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351.
Jana Honová Stanislav Luňák Martin Vala Stanislav Stříteský Ladislav Fekete Martin Weiter Alexander Kovalenko 《Chemical Papers》2016,70(10):1416-1424
An extended study on a group of four soluble diphenyl-amino-stilbene based diphenyl-diketopyrrolo- pyrrole molecules has been carried out. Using the materials in thin-film transistors it was shown that the above-mentioned compounds can be successfully used as donors in organic photovoltaic devices. Influence of the molecular symmetry and solubilizing chain on the morphology and solar cell performance are described. It was shown that a shorter and non-branched ethyl acetate chain leads to higher charge carrier mobility, short circuit current, and better fill factor. After the basic optimization, a power conversion efficiency of about 1.5 % was reached. This, to the best of our knowledge, is the highest reported efficiency of thiophene-free small-molecule diketo-pyrrolopyrroles. 相似文献
352.
353.
Petr Mošner Antonín Račický Ladislav Koudelka 《Journal of Thermal Analysis and Calorimetry》2018,131(2):843-851
Five novel bridged heptaphenyl polyhedral oligomeric silsesquioxanes (POSSs), in which two identical silicon cages R7(SiO1.5)8 (with R = Phenyl) are linked to various aliphatic [(CH2) n with n = 2, 6 and 10] and aromatic (Ar–Ar and Ar–O–Ar, where Ar = p-C6H4) bridges, were synthesized. The obtained compounds were characterized by elemental analysis and 1 H NMR spectroscopy, and the results were in very good agreement with those of expected products. The synthesized heptaphenyl POSSs were thermally degraded, in dynamic heating conditions (25–700 °C), in both flowing nitrogen and static air atmosphere. The temperatures at 5% mass loss (T 5%) and residues at 700 °C were thus determined to evaluate their resistance to thermal degradation, but no substantial difference was found between the values in the two studied environments. The obtained T 5% values were much higher than those of the corresponding isobutyl and cyclopentyl POSSs we investigated in the past. Also, the T 5% values of the phenyl POSSs with aliphatic bridges decreased quite linearly on increasing the number of bridge carbon atoms (n C). This behaviour was interpreted and attributed to the presence of the external corona formed by voluminous phenyl groups. The residue at 700 °C, which was largely higher than those of the corresponding isobutyl and cyclopentyl POSSs, was a further confirmation of the better thermal stability of the compounds here studied. 相似文献
354.
355.
Vladimíra Novotná Ladislav Fekete Věra Hamplová Milada Glogarová Lubor Lejček Martin Cigl 《Liquid crystals》2018,45(8):1155-1163
We have synthesised and studied lactic acid derivatives based on chlorine substituted molecular core, which is created from two biphenyls linked by an ester, and terminated with one or two lactic units in a chiral chain. The compounds with one lactate group exhibit cholesteric phase with rather short helix pitch (200 nm) in a broad temperature range. On contrary, compound with two lactate units reveals a stable TGBA phase, with transition temperatures substantially lower than those for one-lactate derivatives. We have studied mesophase behaviour and electro-optical properties, mostly based on the texture observation in polarising microscope. Additionally, we have used AFM and x-ray techniques to confirm mesophase identification and establish structural properties. 相似文献
356.
Alexandr?JegorovEmail author Ladislav?Cvak Jan??ejka Bohumil?Kratochvíl Petr?Sedmera Vladimír?Havlí?ek 《Journal of chemical crystallography》2005,35(8):621-627
Mollugin was isolated from the extract of Rubia tinctorum roots. Lucidin was obtained by semisynthesis from xanthopurpurin. Mollugin crystallises in space group P-1 (No. 2), a = 8.5857(7), b = 11.473(4), c = 15.024(1) Å, α = 77.64(2)∘, β = 89.36(1)∘, γ = 89.71(2)∘, and V = 1445.5(5) Å3, lucidin crystallises in space group P21/c (No.14), a = 16.800(6), b = 9.637(2), c = 7.073(7) Å, β = 98.01(5)∘, and V = 1134(1) Å3. 相似文献
357.
Marek Burian Ladislav Omelka Silvie Ondrášová Vlasta Brezová 《Monatshefte für Chemie / Chemical Monthly》2003,134(4):501-508
Summary. Several N-phenyl substituted 1,4- and 1,2-phenylenediamines were oxidized using radicals and 3-chloroperbenzoic acid. EPR spectroscopy confirmed the generation of nitroxide radicals originating from the
oxidation of the bridging -NH-group. No radical products suggesting the simultaneous reaction with the NH2-group were observed. Only in the case of 1,4-phenylenediamine, a low concentration of nitroxide radical H–NO–C6H4–NH2 was obtained. In o-aminodiphenylnitroxide the steric effect of the NH2-group causes a partially asymmetrical spin density distribution in both phenyl rings.
Corresponding author. E-mail: omelka@fch.vutbr.cz
Received September 30, 2002; accepted October 4, 2002 相似文献
358.
An algorithm based on a combination of the polyhedral and quadratic approximation is given for finding stationary points for
unconstrained minimization problems with locally Lips-chitz problem functions that are not necessarily convex or differentiable.
Global convergence of the algorithm is established. Under additional assumptions, it is shown that the algorithm generates
Newton iterations and that the convergence is superlinear. Some encouraging numerical experience is reported.
This work was supported by the grant No. 201/96/0918 given by the Czech Republic Grant Agency. 相似文献
359.
360.
Ladislav Bican 《Annali dell'Universita di Ferrara》2005,51(1):61-67
Sunto LetG andH be abstract classes of modules. The classH is said to have theG-property if to each infinite cardinal λ there exists a cardinal κ>λ such that for everyF∈H with |F|≥κ and every its submoduleK with |F/K|≤λ there exists a submoduleL ofK such thatF/L/teG and |F/L|<κ. This condition is stronger than the condition (P) requiringL≠0 instead of |F/L|<κ, which was introduced and investigated in [8]. In this note we are going to study the relations of this more general condition
to the existence of precovers with respect to some classes of modules. As an application we obtain some sufficient conditions
for the existence of σ-torsionfree precovers related to a given hereditary torsion theory σ for the categoryR-mod. This result is closely related to and in some sense extends that of [5].
The research has been partially supported by the Grant Agency of the Czech Republic, grant #GAČR 201/03/0937 and also by the
institutional grant MSM 113 200 007. 相似文献