Vibronic energies and spectra of molecular dimers

We consider three distinct methods of calculating the vibronic levels and absorption spectra of molecular dimers coupled by dipole-dipole interactions. The first method is direct diagonalization of the vibronic Hamiltonian in a basis of monomer eigenstates. The second method is to use creation and annihilation operators leading in harmonic approximation to the Jaynes-Cummings Hamiltonian. The adiabatic approximation to this problem provides insight into spectral behavior in the weak and strong coupling limits. The third method, which serves as a check on the accuracy of the previous methods, is a numerically exact solution of the time-dependent Schrodinger equation. Using these methods, dimer spectra are calculated for three separate dye molecules and show good agreement with measured spectra.     

Colorimetric determination of furfural and its precursors with azulene; application to air pollution

Two procedures in which azulene is used as the reagent for the determination of furfurals and furfurals and their carbohydrate precursors are described. Alipliatic aldcliydes, alcohols, and 2-deoxy sugars and their derivatives gave weak to negative reactions. The methods have been applied to the estimation of furfurals and furfuralprecursor carbohydrates in effluent from a coffee-roasting industrial plant.     

Synthesis,Structure, and Redox Chemistry of a Vitamin-B12s-Related Macrocyclic Complex of Cobalt(I)

(±)-[1-hydro-8H-HDP]cobalt(I) 1

1 Full name of 1: [2,2,3,3,7,7,8,8,12,12,13,13,17,17,18,18,-hexadecamethyl-2,3,7,8,12,13,17,18,-octahydro-1H,23H-10,20-diaza-porphinato]cobalt(I); full name of 2a : dibromo[2,2,3,3,7,7,8,8,12,12,13,13,17,17,18,18-hexadecamethyl-2,3,7,8,12,13,17,18-octahydro-1H,21H-10,20-diazaporphinato]cobalt(III).

2 For the nomenclature of [HDP]-complexes see addendum in [2].

is obtained by chemical or electrochemical four-electron reduction of (±)-dibromo- or (±)-dicano[1-hydroxy-8H-HDP]cobalt(III) 2a or 2b ⁴, respectively. The crystal nad molecular structure of 1 was determined by combination of X-ray analysis and MS, ¹H-, and ¹³C-NMR spectroscopy. Square-planar coordinated Co(I) lies closely to the best plane through the four N-atoms which form the first coordination sphere. Thermodynamic data for the coordination of axial bases with the cation of [1-hydroxy-8H-HDP]cobalt 2 in its different metal oxidation states were determined. The pathway of the overall four-electron reduction of 2a to 1 was elucidated: it involves a two-electron reduction of the central metal, a two-electron reduction of the macrocycle accompanied by elimination of the OH-group and final protonation at C(1). Evidence for an intramolecular electron transfer between the central metal and the macrocycle is presented.     

Die Rückbildung der Sekundär- und Tertiärstruktur denaturierter Eiweißmoleküle

Zusammenfassung Aus Untersuchungen über die Rückbildung des nativen Zustands von Eiweißmolekülen aus dem denaturierten geht hervor, daß ersterer von selbst wieder angestrebt wird und unter den Bedingungen, unter denen die Moleküle nativ vorliegen, der energetisch günstigste Zustand zu sein scheint. In den Worten der Genetiker bedeutet dies, daß die gesamte Information für den sterischen Bau der Moleküle bereits durch die Aminosäuresequenz gegeben ist.Es gibt eine Reihe von Hinweisen darauf, daß die — besonders in vivo — überraschend hohe Geschwindigkeit der Faltung in die hochkomplizierte Struktur dadurch erreicht wird, daß bestimmte Gruppen (aktive Zentren der Renaturierung) bevorzugt zusammentreten und das richtige Register zwischen den Komponenten oder Molekülteilen herstellen. Enzymsysteme scheinen die richtige vor der statistischen Zusammenlagerung zu fördern.Wir danken Herrn ProfessorW. Gramann für viele Anregungen und Diskussionen, sowie der Deutschen Forschungsgemeinschaft für die zur Verfügung gestellte Ultrazentrifuge.     

Über das 2,5-Dimethyl-2,5-endoxy-1,4-dithian

Ohne ZusammenfassungMit 1 Abbildung.