Vibronic spectral behavior of molecules: XVIII. Theoretical contribution to the S1→S0 fluorescence of the isomeric phenyl naphthalenes within the Herzberg-Teller approach

Theoretical vibronic S₁S₀ line spectra of the isomeric phenyl naphthalenes calculated within the Condon as well as the Herzberg-Teller approaches on the basis of completely optimizedS ₀ andS ₁ molecular geometries, are presented and are contrasted with the experimental fluorescence spectra. The theory-experiment comparison is successful only within the Herzberg-Teller approximation by explicitly including the Dushinsky transformation. An analysis of the significant vibrational modes is given.     

Zur Struktur der Tetrahydro-4-phenylspiro([1]benzopyran-2,4′(1′H)-pyrimidin)-2′(3′H)-one bzw.-thione über Heterocyclen, 49. Mitt

The structures of tetrahydro-4-phenylspiro([1]benzopyran-2,4(1H)-pyrimidin)-2(3H)-ones and-thiones4 a, b resp., are proved by synthesis. 3-(2-methoxy-3,5-dimethylphenyl)-3-phenylpropionic acid11 b is prepared from 3,4-dihydro-6,8-dimethyl-4-phenylcoumarin10. The lithium salt of11 b reacts with isobutenyl-lithium to 1-(2-methoxy-3,5-dimethylphenyl)-5-methyl-1-phenyl-4-hexen-3-on12 a. 12 a is transferred with urea in acid medium and NH₄CNS resp. in a mixture of dihydro-6-[2-(2-methoxy-3,5-dimethylphenyl)-2-phenyläthyl]-4,4-dimethyl-2(1H)-pyrimidinone and-thione13 a, b and tetrahydro-6-[2-(2-methoxy-3,5-dimethylphenyl)-2-phenyläthyliden]-4,4-dimethyl-2(1H)-pyrimidinone and-thione14 a, b resp.14 b leads to13 a, b with H₂O₂. Heating of13 a, 14 a and14 b resp. with pyridin-HCl leads to the spiro compounds4 a, b.     

Über kondensierte Heterocyclen aus β-Isothiocyanatoketonen und Aminoalkoholen bzw. Diaminen

2- and 3-aminoalcohols, o-aminobenzylalcohol, o-hydroxybenzylamine and o-amino(thio)-phenol react with 4-isothiocyanato-4-methyl-2-pentanone (1) to yield derivatives of condensed heterocycles (oxazolopyrimidines7, pyrimidooxazine8, pyrimidobenzoxazines9, 10, pyrimidobenzoxazole11 a and pyrimidobenzothiazole11 c respectively). Ethylenediamine or 1,3-diaminopropane react with1 to yield either imidazo-pyrimidine13 and pyrimidopyrimidine14 respectively or the 1,2-ethylene- and trimethylenebisdihydro-2(1H)-pyrimidinethione15 a, b respectively, according to the molar ratio of the reactants. o-Phenylenediamine gives pyrimidobenzimidazole11 d. 11a undergoes ring cleavage in boiling dimethylformamide followed by methylpyrimidine-pyridine rearrangement to dihydrohydroxyphenylamino-2(1H)-pyridinethione12, while15 a is converted into the bis-4-(ethanediimino)-pyridinthione16.     

Analyse von Rutil-Anatas-Gemischen mittels diffuser Reflexionsmessungen

Zusammenfassung Pulvergemische von zwei verschiedenen Modifikationen eines Stoffes oder von zwei Pigmenten lassen sich mit Hilfe diffuser Reflexionsmessungen quantitativ analysieren, wenn die Reflexionsspektren sich in einem zugänglichen Spektralgebiet genügend stark unterscheiden. Die Methode wird am Beispiel der Titandioxyde Rutil und Anatas im einzelnen beschrieben.

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Summary Mixtures of two modifications of solid powdered material can be quantitatively analyzed by diffuse reflectance measurements, if the reflectance spectra are sufficiently different in some wavelength range. The method is described with the example of the titanium dioxides rutile and anatase.

     

Studies on the chemistry of 1,4-oxazines. 18. Synthesis of tricyclic 1,4-benzoxazines via nucleophilic substitution of activated precursors

Starting from activated benzoxazines 1 and 2 new synthetic pathways to the tricyclic compounds 4, 9, 12 and 16 are described. Reaction of the hydrazides 17a,b with thionylchloride leads to the novel thiatriazolo-benzoxazines 18a,b .     

Über 4-Alkylamino-bzw. 4-Arylamino-5,6-dihydro-2(1H)-pyridinthione

Heating 1-alkyl- or 1-aryldihydro-6-methyl-2(1H)-pyrimidinethiones5, 6 in an inert medium causes rearrangement to 4-alkylamino-(4-arylamino-)-5,6-dihydro-2(1H)-pyridinethiones11, 12, probably via the methylene form29, by thermal heterolysis of the N₁/C₂ bond and exchange of the alkylamino (arylamino) group 1 through the carbon atom of the methylene group 6. The aminodihydropyridinethiones11, which can be regarded as cyclic derivatives of 3-aminothiocrotonamide, react with bistrichlorophenylmalonate under diacylation, and with formaldehyde and primary amines to yield aminodialkylation products of the enamine system, tetrahydro-4-hydroxy-7,7-dimethyl-5-thioxopyrido[4,3-b]pyridine-2(1H)-ones13, 14 and hexahydro-7,7-dimethylpyrido[4,3-d]pyrimidine-5(6H)-thiones18, 19, 21 respectively. H₂O₂ converts11 to the corresponding 4-aminodihydro-2(1H)-pyridones22, which can be reconverted into11 with P₄S₁₀.11 reacts with alkyl halides to 2-alkylthiodihydropyridines23, 24, 25. The mechanism of the methylpyrimidine-pyridine rearrangement is discussed.     

Theoretical study on geometry and spectroscopic properties of 1,1′-binaphthyl in the electronic ground and first excited singlet states

Equilibrium geometries for the electronic ground and first excited singlet states of 1,1'-binaphthyl have been calculated by minimization of the total energy with respect to all internal coordinates. Using these results, an interpretation of the fluorescence S₁→ S₀ and absorption spectra S_m ← S₀ and S_n ← S₁ in rigid and fluid solutions is given.For the first time the equilibrium geometry of the first excited singlet state of 1, 1′-binaphthyl has been calculated. On excitation to the S₁ state the dihedral angle θ between the two naphthalene moieties is de- creased from 61 ° to 41 °. A detailed survey of CH bond lengths in the S₀ and S₁ states has been given. This result should be of particular importance for the theoretical treatment of radiationless transitions.Using equilibrium geometries for the S₀ and S₁ states a satisfactory interpretation of the S_m ← S₀ and S_n ← S₁ absorption spectra as well as of the fluorescence spectra in fluid and rigid solutions can be given. Concerning the S_n ← S₁ absorption spectrum in fluid solution, the calculations predict a strong absorption (A ← B transition) in the still uninvestigated region of energies lower than 11000 cm^?1.From the results of this paper and of other calculations it can be concluded that the Warshel-Karplus method yields reliable equilibrium geometries for electronic ground and excited states of unsaturated hydrocarbons [22,23].     

Vibronisches Spektralverhalten von Molekülen: XIV. Zum Einfluß der vibronischen Kopplung auf die S0-S1-Absorption und Fluoreszenz von ausgewählten 1,3-Diketonato-bor-komplexen im Rahmen der Herzberg-Teller-Näherung

Summary Based upon completely-optimized S₀ and S₁ molecular geometries the vibrational structures of S₀-S₁ absorption and fluorescence transitions of selected 1,3-diketonato boron complexes being differently substituted, are calculated within the Herzberg-Teller approach taking into account vibronic coupling contributions. In dependence on substituted diketone as well as on the co-ligand, the influence of vibronic coupling and the consequences of intensity borrowing on the spectral behaviour in absorption and fluorescence are found to be quite different for the studied boron complexes. Consequently, for some complexes their spectroscopic properties may be interpreted exclusively by means of the Herzberg-Teller approach. An analysis of the relevant vibrational modes is given.

     

Direct identification of all oncogenic mutants in KRAS exon 1 by cycling temperature capillary electrophoresis

Over the past few decades, advances in genetics and molecular biology have revolutionized our understanding of cancer initiation and progression. Molecular progression models outlining genetic events have been developed for many solid tumors, including colon cancer. Previous reports in the literature have shown a relationship between different KRAS mutations and prognosis and response to medical treatment in colon cancer patients. Furthermore, the presence of a mutated KRAS has been correlated with different clinicopathological variables including age and gender of patients and tumor location. To our knowledge, few institutions screen for KRAS mutations on regular basis in colon cancer patients despite such evidence that knowledge of KRAS exon 1 status is informative. Here, we report on a mutation analysis method adapted to a 96-capillary electrophoresis instrument that allows identification of all 12 oncogenic mutations in KRAS exon 1 under denaturing conditions. To determine the optimal parameters, a series of DNA constructs generated by site-directed mutagenesis was analyzed and the migration times of all mutant peaks were measured. A classification tree was then made based on the differences in migration time between the mutants and an internal standard. A randomized series of 500 samples constructed with mutagenesis as well as 60 blind samples from sporadic colon carcinomas was analyzed to test the method. No wild-type samples were scored as mutants and all mutants were correctly identified. Post polymerase chain reaction (PCR) analysis time of 96 samples was performed within 40 min.     

Electrochemical solid-phase microextraction of anions and cations using polypyrrole coatings and an integrated three-electrode device

A method for the extraction, transfer and desorption of anions and cations under controlled potential conditions employing a new integrated three-electrode device is described. The device, containing working, reference and counter electrodes, was prepared from tubes that could be moved vertically with respect to each other. In this way, a small amount of solvent, held by capillary force, remained between the electrodes when the device was lifted out of a solution after an extraction. This design allowed the potential control to be maintained at all times. With the new integrated device, it was possible to perform potential controlled desorption into vials containing as little as 200 microl of solution. The required ion exchange capacity was obtained by electrodeposition of a polypyrrole coating on the surface of the glassy carbon working electrode. Solid-phase microextractions of several cations or anions were performed simultaneously under potentiostatic control by doping the polypyrrole coating with different anions such as perchlorate and p-toluenesulfonate. The efficiency of the extractions, which could be altered by varying the potential of the working electrode, could be increased by 150 to 200% compared to extractions using normal solid-phase microextraction conditions under open circuit conditions. A constant potential of +1.0 V and -0.5 V with respect to the silver pseudo reference electrode, was found to be well-suited for the extraction of samples containing ppm concentrations of anions (chloride, nitrite, bromide, nitrate, sulfate and phosphate) and cations (cadmium, cobalt and zinc), respectively.