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951.
The enantioselective synthesis of completely ortho‐fused [9]‐ and [11]helicene‐like molecules has been achieved through a rhodium‐mediated, intramolecular, double [2+2+2] cycloaddition of phenol‐ or 2‐naphthol‐linked hexaynes. Crystal structures and photophysical properties of these [9]‐ and [11]helicene‐like molecules have also been disclosed.  相似文献   
952.
The first stereoselective syntheses of doubly linked (A‐type) oligocatechins, (+)‐procyanidin A2 and (+)‐cinnamtannin B1, have been achieved. Ethylenedioxy‐bridged flavans served as excellent platforms, thus allowing annulation with nucleophilic catechin units in a stereoselective manner. An additional key was the new synthetic approach to selectively protected nucleophilic catechin, thus enabling regioselective construction of the key dioxabicyclo skeleton of the A‐type oligocatechins.  相似文献   
953.
Supramolecular rosettes of oligothiophenes that do not bear long aliphatic tails have been designed as semiconducting nanomaterials for solution‐processable bulk heterojunction solar cells. The rosettes consist of six barbiturated thienyl[oligo(hexylthiophene)] units (Bar‐T‐hTn; n=3,4,5) aggregated by multiple hydrogen bonds, which have been directly visualized by scanning tunneling microscopy (STM) at a solid–liquid interface. 1H NMR spectroscopy in [D8]toluene showed that Bar‐T‐hTn exists as a mixture of monomers and small hydrogen‐bonded aggregates. Hierarchical organization of the hydrogen‐bonded aggregates took place through π–π stacking interactions upon casting their toluene solutions, resulting in the growth of highly ordered nanorods whose widths are consistent with the diameters of the rosettes. The nanorods could be generated in the presence of soluble fullerene derivatives via solution casting or the annealing of the resulting thin films. The solar cells fabricated based on these bulk heterojunction films showed power conversion efficiencies of 1–3 %, which are far higher than those of the non‐hydrogen‐bonded reference oligothiophene and the derivative that possesses long aliphatic tails.  相似文献   
954.
Memory operations based on variation of a molecule’s properties are important because they may lead to device miniaturization to the molecular scale or increasingly complex information processing protocols beyond the binary level. Molecular memory also introduces possibilities related to information‐storage security where chemical information (or reagents) might be used as an encryption key, in this case, acidic/basic reagents. Chemical memory that possesses both volatile and non‐volatile functionality requires reversible conversion between at least two chemically different stable or quasi‐stable states. Here we have developed the phenol–phenoxide equilibrium of phenol fluorophores as a data storage element, which can be used to write or modulate data using chemical reagents. The properties of this system allow data to be stored and erased either in non‐volatile or volatile modes. We also demonstrate non‐binary switching of states made possible by preparation of  a composite containing the molecular memory elements.  相似文献   
955.
956.
Azafulleroid, amino‐bridged [5,6]‐open fullerene, has the ambident N/C basicity of the incorporated enamine moiety. Acid‐catalyzed arylation of N‐substituted azafulleroids proceeded via two types of initial N/C protonation to perform monoarylation or 1,4‐bisarylation for the N‐alkyl substituents and shuttlecock‐type pentakisarylation for the N‐phenyl substituent. The dramatic product change was explained by considering the possible mechanism as well as the DFT computational results.  相似文献   
957.
An efficient method for synthesis of 2-methoxy-l,2-dihydro-3H-indol-3-ones using two successive oxidations of indoles is described.  相似文献   
958.
The renormalization group equations for the parametrization-convention independent quadratic parameters |V ij |2 of the KM matrix are derived. Numerical analysis of these equations shows that the heavy quark family (t, b) tends to mix with the lighter families (c, s) and (u, d) with increasing energy, although the variation is very much slow. The CP-nonconservation effects are shown to get larger with energy.  相似文献   
959.
A minimum degree condition is given for a bipartite graph to contain a 2‐factor each component of which contains a previously specified vertex. © 2004 Wiley Periodicals, Inc. J Graph Theory 46: 145–166, 2004  相似文献   
960.
The SRVL fluorescenee lifetimes and fluorescence excitation spectra of the HNO ã1A″ -X1AA′ transition were measured in a supersonic free jet. The cooling of a rotational temperature in the jet made it possible to clear up the parity-selected perturbations in the asymmetric rotor under higher resolution condition. The fluorescence lifetimes of strongly perturbed levels, i.e. HNO ã1A″ 011 rovibronic levels were observed with dual exponential decay profiles, while non-perturbed levels exhibited single ones. The SRVL fluorescence lifetimes and fluorescence excitation spectra of DNO ã1″ -X1A′ were measured under the same condition as HNO. The rotationll analysis of the DNO ã1A″ 011 rovibronic levels was first carried out in the jet.  相似文献   
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