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排序方式: 共有86条查询结果,搜索用时 15 毫秒
11.
Dominik Lungerich David Reger Helen Hölzel René Riedel Max M. J. C. Martin Dr. Frank Hampel Prof. Dr. Norbert Jux 《Angewandte Chemie (International ed. in English)》2016,55(18):5602-5605
A novel rational synthetic pathway—the “functionalization of para‐nitroaniline” (FpNA)—provides substituted hexaarylbenzenes (HABs) with uncommon symmetries that bear up to five different substituents, fully avoiding regioisomeric product distributions during the reactions. 4‐Nitroaniline is functionalized by a cascade of electrophilic halogenations, Sandmeyer brominations, and Suzuki cross‐coupling reactions, leading to 26 substitution geometries, of which 18 structures are not available by the current established techniques. Furthermore, we demonstrate that this method is applicable to the bulk production of such systems on a multigram scale. Regarding optoelectronic properties, we demonstrate how highly functionalized HABs can show strong luminescent behavior, making these molecules very attractive to organic electronic devices. 相似文献
12.
KM Varier AM Vinodkumar NVSV Prasad PV Madhusudhana Rao DL Sastry Lagy T Baby MC Radhakrishna NG Puttaswamy JJ Das P Sugathan N Madhavan AK Sinha DO Kataria 《Pramana》1999,53(3):529-533
Large enhancements have been observed in the sub-barrier fusion cross sections for Ti+Ni systems in our previous studies.
Coupled channel calculations incorporating couplings to 2+ and 3− states failed to explain these enhancements completely. A possibilty of transfer channels contributing to the residual enhancements
had been suggested. In order to investigate the role of relevant transfer channels, measurements of one- and two-nucleon transfer
were carried out for 46,48Ti+61Ni systems. The present paper gives the results of these studies. 相似文献
13.
Reger DL Gardinier JR Elgin JD Smith MD Hautot D Long GJ Grandjean F 《Inorganic chemistry》2006,45(22):8862-8875
Iron(II) poly(pyrazolyl)borate complexes have been investigated to determine the impact of substituent effects, intramolecular ligand distortions, and intermolecular supramolecular structures on the spin-state crossover (SCO) behavior. The molecular structure of Fe[HB(3,4,5-Me3pz)3]2 (pz = pyrazolyl ring), a complex known to remain high spin when the temperature is lowered, reveals that this complex has an intramolecular ring-twist distortion that is not observed in analogous complexes that do exhibit a SCO at low temperatures, thus indicating that this distortion greatly influences the properties of these complexes. The structure of Fe[B(3-(cy)Prpz)4]2.(CH3OH) ((cy)Pr = cyclopropyl ring) at 294 K has two independent molecules in the unit cell, both of which are high spin; only one of these high-spin iron(II) sites, the site with the lesser ring-twist distortion, is observed to be low-spin iron(II) in the 90 K structure. A careful evaluation of the supramolecular structures of these complexes and several similar complexes reported previously revealed no strong correlation between the supramolecular packing forces and their SCO behavior. Magnetic and M?ssbauer spectral measurements on Fe[B(3-(cy)Prpz)4]2 and Fe[HB(3-(cy)Prpz)3]2 indicate that both complexes exhibit a partial SCO from fully high-spin iron(II) at higher temperatures, respectively, to a 50:50 high-spin/low-spin mixture of iron(II) below 100 K. These results may be understood, in the former case, by the differences in ring-twisting and, in the latter case, by a phase transition; in all complexes in which a phase transition is observed, this change dominates the SCO behavior. A comparison of the M?ssbauer spectral properties of these two complexes and of Fe[HB(3-Mepz)3]2 with that of other complexes reveals correlations between the M?ssbauer-effect isomer shift and the average Fe-N bond distance and between the quadrupole splitting and the average FeN-NB intraligand dihedral torsion angles and the distortion of the average N-Fe-N intraligand bond angles. 相似文献
14.
Daniel L. Reger Mark D. Smith Kenneth J. Brown 《Journal of chemical crystallography》2009,39(8):545-548
Abstract The cation in the solid state structure of [Fe{HC(3,5-Me2pz)3}2][Fe2OCl6] (pz = pyrazolyl ring) contains an octahedral iron(II) center with an average Fe–N bond distance of 2.17 Å, indicating that
the iron(II) is in the high-spin form. While M–N bond distances of this length with κ3-[HC(3,5-Me2pz)3] ligands generally cause tilting of pz to open up the “bite” angle, in this structure the average tilting angle is only 3.1°,
a much lower value than observed in earlier structures of this same cation paired with different anions. The crystals are
monoclinic, space group P21/n, with a = 11.1671(12) Å, b = 10.8091(11) Å, c = 17.4385(17) Å, α = γ = 90°, β = 95.685(2)°, and Z = 2.
Graphical Abstract The cation in the solid state structure of [Fe{HC(3,5-Me2pz)3}2][Fe2OCl6] (pz = pyrazolyl ring) contains an octahedral iron(II) center in the high-spin form with unusual orientations of the pyrazolyl
rings.
相似文献
15.
Hydrophobin coated boehmite nanoparticles have been used to establish tooth-paste like, homogenous emulsions. The surface-modified nanoparticles were simply obtained by mixing aqueous solutions of cationic boehmite particles with the anionic hydrophobin H Star Protein B® (HPB). Surface tension measurements clearly show that 1 wt.% boehmite binds up to 1 wt.% HPB. The strong interaction and aggregation of hydrophobin coated boehmite nanoparticles was proven by Cryo-TEM measurements, too. Interestingly, the combined use of 0.5 wt.% HPB and 0.5 wt.% boehmite as emulsifying agents resulted in very stable, homogenous, high internal phase emulsions (65 wt.% oil) that are stable over months. The established emulsions have also been characterized by rheological measurements. Storage moduli of more than 1000 Pa are characteristic for their high gel-like properties. Furthermore, light microscopy showed an average droplet size close to 1 μm with low polydispersity. Cryo-SEM confirmed that the hydrophobin coated nanoparticles are located at the interface of the oil droplets and therefore stabilize the emulsion systems. 相似文献
16.
Centrosymmetric [Cu(2)(μ-X)(μ-L(m)*)(2)](ClO(4))(3) (X = F(-), Cl(-), Br(-), OH(-), L(m)* = m-bis[bis(3,5-dimethyl-1-pyrazolyl)methyl]benzene)], the first example of a series of bimetallic copper(II) complexes linked by a linearly bridging mononuclear anion, have been prepared and structurally characterized. Very strong antiferromagnetic exchange coupling between the copper(II) ions increases along the series F(-) < Cl(-) < OH(-) < Br(-), where -J = 340, 720, 808, and 945 cm(-1). DFT calculations explain this trend by an increase in the energy along this series of the antibonding antisymmetric combination of the p orbital of the bridging anion interacting with the copper(II) d(z(2)) orbital. 相似文献
17.
N. Reger F. J. Stadermann H. M. Ortner 《Analytical and bioanalytical chemistry》1997,358(1-2):143-145
Electrical charging during SIMS-analysis (secondary ion mass spectrometry) is a severe limitation for the analysis of non-conductive samples. In most cases this charging can be compensated with the aid of an electron gun. This is an already established method to analyze insulating samples. In this work results of a systematic study of electron gun charge compensation in our CAMECA ims5f ion microprobe are described. 相似文献
18.
Oxa[7]superhelicene: A π‐Extended Helical Chromophore Based on Hexa‐peri‐hexabenzocoronenes
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David Reger Philipp Haines Dr. Frank W. Heinemann Prof. Dr. Dirk M. Guldi Prof. Dr. Norbert Jux 《Angewandte Chemie (International ed. in English)》2018,57(20):5938-5942
A novel π‐extended “superhelicene” based on hexa‐peri‐hexabenzocoronenes (HBCs) has been synthesized by an efficient four‐step synthetic procedure starting from diphenyl ether. Comprehensive structural analysis of the helicene was performed by NMR spectroscopy and mass spectrometry measurements together with X‐ray analysis. Physicochemical analysis of the superhelicene and suitable HBC references revealed it had outstanding fluorescent features with quantum yields of over 80 %. 相似文献
19.
Reger DL Gardinier JR Gemmill WR Smith MD Shahin AM Long GJ Rebbouh L Grandjean F 《Journal of the American Chemical Society》2005,127(7):2303-2316
Sonogashira coupling reactions of terminal alkynes with Fe[(p-IC6H4)B(3-Mepz)3]2 (pz = pyrazolyl ring) yield Fe[(p-PhC2C6H4)B(3-Mepz)3]2 (2), Fe[(p-Me3SiC2C6H4)B(3-Rpz)3]2 (R = H, 3a, R = Me, 3b), and Fe[(p-HC2C6H4)B(3-Mepz)3]2 (R = H, 4a, R = Me, 4b), a series of new complexes containing "third generation" poly(pyrazolyl)borate ligands. Complex 2 undergoes a fairly gradual iron(II) electronic spin-state crossover with a 30 K hysteresis, whereas complex 3b is an unusual example of a complex with equivalent iron(II) sites in the high-spin form that shows an abrupt 50% spin crossover. For complex 4b, 50% of the iron(II) sites undergo a gradual spin-state transition between 185 and 350 K with an activation energy of 1590 +/- 30 cm(-1) and a T(1/2) = 280 K and, for the remaining iron(II) sites, an abrupt cooperative spin-state crossover between 106 and 114 K. The crystal structures of 4b obtained for each of the three distinct electronic spin states reveal two crystallographically different iron(II) sites, and analysis of the molecular/supramolecular structures indicates that the difference in the degree of pyrazolyl ring tilting in the ligands between the two sites, rather than the strength of the intermolecular forces, play a prominent role in determining the temperature of the spin-state crossover. 相似文献
20.
Katharina Vollmayr Joseph D. Reger Manfred Scheucher Kurt Binder 《Zeitschrift für Physik B Condensed Matter》1993,91(1):113-125
We consider the rounding and shifting of a firstorder transition in a finited-dimensional hypercubicL
d geometry,L being the linear dimension of the system, and surface effects are avoided by periodic boundary conditions. We assume that upon lowering the temperature the system discontinuously goes to one ofq ordered states, such as it e.g. happens for the Potts model ind=3 forq3, with the correlation length of order parameter fluctuation staying finite at the transition. We then describe each of theseq ordered phases and the disordered phase forL by a properly weighted Gaussian. From this phenomenological ansatz for the total distribution of the order parameter, all moments of interest are calculated straight-forwardly. In particular, it is shown that forL exceeding a characteristic minimum sizeL
min the forthorder cumulantg
L
(T) exhibits a minimum atT
min>T
c, withT
min–T
cL
–d and the value of the cumulant and the minimum (g(T
min)) behaving asg(T
min)L
–d. All cumulantsg
L
(T) forL approximately intersect at a common crossing pointT
crossL
–2d, with a universal valueg(T
cross)=1–n/2q, wheren is the order parameter dimensionality. By searching for such a behavior in numerical simulation data, the first order character of a phase transition can be asserted. The usefulness of this approach is shown using data for theq=3,d=3 Potts ferromagnet. 相似文献