Quinones 1a−q and DCNQIs 2a−g have been synthesized in order to investigate substituent effects. It was necessary to employ novel synthetic routes for the introduction of iodine into 1f (7), the ...trifluoromethyl group into 1g−i, deuterium into 1m−p, and especially for the chloride/fluoride exchange of 1j to 1k, and 1l. With few exceptions both 1 and 2 undergo reversible electron transfer in two steps including thermodynamically very stable radical cations (lg KSEM > 10, cyclic voltammetry). Linear correlations have been found between E2 (OX/SEM) data of 1 and 2 with (σm + σp)/2 and between E2 of 1 and 2. Correlations have also been found between E2 and the LUMO energies of 1 and 2. The crystal structure of quinone 1i shows some special interactions due to the two CF3 groups, whereas the structures of DCNQIs 2d and 2g link up with those evaluated earlier.
The new members of the series of 2,5‐disubstituted DCNQIs, 1d (Cl/OMe), 1e (Br/OMe), 1j (Cl/I), 1k (Br/I), 1l (I/I), form conducting charge‐transfer complexes with TTF (tetrathiofulvalene) which are ...comparable to known DCNQI/TTFs. From these DCNQIs highly conducting radical‐anion salts 2‐X, 5‐Y‐DCNQI2M (M = Li, Na, K, NH4, Tl, Rb, Ag, Cu) can also be prepared either from the DCNQIs and MI (not AgI), on a metal wire (Ag, Cu), or by electrocrystallization (M = Tl, Ag,Cu). For better crystals a method using periodical switching between reduction and partial oxidation has been developed. With CF3 (large, strongly electron‐attracting) as the substituent in DCNQIs 1m (OMe/CF3) and 1n (Me/CF3), conducting TTF complexes remain whereas only 1n yields an insulating copper salt. DCNQI–Cu salts with high conductivities are obtained with alloys containing two or three different DCNQIs. The temperature‐dependent conductivities of DCNQI–M salts (other than copper) are similar to those of metal‐like semiconductors. All new DCNQI–Cu salts are metallic M down to low temperatures, except 1d (Cl/OMe)2Cu which undergoes a sharp phase transition to an insulating stateM → I. By variation of the ligands or their ratios in conducting alloys of DCNQI–Cu salts temperature‐dependent conductivities can be tuned from M → I to M. In addition, alloying three ligands produced for the first time a radical salt with temperature‐independent conductivity from 5 to 300 K. Most remarkably, alloys of the type (2,5‐Me2DCNQI)m Cu/{2,5‐(CD3)2‐DCNQI}n2Cu which exhibit a sharp M → I phase transition on further cooling reenter the conducting state by an I → M transition, with changes of ca. 108 Scm−1 both ways. For the first time in the field of organic metals crystal structures of DCNQI–copper salts have been determined by X‐ray powder diffraction methods and refined by Rietveld analysis. Unit cell data, coordination angles and distances of the π planes are in excellent agreement with the single‐crystal X‐ray data. However, bond lengths and angles of the ligands are to be less accurate. This powder method proves to be most valuable if only microcrystalline material is available.
Imaging of Tautomerism in a Single Molecule Piwoński, Hubert; Stupperich, Clemens; Hartschuh, Achim ...
Journal of the American Chemical Society,
04/2005, Letnik:
127, Številka:
15
Journal Article
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Fluorescence imaging is used to visualize directly the transfer of two inner hydrogen atoms in single porphycene molecules. This reaction leads to a chemically equivalent but differently oriented ...structure and hence results in a rotation of the transition dipole moments. By probing single immobilized molecules with an azimuthally polarized laser beam in the focal spot of a confocal microscope we observe ring-like emission patterns, possible only for a chromophore with two nearly orthogonal transition dipole moments. Numerical simulations of the observed emission patterns yield a value of 72° for the angle between the S0−S1 transition moments in the two tautomeric forms.
Plants regulate the extent of nodulation and root colonization by arbuscular mycorrhizal fungi (AMF), a phenomenon named autoregulation of symbiosis. We tested AMF colonization in split roots of ...various soybean genotypes Glycine max (L.) Merr. cv. Bragg, Enrei, Harosoy and Williams, where precolonization of one side of the split-root system by the AMF Glomus mosseae resulted in reduced mycorrhization of the other. AMF precolonization failed to control secondary mycorrhization in the supernodulating Bragg nonsense mutant nts1007 (Q106*), indicating that the GmNARK gene (predicted to encode a leucine-rich repeats (LRR) receptor kinase related to CLAVATA1 in Arabidopsis) is involved in autoregulation of the AMF symbiosis. Here, we tested whether the allelic En6500 nonsense supernodulating mutant (GmNARK K606*, derived from cv. Enrei) and supernodulating mutants of cv. Williams (Nod1-3 and Nod2-4) with yet-undefined genetic lesions exhibit a similar symbiotic phenotype in mycorrhizal split-root systems. Surprisingly, these supernodulating mutants retained their ability to autoregulate AMF. To examine possible differences between two allelic mutants, we determined levels of IAA, abscisic acid, coumestrol, daidzein and genistein in mycorrhizal and uninoculated control roots. Compared with wild-type plants, both mutants showed reduced IAA accumulation in mycorrhizal roots. Roots of cv. Enrei and En6500 exhibited high levels of isoflavonoids not seen in Bragg or nts1007. Taken together, these findings showed that supernodulation mutants, despite a common nodulation phenotype, differ in their ability to autoregulate AMF root colonization. This suggests either that the GmNARK gene product of some mutants is still partially functional (Q106* vs. K606*) or that varietal differences reflected in altered physiological responses suppress the loss of function.
In bond pitch ranges of 50 to 30 micrometer Thermo Compression Bonding (TCB) is an established bonding technology for example for high bandwidth memory (HBM) using relative small dies. For logic, ...processor and interposer applications, die sizes may be much larger and bonding behavior may be more complicated due to warpage, relative high heater powers, high number of contacts and possible oxidation issues. This paper will describe bonding behavior for up to 80mm x 80mm die sizes including methods using protective/reduction gas during bonding with extreme low gas consumption and effective oxidation prevention.
Modern astronomy has finally been able to observe protoplanetary disks in reasonable resolution and detail, unveiling the processes happening during planet formation. These observed processes are ...understood under the framework of disk-planet interaction, a process studied analytically and modeled numerically for over 40 years. Long a theoreticians' game, the wealth of observational data has been allowing for increasingly stringent tests of the theoretical models. Modeling efforts are crucial to support the interpretation of direct imaging analyses, not just for potential detections but also to put meaningful upper limits on mass accretion rates and other physical quantities in current and future large-scale surveys. This white paper addresses the questions of what efforts on the computational side are required in the next decade to advance our theoretical understanding, explain the observational data, and guide new observations. We identified the nature of accretion, ab initio planet formation, early evolution, and circumplanetary disks as major fields of interest in computational planet formation. We recommend that modelers relax the approximations of alpha-viscosity and isothermal equations of state, on the grounds that these models use flawed assumptions, even if they give good visual qualitative agreement with observations. We similarly recommend that population synthesis move away from 1D hydrodynamics. The computational resources to reach these goals should be developed during the next decade, through improvements in algorithms and the hardware for hybrid CPU/GPU clusters. Coupled with high angular resolution and great line sensitivity in ground based interferometers, ELTs and JWST, these advances in computational efforts should allow for large strides in the field in the next decade.
Welche Wirtschaft? Peter Berger; Peter Eigner; Erich Landsteiner ...
Österreichische Zeitschrift für Geschichtswissenschaften : ÖZG,
12/1996, Letnik:
7, Številka:
4
Journal Article
Fluorescence imaging is used to visualize directly the transfer of two inner hydrogen atoms in single porphycene molecules. This reaction leads to a chemically equivalent but differently oriented ...structure and hence results in a rotation of the transition dipole moments. By probing single immobilized molecules with an azimuthally polarized laser beam in the focal spot of a confocal microscope we observe ring-like emission patterns, possible only for a chromophore with two nearly orthogonal transition dipole moments. Numerical simulations of the observed emission patterns yield a value of 72° for the angle between the S0−S1 transition moments in the two tautomeric forms.
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