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121.
A series of late transition metal complexes, [(bpma)Co(μ – Cl)Cl] 2 , [(bpma)Cu(μ – Cl)Cl] 2 , [(bpma)Zn(μ – Cl)Cl] 2 and [(bpma)Cd(μ – Br)Br] 2 (where bpma is 4‐bromo‐N‐((pyridin‐2‐yl)methylene)benzenamine) have been synthesized and structurally characterized. The X‐ray structures of dimeric complexes [(bpma)M(μ – X)X] 2 (M = Co, Cu and Zn, X = Cl; M = Cd, X = Br) showed a distorted 5‐coordinate trigonal bipyramidal geometry involving two nitrogen atoms of N,N‐bidentate ligand, two bridged and one terminal halogen atoms. The complex [(bpma)Cu(μ – Cl)Cl] 2 revealed the highest catalytic activity for the polymerisation of methyl methacrylate in the presence of modified methylaluminoxane with an activity of 9.14 × 104 g PMMA/mol·Cu·h at 60 °C and afforded syndiotactic poly (methylmethacrylate) (rr = 0.69). 相似文献
122.
Salunke Gawali S. Dalvi R. Ah Khursheed Rane S. 《Journal of Thermal Analysis and Calorimetry》2004,76(3):801-812
Syntheses of phthiocol complexes with Cu(II) in inert media resulted in anhydrous monomer Cu-4: [Cu(NQ)2] and dimer Cu-5: [Cu(NQ)(NSQ)]2, however synthesis in air generates polymeric hydrated Cu-6: [Cu(NQ)2(H2O)2]n. Media and colligation give rise to charge transfers in coordination compounds and lead to different redox ligations of 3-methyl-2-hydroxy-1,4-naphthoquinone.
These redox forms are determined from quantitization of activation energies (E
a) of different pyrolytic steps in TG using the rising temperature expression of Coats and Redfern. 'Tyrosinase'-type mechanism
is discussed for the redox-type ligation. Characteristic six-line EPR signals of dimeric Cu-5 lead to zero field splitting
parameters D=0.01608 cm-1and E=0.01576 cm-1. Cu-6 shows molecular association through hydrogen bonding. Variable temperature magnetic measurement data of Cu-6 from 6
to 300 K is fitted to the polymeric expression of Bonner and Fisher model. The best fit was obtained with antiferrromagnetic
exchange coupling constantJ=-2 cm-1, g=2.2 having R=4.2·10-4.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
123.
组合数学引人入胜的一个特色,是各项貌似不同的课题之间的密切关连。本文试图以二元序列的自相关函数作贯穿主题,引入几种重要的组合结构,虽不能算是全面的综合介绍,也算勾划了这张绚丽图画的一角。 本文先介绍何谓随机序列与伪随机序列,从而带出自相关函数的意义,并考虑四种不同的自相关函数。在通讯科学与电机电子工程的应用上,需要构作具备“良好”性质的自相关函数二元序列。讨论这类问题,自然地引入了各种重要的组合结构,如差集、t-设计、有限几何、阿达玛矩阵、优美图等。本文除了指出这些课题之间的关连,还列举了一些猜想。与此类 相似文献
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Partial Difference Sets with Paley Parameters 总被引:2,自引:0,他引:2
Partial difference sets with parameters (,k,,µ) = (,( 1)/2, ( 5)/4,( 1)/4) are called Paleypartial difference sets. By using finite local rings, we constructa family of Paley PDSs for abelian p-groups with any given exponent.Furthermore, we prove some non-existence results on Paley PDSs.Using these results, we prove that Paley PDSs exist in a rank2 abelian group if and only if the group is isomorphic to Zpr x Zp r where p is an odd prime. 相似文献
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We have investigated adsorption of an O(2) molecule on a double-walled carbon nanotube (DWCNT) edge using density functional theory calculations. An O(2) molecule adsorbs exothermally without an adsorption barrier at open nanotube edges that are energetically favorable with a large adsorption energy of about -9 eV in most cases. Dissociative adsorption of an O(2) molecule induces various spontaneous lip-lip interactions via the bridged carbon atoms, generating the closed tube ends. This explains why the DWCNTs are chemically more stable than the single-walled nanotubes during observed field emission experiments. The field emission takes place via the localized states of the bridged carbon atoms, not via those of the adsorbed oxygen atoms particularly in the armchair nanotubes. We also find that some O(2) precursor states exist as a bridge between tube edges. 相似文献
130.
The dc electrical conductivity of pure and doped ammonium perchlorate (AP) has been studied in two different crystal orientations, with the electric field applied perpendicularly to either (001) or (210) planes. The conductivity along the direction of the c axis was found to be lower than that normal to (210) by a factor of 5 to 10. The dc electrical conductivity of AP is decreased by Pb2+ ions but increased by SO2?4 and CrO2?4 ions. The conductivity of pure AP and of Pb2+-doped AP displays two regions with activation energies for conduction of 0.56 and 0.87 eV, respectively. The conductivity of the anion-doped crystals has a single activation energy, 0.66 eV for SO2?4 and 0.72 eV for CrO2?4. Exposure to ammonia enhances the conductivity of pure AP. A proton conduction mechanism is proposed that takes due regard of the structure of AP. The effect of the various additives on the conductivity are attributed to their influences on the formation of charge-carrying protons. 相似文献