-Spektren von Arylferrocenen und entsprechenden Arylferricenium-Salzen

Zusammenfassung Elektronenabsorptions-Spektren von 22 Arylferrocenen und ihren Arylferricenium-Pentacyanopropenid-Salzen wurden gemessen. VersuchteHammett-Korrelationen des längstwelligen d-d-Überganges (_max) zeigten, daß diese Bande nur von stark elektronenanziehende Substituenten abhängig ist. Im Fall der Arylferricenium-Kationen wurde eine ausgezeichnete Korrelation zwischen _max der d-d-Bande und den ⁺-Konstanten festgestellt. Eine gute Korrelation der _max-Werte wurde auch mit denE _1/2 Oxidationspotentialen gefunden, die durch cyclische Voltametrie meßbar sind.

     

Synthese von Metallkomplexen des Tetra-(2,3-anthra)-tetraazaporphins und Vergleich ihrer Elektronenabsorptionsspektren mit denen anderer anellierter Tetraazaporphinsysteme

Copper, nickel and aluminium derivatives of tetra-2,3-anthratetraazaporphin bearing different substituents in the anthracen part have been prepared. The absorption spectra of these substances in different solvents are given and compared with metal complexes of other linearly annellated tetraazaporphins. In the series of vanadyl complexes of tetraazaporphin (_max 597 nm), tetra-[1,2-(4-tert-butyl)-benzo]-tetraazaporphin (_max 698 nm), tetra-[2,3-(6-tert-butyl)-naphtho]-tetraazaporphin (_max 807 nm), tetra-2,3-(anthra)-tetraazaporphin (_max 932 nm), tetra-2,3-(tetraceno)-tetraazaporphin (_max 1055 nm), the absorption maxima of the Q-band are shifted per annellated benzene ring about 100 nm to longer wave lengths.

     

The kinetic energy components of LCAO-molecular orbitals: A comment on the “Electron-in-a-Box”-“LCAO-MO-Model” analogy

In many textbooks attention is drawn to the close analogy that seems to exist between the Electron-in-a-Box-wave functions _n and their LCAO-MO counterparts _J (J = n) for the movement of an electron in a -system. It is often implied that the wave lengths of _n and of _J (J = n) which satisfy to a high degree the relation =, have the same physical meaning. It is shown that this is not the case. for a linear system (e.g. a one-dimensional Electron-in-a-Box-model) is directly connected with the momentum of the electron and therefore with its kinetic energy according to the deBroglie relation. However, there is no such simple relationship between A and the corresponding kinetic energy component in LCAO-MO's _J . (The necessary two-center kinetic energy integrals have been computed for 1s-type atomic orbitals.)

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Zusammenfassung In vielen elementaren Textbüchern wird die Aufmerksamkeit auf die scheinbar enge Verwandtschaft hingelenkt, die zwischen den Wellenfunktionen _n für ein Electron-in-a-Box-Modell und den entsprechenden LCAO-MOs _J (J=n) für die Bewegung eines Elektrons in einem -System besteht. Unter anderem wird oft implizit angenommen, daß die Wellenlängen der Funktion _n und von _J (J=n), die weitgehend der Bedingung = genügen, die gleiche physikalische Bedeutung haben. In dieser Arbeit wird gezeigt, daß dies nicht der Fall ist. Für ein lineares System (z. B. ein eindimensionales Electron-in-a-Box-Modell) ist über die deBroglie'sche Beziehung direkt mit dem Impuls und damit mit der kinetischen Energie des Elektrons verknüpft. Im Gegensatz dazu existiert keine einfache Beziehung zwischen und der entsprechenden Komponenten der kinetischen Energie in einem LCAO-MO _J . (Die notwendigen Zweizentrenintegrale der kinetischen Energie wurden für Atomorbitale vom 1s-Typus berechnet.)

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Résumé Dans les textes élémentaires de chimie théorique on attire souvent l'attention sur l'analogie qui semble exister entre les fonctions d'onde _n pour un modèle «Electron-in-a-Box» et les fonctions correspondantes LCAO-MO _J (J=n) décrivant le mouvement d'un électron dans un système . En particulier cette comparaison implique que les «longueurs d'onde» de _n et de _J (J=n), qui satisfont pratiquement la relation =, ont la même signification physique. Dans ce travail on montre, que ceci n'est pas le cas. Pour un système linéaire (c.à.d. un modèle linéaire du type «Electron-in-a-Box») est reliée directement à la quantité de mouvement et par là à l'énergie cinétique, par la relation de deBroglie. Par contre on ne trouve pas une dépendance analogue entre et la composante correspondante de l'énergie cinétique dans une orbitale moléculaire LCAO _J. (Les intégrales bicentriques pour les composantes d'énergie cinétique nécessaires à ce calcul ont été déterminées pour des orbitales atomiques du type 1s.)

     

Principal vectors of crystallographic groups and applications

For a crystallographic group acting on ann-dimensional Euclidean space we consider the -invariant linear elliptic differential operatorP with constant coefficients and to it the -automorphic eigenvalue problemP [] + = 0. N() is the number of all eigenvalues smaller than or equal to the frequency bound ^q (q: order ofP). Earlier we found the asymptotic estimationN() c₀ · ⁿ + c₁ · ^n–1 (c ₀,c ₁: certain volumina). Furthermore,N() was interpreted as the number of so-called principal classes of principal lattice vectors within a convex domain. In this paper we demonstrate these results for the casen = 2 for two representative crystallographic groups and the assigned lattices. Above all we demonstrate a counting method for an exact estimation ofN() if a is not too big. In an analogous way we can treat all the 230 space groups of crystallography. It will be seen that these applications are brought about by the so-called principal vectors of these lattices.     

“Blue silver”: transformation of clusters and metal coagulation

The formation and transformations of blue silver ( _max 700 nm) during -irradiation of a weakly alkaline (pH 9) aqueous solution containing AgClO₄, polyacrylic acid (PAA), and isopropanol were studied. We believe that blue silver is a linear silver cluster stabilized on a polymeric molecule. During radiation-chemical reduction the cluster is transformed into new clusters ( _max = 365 and 460 nm). When all of the Ag⁺ ions present in the solution have been reduced, clusters coalesce and a new phase,i.e., colloidal silver particles, forms. The mechanism of the radiation-chemical transformations is discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 35–37, January, 1995.     

Ein Ger?t zur h?chstempfindlichen Differentialspektrophotometrie mit dem Rapidspektroskop

Zusammenfassung Eine Methode zur Differentialspektrophotometrie durch Modulation eines Monochromators wird beschrieben. Der Monochromator oscilliert mit variabler Bandbreite zwischen ₁ und ( ₁+). Wenn ( ₁+) die Wellenlänge des Absorptionsmaximums ist, erscheint am Photo multiplierausgang einer Sinuswelle, deren Amplitude der Extinktions differenz zwischen ¹ und ( ₁+) proportional ist. Die Schaltung zur ultralinearen Messung dieser Amplitude ist angegeben und ihre Anwendung mit dem Zweistrahlphotometer Rapidspektroskop gezeigt. Die Empfindlichkeit wird durch die Kombination um den Faktor 10 bis 100 gesteigert. Der Rauschpegel ist bei der Monochromator-Modulationstechnik etwa 10^–4 E.Das Differentialspektrum stellt die erste Ableitung eines Spektrums dar und gestattet die genauere Lokalisation von Schultern in steilen Flanken eines Spektrums. Die Kombination der beschriebenen Methode mit der Technik des Rapidspektroskops erlaubt es, dasselbe mit gleichem Erfolg wie ein Dual-Wavelength-Gerät einzusetzen.

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Summary A method for differential spectrophotometry by modulation of a single monochromator is described. A single monochromator oscillates with variable bandwidth between ₁ and ( ₁+ ). If ( ₁ + ) is the wavelength at maximal optical density, the photomultiplier output gives a sinus-wave, the amplitude of which is proportional to the optical density difference between ₁ and ( ₁+). The circuit for ultralinear measurement of this amplitude is described and details of its application with the split-beam spectrophotometer Rapidspektroskop are given. The sensitivity of the entire assembly is increased by a factor of between ten and one hundred. The noise level of the monochromator-modulated technique is about 10^–4 optical density units. The differential spectrum represents the first derivative of a spectrum and allows one to determine more exactly the location of shoulders in the slope of a spectrum.The combination of the described method with the techniques of the Rapid spektroskop thus provides facilities which equal those of a dual-wavelength apparatus.

     

Extraction and spectrophotometric determination of copper with 1-phenyl-3-thiobenzoyl thiocarbamide

Summary 1-Phenyl-3-thiobenzoyl thiocarbamide (PTT) is used for the extraction and spectrophotometric determination of copper at trace level. The yellow coloured Cu-PTT complex is extracted in chloroform, shows _max at 360 nm and is stable for 8 days. Beer's law is followed in the range of 0.04 to 0.36g of copper per ml. The effect of the presence of various ions is studied. Copper in alloys has been determined using this method.

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Extraktion und spektrophotometrische Bestimmung von Kupfer mit 1-Phenyl-3-thiobenzoyl-thiocarbamid (PTT)

Zusammenfassung PTT wurde für die Extraktion und spektrophotometrische Bestimmung von Kupfer-Spuren verwendet. Der gelbe Cu-PTT-Komplex wird mit Chloroform extrahiert und ist für 8 Tage beständig. _max liegt bei 360 nm. Das Beersche Gesetz gilt zwischen 0,04 und 0,36g Cu/ml. Der Einfluß verschiedener Fremdionen wurde untersucht. Mit Hilfe der angegebenen Methoden wurde der Kupfergehalt in Legierungen bestimmt.

     

Spectrophotometric estimation of ketotifen fumarate in pharmaceutical formulations

Four simple and sensitive spectrophotometric methods (A–D) for the determination of Ketotifen fumarate in bulk samples and pharmaceutical formulations are described. They are based on the formation of coloured species by the coupling of the diazotised sulphanilamide with the drug (method A, _max 520 nm) or by oxidizing it with excessN-bromo-succinimide and determining the consumed NBS with decrease in colour intensity of celestine blue (method B: _max 540 nm) or by the reduction of Folin-Ciocalteau reagent (method C: _max 720 nm) or by the formation of a chloroform-soluble, coloured ionassociation complex between the drug and Azocarmine G at pH 1.5 (method D: _max 540 nm). Regression analysis of Beer-Lambert plots showed good correlations in the concentration ranges 1–10, 2–12, 4–28 and 2.5–25 g/ml for methods A–D, respectively. The validity of the proposed methods was tested by analysing pharmaceutical formulations containing KTF: the relative standard deviations were within ±1.0%. Recoveries were 98.9–100.2%.     

Assay of cisapride in pharmaceutical formulations by visible spectrophotometry

Three spectrophotometric methods (A-C) for the assay of cisapride (CPD) in pure and dosage forms are described. Method A is based on the oxidative coupling reaction of CPD with 3-methyl-2-benzothiazolinone hydrazone hydrochloride (MBTH) in the presence of ferric chloride to form a coloured species (_max; 565 nm.) Method B is based on the oxidation of CPD with Fe (III) and subsequent chelation of Fe(II) to form a coloured complex with 1,10-phenanthroline (_max: 520 nm). Method C is based on the formation of a coloured charge-transfer complex between CPD and chloranilic acid (_max; 555 nm). Regression analysis of Beer-Lambert plots showed good correlation in the concentration ranges 2.0–32.0, 0.4–6.4 and 25.0–450.0 g/ml for methods A,B and C, respectively. The validity of the proposed methods was tested by analysing pharmaceutical dosage forms containing CPD and the relative standard deviations were within 1.0%     

A Multilayer Model for Gold Nanoparticle Bioconjugates: Application to Study of Gelatin and Human IgG Adsorption Using Extinction and Light Scattering Spectra and the Dynamic Light Scattering Method

A new model of colloidal gold (CG) bioconjugates is proposed. The model consists of a gold core and a primary polymer shell formed during conjugate synthesis. Additionally, the conjugate includes a secondary shell formed during its interaction with target molecules. Each of the inhomogeneous shells is modeled by the arbitrary number of discrete layers. Using Mie theory for multilayered spheres, we calculated the extinction and static light scattering (SLS, at 90°) spectra, as well as differential spectra A(), I() describing the effects of primary and secondary shells. Our calculations are performed for the conjugates with gold particle diameters d = 10–160 nm and two 5-nm shells. The primary shell consists of two 2.5-nm layers with the refractive indices of 1.50 and 1.45; the secondary shell, of two 2- and 3-nm layers with the refractive indices of 1.45 and 1.40. The differential spectra are related to the adsorption of target molecules and possess a characteristic resonance that is shifted to the red region of spectra compared to the usual localized plasmon resonances of gold particles. The maximal values of differential resonances A _max and I _max are observed for gold particles with diameters about 40–60 nm (extinction spectra) or 70–90 nm (the SLS spectra). The adsorption of human gamma-globulin (hIgG) and gelatin onto 15- and 34-nm gold particles was studied using the SLS and extinction spectra in combination with the dynamic light scattering measurements. It is shown that the thickness of adsorbed layer is equal to 5–6 nm for hIgG and to 15–18 nm for gelatin. The experimental extinction and SLS spectra for CG + hIgG conjugates are well explained by a simple model with the gold core and homogeneous polymer coating. For the CG + gelatin conjugates, we used the new model with inhomogeneous polymer coating, which is modeled by 10 discrete layers with the total thickness of 16–18 nm and exponential spatial profile of shell refractive index.     

Sensitive spectrophotometric methods for the determination of pindolol

Two simple, sensitive and reproducible visible spectrophotometric methods for the determination of Pindolol in amounts as low as 1 g are described. The first method is based on the oxidation of Pindolol by sodium nitrite under acidic conditions and the coupling of the oxidised intermediate withN-1-(naphthyl)ethylenediamine dihydrochloride (NED) to the colored product. The spectrum of the colored solution is strongly dependent on the length of the incubation period at room temperature during oxidation (3 min, _max 620 nm; 10 min or above _max 540 nm). Other couplers [diphenylamine (DPA) or 1-naphthylamine (-NA)] or indole derivatives (indole, tryptophan or isatin) when used instead of NED or Pindolol, respectively, also react to give a colored product with same maximum in each case irrespective of the length of the incubation period during oxidation. The second method is based on the coupling reaction involving Pindolol and 1,2-naphthaquinone-4-sulphonic acid sodium salt to form a coloured product (_max 660 nm). Both the methods have been employed to determine Pindolol content in bulk forms and pharmaceutical preparations.     

Beitrag zur mathematischen Beschreibung des Spannungs-Dehnungs-Verhaltens von Elastomeren

Zusammenfassung Ausgehend von der Hypothese vonValanis undLandel, nach der die DehnungsenergieW( _x , _y , _z ) als Summe dreier identischer Funktionenw( _i ) der Dehnungsverhältnisse _i (i=x,y,z) dargestellt werden kann, wird fürw( _i ) ein Ausdruck vorgeschlagen, der sich durch seine relative Einfachheit auszeichnet. Es wird gezeigt, daß die mit Hilfe dieses Ausdruckes abgeleiteten Formeln für das Spannungs-Dehnungs-Verhalten von Elastomeren in der Lage sind, Meßdaten anderer Autoren mit guter Genauigkeit wiederzugeben. Untersucht wurden die Beanspruchungsarten einaxialer Zug, biaxialer Zug und reine Scherung mit Dehnungen bis zu ca. 700%.

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Summary Based on the hypothesis ofValanis andLandel that the strain-energy functionW( _x , _y , _z ) could be represented as the sum of three identical functionsw( _i ) of the principal extension ratios _i (i=x,y,z), an expression forw( _i ) is suggested which is distinguished by its relative simplicity. The stress-strain relations developed from this expression are tested successfully by applying them to experimental results of other authors. The types of strain which were examined were simple extension, biaxial extension and pure shear; the elongations were to about 700%.

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Mit 4 Abbildungen     

Fluorimetric determination of 1-naphthol and mixtures of carbaryl and 1-naphthol in micellar media

Summary The interaction of 1-naphthol with different types of anionic, cationic and non-ionic surfactants has been studied spectrofluorimetrically in order to obtain a sensitivity enhancement in the determination of this compound. At neutral pH, cetyl trimethyl ammonium bromide (CTAB) provides a 2-fold sensitivity enhancement of 1-naphthol and exhibits a weak interaction with carbaryl. In strong alkaline medium carbaryl is hydrolyzed to 1-naphthol and in the presence of CTAB micells, a 5-fold sensitivity enhancement and a limit of detection of 0.2 g·ml^–1 with a 101±3% percentage of recovery is obtained. These facts permit the development of an accurate method for the fluorimetric analysis of 1-naphthol and carbaryl mixtures, comprising the determination of the sum of both compounds (pH 12, 0.1% w/v CTAB, _em=449 nm, _ex=341 nm) and of the concentration of 1-naphthol (neutral pH, 0.4% w/v CTAB, _em=449 nm, _ex=312 nm).     

Molecular and crystal structure of 1∶1 guest-host bis(hexafluoroacetylacetonato)calcium complex with 18-crown-6

We have carried out an X-ray structural study of the title complex (a CAD-4F diffractometer, MoK, graphite monochromator, /2 scan mode, _max, direct methods, 1465 reflections, R=0.036). Crystals are monoclinic with a=17.971(13), b=13.475(3), c=13.379(8) , =106.67(5)°, Z=4CaO₁₀C₂₂H₂₆F₁₂, space group C2/c, d _calc =1.537 g/cm³. The complex (C₂ symmetry) has a molecular structure and belongs to the guest-host type. The Ca atom is located in the center of the 18-crown-6 cavity; bidentate hexafluoroacetylacetonate guest ligands occupy the trans-positions relative to the plane of a maxidentate macrocycle. The Ca–O distances in a ten-vertex Ca polyhedron are 2.474–2.666 . The macrocycle conformation is characterized by six gauche C–C bonds and two gauche and ten trans C–O bonds. The dihedral COCC angle differs significantly (by 38.1°) from the angle of 60°, which is common to a gauche conformation. The six-membered cycle formed by oxygen atoms has a twist form with the annular O–O distances of 5.132–5.329 . Structural features explaining an easy sublimation of the compound are discussed.X-ray structural analysis and the interpretation of results.Synthesis of single crystals.Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 34, No. 6, pp. 56–65, November–December 1993.Translated by T. Yudanova     

Four spectrophotometric methods for determination of nitrofurazone in pharmaceutical formulations

Four simple and sensitive visible spectrophotometric methods (A-D) for the determination of nitrofurazone in bulk samples and pharmaceutical formulations are described. They are based on the formation of colored species by treating either its reduction product with 3-methylbenzothiazolin-2-one hydrazone in the presence of ferric chloride (method A: _max 600 nm) or its hydrolysis product with thiobarbituric acid (method B: _max 520 nm, 440 nm) or barbituric acid (method C: _max 400 nm) or by oxidizing it with excess N-bromosuccinimide and determining the consumed NBS using metol-isonicotinic acid hydrazide (method D: _max 620 nm).     

Simultaneous determination of yohimbine and boldine by first-derivative synchronous spectrofluorimetry

A method for the simultaneous determination of yohimbine and boldine in mixtures by first-derivative synchronous spectrofluorimetry has been developed. The method is based on their native fluorescence in 0.1N sulphuric acid medium. The constant wavelength difference chosen to optimize the determination was =_em -_em=82 nm. Yohimbine was measured at _ex//_em= 285/367 nm, and boldine at _ex/_em=272/354 nm. The range of application is 10–500 g/l for yohimbine and 1–50 g/l for boldine. The method was applied to the determination of yohimbine and boldine in synthetic mixtures and pharmaceuticals, with errors generally 2%. Relative standard deviations were about 2%.Dedicated to Professor Fermin Capitán on his 72th birthday     

Improved spectrophotometric determination of uranium(VI) with 4-(2-pyridylazo)resorcinol in the presence of benzyldimethylstearyltrimethylammonium chloride

An improved spectrophotometric determination of uranium(VI) is proposed using 4-(2-pyridylazo)resorcinol(PAR) in the presence of benzyldimethylstearyltrimethylammonium chloride(BSTAC) as a cationic surfactant. The calibration graph is linear in the range of 0.3–60 g/10 ml uranium(VI), measuring the absorbance at 550 nm. The reproducibility for 19.0 g/10 ml uranium(VI) is 0.57%. The third-derivative method using the third-derivative distance (d³A/d³) among ₁ 530 nm, ₃ 594 nm and ₂ 565 nm was also investigated.     

Modeling chemoadaptive behavior: X-ray structure of the trimethylamine oxide-urea (1∶4) complex

The structure of a trimethylamine oxide (TMAO)-urea 14 complex was investigated by x-ray crystallographic methods. C₃H₉NO, 4CH₄N₂O, M_r=315.33, monoclinic P2₁/n, a=11.004(2), b=9.8259, c=15.419(2),=106.88(4), V=1595.4(2) å₃, Z=4, D_x=1.313(1) g cm^–3, monochromatized Cu (=1.5418 å),=8.94 cm^–1, F(OOO)=680, temperature = 110K, final R=0.067, for 1786 unique observed reflections. Based on these studies and comparison with related compounds a model of the interaction of urea and TMAO with proteins, especially enzymes, is proposed. This is important in the physiology of many organisms, especially elasmobranchs. The counteracting effect of TMAO on urea perturbation of protein structure and function is interpreted in terms of water structure as a balance between the structure breaking effect of urea and the structure-stabilizing effect of TMAO.     

Photoinduced Acylotropic Rearrangement of Crown-Containing 2-[N-Acetyl-N-(4-aminobenzo-15-crown-5)methylene]-2,3-dihydrobenzo[b]thiophen-3-one

2-N-(4-Aminobenzo-15-crown-5)methylene-2,3-dihydrobenzo[b]thiophen-3-one and its acetyl derivative were synthesized. Their treatment with lithium, sodium, or potassium iodide in acetonitrile solution leads to formation of the corresponding crown-metal complexes. Irradiation of the acylated compounds at 436 nm induces NO migration of the acetyl group to give O-acyl isomer which is characterized by a considerable blue shift of the long-wave absorption band ( = 70 nm). The quantum yields of the photo- induced acylotropic reaction for the free ligand and its complexes with alkali metal cations change in the series: _L > K⁺ > Na⁺ > Li⁺.     

Photometrische Wismutbestimmung mit Brenzcatechinviolett

Zusammenfassung Es wurden die Bedingungen der photometrischen Wismutbestimmung mit Brenzcatechinviolett bei der WellenlÄnge _max=580 nm ausgearbeitet und der Einflu\ der Fremdionen untersucht. Das Lambert-Beersche Gesetz gilt in den Konzentrationsgrenzen 0,0–6,2 g Bi/ml bei 1,6 cm Schichtdicke.

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Summary A method is given for the photometric determination of bismuth using pyrocatechol violet, at the wave-length of _max=580 nm. Interferences by foreign ions have been examined. Beer's law is obeyed from 0.0 to 6.2 g Bi/ml (1,6 cm cuvettes).

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Als erste Mitteilung dieser Reihe soll die Arbeit: Malát, M.: Naturwissenschaften 48, 569 (1961) betrachtet werden.