bluuebunny/crossref_metadata_2025 huggingface dataset:
Reinigung und Kristallisation der Aldolase aus Drosophila melanogaster. 14. Mitteilung über Aldolasen [1]
Authors: Brenner‐Holzach O. , Leuthardt F.
Published: December 2004

A method for the preparation of pure crystalline aldolase (type A) from pupae of Drosophila melanogaster is described.
Notiz zur Unterscheidung äquatorial‐äquatorial und äquatorial‐axial substituierter Cyclohexanderivate mit Hilfe der magneto‐optischen Rotationsdispersion (MORD.)
Authors: Wipf H.‐K. , Clerc J. T. , Simon W.
Published: December 2004

Magneto‐optical rotatory dispersion (MORD.) measurements of disubstituted cyclohexane derivatives without heteroatoms show systematic differences between equatorial‐equatorial and equatorial‐axial substitution.
Optische Rotationsdispersion von Indolinalkaloiden mit Ketogruppen
Authors: Klyne W. , Swan R. J. , Gorman A. A. , Guggisberg A. , Schmid H.
Published: December 2004

The optical rotatory dispersion curves of a series of indolines, N(a)‐acetyl‐indolines and N(a)‐methoxycarbonyl‐indolines containing keto groups have been measured. It has been shown that the absolute stereochemistry of N(a)‐acetyl‐indolines containing keto groups can still be determined from the character of the Cotton Effect due to the aromatic chromophore, the ketone Cotton Effect however being more difficult to interpret. The use of N(a)‐methoxycarbonyl‐indoline and indoline chromophores is dangerous due to the complex nature of the Cotton Effect of the former and the overlapping of that of the latter with the ketone Cotton Effect.
Naturstoffe aus Mikroorganismen. 2. Mitteilung [1]. Isolierung von L‐Monapterin aus Pseudomonas roseus fluorescens J. C. MARCHAL 1937 und seine Konstitutionsaufklärung
Authors: Viscontini M. , Bühler‐Moor R.
Published: December 2004

Aus einer Kultur von Pseudomonas roseus fluorescens J. C. MARCHAL 1937 in eisenfreier, synthetischer Nährlösung wurde u.a. ein Pterin isoliert, das sich als (+)‐6‐(L‐threo‐1′,2′,3′‐Trihydroxypropyl)‐pterin erwiesen hat. ‐ Isolierung, Eigenschaften und Konstitutions‐aufklärung des Monapterins werden in dieser Arbeit beschrieben.
Naturstoffe aus Mikroorganismen. 3. Mitteilung [1]. Isolierung von 6‐Hydroxymethyl‐pterin aus Kulturen von Pseudomonas roseus fluorescens J. C. MARCHAL 1937
Authors: Viscontini M. , Frater‐Schroeder M.
Published: December 2004

Die Isolierung des 6‐Hydroxymethyl‐pterins, neben anderen Pteridinen, aus Kulturen von Pseudomonas roseus fluorescens in synthetischer Nährlösung wird beschrieben. Die biologische Bedeutung dieses erstmals als reiner Stoff aus natürlicher Quelle isolierten Pterins wird geschildert.
Photoreaktionen von 5‐Phenyl‐pyrazolinen. Vorläufige Mitteilung
Authors: Rosenkranz H. J. , Schmid H.
Published: December 2004

On irradiation in benzene 1‐methyl‐5‐phenyl‐Δ2‐pyrazoline (1) is partly converted into trans‐ and cis‐1‐methylazo‐2‐phenyl‐cyclopropanes (2 and 3) in the ratio of 23:77. Both 2 and 3 on thermal treatment are reconverted to 1. A concurrent thermal equilibration of 2 and 3 is also observed. 1, 3‐Dimethyl‐5‐phenyl‐Δ2‐pyrazoline (5) on irradiation in benzene yields the corresponding trans‐ and cis‐1‐methylazo‐1‐methyl‐2‐phenyl‐cyclopropanes (6 and 7). In contrast similar treatment of 5‐phenyl‐Δ2‐pyrazoline gives benz‐ and cinnamaldazine (9 and 11) along with the corresponding mixed aldazine (10).
Über die sensibilisierte Photooxydation einiger cyclischer N‐Aryl‐enamine. 3. Mitteilung über Indole, Indolenine und Indoline
Authors: Pfoertner K. , Bernauer Karl
Published: December 2004

Eosine‐sensitized photooxidation of the cyclic N‐aryl‐enamines 1, 6 and 8 results in oxidative splitting of enamine double bonds. Thereby compounds 2, 7 and 9 respectively are formed. From a mixture of the tautomeric quinoline derivatives 12 and 13, on oxidation under similar conditions, the compounds 7, 14 and 16 were isolated.
Zur katalytischen Aktivität von Cu2+‐Komplexen mit vierzähnigen Liganden. Metall‐Ionen und h2o2, 18. Mitteilung
Authors: Erlenmeyer H. , Waldmeier P. , Sigel H.
Published: December 2004

In contrast to earlier reports [2] [8], the pure Cu2+ complex of phthalocyanine‐tetrasulfonic acid (I) is found to be inactive in the decomposition of H2O2. The Cu2+ complexes of 1, 4, 8, 11‐tetraazacyclotetradecan (II) and 2, 12‐dimethyl‐3,7,11,17‐tetraazabicyclo [11.3.1]‐heptadeca‐1(17), 2,11,13,15‐pentaen (III) are equally inactive. The results confirm that only Cu2+ complexes with a not «saturated» coordination sphere catalyse the decomposition of H2O2.
Herstellung und Eigenschaften von Oximen des 4‐Oxo‐4,5,6,7‐tetrahydroindols und ihre Umlagerung in Pyrrolo‐azepine 6. Mitteilung über synthetische Indol‐Verbindungen [1]
Authors: Stoll André P. , Troxler F.
Published: December 2004

The preparation and BECKMANN rearrangement of 4‐tosyloxyimino‐4,5,6,7‐tetrahydroindoles are described. The structures of the stereoisomeric parent oximes, their tosylates, and of the products of their BECKMANN rearrangement have been confirmed by NMR and IR spectroscopy.
Beiträge zur Chemie der Pyrrolo[3,2‐c]azepine und der Pyrrolo [3,2‐b]azepine
Authors: Troxler F. , Stoll André P. , Niklaus P.
Published: December 2004

Some chemical transformations in the series of the pyrrolo [3,2‐b]azepines and the pyrrolo[3,2‐c]azepines are reported: alkylation at the pyrrolo nitrogen and/or the azepino nitrogen, reduction of the lactam group by means of LiAlH4, preparation of lactim ethers and amidines, substitution in position 2 by MANNICH reaction, bromination and condensation with oxalyl chloride or chloral hydrate, and the cyclocondensation with dimethylmalonyl chloride. The structures of the 2‐substitution products have been evaluated by NMR.‐spectroscopy.
Zur Biosynthese von Brefeldin A
Authors: Handschin U. , Sigg H. P. , Tamm Ch.
Published: December 2004

By feeding growing cultures of Penicillium brefeldianum Dodge with [‐14C]‐acetate radioactive brefeldin A (C16H24O4) was obtained. By extensive degradation of [14C]‐brefeldin A, the individual radioactivity of 12 of the 16 carbon atoms was determined quantitatively. The pattern of the distribution of the radioactivity shows that 8 acetate units have been incorporated into the metabolite in a regular manner. These findings suggest an octaketide as an intermediate. Possible mechanisms for the formation of the trans‐fused cyclopentane ring are discussed.
Steroide und Sexualhormone. 236. Mitteilung [1]. Die Synthese der 5α‐ und 5β‐17‐Oxo‐19‐hydroxy‐3‐aza‐3, 19‐cyclo‐A‐homo‐androstane
Authors: Binder R. , Wehrli H.
Published: December 2004

The synthesis of the novel title compounds (2 and 3) is described. These two isomers differ from structure 1, ascribed to the salamander alkaloid cycloneosamandione, with respect to ring A/B fusion and to the ketone position.
Fluorénacènes et fluorénaphènes Synthèses dans la série des indéno‐fluorènes XIII [1]. Dérivés phénylés du cis‐fluorénacène et du trans‐fluorénaphène
Authors: Chardonnens Louis , Chardonnens Henri
Published: December 2004

A partir de la diéthylcétone et de l'α‐phénylchalcone on synthétise, en 6 étapes avec un rendement global de 24%, le phényl‐5‐dihydro‐10, 12‐indéno [2, 1‐b] fluorène, dérivé phénylé du cis‐fluorénacène. En partant de la diméthyl‐2, 6‐diphényl‐3, 5‐cyclohexène‐2‐one‐1, obtenue par condensation de la diéthylcétone sur la chalcone, on aboutit en 5 étapes simultanément au phényl‐11‐dihydro‐10, 12‐indéno [2, 1‐b]fluorène, autre dérivé du cis‐fluorénacène, et au phényl‐6‐dihydro‐7, 12‐indéno [1, 2‐a] fluorène, dérivé phénylé du trans‐fluorénaphène.
Menschliches Calcitonin. IV Die Synthese von Calcitonin M. Vorläufige Mitteilung
Authors: Sieber P. , Brugger M. , Kamber B. , Riniker B. , Rittel W.
Published: December 2004

A preliminary account is giver of the synthesis of calcitonin M (I), isolated from human C‐cell tumour tissue [2] [3]. Identity of the synthetic and the natural hormone was established by thin‐layer chromatography, thin‐layer electrophoresis and conversion to oxidation products, as well as by reference to the pattern of tryptic degradation and by comparing the biological activity of the two hormones. The findings also afforded additional confirmation of the results of structural elucidation [1].

In the synthesis of I, use was made of methods described previously [4] for the preparation of porcine α‐thyrocalcitonin, and also of a new method [5] which easily permits the formation of cyclic cystine peptides.
Zur Biosynthese des Dendrolasins, eines Inhaltsstoffes der Ameise Lasius fuliginosus LATR
Authors: Waldner E. E. , Schlatter C. H. , Schmid H.
Published: December 2004

By feeding the ant Lasius fuliginosus LATR. with [14C]‐1‐acetate, [14C]‐2‐acetate, [14C]‐2‐mevalonate, [14C]‐2‐mevalonate, [14C]‐1‐glucose and [14C]‐U‐glucose, incorporation ratios of 10−4 – 0,15% were obtained in the sesquiterpenoid dendrolasin. It was shown by analysis of the labelling pattern in dendrolasin that the insertions were spread over the whole molecule in exactly the manner that would be expected from terpene biosynthesis.
Umwandlung von Cardenoliden durch Mikroorganismen VI. 7β, 11α‐Dihydroxydigitoxigenin und Abbau von 7β‐Hydroxy‐digitoxigenin zum 3β, 7β‐Diacetoxy‐14‐hydroxy‐5β, 14β, 17αH‐ätiansäure‐methylester. Mitteilung über Reaktionen mit Mikroorganismen [1]
Authors: Scherrer‐Gervai M. , Gsell L. , Tamm Ch.
Published: December 2004

Digitoxigenin (3) was transformed by a Fusarium spec. to 7β‐hydroxydigitoxigenin (1) 1β, 7β‐dihydroxydigitoxigenin (4) and to the hitherto unknown 7β, 11α‐dihydroxydigitoxigenin (9). 7β‐acetoxy‐digitoxigenin (2) was degraded to methyl 3β, 7β‐diacetoxy‐14‐hydroxy‐5β, 14β, 17αH‐etianate (11).
Photochemische Reaktionen 49. Mitteilung [1] Spezifisch π → π*‐induzierte Keton‐Photoreaktionen: Die Doppelbindungsverschiebung von O‐Acetyl‐10α‐testosteron Protonisierung der Doppelbindung seines δ5‐Isomeren
Authors: Kuwata S. , Schaffner K.
Published: December 2004

The α,β‐unsatured ketone 10α‐testosterone has been reported previously [6] to photoisomerize in t‐butanol solution to the β,γ‐unsaturated ketone. The irradiation had been carried out using a high‐pressure mercury lamp in a quartz vessel. For structural reasons this double bond shift cannot proceed through a photoenolization mechanism involving an intramolecular hydrogen transfer from the γ‐position to the enone oxygen as has been suggested to operate in several formally analogous cases of aliphatic enone isomerizations. In the present reinvestigation, O‐acetyl 10α‐testosterone (1) was used, employing selectively either excitation of its n → π* (with wavelengths > 300 nm) or its π → π* absorption band (with 253,7 nm).

In t‐butanol solution the doublebond shift 1 → 2 could be effected with π→* excitation only. Experiments in deuterated solvent (t‐BuOD) resulted in deuterium in corporation in both the δ5‐ketone in the C(4)‐position, cf.(3) and in the conjugated ketone. These results indicate that the reactions is initiated either in the, Sπ,π* state or in a high vibrational mode of the S0 or tππ*state. n→ π* Excitation of 1 in t‐butanol gave essentially no over‐all chemical change, while in benzene solution it resulted again in a double bond isomerization (1 →2). In analogy to results with similar enones [28] under identical conditions the deconjugation in benzene may be the consequence of an intermolecular hydrogen abstraction of the Tn,π* excited state of the enone.

Another specifically π →π* induced photoreaction was observed on irradiation of the β, γ‐unsaturated ketone 2 in t‐BuOD with 253,7 nm. The olefinic hydrogen at C‐6 of 2 was exchanged with deuterium and, to a small extent, isomerization to the conjugated ketone 1 with concomitant deuterium incorporation occurred. It is concluded that from the higher excited state of the β, γ‐unsaturated ketone, but not from its Sn,π* state, an activation mode of the double bond is accessible to effect D+ addition at C‐6 followed by deprotonation to 4 and to deuterated 1, respectively.
Recherches sur la formation et la transformation des esters LXXXI [1]. Sur la réaction d'isothiocyanates avec l'acide hydrazinoéthylphosphorique, et de l'isocyanate de phényle avec l'acide colaminephosphoreux
Authors: Rabinowitz Joseph , Chang Sherwood , Capurro Norine
Published: December 2004

Hydrazinoethyl phosphoric monoester has been prepared by reacting hydrazinoethanol with polyphosphoric acid, and isolated as di‐sodium salt.

Sodium hydrazinoethyl phosphate reacts with phenylisothiocyanate (in H2O+ethanol) to yield mainly the derivative thiocarbamoylated at the substituted nitrogen atom. This derivative, heated for one night at 100° in 0.5 N HCl, is cyclized to 3‐amino‐2‐phenylimino‐thiazolidine in 62% yield. Sodium hydrazinoethyl phosphate reacts with o‐methoxycarbonylphenyl isothiocyanate (in H2O+dioxane) at the unsubstituted nitrogen atom to yield mainly the corresponding quinazoline derivative (IV, X = OPO3Na2). This derivative, heated for one night at 100° in 0.5 N HCl, is cyclized to 2‐o‐carboxyphenylamino‐dihydro‐δ2‐1, 3, 4‐thiadiazine (Va) in 55% yield (hydrolysis of the lactamic function as well).

Aminoethyl phosphorous monoester (colaminephosphorous acid) reacted with phenylisocyanate (in H20+dioxane) in slightly alkaline medium (one equivalent of NaOH) yields sodium N‐phenylcarbamoylaminoethyl phosphite. Refluxed for 20 minutes in 1N NaOH, this carbamoyl derivative is not cyclized but only hydrolyzed to the open‐chained N‐phenyl‐N′‐hydroxyethylurea (VII).
Die Kristallstruktur eines polynuclearen Silber‐Platin‐Mercaptophosphin‐Komplexes
Authors: Strickler P.
Published: December 2004

Crystals of Pt(S–CH2‐Ch2‐P(C2H5)2)2AgNO3 are orthorhombic, a = 14.814, b = 10.926, c = 12.298 Å, space group Pbon, Z = 4. The structure has been solved by FOURIER methods and refined by full‐matrix least‐squares analysis of three dimensional intensity data, measured on the HILGER & WATTS computer‐controlled 4‐circle diffractometer. The structure consists of infinite chains running along the c‐axis; each silver atom is coordinated almost linearly to two sulphur atoms belonging to the square‐planar coordination spheres of two different platinum atoms.
Notiz zur Veröffentlichung von M. VISCONTIN und R. PROVENZALE: «Herstellung von reinem (–)‐L‐Neopterin und (–)‐D‐Monapterin [1]»
Authors: Rembold H.
Published: December 2004

Es wird auf vier massgebende, voneinander unabhängige Methoden zur Reinheitsprüfung von Polyhydroxyalkylpterinen hingewiesen. Die von REMBOLD et al. dargestellten Verbindungen genügen diesen Kriterien.
Synthese kernhydroxylierter Metaboliten des Dimetacrins
Authors: Molnar I. , Wagner‐Jauregg Th.
Published: December 2004

To prove the chemical structure of metabolites of the antidepressant drug (dimetacrin2) (Istonil®3), 2‐ and 3‐hydroxy‐9,9‐dimethyl‐10‐dimethylaminopropyl‐acridane and 2‐hydroxy‐monometacrin4 were synthesized using substituted alkoxy diphenylamines (V) as intermediates. The methoxy compounds on treatment with strong acids cyclized either to the corresponding acridanes or to their O‐demethylated derivatives, VI (X  OCH3 or OH), depending on concentration and temperature.
Untersuchungen über Steroide XLI. Umwandlungsprodukte des 17α‐Strophanthidins
Authors: Manzetti Aldo , Ehrenstein Maximilian
Published: December 2004

Pseudostrophanthidin (2) can be easily prepared by treating strophanthidin (1) with concentrated hydrochloric acid in the cold [1]. 2 has served as the initial product for the preparation of a number of analogues and homologues of steroid hormones [2] [3]. 17α‐Pseudostrophanthidin (4) is considered a suitable starting material for an extension of these investigations.

It was logical to attempt the preparation of 4 from 17α‐strophanthidin (3) under conditions identical with those used in the conversion of 1 into 2. However, these experiments did not lead to 4 but, instead, by way of the unstable 14ξ‐chloro‐14‐deoxy‐17α‐strophanthidin (5) to 14‐anhydro‐17α‐strophanthidin (6). This result is essentially in agreement with findings reported in the literature [5]. To support the structure assigned to 6, this compound was also prepared by a different, unambiguous, route. Treatment of 3 with thionyl chloride in pyridine gave mainly 3β, 5β‐O, Osulfinyl‐14‐anhydro‐17α‐strophanthidin (8), which was converted into 6 by mild hydrolysis. In turn 6, as obtained via the unstable chloro compound 5, gave on treatment with thionyl chloride in pyridine a product identical with 8. – 6 was characterized as the 3‐acetate 7.

As extension of these experiments, 17α‐strophanthidol (10) [6] was treated with concentrated hydrochloric acid in the cold under conditions similar to those used in the conversion of 3 into 6 by way of 5. This led to the isolation of 14‐anhydro‐17α‐strophanthidol (11), which could also be obtained by the reduction of 6 with aluminium amalgam.

As is known [1] [8], strophanthidinic acid (13) can be converted into strophanthidinic acid 19,8‐lactone (14) by treatment with concentrated hydrochloric acid in the cold. In view of the negative results obtained in the attempt to transform 3 into 4 under these conditions, the question arose as to whether the conversion of 17α‐strophanthidinic acid (15) into 17α‐strophanthidinic acid 19,8‐lactone (16) by the same procedure is also impossible. 15 was prepared by treating 3 with hydrogen peroxide and was characterized as the methyl ester 17 and the methyl ester of the 3‐benzoate (18). 15 and 17 have been mentioned in the literature [5], but the physical constants reported differ from those obtained in this laboratory. It was demonstrated that after treating 15 with concentrated hydrochloric acid in the cold, no 16 could be isolated but, instead, an unstable chloro compound 19 which was converted into 14‐anhydro‐17α‐strophanthidinic acid (20). 20 was characterized as the methyl ester 21 and the 3‐acetate 22.
Spectres de masse des composés organiques. 3e Communication.. Perte de méthyle dans la fragmentation des alcanes
Authors: Liardon R. , Gäumann T.
Published: December 2004

The reaction mechanism for the loss of methyl and methane from the parent ion is investigated for n‐alcanes. By using different deuterated species, mainly hexanes, it is shown that these two reactions proceed by two paths, one being the simple split of a C‐C‐bond, whereas the other consists in an internal rearrangement followed by a loss of a C‐atom from within the chain. This process is becoming the main process for this class of fragmentation as the hydrocarbon chain is getting longer. A small internal isotope effect has also been found.
Magnetische Protonenresonanz‐Spektroskopie der Bufadienolide (steroidartigen Krötengifte)
Authors: Gsell L. , Tamm Ch.
Published: December 2004

The NMR. spectra of nearly all bufadienolides (steroidal toad poisons) of known structure (aglycones and acetyl derivatives) were measured (some in various solvents) and evaluated. The results obtained allow the application of the principle of the self‐consistent chemical shift values (‘rule of additivity’) for the calculation of the chemical shifts of the 18‐ and 19‐ methyl groups. The frequencies of resonance and the coupling of the protons of the 17β‐pentadienolide ring and of the α‐protons of the functional groups were analysed. For the determination of the NMR. spectra of polyhydroxylated bufadienolides and cardenolides d6‐dimethylsulfoxide proved to be the most suitable solvent. In this solvent not only the nature but also the relative positions of several hydroxyl groups can be recognized, the rule of additivity being also applicable.

On the basis of the data recorded the position and stereochemistry of functional groups in steroidal toad poisons of unknown structure can be determined with a high degree of probability.
Dopaldehyd: erstmalige Isolierung aus einer Pflanze in Form seines (Z)‐Enol‐(E)‐Kaffeesäureesters
Authors: Arihara Shigenobu , Rüedi Peter , Eugster Conrad Hans
Published: December 2004

Dopaldehyd (homoprotocatechu aldehyd; 3,4‐dihydroxyphenyl acetaldehyd), in form of its (Z)‐enol‐(E)‐caffeic ester, has been detected for the first time as a natural occurring compound. It is a constitutent of the yellow pigments of the glands on the leaves of Plectranthus caninus ROTH (Labiatae).
Skeletal muscle wasting and contractile performance in septic rats
Authors: Minnaard R. , Drost M. R. , Wagenmakers A. J. M. , van Kranenburg G. P. , Kuipers H. , Hesselink M. K. C.
Published: December 2004

We investigated the temporal effects of sepsis on muscle wasting and function in order to study the contribution of wasting to the decline in muscle function; we also studied the fiber‐type specificity of this muscle wasting. Sepsis was induced by injecting rats intraperitoneally with a zymosan suspension. At 2 h and at 2, 6, and 11 days after injection, muscle function was measured using in situ electrical stimulation. Zymosan injection induced severe muscle wasting compared to pair‐fed and ad libitum fed controls. At 6 days, isometric force‐generating capacity was drastically reduced in zymosan‐treated rats. We conclude that this was fully accounted for by the reduction of muscle mass. At day 6, we also observed increased activity of the 20S proteasome in gastrocnemius but not soleus muscle from septic rats. In tibialis anterior but not in soleus, muscle wasting occurred in a fiber‐type specific fashion, i.e., the reduction in cross‐sectional area was significantly smaller in type 1 than type 2A and 2B/X fibers. These findings suggest that both the inherent function of a muscle and the muscle fiber‐type distribution affect the responsiveness to catabolic signals. Muscle Nerve, 2005
Electronic structures and spectra of halogenated purines and pyrimidines III.σ‐Electronic structure and some comments on the mechanism of the xanthine oxidase reaction of 2‐halopurines and related analogs
Authors: Song Pill‐Soon
Published: December 2004

The extended HMO (EHMO) and Pople‐Segal SCF‐MO‐CNDO/2 calculations on purine, 8‐oxopurine, 2‐oxopurine, 2‐fluoropurine, and 2‐chloropurine indicate significant polarizations of the σ cores. It is shown that the polarizations of both σ and π frameworks are mutually opposing in some cases. The results from the two methods are compared for these complex biomolecules. It is found that the EHMO calculations tend to over‐polarize the σ and π frameworks. However, the CNDO shows anomalous π‐electron densities on N(7) and C(8) of the purine rings, and the reason for this anomaly is not certain.

The application of the results to the xanthine oxidase system indicates that the substrate molecules are subject to a specific orientation on the enzyme surface to counteract the electronic reactivity, in support of the previous prediction based on the π‐electron calculations. The CNDO results appear to be more satisfactory than the EHMO in this respect.
A remark on the Born–Oppenheimer approximation
Authors: Seiler Rudolf
Published: December 2004

The method of calculating wave functions for an electron‐nucleon system by a variational method originally suggested by Born and Oppenheimer [1] is rigorously investigated. As an application we sketch the calculation of a simple nonadiabatic wave function for the system.
On partitioning the overlap charge density in self‐consistent charge molecular‐orbital calculations
Authors: Hillier Ian H. , Wyatt John F.
Published: December 2004

Alternatives to the Mulliken method of partitioning the overlap charge density in self‐consistent charge molecular‐orbital calculations are examined. It is found that more realistic methods may lead to significantly different self‐consistent charges, and different ordering of the electronic energy levels.
Une theorie adiabatique de la relaxation spin‐reseau
Authors: Levy Joseph
Published: December 2004

An adiabetic theory of spin lattice relaxation is proposed. It is shown that if one takes account of the adiabatic adaptation of the electrons to the motion of the ionic complex the motor of the relaxation is not the crystalline potential modulation but the fluctuation of the effective magnetic field produced by the complex near the paramagnetic system.
Wellenmechanische absolutrechnung am HeHHe+
Authors: Swanstrøm P. , Janoschek R. , Preuss H.
Published: December 2004

The wave function of the HeHHe+ molecule has been calculated by means of the GENERAL SCF–MO–LC(LCGO) PROGRAM SYSTEM, taking all four electrons into account. The calculations were carried out for a number of linear equidistant, linear non‐equidistant, and bent nuclear arrangements. The minimum energy of −5.7930 a.u. was found for a linear equidistant configuration with a HeH distance of 0.939 Å. The corresponding ionization energy was 37.9 eV. An estimation of the energy of formation of HeHHe+ from HeH+ and He based on SCF‐calculations on HeH+ and He gave 7.9 kcal/mole. The frequencies of the normal vibrations were calculated.
A double self‐consistent‐field method for electron correlation: Applications to LiH, H2O, and cyclopropane
Authors: Liakus A. , Gallup G. A.
Published: December 2004

A computational procedure which introduces some electron correlation into quantum mechanical calculations is described. Diverse applications are given. Among these, the method gives values of 65.6 kcal/mole for the dissociation energy of LiH, 62.0 kcal/mole for the ring‐opening energy of cyclopropane, and 9.123 × 155 dynes/cm for the O–H stretching force constant of H2O. These results, and others given, suggest that our procedure has great potential and provides a very economical method for introducing electron correlation into a wave‐function.
A basis set investigation for the oxygen 1s ionization potential in H2O
Authors: Ågren H. , Svensson S. , Wahlgren U. I.
Published: December 2004

The basis set dependency of the core ionization potential of water was investigated for atomic optimized Cartesian Gaussian basis sets. Basis set parameters optimized for oxygen yielded better IP's than basis set parameters optimized for fluorine. Not much was gained by using different parameters for the ground state and for the 1s hole state.
A numerical integration scheme for iterative calculations on atomic systems
Authors: Blakemore M. , Evans G. A. , Hyslop J.
Published: December 2004

A recursive numerical integration scheme based on the method of Clenshaw and Curtis is proposed for the efficient implementation of the variation–iteration procedure for the computation of approximate energies and wave functions for atomic systems. Extensive numerical tests are carried out to assess the accuracy and efficiency of the method and inaccuracies in some earlier calculations are pointed out.
Floating spherical gaussian orbital open‐shell calculations on the four‐electron H4 system
Authors: Huang Hsing Hua , Pakiari Ali H.
Published: December 2004

Floating spherical Gaussian orbital (FSGO) open‐shell calculations have been made to determine the potential energy surface of planar square and rectangular arrangements of the four‐electron system H4. This surface is discussed in relation to the bimolecular isotope exchange reaction H2+D2‐→ 2HD. The changes in energy and geometry accompanying the coplanar approach of two hydrogen molecules interacting chemically have also been investigated. Calculations on the electronic energies of planar T‐shaped and kite arrangements of H4 of various sizes show that it is unlikely that these configurations can serve as transition states for the exchange reaction. However, the energy curve for linear configurations of H4 (HHH … H), calculated as a function of the H3 … H distance with the symmetric linear H3 (H‐H‐H) unit fixed at the internuclear distance of 1.9080 a.u., is found to have a deep minimum (−1.9176 a.u.) at an r(H3 … H) distance of 1.5846 a.u. The overall results suggest that the following mechanism for the exchange reaction, H2+H2→H2+H+H→H3+H→H+H2+ H→H2+H2 could be advantageous as it requires a barrier height of 0.1604 a.u. which is significantly lower than that calculated from the saddle point energy (0.1950 a.u.). However, the problem of reconciling this with the experimental activation energy of 0.0685 a.u. still remains.
Orthogonal trajectories of the electron density
Authors: Collard Kathleen , Hall George G.
Published: December 2004

Functions of several variables, such as the electron density and the nuclear Born–Oppenheimer potential, may be analysed very effectively using orthogonal trajectories. In particular the behaviour of these trajectories at critical points of the functions is investigated in detail. The use of orthogonal trajectories in the virial partitioning of Bader and in the definition of reaction coordinates is extended. A chemical interpretation of the critical points is suggested. The relevance of catastrophe theory is illustrated.
On some specific properties of systems endowed with dipole–dipole interactions
Authors: Knežević G. , Marinković M. , TošIć B.
Published: December 2004

Specific properties of systems with dipole–dipole interactions in the one‐dimensional structures leading to the violation of the statistical equivalent of the continuity equation resulting in the creation of qualitatively new excitations are analyzed. Those excitations are the result of the interaction between the initial quasiparticle currents. The structures discussed may be of importance in biophysics, and the biophysical aspects of the obtained results are considered. In comparison with other mechanisms, the exciton mechanism is shown to be of a very specific nature as its transport properties are sharply dependent upon the type of exciting light bounded within the range of temperatures covered by living organisms. This can result in an accumulation of interface excitations on a specific lattice molecule and cause its qualitative transformations with corresponding biological consequences.
PCILO calculations on hydrogen bonded complexes. Dimers involving second row atoms
Authors: Weller Th.
Published: December 2004

The PCILO method was used to study systems with the following types of intermolecular hydrogen bonds, involving 2nd row atoms: N…︁HS, S…︁HS, N…︁HCl, Cl…︁HF, Cl…︁HCl, P…︁HN, P…︁HP, P…︁HF, S…︁HF.

In all the cases calculated, the PCILO method yields an accurate qualitative description of the stabilization energies and to some extent quantitatively good agreement with reliable ab initio and experimental results. The corresponding equilibrium distances are in almost all cases smaller (up to 0.6 Å) than the ab initio values of the same compounds.
A new algorithm for the symmetric (Löwdin) orthonormalization
Authors: Scharfenberg Peter
Published: December 2004

A new method for the numerical calculation of (inverse) square roots of real symmetric matrices is proposed. Simplicity of the algorithm, good numerical accuracy, short computational time and the possibility to solve the problem in an (n, n) array are some of its features; in addition a new theoretical view on this problem is presented.
On the convergence of one‐centre partial wave treatments for diatomic molecules. II. Heteronuclear one‐electron diatomic molecules using the 1sσ, 2sσ, 3sσ, 2pσ, 3pσ, and 3pσ, states of HeH++ as models
Authors: Ali M. K. , Meath W. J.
Published: December 2004

Exact separated atom nuclei and centre of nuclear charge centred partial wave solutions for the Schrödinger equation are obtained for the 1sσ, 2sσ, 3sσ, 2pσ, 3dσ, and 3pσ states of HeH++ as a function of the internuclear separation R and the number of partial waves used to represent the wave functions for the molecules. If the expansion centre is chosen appropriately one‐centre techniques are in general very efficient for these Coulomb dominated interactions relative to molecules like H+2(1sσg) which have a large electron exchange contribution to their interaction energy. In general the centre of nuclear charge is not the most suitable expansion centre for heteronuclear molecules for most values of R.
Quantum‐mechanical theory for transport across biological membranes
Authors: Hosur Ramakrishna V.
Published: December 2004

A general quantum‐mechanical description of molecular transport across biological membranes has been developed. The one‐dimensional Schrödinger equation for the motion of ions and molecules across the biological membrane has been solved using reasonable potential barriers. Two types of potential profiles for such transports have been considered: a flat barrier proposed by Hall et al. for lipids and an oscillatory potential proposed by Lauger for lipids and by us in this paper for intrinsic proteins. The general behavior of the transmission coefficient as a function of energy and the variation of the permeability as a function of structural changes in the membrane have been discussed. Finally, the importance and areas of applicability of such a theory have been pointed out.
A generalized formula for the energies of alternant molecular orbitals. II. Heteronuclear molecules
Authors: Tyutyulkov N. N.
Published: December 2004

Using the method of alternant molecular orbitals (AMO), it is shown that the energies of AMOS (Ekσ) for an arbitrary heteronuclear alternant system, having a singlet ground state, are connected with the energies of MOS (ek(k)) obtained by means of the conventional Hartree–Fock (HF) method (SCF‐LCAO‐MO‐PPP) via the formula:

In the general case, the determination of the correlation corrections δi,kσ is connected with the solving of a complicated system of integral equations, which is considerably simplified if the Hubbard approximation is accepted for the electron interaction.

The energy spectrum of a chain with two atoms in the elementary cell (AB)n is considered as an example. It is shown that if nontrivial solutions exist (δi,kσ ≠ 0), the correlation correction for AMOS of different spin are different (δi,kσ ≠ δi,kβ), from which it follows, that the width of the energy gap ΔE∞ for AMOS with different spin is different: ΔE∞,α ≠ ΔE∞,β.
Finite nucleus model for the Fermi contact interaction
Authors: Hannesson Thorsteinn , Blinder S. M.
Published: December 2004

A model for the Fermi contact interaction is proposed in which the charge and magnetic moment of the nucleus are uniformly distributed within a sphere of radius r0. This leads to a Schrödinger equation, which is solvable without perturbation theory. In the mathematical limit r0 → 0, the usual Coulomb plus delta function potential is obtained. It is shown that the magnetic perturbation energy goes to zero for a repulsive delta function, to ‐∞ for an attractive delta function. A projected application is to computation of nuclear spin–spin coupling constants in molecules, particularly HD.
Two‐parameter exponential‐type basis functions for atomic calculations
Authors: Höjer Germund
Published: December 2004

It is found that ordinary STOs fall off too fast in the atomic region in many cases. A new type of basis set, which is more adaptable to the rather different requirements of the various atomic orbitals in an atom, is developed. The suggested functional form χ(r) = Nrn‐1 exp{−α[(βr + 1)1/2 − 1]} contains the STOs as a limiting case. Calculations on a series of atoms from H to Zn show that the new basis gives better results than STOs for equal basis set size. The necessary integrals do not present any problem to evaluate.
Ab initio molecular fragment calculations with pseudopotentials: Hydrocarbon calculations of double‐zeta quality
Authors: Gáspár R. , Gáspár R.
Published: December 2004

Pseudopotential theory is introduced into the ab initio FSGO molecular fragment method. A theoretical background for the pseudopotential fragment description and a method for large molecule formation is presented. Core‐valence electron separation is achieved at both levels of the calculations with the resulting simplification of the molecular calculations. Using pseudopotentials of double‐zeta quality a detailed description of pseudopotential molecular fragments CH4 (tetrahedral) and CH3 (planar) is presented. Applications of the pseudo‐FSGO molecular fragment method to hydrocaroons are discussed. The results are compared to those of the original FSGO method and experiment.
Instability threshold and peculiar solutions of Hartree–Fock equations
Authors: Mestechkin M.
Published: December 2004

Perturbation theory in the vicinity of an RHF closed‐shell instability threshold is developed. Equations determining the appearance of new solutions are formulated solely in terms of the electron interaction operator.
Symmetry properties of graphs of interest in chemistry. II. Desargues–Levi graph
Authors: Randić Milan
Published: December 2004

The Desargues–Levi graph represents important chemical transformations: (1) isomerization routes for some carbonium ion rearrangements, (2) isomerization of trigonal bipyramidal structures, and (3) some pseudorotations of octahedral complexes. The symmetry properties of this graph have not been fully investigated in the past. Using the concept of the smallest binary code, all permutations which form the symmetry operations in the graph are registered. The resulting symmetry group can be represented as the direct product of S5 (the full symmetric permutation group on five objects) and Ci (the inversion in the center). There are 14 classes belonging to the following partitionings: 120(1), 1826(1), 1428(1), 1236(1), 123262(1), 2 63(2), 2244(2), 210(3), 54(1), and 102(1). The total of 240 symmetry operations are distributed among the above 14 classes as follows: 1, 10, 15, 20, 20, 20, 20, 30, 30, 15, 10, 1, 24, and 24, respectively. Since partitioning cannot uniquely characterize a class, it is suggested that the distance between vertices in a cycle be introduced as an additional parameter to discriminate among classes having identical partitioning. Also, a suggestion to a generalization of the Mulliken notation for irreducible representations of the point molecular groups valid for more versatile symmetry groups of graphs is indicated.
Improved interaction potential for alkali halide molecules
Authors: Mohammad S. Noor
Published: December 2004

An improved interaction potential has been devised for diatomic alkali halide molecules. This potential, in addition to similar attraction terms as in the Rittner potential, includes a new exponential for the short‐range repulsion. The constant m in the exponential is seen to be well expressible in terms of the parameters of the Rittner potential. The new potential is also correlated with different properties, as for example, effective charges, effective radii, effective principal quantum numbers, etc., of the combining ions. Various spectroscopic constants, viz., the ionic dissociation energy Di, the vibrational–rotational coupling constant αe, the vibrational anharmonicity constant ωexe, as well as two second‐order spectroscopic constants γe and βe have been calculated for this and for the Rittner potential. From comparisons between these two potentials, the new one has been observed better than the other.
Quadrupole moments, dipole quadrupole A and quadrupole C polarizabilities by means of perturbation theory
Authors: Espinoza LL. , Toro A. , Fuentealba P.
Published: December 2004

Quadrupole moments, dipole quadrupole polarizability A, and quadrupole polarizability C values have been obtained for a set of organic molecules, in both the ground and first singlet excited states, by means of Rayleigh–Schrödinger perturbation theory. Computations for π systems have been carried out using the PPP‐SCF procedure. Results are discussed through the paper and compared with available experimental and theoretical information. Quadrupole moments are shown to be very sensitive to the quality of the wave functions, and the A and C polarizabilities are highly dependent on geometries.
Electronic structure, spectra, and mechanism of photodimerization of pyrimidine bases
Authors: Srivastava S. K. , Mishra P. C.
Published: December 2004

Various electronic indices calculated by the CNDO/s‐CI method for uracil, 5‐fluorouracil, thymine, and cytosine and the Woodward‐Hoffmann rule applied to the photodimerization of these molecules lead us to the following conclusions: (i) decrease of the C5C6 bond order consequent to excitation is generally correlated with the photodimerization reaction for all the biological pyrimidines; (ii) excited pyrimidine molecules may be nonplanar and the excitation would be delocalized over both the molecules which photodimerize; (iii) electrostatic interactions may play a significant role in the initial stages of the photodimerization reaction; (iv) singlet precursors to the stable triplet photodimers may exist; and (v) electron density does not, in general, increase in the C5C6 bond in the excited state as compared to the ground state, contradicting the proposals of some earlier workers. Hybrid population densities and σ‐bond orders have been calculated for the first time for the molecules. Fluorine in 5‐fluorouracil perturbs the hybrid populations as compared to those of uracil mainly in its vicinity.
Definition of invariant molecular tensors in an origin change. I. General formalism
Authors: Duprez‐Quesnoit C. , Tillieu J.
Published: December 2004

Among the tensors used in the published literature to characterize a phenomenon of nonlinear optics, some are not invariant under a change of origin. In this paper, we show that this invariance can be obtained in a general manner, if the densities of electric and magnetic polarization are not separated but replaced by a density of magnetoelectric polarization whose quantum calculation is performed for a molecular crystal.
Definition of invariant molecular tensors in an origin change. II. Refraction and Faraday effect
Authors: Duprez‐Quesnoit C.
Published: December 2004

In the previous paper, a global tensor invariant under origin changes was introduced for all optical phenomena. By applying the results obtained, we determine invariant partial tensors which characterize refraction and the Faraday effect.
Use of molecular properties in the one‐dimensional model of nonadiabatic transitions
Authors: Macías A. , Riera A.
Published: December 2004

A systematic analysis of a diabatization method proposed in a recent publication is presented for the one‐dimensional linear model of nonadiabatic transitions, and the method is extended to the exponential model. The asymptotic behavior of molecular properties is studied, and the usefulness of simple properties like the kinetic energy and multipole moments is examined in detail. The method is easy to use, and provides a reliable a posteriori procedure to deal with the existence of strong radial couplings between adiabatic states, when a program to calculate the radial couplings exactly is not available.
Modification of the NDO model in semiempirical MO theory
Authors: Basilevsky M. V. , Shamov A. G.
Published: December 2004

We suggest the explicit transformation of the parametrized atomic ϕ‐basis semiempirical Hamiltonian to the Löwdin λ basis. A nontrivial problem then arises concerning the transformation of the four‐index electron interaction matrix Γ, for which parametrization is given in the ϕ basis, whereas the NDO approximation is introduced in the λ basis. The main result is that under the CNDO assumption the two‐index Coulomb matrix can be transformed independently of other integrals of Γ. The explicit form of the transformation between the Coulomb matrix γ of parameters given in the ϕ basis and the Coulomb matrix λγ in the λ basis is found. The λγ calculated by this method differs only slightly from the result of the exact complicated four‐index transformation. On the other hand the elements of γ and λγ may differ by several eV when overlap is significant.
Interactions and self‐organization of nucleic bases, nucleotides, and polynucleotides into ordered structures. Effect of ionization and solvent salt composition
Authors: Sukhorukov B. I. , Gukovsky I. Ya. , Petrov A. I. , Gukovskaya A. S. , Mayevsky A. A. , Gusenkova N. M.
Published: December 2004

This paper summarizes our findings on the effects of protons and neutral salt ions on intermolecular interactions and the self‐organization of nucleotide systems in aqueous media, both at monomer and polymer levels. To gain quantitative information about these processes, methods were developed to determine the thermodynamic parameters of monomer association from the data obtained by various experimental techniques (NMR, UV spectroscopy, and spin labeling) and to estimate the individual contributions of base stacking and H‐bonding in ordered structures of polynucleotides and their complexes. The main results obtained using these methods are as follows. (i) A difference was discovered in the effects of positive and negative charges on the stacking interaction between ionized and neutral molecules of nucleic heterocycles. Protonation strongly decreases the heterocycle ability to form ordered stacks whereas deprotonation slightly affects stacking. (ii) Base–phosphate interaction, which has not yet really been investigated, was studied. This interaction, along with base stacking, governs nucleotide association in water media. It appears upon protonation of the base moiety and increases with decreasing ionic strength. (iii) Base stacking was found to become stronger under the action of salt anions stabilizing the water structure and it became weaker under the action of destabilizing salt anions, both in monomer and polymer systems, which is indicative of an indirect mechanism of the anionic effects. It is essential that small salt ion additives acting by such a “distance” mechanism can affect the formation of ordered structures in nucleotide systems as strong as the direct interaction of the bases with protons. (iv) The results obtained suggest that an increase in solvent entropy upon the self‐organization of nucleotide systems in aqueous media may be an important factor promoting these processes. (v) As follows from our data, specific weakening or strengthening of intermolecular interactions by protons and salt ions at small, physiological‐range changes in pH or solvent salt composition seems to be an effective regulatory mechanism for the functioning of nucleotide systems.
Density of non‐Bloch electron states in perfect cubic crystals
Authors: Bulski T. , Olszewski S. , Wierzbicki A.
Published: December 2004

This paper gives an abbreviated method for the calculation of the density of states of a crystal on the basis of that band theory in which the crystal electron states are represented by the standinglike wave functions classified according to the point‐group symmetry species. The crystal is a large but finite sphere filled regularly with atoms, and the wave functions are quantized at the boundary of the sphere. The Bloch theorem is not satisfied in this theory since the wave functions are not basis functions of the irreducible representations of the translation subgroup. On the other hand, a theorem is established that the density of states can be made up of contributions given by all irreducible representations of the crystal point group, any contribution being proportional to the square of the dimension of the irreducible representation. In distinction to a former approach, the band structure is calculated solely from the energy eigenvalues obtained with the aid of the diagonalization process of the Wannier–Slater differential operator. A simple cubic lattice with an s atomic orbital on each lattice site is taken as an example, and the results are compared with Bloch's theory.
Slater‐orbital molecular integrals by numerical Fourier‐transform methods. II. Four‐center integrals over is orbitals
Authors: Graovac Ante , Kovačević Krešimir , Maksi Zvonimir B. , Veseli Ahmet
Published: December 2004

The four‐center nonplanar electron repulsion integrals over 1s Slater‐type atomic orbitals are considered by a numerical Fourier‐transform method. It is shown that the highly oscillating integrand appearing in the Fourier inversion formula could be successfully treated by using Tchebyscheff quadrature. The resulting formulas are thoroughly discussed with particular emphasis on their numerical features and convergence properties. It follows that the aforementioned integrals may be calculated with a good accuracy with a moderate amount of computing time.