bluuebunny/crossref_metadata_2025 huggingface dataset:
Gas‐Chromatographie und Massenspektrometrie der Trimethylsilyl‐enoläther von 5α‐ und 5β‐Cholestan‐3‐on
Authors: Vetter W. , Walther W. , Vecchi M. , Cereghetti M.
Published: December 2004

Trimethylsilyl‐enolethers of 5α‐ and 5β‐cholestan‐3‐on were investigated by gas chromatography and mass spectrometry. These derivatives are readily prepared and well suited for gas chromatographic analysis. In the mass spectrum they show fairly intense fragmentation, which appears to be characteristic for some structural elements in the surroundings of the functional group (excluding stereochemistry). This fragmentation may be useful for the structure elucidation of 3‐oxo‐steroids and related compounds.

For comparison purposes the corresponding enolacetates were also investigated.
Über die Konstitution zweier neuartiger «dimerer» Indolalkaloide Pycnanthin und Pleiomutinin 132. Mitteilung über Alkaloide
Authors: Gorman A. A. , Dastoor N. J. , Hesse M. , von Philipsborn W. , Renner U. , Schmid H.
Published: December 2004

The «dimeric» indole alkaloid (+)‐pycnanthine (2) has been isolated, along with (+)‐pleiocarpamine, (+)‐quebrachamine, (+)‐macusine B and an unknown alkaloid D from Pleiocarpa pycnantha (K. SCHUM.) STAPF, var. pycnantha M. PICHON. An investigation of its chemical and spectroscopic properties has led to the determination of structure 2 for this base. Its 6′,7′‐dihydro derivative has been shown to be identical with the alkaloid pleiomutinine, previously isolated from Pleiocarpa mutica BENTH.
Niederdruck‐Oligomerisation von Mono‐Olefinen mit löslichen Nickel/Aluminium‐Bimetallkatalysatoren, Teil I Entwicklung neuer Katalysatorsysteme auf der Basis von π‐Cyclobutadien‐Nickel(II)‐Verbindungen
Authors: Onsager Olav‐Torgeir , Wang Hagbarth , Blindheim Ulf
Published: December 2004

Mixtures of π‐tetramethylcyclobutadiene‐nickeldihalides and LEWIS acids such as alkylaluminiumhalides in organic solvents represent new highly active homogeneous catalysts for the dimerization of ethylen, propene and butene under mild conditions. As a cocatalyst LEWIS bases may be used, in particular those containing trivalent phosphorous.
Recherches sur la formation et la transformation des esters LXXXII [1]. Sur la différenciation entre structures δ2‐amino‐2 ou imino‐2 dans des composés S, N‐hétérocycliques pentagonaux et hexagonaux à cycle par ailleurs saturé
Authors: Rabinowitz Joseph
Published: December 2004

Comparison of the NMR. spectra in CDCl3 of the heterocyclic bases obtained from the cyclisation of ω‐(N‐thiocarbamoylamino) ethyl (or propyl)‐alcohols (or their orthophosphoric or sulfuric monoesters) to those of model compounds II (n = 1 or 2) and III (n = 1 or 2) has shown that: (1) In the case of five membred rings the CN double bond is always endocyclic (Ib, n = 1) should R be aromatic, araliphatic or aliphatic; (2) In the case of six membered rings the CS double bond is cnclocyclic when R is aliphatic or araliphatic (Ib, n = 2), and exocyclic when R is aromatic (I a, n = 2), with the exception of 2‐(o‐carboxyphcnylamino)‐dihydro‐δ2‐m (Ib, n = 2, K = o‐carboxyphcnyle).

In CF, COOH, all five membered rings (I b, n = 1) show a triplet for the C‐4 methylenic protons, whereas all the six membered rings (Ia or I b, n = 2) with the exception of I b, n = 2, R = o‐carboxyphenyle, are represented b y a double triplet for the C‐4 protons (samt. protonated spccics). Only one triplet is observed when the 3 position is substituted.

Thiocarbamoylation of hydrazinoethanol or its orthophosphoric or sulfuric monoesters canoccur at either of the two nitrogen atoms, thus yielding upon cyclization five‐ (IT′) or six‐membered rings (Va or Vb). The NMR spectra of compounds I V in (CIl,), SO show a singlet for 2 amino pro‐tons (3‐amino) and there is no further structural problem. The NMR spectra of compounds T′ in (CT), SO show a triplet for one amino proton coupling with the neighboring methylenic protons. I n this case, mode1 compounds are needed to assign the position of the CN double bond ( e x cyclic V a or cndocyclic V b). When R = o‐carboxyphenylc, the CN double bond is probably endoc, yclic (Vb) because this ccimpound and 2‐(o‐carboxyphenvlarnino)‐dihydro‐δ2 have very similar UV spectra.
Gymnemagenin, Struktur und O‐Isopropylidenderivate Glykoside und Aglykone. 313. Mitteilung
Authors: Stöcklin W.
Published: December 2004

Several O‐isopropylidene derivatives of gymnemagenin (5), a hexahydroxytriterpene from the leaves of Gymnema sylvestre R. Br. have been prepared, which may perhaps be useful to correlate gymnemagenin with other triterpenes. From the data obtained we conclude that gymnemagenin is 3β, 16β, 21β, 22α, 23, 28‐hexahydroxy‐olean‐12‐ene.
Über die Natur von Schwermetallkomplexen aus 2‐(2‐Hydroxyphenyl)‐4‐carboxy‐2‐H‐napht[1.2‐d]triazolen
Authors: Steiner E. , Schetty G.
Published: December 2004

2‐(2‐hydroxyphenyl)‐4‐carboxy‐naphtho [1.2‐d] triazoles are terdentate ligands which can form 1:1 complexes with CuII and NiII ions, and 1:1 as well as 1:2 complexes with CrIII‐ions. All these complexes are characterized by ortho‐condensed 6/6‐membered rings, the 1:2 chromium complexes having the DREW‐PFITZNER arrangement. This behaviour, which differs from that of comparable o‐hydroxy‐o′‐carboxy‐diaryl azo‐dyestuffs, is due to the different dimensions of the compared ligands.
Die Reaktion von 1,2‐Epoxy‐octan mit 2‐Dimethylamino‐äthanol
Authors: Tobler Erich
Published: December 2004

2‐Dimethylaminoethanol reacts with 1,2‐epoxyoctane presumably via a hydrogen‐bonded complex to form a quaternary ammonium compound which exhibits a fair stability at lower temperatures. At higher temperatures the quaternary structure decomposes with the resulting formation of a wide variety of products. Most of the products have been identified and a reasonable mechanistic picture for their formation is presented. The main products of the reaction are 1‐(ß‐dimethylaminoethoxy)‐2‐octanol (IIIa) and 1‐dimethylamino‐2‐octanol (IV), the latter being formed according to several pathways concurrently with ethylene oxide, 2‐methyl‐4‐hexyl‐1, 3‐dioxolane (VI), and 2‐hexyl‐1, 4‐dioxane (VII). Some of the higher molecular weight products are secondary products resulting from the action of epoxide on the primary reaction products IIIa and IV. The relative amount of each product formed depends on the ratio of starting materials and reaction temperature. In the presence of an additional hydroxylic solvent such as ethanol, the solvent enters also into the reaction.
Die Bildungsenthalpie 1,6‐überbrückter [10] Annulene
Authors: Bremser W. , Hagen R. , Heilbronner E. , Vogel E.
Published: December 2004

The enthalpies of formation of 1.6‐methano‐[10] annulene (IV) (ΔHf298 (IV, g) = 75.2 ± 0.6 kcal mol−1), 1.6‐imino‐[10] annulene (V) (ΔHf298(V, g) = 87.8 ± 0.7 kcal mol−1) and of 1.6‐oxido‐[10] annulene (VI) (ΔHf298(VI, g) = 47.8 ± 1.2 kcal mol−1) have been determined by combustion calorimetry. The difficulties connected with an attempt to derive meaningfull «resonance energies» are discussed.
Die reduktive Spaltung von Azofarbstoffen durch Dihydrochinoxaline
Authors: Schellenberg M. , Steinmetz R.
Published: December 2004

The kinetics of the reduction of substituted azobenzenes by dihydroquinoxalines have been measured. Azo‐compounds with electron‐donating substituents in o‐ or p‐position are reduced to the amines in neutral or acid solution, whereby two molecules of the reducing agent are consumed. If such substituents are absent, the reaction stops at the hydrazo stage. This is also the case with cleaveable azo‐compounds in strongly alcaline solution.

Our kinetic measurements of the reductive cleavage reaction of methylorange are in agreement with only one mechanism, which is discussed in detail. The very high reactivity of protonated methylorange may be attributed to the formation of a mesomeric quinoid structure. Knowing the pH‐dependence of the reaction rate allows the determination of the pK‐value of the extremely unstable hydrazo stage of methylorange. The structure of the dihydroquinoxaline has a strong influence on ΔH‡ and ΔS‡, and therefore on the reaction rate.
Die NO‐katalysierte Isomerisierung von 3‐Methylen‐1,5,5‐trimethyl‐cyclohexen zu 1,3,5,5‐Tetramethyl‐1,3‐cyclohexadien in der Gas‐Phase. Thermodynamische Daten aus Gleichgewichtsmessungen
Authors: Egger Kurt W. , Jola M.
Published: December 2004

The composition of equilibrated gaseous mixtures of 3‐methylene‐1,5,5‐trimethylcyclohexene (MTC) and 1,3,5,5‐tetramethyl‐1,3‐cyclohexadiene (TECD) have been measured for temperatures ranging between 302 and 410°C. Nitrogen oxide was used as catalyst. Equilibrium was approached from either side. The least squares regression analysis of the observed temperature dependence of the equilibrium constants K1.2 = k1/k2 = (TECD)eq./(MTC)eq. yields (with standard errors)

This results in ΔH1.2(300°K) = 0.4 ± 0.3 kcal/mole and ΔS1.2(300°K) = 1.4 ± 0.8 cal/°‐mole. The fact that the reaction is practically thermoneutral implies that the secondary, «biallylic» CH bond in MTC is equally strong as the primary «biallylic» CH bond of the 1‐methyl group in TECD.

The observed enthalpy and entropy differences between the two isomers are in agreement with prediction based on the concept of additivity of thermodynamic increment properties (ref. [5]). The results of this work also yield a value of 23.7 cal/°‐mole for the entropy contribution characteristic of the 1,3‐cyclohexadiene ring structure. When combined with the ARRHENIUS parameters, reported earlier [1] for k1, the results of this work yield for the back reaction log k2 (1/mole‐s) = 8.25–30.2/4.58 × 10−3 T(°K).
Reaktion von Kaolinit mit Kaliumhydroxid
Authors: Sticher H. , Bach R.
Published: December 2004

The reaction of kaolinite with potassium hydroxide (1 to 9N) was investigated between 70 and 90°C. During a first period of the reaction the content of Si and Al in solution increased and reached a maximum in 100 to 240 minutes, depending on KOH concentration and temperature; then an amorphous aluminosilicate gel formed. After an induction period, again depending on KOH concentration and temperature, the concentrations of Si and Al decreased rapidly, due to the formation of a crystalline potassium aluminosilicate.
Photochemistry of 2‐Cyclohexene‐imines and 2,3,4,4a,5,6‐Hexahydroquinolines. Preliminary communication
Authors: Margaretha Paul
Published: December 2004

The 2‐cyclohexene‐imines 2b–2d and the hexahydroquinolines 5a, b are synthesized. n,π*‐Excitation of these α,β‐unsaturated imines leads to (E/Z) isomerization for compounds 2 while compounds 5 are unreactive. No cyclobutanes are formed from 2 or 5 under these conditions in the presence of olefins, and only 2d adds to 2,3‐dimethyl‐2‐butene via the CN bond to give an azetidine. On π,π* excitation 2 and 5 rearrange to the corresponding β,γ‐unsaturated imines 8 and 9 with low efficiency. It is concluded that the failure of such imines to undergo [2+2]‐photocycloadditions with olefins is not mainly due to radiationless decay via (E/Z) isomerization.
Properties and microstructures of epoxy resin/TiO2 and SiO2 hybrids
Authors: Yano Shoichiro , Ito Tatsuro , Shinoda Kenichi , Ikake Hiroki , Hagiwara Toshiki , Sawaguchi Takashi , Kurita Kimio , Seno Manabu
Published: December 2004

Epoxy resin/TiO2 and epoxy resin/SiO2 hybrids were prepared by different procedures, and their mechanical properties were correlated to their microstructures, as indicated by small‐angle X‐ray scattering (SAXS) measurements. Epoxy resin/TiO2 hybrids were prepared by mixing the epoxy resin (EP828) with N‐(2‐aminoethyl)‐3‐aminopropyltrimethoxysilane (S320) in acetone, and then titanium‐n‐butoxide (TnBU) was added. In addition, epoxy/SiO2 hybrids were prepared by mixing EP828 with a curing agent, a diamino heterocyclic compound (B002) in acetone, and an organo silica sol (silica nanoparticles dispersed in methylethylketone) was added. In the EP828/S320/TiO2 hybrid systems, the TiO2 component was attached to both of the chain ends of the epoxy matrix, hence leading to the formation of inorganic domains via the covalent bonds. SAXS profiles of these hybrids showed peaks at q = 2.3 nm−1, caused by interference between the domains. The storage modulus increased with increasing TiO2 content above the Tg, owing to the strong interactions between TiO2 and the epoxy matrix. The tanδ peak position did not change, although the intensity decreased with increasing TiO2 content. The SAXS profiles of the EP828/B002/SiO2 hybrids were very different to those of the corresponding EP828/S320/TiO2 hybrids, and indicated that SiO2 particles with rough surfaces were randomly dispersed in the epoxy matrix. The storage moduli of the EP828/B002/SiO2 hybrid systems increased only slightly with SiO2 content, because of the weak interactions. These mechanical properties are well explained by the microstructures derived from the SAXS profiles. Copyright © 2004 Society of Chemical Industry
Many‐electron problems. I. Energy relations in the theory of neutral atoms
Authors: Gáspár R.
Published: December 2004

Many‐electron atom calculations are analyzed. It is proved that for neutral atoms to a good approximation the electron–electron interaction energy is a constant multiple of the electron–nucleus interaction energy. A consequence of the above theorem is that the total energy of these atoms shows a very simple dependence on the atomic number.
A Tomonaga gas model for aromatic hydrocarbons
Authors: Basu Sadhan
Published: December 2004

Considering the π electrons in aromatic hydrocarbons as forming a two‐dimensional free‐electron gas, the Tomonaga method has been followed to determine the frequency of collective oscillations when an electron is excited in these systems. The calculated and experimental frequency have been found to be in excellent agreement, although the collective coordinate was not conjugate to the collective momentum in these systems containing only few free π electrons.
Generalized brillouin theorem for multiconfigurational SCF theories
Authors: Levy Bernard , Berthier Gaston
Published: December 2004

The matrix elements of the total Hamiltonian between a multiconfigurational SCF wave function and some well‐defined linear combinations of excited Slater determinants are equal to zero. By means of this generalized Brillouin theorem it is possible to estimate the improvements to be expected from a subsequent configuration‐interaction treatment. The expression of the effective potential for the orbitals can be also derived in the frame of a given multiconfigurational theory. As an example, the case of the CMC‐SCF method recently suggested [9] is examined.
A systems and control theoretic approach to dynamic neurotransmitter balance: Normal, abnormal, and “catastrophic”
Authors: Kaufman Joyce J. , Koski Walter S. , Peat David
Published: December 2004

We formulated a pharmacological–physiological systems analysis and control theory based on interactive neuronal feedback loops (the effects of endogenous neurochemical diseases and exogenous psychotropic and other CNS drugs on neurotransmitter synthesis and release, reuptake, and metabolism) for normal, abnormal, and catastrophic situations.

We were concerned primarily with the problems of stability or instability which might lead the system to exhibit catastrophic behavior. We set up the systems diagrams for the neurotransmitter systems and in that single framework were able to describe endogenous neurochemical disorders, the effect their drug treatment modalities had on the dynamic neurochemical balance, the effect psychotropic or other CNS drugs such as narcotics and narcotic antagonists had on neurotransmitter balance, and the interactive effect that multiple drug administration would have on neurotransmitter balance. Endogenous neurochemical disorders such as schizophrenia, Parkinsonism, depression, and mania should show up mathematically either as overly damped solutions if there is too little normal neurotransmitter or as catastrophically divergent instabilities if there is too much normal neurotransmitter. Improper mixed drug therapies, as well as the devastating effect of eating foods such as cheese (which contains sympathomimetic amines which potentiate the release of catecholamines from the presynaptic nerve endings) while on MAOI therapy also show up as mathematical, usually catastrophic, instabilities. We also indicated how this systems analysis and control theory could be put on small interactive computer terminals for use in clinical management and proper drug therapy of patients with neurochemical disorders.
Second quantization for systems with a constant number of particles in the Dirac notation
Authors: Koutecký Jaroslav , Laforgue Alexandre
Published: December 2004

The relation between the completeness condition for an appropriate one‐particle basis set and the occupation number representation (second quantization) is shown for the time‐independent case. The explicit expressions for the basic symmetric operators are derived in the Dirac bra–ket notation. The physical meaning of these operators, the algebra as well as the connections with the one‐electron density matrix and with the projector on the Fermi sea in the one‐electron approximation, follow directly from these expressions. The generalization for a nonorthogonal basis and the algebra for corresponding basic operators are formulated. The connection with the notion of the molecular diagrams of different kinds for the nonorthogonal atomic orbitals is shown. The Mulliken populations and the Chirgwin–Coulson bond orders are equal to the diagonal and offdiagonal elements of the molecular diagram 1, respectively. The matrix elements of the projector on the Fermi sea in the one‐electron approximation in the representation of nonorthogonal atomic orbitals are elements of the molecular diagram 2.
Third‐order many‐body perturbation theory for the ground state of the carbon monoxide molecule
Authors: Bartlett Rodney J. , Wilson Stephen , Silver David M.
Published: December 2004

Many‐body perturbation calculations have been performed for the ground state of the carbon monoxide molecule at its equilibrium internuclear separation. The calculations are complete through third order within the algebraic approximation; i.e., the state functions are parameterized by expansion in a finite basis set. All two‐, three‐, and four‐body terms are rigorously determined, and many‐body effects are found to be very important. A detailed comparison is made with a previously reported configuration interaction study. Padé approximants to the energy expansion are constructed. The many‐body perturbative wave function is used in the Rayleigh quotient to produce upper bounds to the electronic energy.
Electronic absorption spectra of V2O5
Authors: Lazukova N. I. , Gubanov V. A. , Mokerov V. G.
Published: December 2004

MO calculations of electronic structure and optical transitions for [VOn]5 −; 2n (n = 4, 5, 6) clusters in V2O5 monocrystals have been carried out by means of the semiempirical CNDO CI method. Using the calculated results, a complete analysis of V2O5 optical data as available in the literature and as obtained in the electroreflectivity experiments presented in this paper is performed. An identification of optical transitions in a wide energy range is presented. The optical properties of vanadium pentoxide are shown to be due to the localized charge transfer electronic transitions in the clusters. The fine structure of optical spectra is connected with the covalent splittings of the vanadium 3d and oxygen 2p atomic levels.
A simplified model for the predissociation of diatomic molecules
Authors: Berrondo M. , Flores‐Riveros A.
Published: December 2004

A model consisting of a harmonic oscillator well and a repulsive inverse square potential, coupled by a delta function, is solved. We find the S‐function for this case and study its poles as a function of the coupling strength. These poles show how the harmonic levels shift and broaden as the two potential curves couple and predissociation occurs. A “new state” is found when the energy threshold is just below the first excited state of the harmonic oscillator.
Stationarity of resonant pole trajectories in complex scaling
Authors: Canuto Sylvio , Goscinski Osvaldo
Published: December 2004

A reciprocity theorem relating the real parameters η and α that define the complex scaling transformation r →η reiα in the theory of complex scaling for resonant states is demonstrated. The virial theorem is used in connection with the stationarity of the pole trajectory. The Stark broadening in the hydrogen atom using a basis set generated by Rayleigh–Schrödinger perturbation theory is treated as an example.
Complex coordinates and the Stark effect
Authors: Cerjan C. , Hedges R. , Holt C. , Reinhardt W. P. , Scheibner K. , Wendoloski J. J.
Published: December 2004

The theories of the dilatation, r → r eiθ, and translation, x → x + iq, transformations as related to the Stark problem are reviewed, and new results obtained. Results for the hydrogen atom n = 1 and n = 2 levels and the 1P0, 2s2p H− shape resonance in dc fields are presented, and the extension to the ac Stark effect made. Spectral estimates are made using the technique of the numerical range and via discussion of several model problems, using both coordinate rotation and coordinate translation.
Refined AMOS for some organic semiconductors
Authors: Roustan J. , Dugay M.
Published: December 2004

For a few organic semiconductors we present calculations performed on a simple model by means of the field‐theoretical formulation of the “different‐orbitals‐for‐different‐spins” method. The numerical methods are extensively described and the results are discussed in comparison with other methods existing in the same domain.
Ab initio valence bond calculations. X. Vertical valence ionization potentials of allene and butatriene
Authors: Tantardini Gian Franco , Simonetta Massimo
Published: December 2004

The ground and vertical valence ionized states of allene and butatriene have been studied in the ab initio valence bond framework using the 6–31G basis set after contraction and introducing the core–valence shell separation. The final wave functions have been analyzed in terms of VB structures by means of population analysis.
Spin‐Free Quantum Chemistry. XXI. Hartree–Fock theory
Authors: Matsen F. A. , Nelin C. J.
Published: December 2004

The theory of the open‐and closed‐shell restricted Hartree–Fock method is given a unitary group formulation. Both extremum and stability conditions are employed, the former leading to a generalized Brillouin theorem.
Dependence of approximate ab initio molecular loge sizes on the quality of basis functions
Authors: Mezey Paul G. , Daudel Raymond , Csizmadia Imre G.
Published: December 2004

Size and shape parameters for the core, bonding, and lone electron pairs of the ten‐electron hydrides (CH4, NH3, H2O, HF) were determined from ab initio MO wave functions using various Gaussian basis sets. The fundamental features of approximate electron pair loge representation are somewhat more sensitive to the quality of the basis functions than the molecular total energy. The total size of the molecular electron distribution is less affected by basis set variations than its components: the core, bonding, and lone pair sizes. There is an apparent tendency to “preserve” the total size of molecular distribution.
Comments on the exclusion‐principle‐violating diagrams cancellation in correlations energy calculation by many‐body Rayleigh–Schrödinger perturbation theory
Authors: Hubač Ivan
Published: December 2004

When calculating the correlation energy where the effect of higher than double excitations is included by means of many‐body Rayleigh–Schrödinger perturbation theory (MB‐RSPT) through fourth order the problem of cancellation of exclusion‐principle‐violating (EPV) diagrams arises. The cancellation of EPV diagrams in fourth order of MB‐RSPT is demonstrated for diagrams which include the effect of tetraexcitations.
Resonances in the elastic electron‐SF6 molecule scattering
Authors: Gyemant I. , Varga Zs. , Benedict M. G.
Published: December 2004

In agreement with previous calculations by the authors, three definite resonances in the elastic electron‐SF6 molecule scattering in the energy range 5–40 eV have been obtained with a multiple scattering method, elaborated originally for molecular bound states and modified here for scattering states. Results with various more‐reliable one‐electron potentials have been compared with previous calculations and available experimental data.
Use of the Hiller–Sucher–Feinberg identity for spin‐density calculations
Authors: Harriman John E.
Published: December 2004

The identity recently presented by Hiller, Sucher, and Feinberg relating the expectation value of a δ‐function operator to that of another operator is rederived for the case of the Fermi contact interaction and the required expectation values expressed in terms of the spin‐density and conditional spin‐density matrices. The ground state of the H atom is considered as an example and it is shown that, for approximation by a linear combination of Gaussian orbitals, use of the identity improves the estimate of spin density at the nucleus by an order of magnitude or more.
Model potential Xα method for the electronic structure calculations
Authors: Katsuki Shinichi , Taketa Hiroshi
Published: December 2004

A new method is presented for the electronic structure calculations with use of Bonifacic and Huzinaga's model potential and Slater's Xα local‐statistical‐exchange potential. The density of the valence electrons and its cube root are least‐square fitted to ls‐type Gaussians to evaluate the Coulomb potential and the Xα potential analytically. Preliminary results of the applications of the method to molecules consisting of the second‐row atoms are given. Agreement with experimental ionization energies is satisfactory.
Ab initio unrestricted Hartree–Fock (UHF) and UHF–natural orbital CI studies of ozone
Authors: Yamaguchi Kizashi
Published: December 2004

The electronic structures of both the ground and excited states of ozone (O3) are investigated by the ab initio unrestricted Hartree–Fock (UHF) and UHF‐natural orbital (NO) CI methods. It is found that the ab initio UHF‐NO CI method provides reasonable descriptions of both the states of O3.
Ab initioLCAO MO SCF calculation of potential surface of the NO2 molecule
Authors: Morita Keiko , Sato Hiroshi , Ishiguro Eiichi
Published: December 2004

The SCF potential surface of the ground state for NO2 was calculated by using program JAMOL 3. The McLean–Loew–Berkowitz CGTO's were used as basis functions. One of the two NO distance R is fixed to 2.25 a.u. and the other one r and the ONO angle θ are varied from 2.25 to 5.0 a.u. and from 0° to 180°, respectively. The potential surface has the minimum around r = 2.50 a.u. and θ = 120°, where the energy is found to be −203.954 a.u.
Novel sign‐alternation rule for the triplet state in aromatic systems
Authors: Gondo Yasuhiko , Kanda Yoshiya
Published: December 2004

Within the framework of the LCAO‐MO theory, a novel sign‐alternation rule has been found empirically for the lowest excited ππ* triplet state in the alternant aromatic system. This rule can be applied to identify the phosphorescent state.
Theory of the Bose particle representation for geminals
Authors: Okido Sadao , Tanimoto Osamu
Published: December 2004

An electron pair in a molecule is a complex entity and is incompletely described by the independent particle picture. Electron pairs are treated as Bose particles to include correlation of intrapair interaction effectively by the use of the Dyson transformation. The use of a Bose‐type Hamiltonian permits a straight forward interpretation for geminals and facilitates the calculation of electronic energies. A Bose‐type representation method is applied to the calculation of electronic energies of a lithium hydride molecule.
ESCA peak intensities for small molecules in the sudden approximation
Authors: Palma A. , González E. , Goscinski O.
Published: December 2004

A simple transition probability formula is applied to the core hole ionization in CO, satisfactorily predicting the ratio between the intensity of the two inner‐shell peaks. The formula is also applied to the full ESCA spectra of water and methane; the theoretical results agree reasonably well with the experiment.
Photoionization cross section calculated by dynamical theory
Authors: Fujikawa Takashi , Kuroda Haruo
Published: December 2004

A new theoretical method to calculate the photoionization cross sections of complex molecules and solids is derived in the framework of the dynamical theory by using the Green's function method. The approximations applicable to treat the photoionization by x‐rays are also discussed.
Electron distribution in water by high‐energy electron scattering
Authors: Shibata S. , Hirota F. , Kakuta N. , Muramatsu T.
Published: December 2004

The differential cross‐sections for high‐energy electrons scattered from water have been measured over a wide range of momentum transfers. The effect of chemical binding was seen from the comparison between the experiment and the calculation for an independent‐atom model. The ab initio calculation using SCF MO was carried out with respect to the elastic scattering. It was in a good agreement with the experiment and thus a reliable electron distribution in water was obtained.
INDO Studies on the structure of benzosemiquinone radicals
Authors: Shinagawa Yoshiya , Shinagawa Yasuko , Uyesaka Nobuhiro , Fukuda Kohji
Published: December 2004

The spin densities of the radical anions from 4‐methylcatechol, 4‐carboxylic catechol, and 3‐methylcatechol were calculated by means of the INDO method with the geometrical parameter adjusting method. The observed protion hyperfine coupling constants were exactly reproduced.
Nuclear distortion of the equidistant arrangement in trans‐polyacetylene, (CH)x
Authors: Kertész M. , Koller J. , Ažman A.
Published: December 2004

The occurrence of broken‐symmetry Hartree‐Fock solutions may indicate instability of the lattice depending on the symmetry of the charge‐density wave (CDW). In case of polyacetylene, (CH)x, we have found such solutions having an off‐diagonal CDW. It is pointed out that this sort of instability is principally different from the Peierls instability. The importance of correct (symmetrical) cutoff of interactions in direct space (“finite neighbor's approximation”) is emphasized. A basic difference in the potential‐energy curve of trans‐(CH)x and the isoelectronic (HCN)x around the equidistant configuration is shown.
Dynamique moléculaire du cristal ammoniac. Calcul ab initioSCF de l'energie electronique
Authors: Et S. Odiot J. Bridet , Fliszar S.
Published: December 2004

The wave function and total energy of ammonia crystal are determined from the results of a totally optimized STO‐3G ab initio calculation of the tetramer, pattern of the crystal. The crystal electronic energy is expressed in terms of the interatomic distances and charge density matrix elements. The geometry obtained from optimization of the tetramer energy on geometric parameters is in very good agreement with the experimental data of the crystal.
Role of CA2+ ion in the abortifacient action of prostaglandins. II. Molecular orbital and conformation energy calculations of PGA1
Authors: Kothekar V. , Dutta S.
Published: December 2004

This paper reports some theoretical studies of PGA1 using conformational and molecular orbital techniques. The conformation energy (CE) calculations, using empirical potential‐energy functions, for intrinsic torsional rotations around C12C13 (θ), C7C8 (Ψ), and C14C15 (ϕ) show a number of energy minima. The relative value of the CE for these minima ranges from 4.09 to 8.01 kcal/mol. An additional rotation around C4C5 (χ) giving “twist” to the carboxyl chains lowers the CE value by 2–3 kcal/mol and a conformation with CE value 2.39 kcal/mol less than crystallographic one is obtained. The interchain interaction energy showed changes with conformations. No significant change in the interchain interaction energy was observed due to “twist” in the carboxyl chain. The isopotential mapping study demonstrated the probable ionic binding site near the carboxyl and the ring (O9) oxygens. Conformational and molecular orbital results are discussed in the light of the reduced abortifacient potency of PGA1 with respect to PGF2α and the possible role of Ca2+ ions in this action.
Geometry of a quantal system
Authors: García‐Sucre Máximo , Bunge Mario
Published: December 2004

Classically every physical thing has some geometry or other, but in the quantum theory the notions of spatial structure, shape, and size seem to become hazy if not outright inapplicable. In particular, elementary entities are by definition structureless and seem to have no size or shape other than those imposed by their environmént—as represented, e.g., by the boundary conditions. However, this does not entail that systems of interacting components, such as molecules, lack a geometry as well, as has been argued in recent times. The purpose of this paper is to investigate this claim. Since the solution to the problem whether a quantum‐mechanical system possesses a geometry depends critically upon the definition of the latter, we elucidate the notions of extension, shape, and spatial configuration of a system. We do so first classically in terms of the energy density, then quantum mechanically in terms of a suitably constructed position distribution function that depends upon the spatial coordinates (and is thus a field quantity) rather than on the particle coordinates. In this way we construct both classical and quantal concepts of the geometry of a system. We also define the notions of spatial structure and chemical structure of a quantal system. Our quantum‐mechanical concepts are quite general and constitute smooth extensions of the corresponding classical concepts. The upshot of this investigation is that a quantal system does have a geometry, albeit not as clearcut a one as a classical system, that is primarily determined by the interactions among its components. (Thus, physics determines geometry of physical systems, not the other way around.) This conclusion is obtained within nonrelativistic quantum mechanics without adding any extra assumptions. Our result vindicates the ball‐and‐spoke models of molecules and thus shows once again that quantum chemistry, although different from classical chemistry, stays close to the chemist's work bench.
Application of the strong‐coupling correspondence principle to atom–triatom collinear collisions
Authors: Farantos S. C. , Murrell J. N.
Published: December 2004

The strong‐coupling correspondence principle has been used to calculate the T–V transition probabilities in the collinear collision of He and Kr with CO2. For a harmonic CO2 potential the results for He agree well with published quantum mechanical probabilities. For Kr the agreement is less satisfactory but at worst the ratio of quantum to semiclassical transition probability is approximately 0.2. Introduction of anharmonicity in the CO2 potential was found to increase the semiclassical transition probabilities but this may just be due to the lowering of the vibration frequencies.
Quantum mechanical calculations of vibrational transition probabilities in collinear atom–triatom collisions
Authors: Erkoç S. , Murrell J. N.
Published: December 2004

Quantum mechanical calculations have been made of vibrational transition probabilities in the collinear collision of an inert gas atom with either CO2 or OCS. The dependence of the transition probability on the relative translational energy and the reduced mass is similar to that found for atom–diatom collisions. The transition P00 → 10 (excitation of the first stretching mode) is much greater than P00 → 01 (the second stretching mode). This is largely due to the difference in frequencies but it has been shown that there is an independent mass factor responsible for this difference.
Steady states and quasienergies of a system in an oscillating field within the perturbation configuration interaction method
Authors: Dmitriev J. , Lochmann R. , Weller Th.
Published: December 2004

A perturbation configuration interaction method is formulated for a system in an external oscillating field (PCILOSC). It is closely connected with the static PCILO method and can be used for the conformational analysis of molecules and molecular crystals with localized bonds in external fields.
Exact solutions for interacting finite potential wells
Authors: Heffernan Daniel M. , Liboff Richard L.
Published: December 2004

Exact wave functions and eigenenergy relations are obtained for a biwell potential as a function of interwell displacement and single well parameters. The proliferation of energies is shown explicitly as the wells are brought into close proximity. The model is compared with the opaque division‐wall model. These results find important application in laser and nuclear physics.
Dynamic nonlinear Jahn–Teller effect of the type E ⊗ ϵ
Authors: Singh Jai
Published: December 2004

By applying the projection operator method it is shown that the complicated Hamiltonian of a E ⊗ ϵ JT system with nonlinear coupling coefficients can be written in terms of two Hamiltonians which are simple to handle and transform according to irreducible representations E, A1, and A2 of C3v point group. A variational approach is then used to calculate the ground state energy, using the Hamiltonian that transforms according to E, as an explicit function of the linear and nonlinear coupling parameters. The energies calculated in the strong coupling limit are finally compared with the corresponding previously calculated energies.
Atomic calculations with an effective one‐body potential
Authors: Daudey J. P. , Berrondo M.
Published: December 2004

The accuracy of a new effective one‐body potential is assessed by the study of the electronic structure of atoms from He to Kr. The exchange part of this potential is obtained from a local approximation. Several simplified representations of the electronic density which lead to analytic Coulomb potentials are tested. It is shown that the introduction of the shell structure of the density is necessary, at least for third row atoms. The screening parameters of the potential are variationally optimized with respect to the total energy of the atom. With the most elaborate form of the Coulomb potential which contains one screening parameter for each shell, the comparison of the results with exact Hartree–Fock calculations is very promising. The relative difference is on the order of 10−5 for the total energy and on the order of 10−2 for the orbital energies. Multiplet splitting is reproduced accurately and F− is predicted to be stable (in contrast some others local potentials) by an amount of 0.046 a.u., compared with 0.050 a.u. for an exact Hartree–Fock calculation.
Structure and function of propranolol: A β‐adrenergic blocking drug
Authors: Phadke Ratna S. , Kumar N. Vasanth , Hosur R. V. , Saran Anil , Govil Girjesh
Published: December 2004

In our earlier studies using quantum chemical methods we had proposed that propranolol has an extended structure. These results were confirmed using proton NMR. We have now carried out extensive magnetic resonance and model building studies to examine the interaction of this drug with model membranes. The effect of propranolol on organization of lipid bilayers has been studied using ESR spin labeling technique. Spin label Tempo and spin labeled stearic acid (5 SASL) have been used to monitor changes in the fluidity of model membranes. Presence of the drug is found to fluidize the lipids. In case of 0.2M dipalmitoyl phosphatidyl choline (DPPC), presence of drug (0.1M) is found to decrease the gel‐liquid crystalline phase transition temperature by about 10°C. The order parameter measured from the spectrum of 5 SASL shows a 4% decrease on incorporation of the drug in membranes. 13C spin lattice relaxation time (T1) measurements have been carried out for different nuclear sites of the drug. The aromatic moiety shows a high degree of molecular rigidity when the drug is bound to the lipid bilayers. The oxypropanolamine group is however relatively flexible. It appears from these studies that the aromatic group binds strongly to the hydrophobic regions of the lipid bilayer, while the oxypropanolamine moiety remains relatively free and lies in the hydrophilic region. The 13C chemical shifts indicate the involvement of the β‐hydroxyl group in hydrogen bonding with the lipids. The NH group may be involved in electrostatic interactions with the negatively charged phosphate group of the lipid bilayers.
Cholesterol and phospholipids in membranes: The hydrogen bonding problem
Authors: Lala Anil K.
Published: December 2004

Cholesterol and phospholipids are major components of biological membranes. The role of cholesterol in membranes is not metabolic and is known to be a regulator of membrane fluidity which in turn regulates various biological phenomena. We have studied the nature of cholesterol and phospholipid interaction in artificial membranes using 13C NMR spectroscopy. This involved preparation of phospholipids specifically labeled with 13C in the ester carbonyl group. Though the chemical shift data did not provide very useful information the T1 and T2 measurements indicated that previously proposed H bonding between the ester carbonyl group and hydroxyl group of cholesterol seems unprobable.
Conformational analysis of some mannose‐containing and milk oligosaccharides: Correlation of their shape with inhibitory properties in antigen/antibody interactions
Authors: Biswas Margaret , Rao V. S. R.
Published: December 2004

Possible conformations of two mannotetraoses and several milk oligosaccharides have been studied by an energy minimization procedure using semi‐empirical potential functions. Changes in the terminal residue at the reducing end (cyclic to acyclic form) of these molecules do not affect the favored conformations of the remaining oligosaccharide moiety. However, differences in the overall shape of the native and reduced forms of the mannotetraose, mannose α(1–3) mannose α(1–2) mannose α(1–2) mannose are much less marked than between the native and reduced forms of lacto‐N‐tetraose. These differences are related to the effectiveness of the native forms as inhibitors of antibodies produced using synthetic antigens. Changes in the linkage of the residues at the nonreducing end of these molecules affect significantly the overall shape of these molecules. These differences also are related to their effectiveness as inhibitors. In the fucose‐containing milk oligosaccharides the additional fucose residues only restrict the orientation of the backbone tetrasaccharide and do not push it into a totally new conformation. The fucose residues come on a surface of the molecule which is away from the region which may be important for binding. The present studies show that it is the overall shape of the molecule which is important in determining its inhibitory properties and give information as to how best to use the immune method for identification of unknown oligosaccharide sequences by specially prepared antibodies.
Estimation of binding sites from the adsorption profile of complexed DNA
Authors: Ghosh Subhendu , Mookerjee Anjali
Published: December 2004

The adsorption profiles of free and Daunomycin bound DNA at an alumina–H2O interface have been studied. Proper experimental conditions were maintained to considerably reduce intercalation and to make electrostatic binding predominant in the DNA–Daunomycin complex. For both free and complexed DNA, Langmuir plots gave straight lines. Adsorption of drug bound DNA was less than that of free DNA. This has been explained from the viewpoint of electrostatic interactions between adsorbate and adsorbent. A Langmuir‐type model for adsorption of polymers combined with Scatchard equation have been used to estimate the average value of percent of phosphates in DNA stacked with Daunomycin.
Impact of lone pairs on the conformation and configuration statistics of poly(lactic acid) chains
Authors: Prasad C. V. , Sundaram K.
Published: December 2004

Nonbonded interaction energies have been calculated for various conformations of the diester giving explicit consideration to the lone‐pair electrons. As suspected from an earlier calculation on the dipeptide, such inclusion of the lone‐pair effect leads to significant differences in the conformational potential energy map. The diester is shown to be more constrained than the dipeptide. The impact of this constrained geometry and the possible occurrence of cis residues on configuration statistics of poly(lactic acid) chains have been studied. Contrary to expectation the inclusion of cis isomers does not explain the paradoxical high negative temperature coefficient of ln C∞.
Intermolecular interactions in porphin dimers: A quantum mechanical study
Authors: Sudhindra B. S. , Fuhrhop J.‐H.
Published: December 2004

Both short‐range and long‐range intermolecular interaction energies between two prophin molecules, both in their ground state, separated by a range of interplanar distances from 3 to 4.5 Å, are estimated using the standard perturbation theory. The results indicate that a 60° rotated sandwich structure is the most stable conformation for the dimer. Certain translated as well as the perfect sandwich forms are other favoured structures. The stability of the dimer is mainly due to the van der Waals interactions with no significant contribution from the charge‐transfer interactions. Biochemical implications of these findings are discussed.
Virial theorem and boundary conditions for approximate wave functions
Authors: Fernández Francisco M. , Castro Eduardo A.
Published: December 2004

The quantum‐mechanical virial theorem is analyzed for those systems which obey nontrivial boundary conditions and for approximate wave functions. The conditions that trial functions have to fulfill are set up in order that every expression derived from the virial theorem can be properly used.
Explicitly correlated configuration interaction studies using spherical Gaussians. II. Exploratory studies on LiH
Authors: Karunakaran K. M. , Christoffersen Ralph E.
Published: December 2004

Ab initio self‐consistent‐field and configuration interaction studies have been carried out on the ground state of the LiH molecule at its equilibrium distance. Floating spherical Gaussian basis orbitals (FSGO) were employed, along with spherical Gaussian correlation factors, using the procedure described in the preceding paper. A near‐Hartree–Fock function was found using only 13 FSGO. Exploratory configuration interaction studies recovered approximately 73% of the inner shell correlation energy and approximately 56% of the total correlation energy with five configurations plus the Hartree–Fock configuration. These studies indicate that, by using spherical Gaussian correlation factors, direct introduction of interelectronic coordinates into trial wave functions can be accomplished for molecular systems. It was also shown that correlating configurations need not utilize the full Hartree–Fock basis, but may use substantially smaller bases and still recover correlation energy effectively. Finally, the results indicate that, in spite of their improper cusp behavior, FSGOS and spherical Gaussian correlation factors can be used for construction of high accuracy wave functions.
Vibronic coupling of electronic states. II. mathematical description of the model
Authors: Gustav Klaus , Colditz Roland
Published: December 2004

A model of vibronic coupling of crude Born–Oppenheimer (CBO) potentials within the scope of the linear variational procedure is presented. First numerical results testing the model are discussed.