A very short uranium-uranium bond: the predicted metastable U(2)2+

Quantum chemical calculations, based on multiconfigurational wave functions and including relativistic effects, show that the U(2)2+ system has a large number of low-lying electronic states with S of 0 to 2 and Lambda ranging from zero to ten. These states share a very small bond length of about 2.30 A, compared to 2.43 A in neutral U2. The Coulomb explosion to 2 U+ lowers the energy by only 1.6 eV and is separated by a broad barrier.     

Two-point self-coordination of a dizinc(II) bispyridylporphyrin ruthenium complex leading selectively to a discrete molecular assembly: solution and solid-state characterization

The dizinc(II) bispyridylporphyrin ruthenium complex trans,cis,cis[RuCl2(CO)2(Zn.4'-cisDPyP)2] (1Zn, 4'-cisDPyP = 5,10-bis(4'-pyridyl)-15,20-diphenylporphyrin) features two donor (the uncoordinated 4'-N(py) atoms) and two acceptor (the Zn atoms) sites and is thus a building block suited for two-point coordination. 1H NMR spectroscopy indicates that 1Zn self-assembles in solution through Zn-4'-N(py) interactions to yield selectively a highly symmetrical discrete species, in which all donor and all acceptor sites of 1Zn are mutually saturated. Single-crystal X-ray analysis established that this adduct is a dimeric species, (1Zn)2, with a global S4 symmetry, in which the four porphyrins have a propeller-like arrangement. The dimeric species (1Zn)2 is a meso form derived from the combination of two 1Zn units with opposite helical chirality. The geometry of this highly symmetrical tetraporphyrin assembly in solution, as determined by NMR spectroscopy, is essentially the same as that found in the solid state. Thus 1Zn is an unprecedented example of metal-containing self-complementary building block that selectively recognizes itself through four Zn-N(py) interactions, and thus yields a very stable and symmetrical dimeric species, (1Zn)2, that features four porphyrins and six metal atoms (two Ru and four Zn).     

How to derive priorities in AHP: a comparative study

A heated discussion has arisen over the “best” priorities derivation method. Using a Monte Carlo simulation this article compares and evaluates the solutions of four AHP ratio scaling methods: the right eigenvalue method, the left eigenvalue method, the geometric mean and the mean of normalized values. Matrices with different dimensions and degree of impurities are randomly constructed. We observe a high level of agreement between the different scaling techniques. The number of ranking contradictions increases with the dimension of the matrix and the inconsistencies. However, these contradictions affect only close priorities.     

Über das koordinationschemische Verhalten 2-substituierter Benzimidazole. I

Zusammenfassung Das Reaktionsverhalten von 2-Guanidino-benzimidazol (GBI) und 2-(o-Aminophenyl)-benzimidazol (APBI) gegenüber verschiedenen Metallen und deren Anionen wird beschrieben. Die meist gut kristallisierten Verbindungen werden hinsichtlich ihrer Zusammensetzung und Konstitution durch Elementaranalysen, spektroskopisch und thermogravimetrisch untersucht sowie etliche Stabilitätskonstanten gemessen. Arbeitsvorschritfen zur Herstellung dieser Metallkomplexe werden angegeben.

---

The coordination-chemical behaviour of 2-substituted benzimidazoles. I

Summary The behaviour of 2-guanidino-benzimidazole (GBI) and 2-(o-amino-phenyl)-benzimidazole (APBI) with various metals and corresponding anions is investigated. The constitution of the crystalline compounds is examined by means of elementary analysis, spectroscopic and thermogravimetric methods. Some stability constants are reported and procedures for the preparation of the metal-ligand-complexes are described.

     

The lateral distribution of energetic shower muons

Summary The customary assumption of a unique structure function of the formf(r)∞r ^−αexp[−r/R ₀] with parameters independent of the shower size and the nature of the primary is tested against evidence on the multiplicity distribution of shower muons. The experimental data were obtained with an array of three spark chamber telescopes installed at the Mt. Cappuccini underground station, Torino, at depths of about 40 to 60 hg/cm². They pertain to events with mean shower sizes between about 10⁵ and a few 10⁷ electrons. It is shown that the results are incompatible with this assumption, whatever values are assigned to the exponent α and to the characteristic radiusR ₀ of the structure function. A modified representation allowing for a variation ofR ₀ with the shower size and with the massA of the primary is suggested. The resulting distribution is in reasonable agreement both with thorough Monte Carlo evaluations for proton and iron primaries and with direct experimental observations of other authors.

---

Riassunto L'ipotesi usuale di una funzione di struttura unica della formaf(r)∞r ^−αexp[−r/R ₀] con parametri indipendenti dalle dimensioni dello sciame e dalla natura dei primari è provata rispetto alle prove sperimentali sulla distribuzione di molteplicità dei muoni dello sciame. I dati sperimentali sono stati ottenuti con un sistema di tre telescopi con camere a scintille istallati nella stazione sotterranea del Monte dei Capuccini, Torino, a profondità da 40 a 60 hg/cm². Essi riguardano eventi con grandezze medie di sciami tra circa 10⁵ e pochi 10⁷ elettroni. Si mostra che i risultati non sono compatibili con questa ipotesi, qualsiasi valore sia assegnato all'esponente α e al raggio caratteristicoR ₀ della funzione di struttura. Si suggerisce una rappresentazione modificata che consente una variazione diR ₀ con la grandezza dello sciame e con la massaA dei primari. La distribuzione risultante è in ragionevole accordo sia con tutte le valutazioni di Montecarlo per primari di protoni e di ferro e con osservazioni sperimentali dirette di altri autori.

---

Резюме Исследуется обычное предположение о единственной структурной функции видаf(r)∼r ^−αexp[−r/R ₀], с параметрами, не зависяцими от размеров ливня и природы первичной частицы, на основе данных о распределении множественности мюонов в ливне. Зкспериментальные данные получены с помошью системы трех телескпов искровых камеп, установленных на подземной стандии Капучини в Турине, на глубинах от 40 до 60 гг/см². Полученные данные относятся к событиям со средними размерами ливня от 10⁵ до 10⁷ злектронов. Показывается, что полученные результаты являются несовместимыми с зтим предположением, какие бы значения зкспоненте α и характерному радиусуR ₀ структурной функции не были бы приписаны. Предлагается модифицированное представление, учитывающее изменение велиьиныR ₀ с размером ливия и с массойA первичной частицы. Полученное распределение хорошо согласуется и с оценками по Монте-Карло для первичных протонов и ядер железа и с непосредственными экспериментальными результатами других авторов.

     

Ma?analytische Bestimmung von Barium mit Ammonium-Cer(IV)-nitrat

Zusammenfassung Barium gibt mit Oxaldihydroxamat quantitativ einen weißen Niederschlag, der gut filtrierbar ist. Die Oxaldihydroxamsäure läßt sich bei Gegenwart von Sulfamidsäure mit (NH₄)₂Ce(NO₃)₆-Titerlösung und Nitroferroin als Indicator maßanalytisch bestimmen. Versuche, das Barium über das Oxalat cerimetrisch zu bestimmen, verliefen negativ. Zur Bestimmung des Bariums wird mit Hydroxamat gefällt und dieses nach Lösen des Niederschlages cerimetrisch bestimmt.

---

Summary Barium may be precipitate quantitatively with oxaldihydroxamate. The white, crystalline precipitate can be filtered easily. Oxaldihydroxamic acid may be titrated in presence of sulphamic acid with a (NH₄)₂Ce(NO₃)₆ standard solution using nitroferron as indicator. The cerimetric determination of barium via the oxalate has been tried without success. In the proposed method barium is precipitated with hydroxamate and the latter is determined by cerimetry after dissolution of the precipitate.

     

An intermolecular force field for chlorinated benzene crystals

Intermolecular potential parameters corresponding to atom—atom interactions of the Buckingham form are refined on the basis of static and dynamic properties of some chlorinated benzene crystals. The model reproduces well the observed properties, including k ≠ 0 vibrations.     

Thiolutidinsäure-N,N′-dimethylamid als empfindliches Eisenreagens

Zusammenfassung Thiolutidinsäure-N,N-dimethylamid (TLSMA) bildet bei pH 14 ein violett gefärbtes Eisen(II)chelat mit hohem molarem Extinktionskoeffizienten. Das Reagens ist sehr empfindlich und hat in saurem Milieu reduzierende Eigenschaften. pH-Abhängigkeit, zeitlicher Verlauf der Komplexbildung und die Zusammensetzung des Chelats wurden untersucht. Ein Verfahren zur spektralphotometrischen Bestimmung von Eisenspuren (0,04–4g/ml) wurde beschrieben.

---

Thiolutidinic acid-N,N-dimethylamide as sensitive iron reagent

Summary At pH 14, thiolutidinic acid-N,N-dimethylamide yields a violet iron(II)-chelate with a high molar extinction coefficient. The reagent is very sensitive and has reducing properties in acid milieu. Its pH-dependence, the relation of time to the complex formation and the composition of the chelate were investigated. A procedure for the spectrophotometric determination of traces of iron (0.04 to 4g/ml) is decribed.

---

---

Herrn Prof. Dr. Erich Ziegler zum 60. Geburtstag gewidmet.     

Killing Symmetries of Generalized Minkowski Spaces, 3: Spacetime Translations in Four Dimensions

In this paper, we continue the study of the Killing symmetries of a N-dimensional generalized Minkowski space, i.e., a space endowed with a (in general non-diagonal) metric tensor, whose coefficients do depend on a set of non-metrical coordinates. We discuss here the translations in such spaces, by confining ourselves (without loss of generality) to the four-dimensional case. In particular, the results obtained are specialized to the case of a deformed Minkowski space (i.e. a pseudoeuclidean space with metric coefficients depending on energy).