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101.
Metal-macrocycle framework (MMF): supramolecular nano-channel surfaces with shape sorting capability
Hollow nanostructures for the functional assembly of chemical groups with inner surface geometry and regulable stoichiometry enable steric design of interior reaction centers. Herein we report a metal-macrocycle framework (MMF) that forms single-crystalline nanochannels with five distinct enantiomeric pairs of guest binding pockets. During crystal-soaking experiments, the MMF crystals can encapsulate aromatic molecules with high site selectivity. First, constitutional isomers of dibromobenzene are captured and sorted into different binding pockets. Second, each of the optical isomers of (1R/1S)-1-(3-chlorophenyl)ethanol is included diastereoselectively into one of an enantiomeric pair of binding pockets. An advantage of this strategy is that the interior walls can be "repainted" via replacement of the trapped molecules with alternatives. Such guest uptake behaviors would allow highly regioselective or stereoselective reactions within the nanochannel. 相似文献
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103.
Junji Saito Mitsuhiko Onda Shigekazu Matsui Makoto Mitani Rieko Furuyama Hidetsugu Tanaka Terunori Fujita 《Macromolecular rapid communications》2002,23(18):1118-1123
The catalytic behavior of three bis(phenoxy‐imine) group‐4 transition‐metal complexes (M = Ti, Zr, Hf), with iBu3Al/Ph3CB(C6F5)4 cocatalyst systems towards propylene polymerization was investigated under atmospheric pressure at 25 °C. The Ti complex produced ultrahigh‐molecular‐weight atactic poly(propylene), whereas Zr and Hf complexes formed high‐molecular‐weight isotactic poly(propylene)s via a site‐control mechanism. The isotactic poly(propylene) obtained with the Hf complex displayed a high melting temperature of 123.8 °C.
104.
105.
Junji Saito Makoto Mitani Mitsuhiko Onda Jun‐Ichi Mohri Sei‐Ichi Ishii Yasunori Yoshida Takashi Nakano Hidetsugu Tanaka Tomoaki Matsugi Shin‐Ichi Kojoh Norio Kashiwa Terunori Fujita 《Macromolecular rapid communications》2001,22(13):1072-1075
Highly syndiotactic “living” poly(propylene)s were synthesized at 25°C using a bis[N‐(3‐tert‐butylsalicylidene)‐2,3,4,5,6‐pentafluoroanilinato]titanium (IV) dichloride/MAO catalyst system, and microstructures of the polymer were analyzed by means of 13C NMR spectroscopy. The syndiotactic poly(propylene) contains isobutyl, isopentyl and propyl end groups, suggesting that the living polymerization of propylene was initiated via 1,2‐insertion, followed by 2,1‐insertion as the principal mode of polymerization. Pentad distribution analysis revealed that the syndiospecific polymerization proceeds under chain‐end control. 相似文献
106.
107.
Improvement of hearing ability by directional information 总被引:1,自引:0,他引:1
108.
A new method for aggregating ordinal assessments of individuals is proposed to obtain a collective preference ordering of alternatives. The method converts the ordinal assessments to collective pairwise comparisons of the alternatives and incorporates a deduction process to yield transitively consistent pairwise comparisons with respect to majority principle, and hence yields a linear order of the alternatives. Its algorithm is presented and its properties are studied. The method is applied to an opinion survey concerning quality of life, and a collective ordering of items pertaining to the quality of life is obtained with respect to their importance. 相似文献
109.
Xian He Bu Dao Li An Yun Ti Chen Mitsuhiko Shionoya Eiichi Kimura 《Journal of inclusion phenomena and macrocyclic chemistry》1997,28(3):245-258
The IR spectra of the crystalline complexes of 3-and 4-nitrophenol with crown ethers were studied, viz.,18-crown-6 (18C6), benzo-18-crown-6 (B18C6),dibenzo-18-crown-6 (DB18C6), dicyclohexano-18-crown-6 (DC18C6) and dibenzo-24-crown-8 (DB24C8). The spectra of uncomplexed crown ethers showed water absorption bands which indicate the presence of two types of bound water molecules, viz., cavitant water enclosed by the strong ether-cavity field and outer-layer hydrogen-bonded water molecules. Upon complexation with 3- and 4-nitrophenol, the bands attributed to cavitant water disappeared, leaving the outer layer water to act as a bridge between the host crown ether and the guest phenols. The results further showed that of the crown ethers and of the phenols, B18C6 and DC18C6 and 3-nitrophenol, have the strongest interaction. The behaviour of the phenols was explained by the increased contribution of the inductive-moment over the resonance -moment in thecomplexes. 相似文献
110.
Winyu Tanthapanichakoon Mitsuhiko Hata Koh-hei Nitta Masami Furuuchi Yoshio Otani 《Polymer Degradation and Stability》2006,91(11):2614-2621
Polyphenylene sulfide (PPS) is known as a material resistant to high temperature and chemicals; however, there are arguments on the durability of PPS non-woven fabrics to chemicals, such as nitric acid (HNO3), sulfuric acid (H2SO4), and hydrochloric acid (HCl). Therefore, this work aims at investigating the degradation of PPS non-woven fabrics in HNO3, H2SO4 and HCl, and at confirming acid durability of PPS non-woven fabrics. In addition, this paper also studies the interaction among these three acids by measuring the retention of strength in binary or tertiary mixtures of these three acids. A discussion has been made on the acceleration/retardation of PPS degradation by the interactive effects, and also on the chemistry related to the degradation by these acids. Furthermore, there is a linear relationship between the nitric acid concentration and the proportion of carbon in the remaining PPS structures after 100 h of acid exposure. Also, this proportion of carbon is a good indicator of the retained strength in PPS fabrics. 相似文献