Quantum field theoretical methods in chemically bonded systems II

Summary Many-body perturbation theory is derived for chemical bonds. Paired quasiparticles represent the bonds. Products of the paired quasiparticles define a model Bardeen-Cooper-Schrieffer function. The pairing force is added as a model interaction to the self-consistent problem. The starting model is based on valency and adiabatic symmetry correlation. Symmetries are enforced by the model Hamiltonian. Perturbative corrections are expressed as ordinary Feynman diagrams. The number of diagrams needed is the same as for particle-hole theory.This work was supported in part by the U.S. Department of the Navy, Space and Naval Warfare Systems Command under Contract N00039-89-C-0001, and in part by NATO Research Grant 1861. It was presented, in part, at the A.C. Wahl Memorial Session, Molecular Spectroscopy Symposium, Columbus, Ohio, 1984; and Midwest Theoretical Chemistry Conference, Milwaukee, Wisconsin, 1985.     

Über ein Verfahren zur Erzeugung zweiseitig eingespannter,kurzer Polyethylen-Modellketten

Zusammenfassung Ein Algorithmus zur Erzeugung zweiseitig eingespannter Polyethylen-Modellketten im Diamantgitter wird vorgestellt, dessen Grundidee folgendermaßen angegeben werden kann: Die Gesamtheit der Modellketten bestimmter Kettenlängen zu einem vorgegebenen Anfang-End-Vektor erhält man, indem man zunächst die Grundverteilung zu diesem Anfang-End-Vektor bestimmt, durch Hinzufügen von geeigneten Paaren einander entgegengesetzter Gittervektoren die für die gegebene Kettenlänge möglichen Vektorverteilungen ermittelt und schließlich zu diesen alle möglichen Anordnungsmöglichkeiten der Gittervektoren sucht. Der Algorithmus wird im Abschnitt 2.1. am Beispiel des ebenen Wabengitters erläutert und dann im Abschnitt 2.2. auf das dreidimensionale Diamantgitter angewendet. Das Flußschema des entsprechenden Computerprogramms ist im Anhang angegeben.

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An instruction is given for generating polyethylene model chains fixed at their two ends in the diamond lattice. The fundamental thought is as follows: The ensemble of model chains of given length and end-to-end vector is obtained in three steps. First of all the basic distributions of chain vectors belonging to is determined. Secondly, all the possible distribution of chain vectors consistent with given chain length are found by addition of suitable pairs of opposite chain vectors to the basic distribution. Thirdly, all the allowed sequences of chain vectors are arranged.In section 2.1. this method is demonstrated for the plane honeycomb lattice. In section 2.2. it is applied to the tridimensional diamond lattice.The flow diagram of the computer programme is given in the appendix.

     

Calculation of number and free energy of the conformers of linear alkanes with medium and long chains. Implications for catalysis

A method for calculating the number of rotamers of a linear alkane and of the number of rotamers with a given number of gauche conformations along the chain as a function of the total number of atoms in the chain, using general equations, is presented. A graphical method for generating individual rotamers was applied to the homologs up to decane, which has 1134 rotamers. The steric energies calculated by molecular mechanics (MM2 force field) were used as measures of the heat of formation for the coiled conformations relative to the anti conformer for each molecule, whereas the statistical entropy differences were calculated for classes of coiled rotamers grouped by the number of gauche bonds and steric energy. The free energy values calculated from these components show that already at 400 K hexane exists preferentially in conformations containing gauche bonds. For larger chains the free energy advantage for the coiled chains increases very steeply. The implications for the question of reactions of linear alkanes occurring on the surface or inside the channels of small- and medium-pore zeolites are briefly examined.     

Application of Phosphorus-31 Nuclear Magnetic Resonance Spectrosocopy for the Study of Human Diabetic Cataractogenesis

Intact human Senses incubated at 5.5 mM (normal) and 35.5 mM glucose were examined by phosphorus-31 nuclear magnetic resonance (31P NMR) spectroscopy. Lense in 35.5 mM glucose showed an altered metabolic steady-state characterized by a lowered adenosine triphosphate/inorganic orthophosphate ratio. ³¹P NMR spectroscopy can be used to measure metabolic changes in the lens. This model offers an important means to study dynamic metabolism in the human lens in the setting of diabetic cataractogenesis.     

Chemie der lithium-enolat-heptafulvene: regiospezifische aldol-addition

Aldehydes and ketones add to the cycloheptatriene ester anion $\text{2a}$ and to the carboxylic acid dianion $\text{2b}$ at C-7 (α-attack) or C-2 (C-5) (γ-attack), depending on the starting compounds.     

Heterocyclische und carbocyclische 12-π- and 14-π-Molekülsysteme, 47. Mitteilung. Herstellung von 7, 9-Dimethyl-4, 5-dihydro-3 H-benz [cd]- azulen-3-on and 7,9-Dimethyl-3H-benz [cd]azulen-3-on. Eine einfache Synthese eines Azulenopseudophenalenons

Heterocyclic and Carbocyclic 12-π-and 14-π-Systems, 47th Commnunication¹. Synthesis of 7,9-Dimethyl-4,5-dihydro-3H-benz[cd]azualene-3-one and 7,9-Dimethyl-3H-benz[cd]azulene-3-one. A Simple Synthesis of Azulenopseudophenalenons 4, 6, 8-Trimethylazulene ( 3 ) reacts after metalation with lithiumdiisopropyl-amide in ether with bromoacetic acid to the 6, 8-dimethylaltulene-4-propionic acid ( 4 ), which undergoes cyclization to the 7, 9-dimethyl-4, 5-dihydro-3H-benz [cd]-azulene-3-one ( 5 ) in the presence of p-toluenesulfonic acid; oxidation of 5 with 2, 3-dichloro-5, 6-dicyanobenzoquinone yields 7, 9-dimethyl-3H-benz [cd]azulene-3--one ( 1b ). Alkylation of 1b with triethyloxonium tetrafluoroborate in CH₂C1₂ gives the 3-ethoxy [cd]benzazulenium tetrafluoroborate ( 6 ).     

meso- and β-Pyrrole-Linked Chlorin-Bacteriochlorin Dyads for Promoting Far-Red FRET and Singlet Oxygen Production

A series of chlorin-bacteriochlorin dyads (derived from naturally occurring chlorophyll-a and bacteriochlorophyll-a), covalently connected either through the meso-aryl or β-pyrrole position (position-3) via an ester linkage have been synthesized and characterized as a new class of far-red emitting fluorescence resonance energy transfer (FRET) imaging, and heavy atom-lacking singlet oxygen-producing agents. From systematic absorption, fluorescence, electrochemical, and computational studies, the role of chlorin as an energy donor and bacteriochlorin as an energy acceptor in these wide-band-capturing dyads was established. Efficiency of FRET evaluated from spectral overlap was found to be 95 and 98 % for the meso-linked and β-pyrrole-linked dyads, respectively. Furthermore, evidence for the occurrence of FRET from singlet-excited chlorin to bacteriochlorin was secured from studies involving femtosecond transient absorption studies in toluene. The measured FRET rate constants, k_FRET, were in the order of 10¹¹ s⁻¹, suggesting the occurrence of ultrafast energy transfer in these dyads. Nanosecond transient absorption studies confirmed relaxation of the energy transfer product, ¹BChl*, to its triplet state, ³Bchl*. The ³Bchl* thus generated was capable of producing singlet oxygen with quantum yields comparable to their monomeric entities. The occurrence of efficient FRET emitting in the far-red region and the ability to produce singlet oxygen make the present series of dyads useful for photonic, imaging and therapy applications.