Klaus Krickeberg und Vietnam. Erinnerungen

Ohne Zusammenfassung

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Original Russian Text ? X.X.Nguyen, 2009, published in Izvestiya NAN Armenii. Matematika, 2009, No. 1, pp. 26–31.     

Interaction of diatomic germanium with lithium atoms: electronic structure and stability

Quantum chemical calculations were applied to investigate the electronic structure of mono-, di-, and trilithiated digermanium (Ge2Lin) and their cations (n=0-3). Computations using a multiconfigurational quasidegenerate perturbation approach based on complete active space self-consistent-field wave functions, and density functional theory reveal that Ge2Li has a 2B1 ground state with a doublet-quartet energy gap of 33 kcal/mol. Ge2Li2 has a singlet ground state with a 3Au-1A1 gap of 29 kcal/mol, and Ge2Li3 a doublet ground state with a 4B2-2A2 separation of 22 kcal/mol. The cation Ge2Li+ has a 3B1 ground state, being 13 kcal/mol below the open-shell 1B1 state. The computed electron affinities for diatomic germanium are EA(1)=1.9 eV, EA(2)=-2.5 eV, and EA(3)=-6.0 eV, for Ge2-, Ge2 (2-), and Ge2 (3-), respectively, indicating that only the monoanion is stable with respect to electron detachment, in such a way that Ge2Li is composed by Ge2-Li+ ions. An "atoms-in-molecules" analysis shows the absence of a ring critical point in Ge(2)Li. An electron localization function analysis on Ge2Li supports the view that the Ge-Li bond is predominantly ionic; however, a small covalent character could be anticipated from the analysis of the Laplacian at the Ge-Li bond critical point. The ionic picture of the Ge-Li bond is further supported by a natural-bond-order analysis and the Laplacian of the electron density. The calculated Li affinity value for Ge2 is 2.08 eV, while the Li+ cation affinity value for Ge2- is 5.7 eV. The larger Li+ cation affinity value of Ge2- suggests a Ge2-Li+ interaction and thus supports the ionic nature of Ge-Li bond. In GeLi4 and Ge2Li, the presence of trisynaptic basins indicates a three-center bond connecting the germanium and lithium atoms.     

Multifunctional polymeric nanoparticles from diverse bioactive agents

We present a rational approach for assembling diverse bioactive agents, such as DNA, proteins, and drug molecules, into core-shell multifunctional polymeric nanoparticles (PNPs) that can be internalized in human breast cancer cells. Using ring-opening metathesis polymerization (ROMP), block copolymers containing small-molecule drug segments (>50% w/w) and tosylated hexaethylene glycol segments were prepared and assembled into PNPs that allowed for the surface conjugation of single-stranded DNA sequences and/or tumor-targeting antibodies. The resulting antibody-functionalized particles were readily uptaken by breast cancer cells that overexpressed the corresponding antigens.     

Control of interchain contacts, solid-state fluorescence quantum yield, and charge transport of cationic conjugated polyelectrolytes by choice of anion

Simple procedures are provided for exchanging charge-compensating ions in conjugated polyelectrolytes by progressive dilution of the original species and for determining the degree of ion exchange by using X-ray photoelectron spectroscopy. By using these methods, the bromide ions in poly[(9,9-bis(6'-N,N,N-trimethylammoniumbromide)hexyl)fluorene-co-alt-4,7-(2,1,3-benzothiadiazole)]were exchanged with BF4-, CF3SO3-, PF6-, BPh4-, and B(3,5-(CF3)2C6H3)4- (BArF4-). Absorption, photoluminescence (PL), and PL quantum yields (Phi) were measured in different solvents and in solid films cast from methanol. Examination of the resulting trends, together with the spectral bandshapes in different solvents, suggests that increasing the counteranion (CA) size decreases interchain contacts and aggregation and leads to a substantial increase of Phi in the bulk. Size analysis of polymers containing Br- and BArF4- in water by dynamic light scattering techniques indicates suppression of aggregation by BArF4-. Nanoscale current-voltage measurements of films using conducting atomic force microscopy show that hole mobilities and, more significantly, charge injection barriers are CA dependent. These results show that it is possible to significantly modify the optoelectronic properties of conjugated polyelectrolytes by choosing different counterions. A parent conjugated backbone can thus be fine-tuned for specific applications.     

Performances under representative pressure and temperature conditions of the gas chromatography-mass spectrometry space experiment to investigate Titan's atmospheric composition

In the frame of the calibration of the aerosol collector and pyrolyser, and gas chromatography-mass spectrometry experiments of the Huygens probe arrived at Titan, systematic experimental studies were led to estimate the influence of the operating conditions on the analyses that should have been achieved in the Titan's atmosphere. The primary objective of this study was to estimate the influence of operating conditions variations induced by (i) instrumental modifications made shortly before the probe launch which can have changed the operating pressures; (ii) the change of the probe environmental conditions (pressure, temperature) during its descent in the atmosphere; (iii) a possible deviation of pressure and temperature regulations from their nominal values because of the long journey of the instrument in space, or of other external events. The secondary objective of this work was to create an analytical database that can be used as a reference to treat the chromatograms obtained in situ, and help to identify chromatographically the analyzed species, complementary to mass spectrometry. Beyond the application to a specific instrument, this work was also useful to experimentally estimate the fundamental evolution of the separation as a function of the changes of operating conditions with time. The obtained results show (i) the significant influence of inlet and outlet pressure variation on the time of analysis, but not on the separation power. It thus enables to significantly shorten the analysis duration, and thus to analyze more compounds within the fixed time of analysis of the instrument; (ii) the significant influence of temperature on the retention. In this frame, the enthalpies of exchange between the gas phase and the stationary phase of the species were determined to be used to retrieve the analyzed species in case of deviation of the operating temperature; (iii) that the possible aging of the columns does not have influence on the columns efficiency and separation power; (iv) the analytical capabilities of the gas chromatography-mass spectrometry experiment within operating conditions representative of those encountered in situ. Finally, in spite of possible operating condition changes, it is shown that results coming from the gas chromatograph-mass spectrometer experiment, which are currently under analysis, could bring important information on the Titan's atmosphere and its history.     

Total synthesis of oxyfagaronine, phenolic benzo[c]phenanthridine and general synthetic way of 2,3,7,8- and 2,3,8,9-tetrasubstituted benzo[c]phenanthridine alkaloids

Benzo[c]phenanthridine alkaloids such as oxynitidine, oxysanguinarine, oxyavicine and phenolic oxyfagaronine were synthesized from easily available starting benzonitriles 5 and toluamides 6 using a lithiated toluamide-benzonitrile cycloaddition reaction. The coupling reaction provided 3-arylisoquinolinones that were transformed to the benzo[c]phenanthridones. This method is highly efficient and could be useful for preparing diverse substituted aromatic benzo[c]phenanthridine compounds on a multi gram scale.     

Synthesis, properties and molecular structure of a novel dicyanoheptafulvene derivative, 4′-dicyanomethylidenedispiro[cyclohexane-1, 1′-(1′,4′,7′-trihydrocyclopenta[f]azulene)-7′,1″-cyclohexane]

A novel dicyanoheptafulvene 9 annulated by two spiro[4,5]deca-1,3-dienes was synthesized by the reaction of dispirocyclopentaazulenium cation 8 with bromomalononitrile. Although 9 was found to have a nonplanar heptafulvene structure by its X-ray crystallographic analysis, it is still capable of π-conjugation and thus shows appreciable contribution of the dipolar resonance form 9B based on its spectroscopic data. The degree of the contribution was further evaluated for various dicyanoheptafulvenes in terms of the partial sum of atomic charges of the dicyanomethylene group in the calculated structures besides the interplanar angles of the heptafulvene part and the length of the exocyclic double bond in the crystal structures.     

Sodium zinc hydroxide sulfite with a novel Zn3OH geometry

The synthesis and crystal structure of a new sodium zinc hydroxide sulfite, Na[(Zn(OH)]3(SO3)2, with novel structural features and bonding geometry are reported. In Na[(Zn(OH)]3(SO3)2, Zn2+ and O2- alternate to form an interesting corrugated hexagonal sheet with rings consisting of (ZnO)3. Another rare occurrence is the bonding geometry of one-third of the O sites within the sheet. These O sites form a planar Zn3O unit, unlike other known compounds, in which Zn3O is pyramidal.     

A method for simultaneously determining the zeta potentials of the channel surface and the tracer particles using microparticle image velocimetry technique

The zeta potentials of channel surfaces and tracer particles are of importance to the design of electrokinetic microfluidic devices, the characterization of channel materials, and the quantification of the microparticle image velocimetry (microPIV) measurement of EOFs. A method is proposed to simultaneously measure the zeta potentials of the channel surface and the tracer particles in aqueous solutions using the microPIV technique. Through the measurement of the steady velocity distributions of the tracer particles in both open- and closed-end rectangular microchannels under the same water chemistry condition, the electrophoretic velocity of the tracer particles and the EOF field of the microchannel are determined using the expressions derived in this study for the velocity distributions of charged tracer particles in the open- and closed-end rectangular microchannels. Thus, the zeta potentials of the tracer particles and the channel surfaces are simultaneously obtained using the least-square method to fit the microPIV measured velocity distribution of the tracer particles. Measurements were carried out with a microPIV system to determine the zeta potentials of the channel wall and the fluorescent tracer particles in deionized water and sodium chloride and boric acid solutions of various concentrations.     

Multichannel vector sum phase shifter

A novel multichannel vector sum phase shifter that is suitable for phased array antenna applications is demonstrated. Each channel is implemented using a distinct optical wavelength. Selective control of each channel is performed using an acousto-optic polarization coupler. The concept is successfully demonstrated for two individually controlled channels. For each channel, a continuously variable frequency linear phase shift is demonstrated between DC and 7 GHz, with the phasing range exceeding 100 degrees.