Dendritic positive

Coin and Button Cell Commercial Systems. Initial commercialization of rechargeable lithium technology has been through the introduction of coin or button cells. The eadiest of these systems was the Li—C system commercialized by Matsushita Electric Industries (MEI) in 1985 (26,27). The negative electrode consists of a lithium alloy and the positive electrode consists of activated carbon [7440-44-0J, carbon black, and binder. The discharge curve is not flat, but rather slopes from about 3 V to 1.5 V in a manner similar to a capacitor. Use of lithium alloy circumvents problems with cycle life, dendrite formation, and safety. However, the system suffers from generally low energy density. 

Dendrimers 5-8 were obtained by taking advantage of the versatile regiose-lective reaction developed in the group of Diederich [24], which led to macro-cyclic bis-adducts of Cgg by a cyclization reaction at the C sphere with bis-mal-onate derivatives in a double Bingel cyclopropanation [25]. Reaction of the dendritic malonates with Cgg, I2, and l,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in toluene at room temperature afforded the corresponding cyclization products 5-8 (Fig. 2). The relative position of the two cyclopropane rings in 5-8 on the Cgo core was determined based on the molecular symmetry deduced from the and NMR spectra (Cs) as well as on their UV/Vis spectra. It is well estabhshed... 

To investigate this dendritic effect, a dimeric model compound was synthesized which mimics the tethered relationship of two catalytic units within one branch of the PAMAM dendrimer. All dendritic catalysts were more active in the HKR than the parent complex. Furthermore, the dendritic catalysts also displayed significantly higher activity than the dimeric model compound. The authors proposed that this positive dendritic effect arises from restricted conformation imposed by the dendrimer structure, thereby creating a bigger effective molarity of [Co(salen)] units. Alternatively, the multimeric nature of the dendrimer, may lead to higher order in productive cooperative interactions between the catalytic units. 

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