Effects of complex-valued electronic wave functions on nuclear motions

Moleculer species and colliding groups of atoms are considered for which the electronic wave functions are complex-valued, having arguments that depend parametrically on the nuclear coordinates. The effective Hamiltonian for nuclear motions in the adiabatic approximation that arises in the present case differs from the ordinary Born–Oppeneheimer Hamiltonian, the latter being obtained when restriction to real-valued electronic functions is made. The asymptotic boundary conditions imposed in collision theory lead to in- and out- states [8], and hence to complex-valued wave functions in the coordinate representation. The study of the influence of electron–molecule scattering on nuclear motions therefore necessitates the use of the new effective Hamiltonian, which leads to results differing from those predicted on the basis of the Born–Oppenheimer operator. It is shown that momentum-dependent potentials occurring in the new Hamiltonian might cause “distortions” to the vibrational patterns of some electron–molecule metastable states. Also, these terms can give rise to non-Born–Oppenheimer resonances when motions in an internuclear coordinate become unbounded. We derive expressions for the relevant level widths and line shapes, showing them to be subject to an isotope effect. Even when real-valued electronic functions may be used, the selections of complex-valued functions in their linear span is still optional. Although exact treatments lead to the same results in both real and complex cases we show how the choice of the argument of the electronic function to be non-zero and dependent on nuclear coordinates may be useful for the application of certain approximation schemes. It is demonstrated that for certain systems a suitable choice of the argument assures convergence when the related Lippmann–Schwinger Equation is iterated. It is also shown that in this way an nth order term in the series expansion of the T matrix [8] for moleculer systems can be made negligibly small.     

Spectrophotometric determination of thiourea in microgram quantities

Summary Copper(II) forms a stable colourless complex with thiourea. This property has been utilized to develop a Spectrophotometric method for the determination ofg quantities of thiourea. The complex absorbs in ultraviolet region and the determinations are carried out at 250 nm. The method permits the determination of thiourea from 10–60g with error not exceeding ± 1.0%.

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Zusammenfassung Kupfer(II) bildet mit Thioharnstoff eine farblosa Komplexverbindung, die sich auf Grund ihrer Absorption bei 250 nm zur spektrophotometrischen Bestimmung von Mikrogrammengen Thioharnstoff eignet. 10 bis 60g Thioharnstoff lassen sieh mit einem Fehler von höchstens ± 1,0% bestimmen.

     

Potential energy surfaces for HenNe+ ions: ab initio and diatomics-in-molecule results

The potential energy surface of He2Ne+ has been reinvestigated using a combination of ab initio and diatomics-in-molecule (DIM) calculations. In contrast to the reports of two recent studies the ion is found to have an asymmetric linear He-Ne-He structure, with no barrier to formation from the separated atoms on the ground-state surface. The He-Ne+ bond lengths at the potential minimum are 1.51 and 1.81 A, and the total bonding energy is 0.717 eV. Comparing the He2Ne+ energy to that of HeNe+, the bonding energy for the second helium atom is 0.06 eV, about 10% of that of the first He atom. The saddle point between the two equivalent minima is a symmetric structure, 0.0074 eV above the potential minimum. A symmetric geometry becomes the overall potential minimum if the 2s hole on the Ne is excluded from the reference states of a multireference configuration interaction calculation. A DIM potential was created for the HenNe+ family of ions. The DIM potential is consistent with the asymmetric He2Ne+ ion serving as a core; it predicts a slightly more asymmetric geometry than the ab initio results. Additional helium atoms form five-membered rings around the bonds of the core ion to fill the first shell and then add to the ends of the cluster. The asymmetric core ion and the highly compact structure help to account for the lack of apparent shell structure in the mass spectrometry of HenNe+ clusters. Finally, we recommend that the value De=0.63+/-0.04 eV be adopted for the ground state of HeNe+.     

Synthesis and structure of pyrazolo[5,1-a]isoindol-8-ones from Aromatic Ortho Diesters

The title compounds 2 , have now been shown to arise in certain cases from condensation of aromatic ortho-diesters with ketone, where formerly only indeno[1,2-c]pyrazol-4(1H)-ones 3 have been reported from such reaction. Heretofore 2 was obtained in a less direct fashion from phthalaldehydic acid esters. When hetero-aromatic diesters were employed, new heterocyclic ring systems as represented by 2a,b ,c were prepared for the first time. Structures of 2 have been verified from detailed ¹H and ¹³C nmr studies, while representative intermediates 4–9 in the condensation of diesters to 2 have been isolated and identified.     

Effect of radial distribution functions and poisson reparatition of reactants on the analysis of reactions involving long distance energy transfer

Starting from a uniform distribution and knowing the space dependent rate constant, it is possible to express the fluorescence quenching effect. In the case of long distance energy transfer (Forster), we show that the introduction of radial distribution functions and of non-uniform repartition of quenchers has only small effects on the kinetics of such reactions.

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. (Forster) , .

     

The infrared spectra of complexes with planar dithiooxamides X. The Cu(LH2)2X1 complexes

In this article, the preparation, X-ray powder results and vibrational properties of a new type of complex with planar dithiooxamides are discussed. In acetonitrile, Cu(I) can form complexes with the formula Cu(LH₂)₂X₁ (X = Cl, Br) where LH₂ is an N,N'-disubstituted dithiooxamide. Complexes with N,N'-dimethyldithiooxamide and N,N'-diethyldithiooxamide have been prepared. A thorough vibrational analysis with infrared and Raman techniques was performed, assisted by H/D and ⁶³Cu/⁶⁵Cu isotope substitution. The vibrational study indicates the presence of an inversion centre in the structure. This leads to the proposal of a very unusual six-coordinate structure for these compounds, with the two dithiooxamide ligands, having S-cis conformation, coordinated to the same copper and with the halogens bridged between two different copper atoms. Confirmation of this result was attempted by X-ray analysis, but although several methods were tried to obtain crystals, only powder X-ray data could be obtained, which could not give a definitive answer. Since such six-coordinate Cu(I) has never been described before, a less rigourous interpretation of the vibrational data was followed, leading to a square-pyramidal five-coordinate structure, with a rather weak bond between Cu(I) and a terminal halogen. The latter structure, with the data available up to now, seems a bit more likely, since five-coordination for Cu(I) has already been described.     

Rapid determination of PAHs in soil samples by HPLC with fluorimetric detection following sonication extraction

A rapid method for the determination of PAHs in soil samples based on their extraction with methylene chloride by sonication and subsequent separation by HPLC with fluorimetric detection is proposed. A Hypersil Green PAH column was used with a gradient of acetonitrile/water as the mobile phase, together with a program of nine excitation and emission wavelength pairs. Recoveries were in the range 70-98%, except for acenaphthene and naphthalene, at concentration levels 1.08-442 microg/kg with relative standard deviations in the range 2-15% (n = 4). Total PAHs found in soil samples were in the range 15-282 microg/kg. The results were compared with those obtained by applying the 3540 EPA method for two samples.     

Theoretical investigations of Fe porphyrins. V. Low-lying electronic states of bisammineporphinatoiron(III)

Ab initio CI calculations are reported on the lowest doublet, quartet, and sextet states of [Fe^III(P)(NH₃)₂]⁺. The low-spin ground state is calculated as (d_xy² (d_π)³ with d_xy(d_π)⁴ higher by 0.15 eV. The near-ir bands at ～1 eV observed in low-spin ferriheme proteins are attributed to (π → d_π) transitions. The lowest high-spin state is ⁶A_1g, and the near-ir transitions of the high-spin ferriheme proteins observed at ～1.2 eV are attributed to higher ⁶[tripsextet] excited states [i.e., ring triplet, metal sextet]. The 30-ps “triplet” transient populated with low quantum yield observed in laser-flash studies on Fe^III(TPP)CI [TPP = tetrapbenylporphyrin] may be an ¹[tripsextet] state.     

Rapid imaging, using a cooled charge-coupled-device, of fluorescent two-dimensional polyacrylamide gels produced by labelling proteins in the first-dimensional isoelectric focusing gel with the fluorophore 2-methoxy-2,4-diphenyl-3(2H)furanone

A new method for visualising proteins in two-dimensional polyacrylamide gels was developed. Proteins were labelled with the fluorophore 2-methoxy-2,4-diphenyl-3(2H)furanone (MDPF) while present in the first-dimensional gel after isoelectric focusing and subsequently electrophoresed into the second-dimensional gel. High resolution spot patterns were produced and compared with other methods of visualisation. A new rapid imaging system based on a cooled charge-coupled-device was used to view the two-dimensional fluorescent protein spot patterns. The method allows the immediate and rapid imaging of two-dimensional gels at the end of electrophoresis with no further processing.     

Characterization of a complex dispersion of multilamellar vesicles

Spherulites ^® are multilamellar vesicles made up of surfactant bilayers. These vesicles would potentially be very useful for the encapsulation and protection of molecules; however, traditional formulations of these vesicles are poor at retaining small hydrophilic molecules (below 1000 g/mol). In this study, we present new systems of Spherulites called complex dispersions. These are prepared by dispersing Spherulites in an oil medium, and then emulsifying this oily dispersion of Spherulites within an aqueous solvent. These new systems provide an additional oil barrier between encapsulated molecules and an external aqueous phase. We have used polarized light optical microscopy, X-ray diffraction and freeze–fracture electron microscopy to study a complex dispersion of Spherulites at all stages of its preparation. We first studied the sheared lamellar phase, followed by the dispersion of the multilamellar vesicles in the oily medium and finally the emulsification of the oily dispersion within the aqueous solvent. We compared our results on lamellar phases with previous results obtained with Spherulites directly dispersible in an aqueous medium. Since the formulation of our lamellar phase included a large percentage of oil as a component, we studied the localization of the oil in the lamellar structure. We also studied the influence of osmotic pressure on complex dispersions, because complex dispersions possess a double structure similar to that of water-in-oil-in-water emulsions and multiple emulsions are known to be sensitive to osmotic pressure. In conclusion, complex dispersions proved to be new potential carriers exhibiting some unique physical properties.