bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Chemical Study of Burley Tobacco Flavour (Nicotiana tabacum L.). I. Volatile to medium‐volatile constituents (b.p. ≦ 84°/0.001 Torr
Authors: Demole Edouard , Berthet Dominique 
Published: December 2004

AbstractThe fraction b.p. ≦ 84° (0.001 Torr) from Burley tobacco condensate was carefully investigated using fractional distillation and preparative column and gas liquid chromatography aided by GLC/MS coupling. Among the 193 compounds thus separated and characterized by their spectral data, 81 were newly identified tobacco constituents.Most of the compounds isolated in the course of this work display flavouring properties which make them highly suitable for improving the flavour and aroma of tobacco and tobacco smoke.
Synthèses dans la série des‐indéno‐fluorénes, VII. Le trioxo‐5,12,13‐dihydro‐12,13‐5H‐bis‐indéno[2.1‐a; 2′.1′‐g] fluoréne
Authors: Chardonnens Louis , Chen Te Tseng 
Published: December 2004

AbstractStarting from 9‐oxo‐fluorene‐1‐carbaldehyde, the title compound, XII, a trioxoderivative of a new biangular diindenofluorene system, has been synthesized in 5 steps (overall yield 37,5%). The corresponding hydrocarbon could not be obtained by reduction of XII. Attempts to synthesize the isomer XX of the trioxoderivative XII are described.
Arbeiten über Phosphorsäure‐ und Thiophosphorsäureester mit einem heterocyclischen Substituenten. 5. Mitteilung. 2‐Alkoxy‐ und 2‐Alkylthio‐5‐chlormethy1‐‐1, 3,4‐thiadiazole, 2‐Alkyl‐ 5‐chlormethy1‐1,3,4‐oxadiazole und daraus hergestellte Thio‐ und Dithiophosphorsäure‐O, O‐dialkyl‐S‐[(2‐alkoxy‐ und 2‐alkylthio‐1, 3, 4‐ thiadiazol‐5‐yl)‐methyl]‐ bzw. ‐S‐[(2‐alky1‐1, 3, 4‐oxadiazol‐5‐yl)‐methyl‐ester
Authors: Rüfenacht K. 
Published: December 2004

Abstract2‐Alkoxy‐5‐chloromethy1‐1,3,4‐thiadiazoles are prepared by ring closure of 3‐chloroacetyl‐thiocarbazic acid O‐alkyl esters with concentrated sulfuric acid, 2‐alkylthio‐5‐chloro‐methy1‐1,3,4‐thiadiazoles directly from dithiocarbazic acid alkylesters with chloroacetylchloride in benzene in a one step synthesis omitting the 3‐chloroacetyl‐derivatives and 2‐alkyl‐5‐chloro‐methy1‐1,3,4‐oxadiazoles from 1‐chloroacetyl‐2‐acyl‐hydrazines with POCl3. These three types of chloromethyl heterocycles easily react with salts of thio‐ and dithiophosphoric acids to form the corresponding O,O‐dialkyl‐S‐[(2‐alkoxy‐ and 2‐alkylthio‐1,3,4‐thiadiazol‐5‐yl)‐methyl]‐ and ‐S‐[(2‐alky1‐1,3,4‐oxadiazol‐5‐yl)‐methyl]‐thio‐ and ‐dithiophosphates.
Surface chemistry of polymers Adsorption and absorption of gases by polyvinylchloride
Authors: Perret E. A. , Stoeckli H. F. , Jeanneret C. 
Published: December 2004

AbstractNitrogen and carbon monoxide are physically adsorbed on polyvinylchloride between 78 and 86 K, without hysteresis. At higher temperatures, carbon dioxide (195 K), sulfur dioxide (273 and 293 K) and chloroethane (293 K) are strongly absorbed by the solid, with hysteresis. The possibility of trapping CO inside the solid indicates that PVC has an open structure at higher temperatures. The effect of heating on the polymer was also investigated.
Struktur von Coleon E, einem neuen diterpenoiden Methylenchino aus der Coleus barbatus‐Gruppe (Labiatae)
Authors: Rüedi P. , Eugster C. H. 
Published: December 2004

AbstractWe have isolated from the glands on the leaves of Coleus barbatus (Benth.) Agnew C. Kilimandschari (Gürcke) Agnew and a C. species P. R.O. Bally No. 10431, all of East Africa origin, a new, very labile, deeply red coloured quinone methide, Coleon E, C20H22O5. Degradations and spectra (including 13C‐NMR.) have been interpreted in terms of the unusual irregular diterpenoid structure 1. Its fully conjugated unsaturated system extends over 3 rings. The CH3‐group at C(3) and n‐propyl side chain at C(13) instead of the usual isopropyl group are regarded as arising by modification of an abietane precursor. Coleon E, after reduction and methylation, has been found to undergo a skeletal rearrangement leading to a formal interchange of the alkyl side chain with a phenolic OH‐group.
Carbon Magnetic Resonance Spectra of α, β, γ, δ‐ and α, β, α′, β′‐ Unsaturated Ketones
Authors: Hollenstein R. , von Philipsborn W. 
Published: December 2004

AbstractCarbon‐13 spectra of a series of 26 unsaturated ketones (ortho‐ and para‐cyclo‐hexadienones and corresponding open‐chain analogues) have been measured by Fourier‐transform. Pulse spectroscopy. A complete analysis has been achieved by means of double resonance experiments using noise‐modulated and coherent off‐resonance proton irradiation and with the aid of non‐decoupled spectra. Chemical shifts are interpreted in terms of charge distribution in the dienone system and of methyl substituent effects. Carbon chemical shifts were also obtained for O‐protonated ortho‐ and para‐cyclohexadienones. One‐bond and long‐range carbon‐proton and carbon‐fluorine spin coupling constants are reported for several compounds.
Über die Alkaloide von Anisocyclea grandidieri H. Bn. (Menispermaceae)
Authors: Schlittler Emil , Weber Nikolaus 
Published: December 2004

AbstractFour alkaloids were isolated from Anisocyclea grandidieri (Fam. Menispermaceae). Trilobine and stebisimine have already been found in other menispermaceous plants, whereas (−)‐epistephanine and 12′‐O‐desmethyltrilobine have not been isolated before.
Electrophilic Aromatic Substitution of Groups other than Hydrogen. Part II: SN1‐Type Desulfonation of 2‐Naphthol‐1‐sulfonic Acid by Diazonium Ions in Aprotic Apolar Solvents. 27th communication on diazo coupling reactions
Authors: Fischer P. B. , Zollinger H. 
Published: December 2004

AbstractThe rates of formation of 1‐(4′‐chlorophenylazo‐)‐2‐naphthol by SO3 of release from the π‐complex [2‐naphthol‐1‐sulfonate anion …︁ p‐chlorobenzenediazonium cation] have been measured in chloroform and in methylene chloride; they are first‐order with respect to the complex. They are catalysed by pyridine and co‐catalysed by acetic acid. Acids alone, in stoichiometric or higher concentrations, inhibit the reaction. A mechanism is postulated involving proton transfer to the sulfonate group, followed by rearrangement to the σ‐complex which, in the catalysed reaction, first loses a proton to the base and then releases SO3, but in the uncatalysed reaction loses SO3H⊕. The function of the co‐catalyst (pyridinium ion) is explained (see text). This reaction is ‐ in contrast to electrophilic aromatic substitutions in which the leaving group is a protonan SN1‐type re‐aromatization of the σ‐complex to the product.
Magnetic Circular Dichroism Studies XXIII [1] Magnetic Circular Dichroism Spectra of Indole Alkaloids
Authors: Barth Günter , Linder Robert E. , Bunnenberg Edward , Djerassi Carl 
Published: December 2004

AbstractThe magnetic circular dichroism spectra of a number of indole alkaloids show two B‐terms of opposite sign in the 250–330 nm wavelength region associated with the 1Lb and 1La electronic transitions, the long wavelength, 1Lb, band being of positive sign, whereas both bands strongly overlap in absorption. Various substituents in different positions of the indole ring cause a red shift of both bands and a broadening of the long wavelength B‐term. The sign pattern, howver, remains unchanged in all examples thus far investigated. Dihydroindole and oxindole, on the other hand, exhibit MCD. bands with the opposite sign sequence as compared to the indole chromophore. This observation allows identification of the indole chromophore in alkaloids from the sign pattern of the MCD. bands.
α‐Chlor‐nitrone III: Ein Weg zur indirekten «carboxolytischen» Spaltung von Olefin‐Doppelbindungen. Über synthetische Methoden, 7. (vorläufige) Mitteilung
Authors: Gygax P. , Das Gupta T. K. , Eschenmoser A. 
Published: December 2004

AbstractThe enaminoid derivatives formed by deprotonation of the olefin‐α‐chloro‐nitrone cycloadducts (see preceding communications) undergo a beautifully clean cycloreversion at ambient or slightly elevated temperatures. The sequence (2+4)‐cycloaddition → deprotonation → (2′+4)‐cycloreversion constitutes a potentially useful method for the oxidative cleavage of olefinic double bonds with concomitant extension of the carbon chain at one of the double bond termini (indirect «carboxolytic» cleavage of double bonds; see schemes 1 and 3).
The Reaction of Bicyclo [3.2.1] octenyl Halides with Metal Hydrides
Authors: Jefford C. W. , Sweeney A. , Delay F. 
Published: December 2004

AbstractReduction of 2‐phenyl‐ and 2‐methyl‐exo‐3,4‐dichlorobicyclo[3.2.1]oct‐2‐enes with lithium aluminium hydride (LAH) or tributyltin hydride (TBTH) gave endo‐2‐phenyl‐3‐chlorobicyclo[3.2.1]oct‐3‐ene, 2‐phenyl‐3‐chlorobicyclo[3.2.1]oct‐2‐ene and their methyl analogues. The action of both reagents on 2‐phenyl‐exo‐3, 4‐dibromobicyclo[3.2.1]oct‐2‐ene similarly resulted in reductive monodebromination to give normal and allylically rearranged products. Additionally, further reduction occurred to give endo‐2‐phenylbicyclo[3.2.1]oct‐3‐ene and 2‐phenylbicyclo[3.2.1]‐oct‐2‐ene. In all cases, LAH gave mainly the allylic rearrangement product whereas TBTH gave mostly unrearranged product. The reason for these differences could have been due either to the intervention of allylic radicals in the TBTH reduction or to differences in nucleophilicity. The results also show that LAH is equally efficaceous as TBTH in the reduction of these allylic halides and equally selective in the reduction of the vinyl bromides. The stereochemistry of the allylic rearrangement was shown to be synfacial in that hydride replaced halide on the same face of the molecule.
The Acid‐catalyzed Isomerization of an α‐Ketoester into β‐Ketoesters and the Unusual Fragmentation of an α‐Ketoester. Preliminary communication
Authors: Kagan Jacques , Agdeppa Dalmacio A. 
Published: December 2004

AbstractThe first example of an acid‐catalyzed isomerization of an α‐ketoester into β‐ketoesters is described. Ethyl 2‐keto‐3,3‐diphenylbutyrate rearranged in fluorosulfonic acid at 0° into ethyl 2‐benzoyl‐2‐phenylpropionate and ethyl 2,2‐diphenylacetoacetate. In contrast, fragmentation of ethyl 3,3‐diphenylpyruvate to benzophenone occurred in the same conditions.
Über das Lipoxygenase‐« Lipoperoxidase »‐System in Cerealien: III. Zur Kinetik des enzymatischen Abbaues von Linolsäurehydroperoxiden
Authors: Heimann W. , Reinartz F. , Schreier P. 
Published: December 2004

AbstractDurch Untersuchung der Kinetik der Peroxidase‐katalysierten Linolsäure‐hydroperoxid (LHPO)‐Abbaureaktion mit einem Hafer‐Ammoniumsulfatpräparat wird gezeigt, dass es sich um eine bimolekulare Reaktion in zwei Ein‐Elektron‐Schritten des Peroxidase‐Hydroperoxid‐Komplexes mit dem Wasserstoffdonator handelt. Der Nachweis wird durch die Übereinstimmung der Versuchswerte mit einer aus der Theorie der binären Komplexbildung abgeleiteten mathematischen Funktion erbraeht.
Synthese der enantiomeren 1,6‐Spiro[4.4]nonadiene
Authors: Gerlach H. , Müller W. 
Published: December 2004

AbstractTwo new syntheses of spiro[4.4]nonane‐1, 6‐dione (I) are described: one by rearrangement of 1,6‐epoxy‐bicyclo[4.3.0]‐nonane‐2‐one (IV) with boron trifluoride, the other by an acid catalyzed, intramolecular Claisen condensation of 4‐(2‐oxocyclopentyl)‐butyric acid. Spiro[4.4]‐nonane‐1,6‐dione is converted into trans, trans‐spiro[4.4]nonane‐1,6‐diol which is resolved into enantiomers via the diastereomeric esters with (−)‐camphanic acid. (+)‐(5S)‐Spiro[4.4]nona‐1,6‐diene (III) is prepared from (1R, 6R)‐trans,trans‐spiro[4.4]nonane‐1,6‐diol (II) by pyrolysis of the corresponding bis‐4‐methylphenyl‐thionocarbonate. This modification of the Chugaev reaction is particularly useful with sterically hindered alcohols which cannot be converted into S‐me‐thylxanthates. The circular dichroism, UV.‐ and NMR.‐spectrum of optically active spiro[4.4]‐nonane‐1,6‐diene are discussed.
Stoffwechselprodukte von Mikroorganismen 102. Mitteilung. Über die Struktur der Venturicidine A und B
Authors: Brufani M. , Cellai L. , Musu C. , Keller‐Schierlein W. 
Published: December 2004

AbstractChemical degradations and spectroscopic investigations of the macrolide antibiotics venturicidin A and B are described. In combination with an X‐ray crystallographic analysis they lead to complete structures.
σ, π‐Isomerisierungen von Monohetero‐σ‐bishomobenzol‐Derivaten. Vorläufige Mitteilung
Authors: Stusche D. , Breuninger M. , Prinzbach H. 
Published: December 2004

AbstractThe cis‐oxa‐ (13a‐d) and ‐aza‐σ‐bishomobenzene (13 e) derivatives have been synthesized; they are sufficiently stable to be isolated in pure form. On heating, 13a‐e are easily isomerized into the π‐bishomobenzene analogues 14a‐e, the processes 13 a ⇄ 14 a, 13 b ⇄ 14b and 13d ⇄ 14d being reversible. Some kinetic and thermodynamic data for these σ, π,bishomobenzene transformations are presented.
Zur Kenntnis der sesquiterpenoiden C12‐Ketone des ätherischen Öls von Vetiveria zizanioides (L.) Nash
Authors: Maurer B. , Fracheboud M. , Grieder A. , Ohloff G. 
Published: December 2004

AbstractTwo new C12‐ketones, (+)‐(1S, 10R)‐1,10‐dimethylbicyclo[4.4.0]dec‐6‐en‐3‐one (5) and (+)‐(6S, 10S)‐6,10‐dimethylbicyclo[4.4.0]dec‐1‐en‐3‐one (6), have been isolated from Reunion vetiver oil (Vetiveria zizanioides (L.) Nash). Structure and absolute configuration of 5 were established by a four‐step synthesis from (+)‐isonootkatone ((+)‐α‐vetivone) (1). The structure of 6 followed from its spectroscopic properties and was confirmed by direct comparison with an authentic racemic sample. The absolute configuration of 6 was established by chemical correlation with (+)‐α‐eudesmol (13).
Eine verbesserte Synthese von Chinuclidin‐4‐carbonsäure. Chinuclidinreihe, 10. Mitteilung
Authors: Eckhardt W. , Grob C. A. , Treffert W. D. 
Published: December 2004

AbstractAn improved synthesis of 4‐carbethoxyquinuclidine from 1‐benzyl‐4‐piperidone is described.
Synthese und Eigenschaften von Spiro[1,3‐benzodioxol‐2,3′‐pyrrolidin]
Authors: Berthold R. , Gmünder J. , Troxler F. 
Published: December 2004

AbstractSpiro[1,3‐benzodioxole‐2,3′‐pyrrolidine] was synthesized in several steps from ethyl 2‐ethoxycarbonyl‐1, 3‐benzodioxole‐2‐acetate, prepared by condensation of pyrocatechol with either diethyl meso‐dibromosuccinate, diethyl acetylenedicarboxylate or diethyl bromo maleate. The structural factors leading to the formation of the benzodioxole rather than the benzodioxan and some possible reaction mechanisms are discussed.
Parmon, eine Phantomverbindung im Veilchenblütenöl
Authors: Uhde G. , Ohloff G. 
Published: December 2004

AbstractDas Blütenöl des Parma‐ sowie des Viktoria‐Veilchens geörte am Anfang unseres Jahrhunderts zu den kostbarsten Ingredienzien der feinen Parfümerie. Sein Wohlgeruch faszinierte jedoch nicht nur die Noblen der damaligen Haute‐Volée, sondern es regte ebenfalls in segensreiche Weise die Phantasie des Naturstoffchemikers jener Epoche an1). Der extrem hohen Herstellungskosten2) wegen ist das Veilchenblütenöl seit langem aus dem Handel verschwunden. Sicherlich liegt aus diesem Grund bis heute lediglich ein einziger Bericht über die chemische Zusammensetzung dieses ätherischen Öles vor [3].
Die übergangsmetall‐katalysierte reduktive Carbonylierung von Arylaziden zu 1,3‐Diarylharnstoffen
Authors: Iqbal Abul F. M. 
Published: December 2004

AbstractSeveral group VIII metal carbonyls catalyze decomposition of aryl azides to yield in the presence of carbon monoxide and a low concentration of hydrogen the corresponding symmetrical disubstituted ureas. Based on the formation of nitrenoid intermediates, probable and alternative reaction mechanism pathways have been examined.
Steroid Total Synthesis, Part VIII; (+)‐estr‐4‐ene‐3,17‐dione
Authors: Rosenberger M. , Duggan A. J. , Borer R. , Müller R. , Saucy G. 
Published: December 2004

AbstractA novel synthesis of the title compound, involving the resolution of a Mannichbase derived from racemic 11,11‐o‐phenylenedioxy‐7‐hydroxy‐1‐dodecen‐3‐one is described. In an alternate approach 2(S)‐acetamido‐6,6‐o‐phenylenedioxy‐heptanoic acid was used as the optically active starting material. This scheme features the preparation of a chiral 1,2‐epoxide and its regiospecific alkylation with lithio‐1, 1‐diethoxy‐2‐propyne.
Electron Spin Resonance Studies of Free Radicals Arising from α‐Hydrogen Abstraction from Thioethers
Authors: Lucken E. A. C. , Poncioni B. 
Published: December 2004

AbstractOn rapporte les spectres de résonance paramagnétique de radicaux libres du type RSCR1R2, créés par photolyse d'un mélange de t‐butylperoxyde et d'un thioéther. Pour les thioéthers cycliques, tétrahydrothiophène et thiopyranne, les spectres indiquent une interconversion rapide du cycle qui est empêchée dans le 4 t‐butyl‐thiopyranne, permettant ainsi l'attribution des couplages aux divers protons axiaux et équatoriaux.
Affinity Chromatography with ε‐Aminocaproyl‐choline Derivatives. (Preliminary Communication)
Authors: Schwyzer Robert , Frank Jörg 
Published: December 2004

AbstractAn Sepharose 2 B gebundene Derivate von ε‐Aminocaproylcholin vermögen Acetylcholinesterase und andere, vermutlich ebenfalls für Acetylcholin spezifische Proteine aus Elektroplax von Electyophorus electricus bevorzugt zu adsorbieren. Die Elution erfolgt mit Tetramethylammonium‐chlorid.
NMR.‐Investigation of the Formaldehyde Addition and Oligomerisation Equilibria in the System Formaldehyde/Water/Acetic Acid/Hydrochloric Acid
Authors: Gorrie T. M. , Raman S. Kalyana , Rouette H. K. , Zollinger Heinrich 
Published: December 2004

AbstractAn NMR. investigation of the state of formaldehyde in acidic solutions has been carried out. Solutions of DCl/D2O/CD3COOD containing two sources of formaldehyde, i.e. paraformaldehyde (I) and trioxane (II), were used for this purpose. In systems I and II the effect of various D2O/CD3COOD ratios, at a constant DCl concentration, was studied, while for II the effect of changing DCl concentration was also investigated. The results show that in aqueous solution, formaldehyde exists primarily as the monomeric and linear oligomeric forms of methylene glycol. Reducing the amount of D2O (at constant DCl concentration), while increasing the CD3COOD content, results in an increase in the polymeric species and in trioxane. In addition, substitution of water by acetic acid results in systems that are catalytically more active than aqueous solutions of the same hydrochloric acid concentration. Along with the usual polymer‐monomer equilibria which exist in such solutions, side reactions of methylene glycol with the hydrochloric acid present also occur to a small extent, e.g. acetylation, substitution of OH by Cl and the Cannizzaro reaction. It is suggested that these findings will result in a better understanding of the formaldehyde crosslinking reactions in cotton cellulose.
Lösungsmittelbedingte Temperaturabhängigkeit des Dipolmoments polarer Molekeln in apolaren Medien
Authors: Christen H. , Eicke H.‐F. , Jungen M. 
Published: December 2004

AbstractSolute‐solvent interactions of polar molecules generally result in an apparent temperature dependence of dipole moments. Variations of the dielectric constants with temperature of solutions of mono‐ and 1,2‐dichlorobenzene in different apolar solvents confirm the repeatedly observed solvent‐influenced apparent temperature dependence of the dipole moments. An attempt has been made for the first time to interpret these temperature effects on the basis of a statistical (Monte‐Carlo‐Method) and a continuum model. Both models permit the description of the typical curve of the dipole moments as a function of temperature and in addition reproduce the observed effects as to the order of magnitude.
ESR. Spectra of Radical Anions in the Cyclazine Series
Authors: Gerson Fabian , Jachimowicz Joanna , Kowert B. , Leaver D. 
Published: December 2004

AbstractThe ESR. spectra of the radical anions of three cyclazines are described. Their π‐spin distributions are discussed in terms of simple MO theory and compared with those of structurally related species.
Sur l'acylation des méthylfluorènes VI. Formylation du méthyl‐2‐fluorène et du méthyl‐3‐fluorène selon Rieche
Authors: Chardonnens Louis , Noël François 
Published: December 2004

AbstractThe formylation of 2‐methylfluorene and of 3‐methylfluorene according Rieche yields 2‐methyl‐7‐fluorene‐carbaldehyde and 3‐methyl‐2‐fluorenecarbaldehyde respectively. The constitution of the obtained aldehydes is proved by their conversion into the known 2,7‐dimethyl‐fluorene and 2,7‐dimethyl‐9‐fluorenone, respectively into the known 2,3‐dimethylfluorene and 2,3‐dimethyl‐9‐fluorenone.
Synthetische Übergänge von der Jonon‐ in die Damasconreihe
Authors: Schulte‐Elte K. H. , Müller B. L. , Ohloff Günter 
Published: December 2004

AbstractNew preparative routes to the isomeric damascones (2, 4 and 9) and β‐damascenone (1) starting from the readily accessible ionone isoxazoles [11] are described. γ‐Damascone (9) was prepared from 10 following the Büchi‐Vederas transformation [11], while α‐ and β‐damascone (4 and 2) were obtained as the end products of the reaction sequence: β‐aminodamascones [11]→β‐ketodihydrodamascones (20 and 21) → β‐hydroxydihydrodamascones (24 and 25). β‐Damas cenone (1), however, is formed from the epoxides of β‐ionone isoxazole (14) by Birch reduction followed by treatment with acid.The unusual behaviour towards metal hydrides of the crotonyl group in the damascones and damascenones is described.
Silylierte Polyphenyläther; ihre Darstellung und einige physikalische Eigenschaften
Authors: Fink Walter 
Published: December 2004

AbstractChemical modification of aromatic polyphenyl ethers by silylation (trimethylsilyl, dimethylphenylsilyl, methyldiphenylsilyl and siloxanyl groups), has been investigated and shown to give products with improved low‐temperature fluidity without change of thermal stability.
Isomeriefälle bei CrIII‐ und CoIII‐1:2‐Komplexen aus 8‐(2′‐Carboxyphenyl)‐amino‐chinolinen: Zur Frage der pyramidalen Struktur des koordinierten, dreibindigen Stickstoffatoms von Metallchelaten
Authors: Steiner E. , Schetty Guido 
Published: December 2004

Abstract8‐(2′‐Carboxyphenyl)‐aminoquinolines are tridentate ligands. They form on complexation with CoIIIor CrIIIsingly negatively charged 1:2 complexes by loss of two protons. In these octahedral complexes the ligands are very probably coordinated equatorially. Nevertheless up to 3 isomeric 1:2 complexes are formed. According to the NMR.‐spectra two of them an symmetrical the third is asymmetrical. The basis of our assumption is that a trivalent N‐atom which is co‐ordinated to a metal ion and which is a link of two annelated rings can possess pyramidal valence structure. The ligand in the complex would thus be bent, which renders the possibility to form three conformers.
Kinetics of Photochemical Systems with Modulated Optical Excitation
Authors: Forster M. , Fringeli U. P. , Günthard Hs. H. 
Published: December 2004

AbstractThe kinetic equations of a photochemical system are discussed in which the transitions from the ground to the first excited state are produced by a sinusoidally modulated photon source. The system includes irreversible reactions starting from the first excited singlet state S1 and the first triplet state T1 (cf. Fig. 1). Explicit solutions are given for a linear approximation of the equations of motion for the parametrically modulated system. The solutions apply only when there is weak optical pumping, low quantum yields of the photochemical end‐products and for certain conditions, of the modulation frequency. The concentrations of all particles occurring are shown to consist of modulated and unmodulated components where the amplitudes of the modulated components are slowly decaying exponentials. Thc phases of the modulated components are shown to be non‐decreasing along a sequence of irreversible steps. Formulae are given which permit determination of the photochemical system rate constants and location of a particle in a sequence of irreversible reactions.